In situ non-radioactive detection of nuclear factors in paraffin sections by Southwestern histochemistry

Interplay between HSP90 and Nrf2 pathways in diabetes-associated atherosclerosis

INTRODUCTION

Oxidative stress and inflammation are determinant processes in the development of diabetic vascular complications. Heat shock protein 90 (HSP90) overexpression in atherosclerotic plaques plays a role in sustaining inflammatory mechanisms, and its specific inhibition prevents atherosclerosis. The present work investigates, in a mouse model of diabetes-driven atherosclerosis, whether atheroprotection by pharmacological HSP90 inhibition is accomplished by bolstering antioxidant defense mechanisms headed by nuclear factor erythroid-derived 2-like 2 (Nrf2).

METHODS

Streptozotocin-induced diabetic apolipoprotein E-deficient mice were randomized to receive vehicle or HSP90 inhibitor (17-dimethylaminoethylamino-17-demethoxygeldanamycin, 4mg/kg) for 10 weeks. Aortic root sections were analyzed for plaque size and composition, transcription factor activity, and expression of inflammatory and antioxidant markers. In vitro studies were performed in murine macrophages cultured under hyperglycemic conditions.

RESULTS

Treatment with HSP90 inhibitor promoted the activation of Nrf2 in the aortic tissue of diabetic mice (predominantly localized in macrophages and smooth muscle cells) and also in cultured cells. Nrf2 induction was associated with a concomitant inhibition of nuclear factor-κB (NF-κB) in atherosclerotic plaques, thus resulting in a significant reduction in lesion size and inflammatory component (leukocytes and cytokines). Furthermore, atheroprotection by HSP90 inhibition was linked to the induction of cytoprotective HSP70, antioxidant enzymes (heme oxygenase-1, superoxide dismutase and catalase) and autophagy machinery (LC3 and p62/SQSTM1) in aortic tissue.

CONCLUSION

HSP90 inhibition protects from atherosclerosis in experimental diabetes through the induction of Nrf2-dependent cytoprotective mechanisms, reinforcing its therapeutic potential.

Litsea japonica extract inhibits neuronal apoptosis and the accumulation of advanced glycation end products in the diabetic mouse retina

The retinal accumulation of advanced glycation end products (AGEs) is a condition, which is found in diabetic retinopathy. The purpose of the present study was to investigate the protective effect of Litsea japonica extract (LJE) and to elucidate its underlying protective mechanism in model diabetic db/db mice. Male, 7 -week-old db/db mice were treated with LJE (100 or 250 mg/kg body weight) once a day orally for 12 weeks. The expression levels of AGEs and their receptor (RAGE) were subsequently assessed by immunohistochemistry. An electrophoretic mobility shift assay and southwestern histochemistry were used to detect activated nuclear factor κB (NF-κB). The immunohistochemical analysis demonstrated that LJE significantly reduced the expression levels of the AGEs and RAGE in the neural retinas of the db/db mice. LJE markedly inhibited the apop-tosis of retinal ganglion cells. In addition, LJE suppressed the activation of NF-κB. These results suggested that LJE may be beneficial for the treatment of diabetes-induced retinal neurodegeneration, and the ability of LJE to attenuate retinal ganglion cell loss may be mediated by inhibition of the accumulation of AGEs.

The interleukin-1 receptor antagonist anakinra improves endothelial dysfunction in streptozotocin-induced diabetic rats

Background

Endothelial dysfunction is a crucial early phenomenon in vascular diseases linked to diabetes mellitus and associated to enhanced oxidative stress. There is increasing evidence about the role for pro-inflammatory cytokines, like interleukin-1β (IL-1β), in developing diabetic vasculopathy. We aimed to determine the possible involvement of this cytokine in the development of diabetic endothelial dysfunction, analysing whether anakinra, an antagonist of IL-1 receptors, could reduce this endothelial alteration by interfering with pro-oxidant and pro-inflammatory pathways into the vascular wall.

Results

In control and two weeks evolution streptozotocin-induced diabetic rats, either untreated or receiving anakinra, vascular reactivity and NADPH oxidase activity were measured, respectively, in isolated rings and homogenates from mesenteric microvessels, while nuclear factor (NF)-κB activation was determined in aortas. Plasma levels of IL-1β and tumor necrosis factor (TNF)-α were measured by ELISA. In isolated mesenteric microvessels from control rats, two hours incubation with IL-1β (1 to 10 ng/mL) produced a concentration-dependent impairment of endothelium-dependent relaxations, which were mediated by enhanced NADPH oxidase activity via IL-1 receptors. In diabetic rats treated with anakinra (100 or 160 mg/Kg/day for 3 or 7 days before sacrifice) a partial improvement of diabetic endothelial dysfunction occurred, together with a reduction of vascular NADPH oxidase and NF-κB activation. Endothelial dysfunction in diabetic animals was also associated to higher activities of the pro-inflammatory enzymes cyclooxygenase (COX) and the inducible isoform of nitric oxide synthase (iNOS), which were markedly reduced after anakinra treatment. Circulating IL-1β and TNF-α levels did not change in diabetic rats, but they were lowered by anakinra treatment.

Conclusions

In this short-term model of type 1 diabetes, endothelial dysfunction is associated to an IL-1 receptor-mediated activation of vascular NADPH oxidase and NF-κB, as well as to vascular inflammation. Moreover, endothelial dysfunction, vascular oxidative stress and inflammation were reduced after anakinra treatment. Whether this mechanism can be extrapolated to a chronic situation or whether it may apply to diabetic patients remain to be established. However, it may provide new insights to further investigate the therapeutic use of IL-1 receptor antagonists to obtain vascular benefits in patients with diabetes mellitus and/or atherosclerosis.

NFκB activation in cutaneous lesions of leprosy is associated with development of multibacillary infection

Background

Nuclear factor kappa B (NFκB) transcription factors play a central role in controlling the expression of genes involved in inflammatory reactions, proliferation, and survival of human cells. However, the in situ evaluation of NFκB activity in leprosy has not been completed previously. The aim of this study was to determine whether NFκB activity correlates with susceptibility or resistance to Mycobacterium leprae infection in biopsies from skin lesions of 38 patients with the clinical and laboratory diagnosis of leprosy.

Methods

The NFκB activation profile was evaluated in biopsies from skin lesions of 38 patients with the clinical and laboratory diagnosis of leprosy. NFκB activation was evaluated and quantified by Southwestern histochemistry, and its activation index (range, 0–4) was calculated according to the percentage of nuclear positivity by the histochemistry. Activation index >1 was considered representative of activation of NFκB.

Results

Fifteen patients (39.5%) demonstrated activated NFκB. Multibacillary leprosy was associated with activated NFκB (54.5%, P=0.028). Borderline leprosy was most strongly associated with NFκB activation (80%), with an odds ratio of 32.7 (P=0.016). These clinical forms are characterized by increased susceptibility to M. leprae and by immunological instability. Activation of NFκB was absent in the granulomas in tuberculoid leprosy, which represents an effective inflammatory reaction pattern against M. leprae.

Conclusion

These results indicate that NFκB activation could favor susceptibility and immunological instability to M. leprae infection, potentially by the stimulation of phagocytosis and the regulation of apoptotic mechanisms of infected cells, leading to the proliferation of this intracellular bacillus. Further studies are needed to evaluate if inhibition of NFκB activation in multibacillary leprosy could favor resistance and an effective granulomatous immune response.

[Atorvastatin inhibits the atherosclerotic lesion induced by tumor necrosis factor-like weak inducer of apoptosis in apolipoprotein E deficient mice]

AIM

Interaction of tumor necrosis factor-like weak inducer of apoptosis (TWEAK) with its receptor Fn14 accelerates atherosclerotic plaque development in ApoE deficient mice (ApoE KO). In this work, an analysis has been made on the effect of an HMG-CoA reductase inhibitor, atorvastatin, on atherosclerotic plaque development accelerated by TWEAK in ApoE KO mice.

MATERIALS AND METHODS

Eight week-old ApoE KO mice were fed with a high cholesterol diet for 4 weeks. The animals were then randomized into 3 groups: mice injected i.p. with saline, recombinant TWEAK (10 μg/kg/twice a week), or recombinant TWEAK plus atorvastatin (1 mg/kg/day) for 4 weeks. The lesion size, cellular composition, lipid and collagen content were analyzed, as well as inflammatory response in atherosclerotic plaques present in aortic root of mice.

RESULTS

TWEAK treated mice showed an increase in atherosclerotic plaque size, as well as in collagen/lipid ratio compared with control mice. In addition, macrophage content, MCP-1 and RANTES expression, and NF-κB activation were augmented in atherosclerotic plaques present in aortic root of TWEAK treated mice compared with control mice. Treatment with atorvastatin prevented all these changes induced by TWEAK in atherosclerotic lesions. Atorvastatin treatment also decreased Fn14 expression in the atherosclerotic plaques of ApoE KO mice.

CONCLUSIONS

Atorvastatin prevents the pro-atherogenic effects induced by TWEAK in ApoE KO mice, which could be related to the inhibition of Fn14 expression. The results of this study provide new information on the beneficial effects of statin treatment in cardiovascular diseases.

Andrographolide attenuates skeletal muscle dystrophy in mdx mice and increases efficiency of cell therapy by reducing fibrosis

Background

Duchenne muscular dystrophy (DMD) is characterized by the absence of the cytoskeletal protein dystrophin, muscle wasting, increased transforming growth factor type beta (TGF-β) signaling, and fibrosis. At the present time, the only clinically validated treatments for DMD are glucocorticoids. These drugs prolong muscle strength and ambulation of patients for a short term only and have severe adverse effects. Andrographolide, a bicyclic diterpenoid lactone, has traditionally been used for the treatment of colds, fever, laryngitis, and other infections with no or minimal side effects. We determined whether andrographolide treatment of mdx mice, an animal model for DMD, affects muscle damage, physiology, fibrosis, and efficiency of cell therapy.

Methods

mdx mice were treated with andrographolide for three months and skeletal muscle histology, creatine kinase activity, and permeability of muscle fibers were evaluated. Fibrosis and TGF-β signaling were evaluated by indirect immunofluorescence and Western blot analyses. Muscle strength was determined in isolated skeletal muscles and by a running test. Efficiency of cell therapy was determined by grafting isolated skeletal muscle satellite cells onto the tibialis anterior of mdx mice.

Results

mdx mice treated with andrographolide exhibited less severe muscular dystrophy than untreated dystrophic mice. They performed better in an exercise endurance test and had improved muscle strength in isolated muscles, reduced skeletal muscle impairment, diminished fibrosis and a significant reduction in TGF-β signaling. Moreover, andrographolide treatment of mdx mice improved grafting efficiency upon intramuscular injection of dystrophin-positive satellite cells.

Conclusions

These results suggest that andrographolide could be used to improve quality of life in individuals with DMD.

Genetic deletion or TWEAK blocking antibody administration reduce atherosclerosis and enhance plaque stability in mice

Clinical complications associated with atherosclerotic plaques arise from luminal obstruction due to plaque growth or destabilization leading to rupture. Tumour necrosis factor ligand superfamily member 12 (TNFSF12) also known as TNF-related weak inducer of apoptosis (TWEAK) is a proinflammatory cytokine that participates in atherosclerotic plaque development, but its role in plaque stability remains unclear. Using two different approaches, genetic deletion of TNFSF12 and treatment with a TWEAK blocking mAb in atherosclerosis-prone mice, we have analysed the effect of TWEAK inhibition on atherosclerotic plaques progression and stability. Mice lacking both TNFSF12 and Apolipoprotein E (TNFSF12^−/−ApoE^−/−) exhibited a diminished atherosclerotic burden and lesion size in their aorta. Advanced atherosclerotic plaques of TNFSF12^−/−ApoE^−/− or anti-TWEAK treated mice exhibited an increase collagen/lipid and vascular smooth muscle cell/macrophage ratios compared with TNFSF12^+/+ApoE^−/− control mice, reflecting a more stable plaque phenotype. These changes are related with two different mechanisms, reduction of the inflammatory response (chemokines expression and secretion and nuclear factor kappa B activation) and decrease of metalloproteinase activity in atherosclerotic plaques of TNFSF12^−/−ApoE^−/−. A similar phenotype was observed with anti-TWEAK mAb treatment in TNFSF12^+/+ApoE^−/− mice. Brachiocephalic arteries were also examined since they exhibit additional features akin to human atherosclerotic plaques associated with instability and rupture. Features of greater plaque stability including augmented collagen/lipid ratio, reduced macrophage content, and less presence of lateral xanthomas, buried caps, medial erosion, intraplaque haemorrhage and calcium content were present in TNFSF12^−/−ApoE^−/− or anti-TWEAK treatment in TNFSF12^+/+ApoE^−/− mice. Overall, our data indicate that anti-TWEAK treatment has the capacity to diminish proinflamatory response associated with atherosclerotic plaque progression and to alter plaque morphology towards a stable phenotype.

Gene Deficiency in Activating Fcγ Receptors Influences the Macrophage Phenotypic Balance and Reduces Atherosclerosis in Mice

Immunity contributes to arterial inflammation during atherosclerosis. Oxidized low-density lipoproteins induce an autoimmune response characterized by specific antibodies and immune complexes in atherosclerotic patients. We hypothesize that specific Fcγ receptors for IgG constant region participate in atherogenesis by regulating the inflammatory state of lesional macrophages. In vivo we examined the role of activating Fcγ receptors in atherosclerosis progression using bone marrow transplantation from mice deficient in γ-chain (the common signaling subunit of activating Fcγ receptors) to hyperlipidemic mice. Hematopoietic deficiency of Fcγ receptors significantly reduced atherosclerotic lesion size, which was associated with decreased number of macrophages and T lymphocytes, and increased T regulatory cell function. Lesions of Fcγ receptor deficient mice exhibited increased plaque stability, as evidenced by higher collagen and smooth muscle cell content and decreased apoptosis. These effects were independent of changes in serum lipids and antibody response to oxidized low-density lipoproteins. Activating Fcγ receptor deficiency reduced pro-inflammatory gene expression, nuclear factor-κB activity, and M1 macrophages at the lesion site, while increasing anti-inflammatory genes and M2 macrophages. The decreased inflammation in the lesions was mirrored by a reduced number of classical inflammatory monocytes in blood. In vitro, lack of activating Fcγ receptors attenuated foam cell formation, oxidative stress and pro-inflammatory gene expression, and increased M2-associated genes in murine macrophages. Our study demonstrates that activating Fcγ receptors influence the macrophage phenotypic balance in the artery wall of atherosclerotic mice and suggests that modulation of Fcγ receptor-mediated inflammatory responses could effectively suppress atherosclerosis.

Peptide inhibitor of NF-κB translocation ameliorates experimental atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the arterial wall. NF-κB is a major regulator of inflammation that controls the expression of many genes involved in atherogenesis. Activated NF-κB was detected in human atherosclerotic plaques, and modulation of NF-κB inflammatory activity limits disease progression in mice. Herein, we investigate the anti-inflammatory and atheroprotective effects of a cell-permeable peptide containing the NF-κB nuclear localization sequence (NLS). In vascular smooth muscle cells and macrophages, NLS peptide specifically blocked the importin α-mediated nuclear import of NF-κB and prevented lipopolysaccharide-induced pro-inflammatory gene expression, cell migration, and oxidative stress. In experimental atherosclerosis (apolipoprotein E-knockout mice fed a high-fat diet), i.p., 0.13 μmol/day NLS peptide administration for 5 weeks attenuated NF-κB activation in atherosclerotic plaques. NLS peptide significantly inhibited lesion development at both early (age 10 weeks) and advanced (age 28 weeks) stages of atherosclerosis in mice, without affecting serum lipid levels. Plaques from NLS-treated mice contained fewer macrophages of pro-inflammatory M1 subtype than those from respective untreated controls. By contrast, the relative smooth muscle cell and collagen content was increased, indicating a more stable plaque phenotype. NLS peptide also attenuated pro-inflammatory gene expression and oxidative stress in aortic lesions. Our study demonstrates that targeting NF-κB nuclear translocation hampers inflammation and atherosclerosis development and identifies cell-permeable NLS peptide as a potential anti-atherosclerotic agent.

KIOM-79 protects AGE-induced retinal pericyte apoptosis via inhibition of NF-kappaB activation in vitro and in vivo

KIOM-79 is an herbal mixture of parched Puerariae radix, gingered Magnoliae cortex, Glycyrrhizae radix and Euphorbiae radix. In the present study, we determined the efficacy and possible mechanism of KIOM-79 on the advanced glycation end product (AGE)-modified bovine serum albumin (BSA)-induced apoptosis of cultured bovine retinal pericytes and rat retinal pericytes in Zucker diabetic fatty (ZDF) rats. Seven-week-old male ZDF rats were treated with KIOM-79 (50 mg/kg body weight) once a day orally for 13 weeks. KIOM-79 significantly inhibited pericyte apoptosis which were induced by the AGE-BSA treatment. The KIOM-79 treatment markedly suppressed the activation of nuclear factor-kappaB (NF-κB) through the inhibition of inhibitory κB kinase complex. In addition, the oral administration of KIOM-79 inhibited the changes in retinal vasculature (vascular hyperpermeability, acellular capillary). KIOM-79 strongly inhibited pericyte apoptosis, NF-κB activation and the expression of pro-apoptotic Bax and tumor necrosis factor-α. Our results suggest that KIOM-79 may exert inhibitory effects on AGE-induced pericyte apoptosis by blocking NF-κB activation, thereby ameliorating retinal microvascular dysfunction.

AP-1 transcription factor JunD confers protection from accelerated nephrotoxic nephritis and control podocyte-specific Vegfa expression

Genetic investigation of crescentic glomerulonephritis (Crgn) susceptibility in the Wistar Kyoto rat, a strain uniquely susceptible to nephrotoxic nephritis (NTN), allowed us to positionally clone the activator protein-1 transcription factor Jund as a susceptibility gene associated with Crgn. To study the influence of Jund deficiency (Jund^-/-) on immune-mediated renal disease, susceptibility to accelerated NTN was examined in Jund^-/- mice and C57BL/6 wild-type (WT) controls. Jund^-/- mice showed exacerbated glomerular crescent formation and macrophage infiltration, 10 days after NTN induction. Serum urea levels were also significantly increased in the Jund^-/- mice compared with the WT controls. There was no evidence of immune response differences between Jund^-/- and WT animals because the quantitative immunofluorescence for sheep and mouse IgG deposition in glomeruli was similar. Because murine Jund was inactivated by replacement with a bacterial LacZ reporter gene, we then investigated its glomerular expression by IHC and found that the Jund promoter is mainly active in Jund^-/- podocytes. Furthermore, cultured glomeruli from Jund^-/- mice showed relatively increased expression of vascular endothelial growth factor A (Vegfa), Cxcr4, and Cxcl12, well-known HIF target genes. Accordingly, small-interfering RNA–mediated JUND knockdown in conditionally immortalized human podocyte cell lines led to increased VEGFA and HIF1A expression. Our findings suggest that deficiency of Jund may cause increased oxidative stress in podocytes, leading to altered VEGFA expression and subsequent glomerular injury in Crgn.

KIOM-79 Prevents Lens Epithelial Cell Apoptosis and Lens Opacification in Zucker Diabetic Fatty Rats

Damage of lens epithelial cells (LECs) has been implicated in cataract formation. The aim of this study was to investigate the protective effect of KIOM-79, a combination of four plant extracts, on LECs. We examined the levels of advanced glycation end products (AGEs), nuclear factor-kappaB (NF-κB) activation and inducible nitric oxide synthase (iNOS) expression in LECs during cataract development using the Zucker diabetic fatty (ZDF) rat, an animal model of type 2 diabetes. KIOM-79 was orally administered by gavage to ZDF rats once a day for 13 weeks. Apoptosis was detected by TUNEL assay, and NF-κB activation and iNOS expression were studied by southwestern histochemistry and immunohistochemistry, respectively. In diabetic cataractous lenses, TUNEL-positive LECs were markedly increased 20-fold, and AGEs were highly accumulated (2.7-fold) in LECs. In addition, both NF-κB activation, and iNOS expression were significantly enhanced 3- to 5-fold, respectively, compared to levels found in normal ZL rats. However, the administration of KIOM-79 delayed the development of diabetic cataracts and prevented LEC apoptosis (70%) through the inhibition of AGEs, NF-κB-activation and iNOS expression. These observations suggest that KIOM-79 is useful in inhibiting diabetic cataractogenesis and acts through an antiapoptotic mechanism to protect LECs from injury.

Local non-esterified fatty acids correlate with inflammation in atheroma plaques of patients with type 2 diabetes

OBJECTIVE

Atherosclerosis is prevalent in diabetic patients, but there is little information on the localization of nonesterified fatty acids (NEFAs) within the plaque and their relationship with inflammation. We sought to characterize the NEFA composition and location in human diabetic atheroma plaques by metabolomic analysis and imaging and to address their relationship with inflammation activity.

RESEARCH DESIGN AND METHODS

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used for metabolomic analysis imaging of frozen carotid atheroma plaques. Carotid endarterectomy specimens were used for conventional immunohistochemistry, laser-capture microdissection quantitative PCR, and in situ Southwestern hybridization. Biological actions of linoleic acid were studied in cultured vascular smooth muscle cells (VSMCs).

RESULTS

TOF-SIMS imaging evidenced a significant increase in the quantity of several NEFA in diabetic versus nondiabetic atheroma plaques. Higher levels of NEFA were also found in diabetic sera. The presence of LPL mRNA in NEFA-rich areas of the atheroma plaque, as well as the lack of correlation between serum and plaque NEFA, suggests a local origin for plaque NEFA. The pattern of distribution of plaque NEFA is similar to that of MCP-1, LPL, and activated NF-kappaB. Diabetic endarterectomy specimens showed higher numbers of infiltrating macrophages and T-lymphocytes-a finding that associated with higher NEFA levels. Finally, linoleic acid activates NF-kappaB and upregulates NF-kappaB-mediated LPL and MCP-1 expression in cultured VSMC.

DISCUSSION

There is an increased presence of NEFA in diabetic plaque neointima. NEFA levels are higher in diabetic atheroma plaques than in nondiabetic subjects. We hypothesize that NEFA may be produced locally and contribute to local inflammation.

Lens epithelial cell apoptosis initiates diabetic cataractogenesis in the Zucker diabetic fatty rat

BACKGROUND

It has been suggested that damage of lens epithelial cell (LEC) may play an important role in cataract formation. Nitric oxide is involved in cataract development. Here, we investigated the relationship between LEC damage and iNOS expression in the Zucker diabetic fatty (ZDF) rat.

METHODS

At 21 weeks of age, the eyes were enucleated and the lens opacity was then examined. Apoptosis were detected by TUNEL assay, and the expression of iNOS and NF-kappaB activation were studied by immunohistochemistry and southwestern histochemistry respectively.

RESULTS

In 21-week-old male ZDF rats, cataract was developed, TUNEL-positive LECs were markedly increased, and the expression levels of iNOS mRNA and protein were significantly upregulated. The expression pattern of iNOS was closely correlated with apoptotic change of LECs. In addition, advanced glycation end products (AGEs) were accumulated in cytoplasm of LECs. Activated NF-kappaB was mainly detected in nucleus of LECs.

CONCLUSIONS

The higher expressions of AGEs, NF-kappaB and iNOS in LECs of diabetic rats suggest that these factors are involved in apoptosis of LEC alterations related to diabetic cataract.

Slight activation of nuclear factor kappa-B is associated with increased hepatic stellate cell apoptosis in human schistosomal fibrosis

To investigate the relationship between NF-kappaB activation and hepatic stellate cell (HSC) apoptosis in hepatosplenic schistosomiasis, hepatic biopsies from patients with Schistosoma mansoni-induced periportal fibrosis, hepatitis C virus-induced cirrhosis, and normal liver were submitted to alpha-smooth muscle actin (alpha-SMA) and NF-kappaB p65 immunohistochemistry, as well as to NF-kappaB Southwestern histochemistry and TUNEL assay. The numbers of alpha-SMA-positive cells and NF-kappaB- and NF-kappaB p65-positive HSC nuclei were reduced in schistosomal fibrosis relative to liver cirrhosis. In addition, increased HSC NF-kappaB p65 and TUNEL labeling was observed in schistosomiasis when compared to cirrhosis.These results suggest a possible relationship between the slight activation of the NF-kappaB complex and the increase of apoptotic HSC number in schistosome-induced fibrosis, taking place to a reduced HSC number in schistosomiasis in relation to liver cirrhosis. Therefore, the NF-kappaB pathway may constitute an important down-regulatory mechanism in the pathogenesis of human schistosomiasis mansoni, although further studies are needed to refine the understanding of this process.

Tumor Necrosis Factor–Like Weak Inducer of Apoptosis (TWEAK) Enhances Vascular and Renal Damage Induced by Hyperlipidemic Diet in ApoE-Knockout Mice

Objective— Tumor necrosis factor–like weak inducer of apoptosis (TWEAK) is a member of the tumor necrosis factor superfamily of cytokines. TWEAK binds and activates the Fn14 receptor, and may regulate apoptosis, inflammation, and angiogenesis, in different pathological conditions. We have evaluated the effect of exogenous TWEAK administration as well as the role of endogenous TWEAK on proinflammatory cytokine expression and vascular and renal injury severity in hyperlipidemic ApoE-knockout mice.

Methods and Results— ApoE −/− mice were fed with hyperlipidemic diet for 4 to 10 weeks, then randomized and treated with saline (controls), TWEAK (10 μg/kg/d), anti-TWEAK neutralizing mAb (1000 μg/kg/d), TWEAK plus anti-TWEAK antibody (10 μg TWEAK +1000 μg anti-TWEAK/kg/d), or nonspecific IgG (1000 μg/kg/d) daily for 9 days. In ApoE −/− mice, exogenous TWEAK administration in ApoE −/− mice induced activation of NF-κB, a key transcription factor implicated in the regulation of the inflammatory response, in vascular and renal lesions. Furthermore, TWEAK treatment increased chemokine expression (RANTES and MCP-1), as well as macrophage infiltration in atherosclerotic plaques and renal lesions. These effects were associated with exacerbation of vascular and renal damage. Conversely, treatment of ApoE −/− mice with an anti-TWEAK blocking mAb decreased NF-κB activation, proinflammatory cytokine expression, macrophage infiltration, and vascular and renal injury severity, indicating a pathological role for endogenous TWEAK. Finally, in murine vascular smooth muscle cells or tubular cells, either ox-LDL or TWEAK treatment increased expression and secretion of both RANTES and MCP-1. Furthermore, ox-LDL and TWEAK synergized for induction of MCP-1 and RANTES expression and secretion.

Conclusion— Our results suggest that TWEAK exacerbates the inflammatory response associated with a high lipid–rich diet. TWEAK may be a novel therapeutic target to prevent vascular and renal damage associated with hyperlipidemia.

Endothelial dysfunction in aged humans is related with oxidative stress and vascular inflammation

Vascular endothelial dysfunction occurs during the human aging process, and it is considered as a crucial event in the development of many vasculopathies. We investigated the underlying mechanisms of this process, particularly those related with oxidative stress and inflammation, in the vasculature of subjects aged 18-91 years without cardiovascular disease or risk factors. In isolated mesenteric microvessels from these subjects, an age-dependent impairment of the endothelium-dependent relaxations to bradykinin was observed. Similar results were observed by plethysmography in the forearm blood flow in response to acetylcholine. In microvessels from subjects aged less than 60 years, most of the bradykinin-induced relaxation was due to nitric oxide release while the rest was sensitive to cyclooxygenase (COX) blockade. In microvessels from subjects older than 60 years, this COX-derived vasodilatation was lost but a COX-derived vasoconstriction occurred. Evidence for age-related vascular oxidant and inflammatory environment was observed, which could be related to the development of endothelial dysfunction. Indeed, aged microvessels showed superoxide anions (O(2)(-)) and peroxynitrite (ONOO(-)) formation, enhancement of NADPH oxidase and inducible NO synthase expression. Pharmacological interference of COX, thromboxane A(2)/prostaglandin H(2) receptor, O(2)(-), ONOO(-), inducible NO synthase, and NADPH oxidase improved the age-related endothelial dysfunction. In situ vascular nuclear factor-kappaB activation was enhanced with age, which correlated with endothelial dysfunction. We conclude that the age-dependent endothelial dysfunction in human vessels is due to the combined effect of oxidative stress and vascular wall inflammation.

Resolution of renal inflammation: a new role for NF-kappaB1 (p50) in inflammatory kidney diseases

In renal tissue injury, activation of the transcription factor NF-kappaB has a central role in the induction of proinflammatory gene expression, which are involved in the development of progressive renal inflammatory disease. The function of NF-kappaB during the switch from the inflammatory process toward resolution, however, is largely unknown. Therefore, we assessed the time-dependent activation and function of NF-kappaB in two different models of acute nephritis. Our experiments demonstrate a biphasic activation of NF-kappaB in the anti-Thy-1 model of glomerulonephritis in rats and the LPS-induced nephritis in mice, with a first peak during the induction phase and a second peak during the resolution period. After induction of glomerular immune injury in rats, predominantly NF-kappaB p65/p50 heterodimer complexes are shifted to the nucleus whereas during the resolution phase predominantly p50 homodimers could be demonstrated in the nuclear compartment. In addition, we could demonstrate that p50 protein plays a pivotal role in the resolution of LPS-induced renal inflammation since NF-kappaB p50 knockout mice demonstrate significantly higher chemokine expression, prolonged renal inflammatory cell infiltration with consecutive tissue injury, and reduced survival. In conclusion, our studies indicate that NF-kappaB subunit p50 proteins have critical in vivo functions in immunologically mediated renal disease by downregulating inflammation during the resolution period.

Differential expression of nuclear factor-kappaB mediates increased pulmonary expression of tumor necrosis factor-alpha and virus-induced asthma

Infections with respiratory pathogens such as respiratory syncytial virus and rhinovirus have been associated with the development of long-term chronic airway disease. To better understand the events responsible for this clinical outcome, a rodent model of virus-induced chronic airway disease has been characterized. Upon infection with Sendai virus (parainfluenza virus type-1), Brown Norway (BN) rats develop an asthma-like clinical syndrome, while Fischer 344 (F344) rats fully recover. Our previous studies demonstrated that after infection, tumor necrosis factor-alpha (TNF-alpha) expression is substantially higher in BN rats compared to F344 rats, and this may at least partially mediate the virus-induced airway abnormalities. To investigate the underlying mechanism(s) for the increased TNF-alpha expression, the role of nuclear factor-kappaB (NF-kappaB), an important regulator of TNF-alpha gene transcription, was examined. Supershift electrophoretic mobility shift assays (EMSAs) indicate that normal F344 rats predominantly express the p65 subunit of NF-kappaB in the lungs, and virus infection temporarily increases expression of the p50 subunit. In contrast, normal BN rats have higher expression of the p50 subunit in the pulmonary tract. Upon infection, p50-subunit expression in BN rats increases to levels higher than those observed in virus-infected F344 rats. Interestingly, treatment of infected BN rats with dexamethasone at doses known to prevent virus-induced airway abnormalities increases pulmonary expression of the p65 subunit, and decreases TNF-alpha mRNA levels in the lungs. Furthermore, direct inhibition of TNF-alpha also increases pulmonary expression of p65 in virus-infected BN, but not F344, rats. Taken together, these results suggest that differential expression of NF-kappaB subunits may play an important role in the development of post-viral chronic airway abnormalities.

Pathogenic role of NF-kappaB activation in tubulointerstitial inflammatory lesions in human lupus nephritis

In vitro and in vivo experimental studies suggest that the transcription factor NF-kappaB plays a role in tubulointerstitial injury. We investigated possible cellular and molecular mechanisms involving NF-kappaB activation in the progression of tubulointerstitial lesions in human lupus nephritis (LN). Paraffin-embedded renal biopsies from 50 patients with LN and six control patients with minimal change disease (MCD) were examined by Southwestern histochemistry for in situ detection of active NF-kappaB and AP-1. Immunohistochemistry was performed to examine the expression of NF-kappaB, AP-1, and NF-kappaB regulatory proteins (IkappaB-alpha, p-IkappaB-alpha, and IKK-alpha proteins), as well as NF-kappaB and AP-1 downstream target proinflammatory molecules (ICAM-1, TNF-alpha, IL-1beta, IL-6, and GM-CSF) and NF-kappaB upstream signaling molecules (CD40 and CD40L). We observed extensive upregulation of activated NF-kappaB in renal tubular cells and interstitial cells, in parallel with overactivation of transcription factor AP-1 in LN, as compared with normal controls and MCD. Tubular expression of activated NF-kappaB correlated well with the degree of tubulointerstitial histopathological indices and/or renal function. Tubulointerstitial IKK-alpha expression was specifically upregulated in LN. IkappaB-alpha and p-IkappaB-alpha were detected only in interstitial cells in LN. Tubulointerstitial expression levels of NF-kappaB and AP-1 downstream inflammatory molecules and NF-kappaB upstream signaling molecules CD40 and CD40L were markedly enhanced in LN as compared with MCD or normal controls and were associated with tubulointerstitial histopathological indices and/or renal function. The results suggest that altered IKK-alpha expression and NF-kappaB activation along with AP-1 overexpression may play a pathogenic role in tubulointerstitial injury in human LN mediated through a network of downstream proinflammatory molecules.

Proteomic analysis of early left ventricular hypertrophy secondary to hypertension: modulation by antihypertensive therapies

Untreated or poorly controlled arterial hypertension induced development of pathologic left ventricular hypertrophy (LVH), a common finding in hypertensive patients and a strong predictor of cardiovascular morbidity and mortality. The proteomic approach is a powerful technique to analyze a complex mixture of proteins in various settings. An experimental model of hypertension-induced early LVH was performed in spontaneously hypertensive rats, and the cardiac protein pattern compared with the normotensive Wistar Kyoto counterpart was analyzed. Fifteen altered protein spots were shown in the early stage of LVH. Compared with a previous animal model of established and regressed LVH, three protein spots were common in both models. These three altered protein spots corresponded to two unique proteins that were identified as Calsarcin-1 (CS-1) and ubiquinone biosynthesis protein COQ7 homolog. CS-1 is a negative regulator of the calcineurin/NF-AT pathway. Because upregulation in the expression levels of this protein was observed, the activation level of NF-kappaB by oxidative stress as an alternative pathway was investigated. It was found that antihypertensive therapies partially decreased oxidative stress and normalized the activation of NF-kappaB in the kidneys and aorta NF-kappaB activation but just moderately in the heart. This could be due to the interaction of any specific cardiac protein with any component of the NF-kappaB pathway. In this sense, CS-1 could be a good candidate because it is expressed preferentially in heart, to a lesser extent in smooth muscle cells, but not in kidney. Further investigations are necessary to elucidate the exact role of CS-1 and ubiquinone biosynthesis protein COQ7 in the setting of hypertension-induced LVH.

Glomerular and tubular induction of the transcription factor c-Jun in human renal disease

The transcription factor c-Jun regulates the expression of genes involved in proliferation and inflammation in many cell types but its role in human renal disease is largely unclear. In the current study we investigated whether c-Jun activation is associated with human renal disease and if c-Jun activation regulates pro-inflammatory and pro-fibrotic genes in renal cells. Activation of c-Jun was quantified by scoring renal expression of phosphorylated c-Jun (pc-Jun) in control human renal tissue and in biopsies from patients with various renal diseases (diabetic nephropathy, focal glomerulosclerosis, hypertension, IgA nephropathy, membranous glomerulopathy, minimal change disease, membranoproliferative glomerulonephritis, systemic lupus erythematosus, acute rejection, and Wegener's granulomatosis); this was correlated with parameters of renal damage. Furthermore, we studied the functional role of c-Jun activation in human tubular epithelial cells (HK-2) stimulated with TGF-beta. Activated c-Jun was present in nuclei of glomerular and tubular cells in all human renal diseases, but only sporadically in controls. Across the diseases, the extent of pc-Jun expression correlated with the degree of focal glomerulosclerosis, interstitial fibrosis, cell proliferation, kidney injury molecule-1 (Kim-1) expression, macrophage accumulation, and impairment of renal function. In HK-2 cells, TGF-beta induced c-Jun activation after 1 h (+40%, p < 0.001) and 24 h (+160%, p < 0.001). The specific c-Jun N-terminal kinase (JNK) inhibitor SP600125 abolished c-Jun phosphorylation at all time points and blunted TGF-beta- or BSA-induced procollagen-1alpha 1 and MCP-1 gene expression in HK-2 cells. We conclude that in human renal disease, the transcription factor c-Jun is activated in glomerular and tubular cells. Activation of c-Jun may be involved in the regulation of inflammation and/or fibrosis in human renal disease.

Fcgamma receptor deficiency confers protection against atherosclerosis in apolipoprotein E knockout mice

IgG Fc receptors (FcgammaRs) play a role in activating the immune system and in maintaining peripheral tolerance, but their role in atherosclerosis is unknown. We generated double-knockout (DKO) mice by crossing apolipoprotein E-deficient mice (apoE(-/-)) with FcgammaR gamma chain-deficient mice (gamma(-/-)). The size of atherosclerotic lesions along the aorta was approximately 50% lower in DKO compared with apoE(-/-) control mice, without differences in serum lipid levels. The macrophage and T-cell content of lesions in the DKO were reduced by 49+/-6% and 56+/-8%, respectively, compared with the content in apoE(-/-) lesions. Furthermore, the expression of monocyte chemoattractant protein-1 (MCP-1), RANTES (Regulated on Activated Normal T-cell Expressed and Secreted), and intercellular adhesion molecule-1 (ICAM-1) and the activation of nuclear factor-kappaB (NF-kappaB) were significantly reduced in aortic lesions from DKO mice. In vitro, vascular smooth muscle cells (VSMCs) from both gamma(-/-) and DKO mice failed to respond to immune complexes, as shown by impaired chemokine expression and NF-kappaB activation. ApoE(-/-) mice have higher levels of activating FcgammaRI and FcgammaRIIIA, and inhibitory FcgammaRIIB, compared with wild-type mice. The DKO mice express only the inhibitory FcgammaRIIB receptor. We conclude that FcgammaR deficiency limits development and progression of atherosclerosis. In addition to leukocytes, FcgammaR activation in VSMCs contributes to the inflammatory process, in part, by regulating chemokine expression and leukocyte invasion of the vessel wall. These results underscore the critical role of FcgammaRs in atherogenesis and support the use of immunotherapy in the treatment of this disease.

Renal cell apoptosis and proliferation may be linked to nuclear factor-kappaB activation and expression of inducible nitric oxide synthase in patients with lupus nephritis

The mechanism of renal cell apoptosis involves transcriptional activation of the inducible nitric oxide synthase (iNOS) gene by nuclear factor (NF)-kappaB. The role of apoptosis in mediating tubulointerstitial injury in human lupus nephritis (LN) remains unclear. We examined the relationship between alterations in NF-kappaB activation and iNOS expression levels and the degree of apoptosis in both glomerular and tubulointerstitial compartments of subjects with LN. Studies were done in renal biopsies from 49 patients with LN and 10 normal kidney tissues. Apoptotic and proliferating cells were identified by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling and staining with anti-proliferating cell nuclear antigen antibody, respectively. Nuclear factor-kappaB and iNOS expression was examined by Southwestern histochemistry and immunohistochemistry, respectively. Glomerular cell apoptosis and proliferation increased concomitantly in LN. Glomerular apoptosis correlated with the activity index, the degree of proliferation, and the level of glomerular overexpression of iNOS and activated NF-kappaB in LN. Tubular cell apoptosis correlated with the activity and chronicity indices, the degree of tubular atrophy, and decline in renal function at the time of biopsy. Tubular expression of iNOS and activated NF-kappaB correlated with tubular cell proliferation in LN. Nuclear factor-kappaB activation accompanied overexpression of iNOS in both glomerular and tubulointerstitium compartments in LN. Apoptosis of renal cells associated with NF-kappaB activation and iNOS overexpression may play an important role in mediating chronic renal injury, especially tubulointerstitial lesions that may manifest clinically as progressive renal insufficiency.

Parthenolide modulates the NF-kappaB-mediated inflammatory responses in experimental atherosclerosis

OBJECTIVE

Activation of transcription factor NF-kappaB is an important step in the development of vascular damage, because it controls inducible genes, including many inflammatory mediators. The pharmacological modulation of this process is the main objective in the design of new therapies for atherosclerosis. In this work we analyzed the effects of the natural compound parthenolide (PTN), an NF-kappaB inhibitor.

METHODS AND RESULTS

In vascular smooth muscle cells (VSMCs) and monocytes stimulated with lipopolysaccharide (LPS), nontoxic doses of PTN reduced IkappaBalpha degradation, NF-kappaB activation, and MCP-1 expression, without inhibiting AP-1 and MAPK. In apoE mice, treatment with low (2 mg/kg, 20 weeks), medium (4 mg/kg, 10 weeks), and high (10 mg/kg, 10 weeks) dose of PTN reduced the size of aortic lesion, decreased macrophage, and increased VSMC content in the lesions. Treated mice showed reduced serum levels of MCP-1 and attenuated NF-kappaB activity, but not AP-1, in the lesions. Moreover, PTN affects neither apoptotic cell death nor oxidative stress in cultured cells and mice.

CONCLUSIONS

NF-kappaB inhibition by PTN retards atherosclerotic lesions in apoE mice, by reducing lesion size and changing plaque composition. This natural compound could represent a novel therapeutic approach to inflammation during vascular damage.

Priming of glomerular mesangial cells by activated macrophages causes blunted responses to proinflammatory stimuli

Macrophage-mesangial cell interaction plays a crucial role in the pathogenesis of glomerulonephritis. Activated macrophages trigger mesangial cells to express an array of inflammation-associated genes via activation of NF-kappaB and AP-1. However, this inflammatory response is often transient and subsides spontaneously. We found that mesangial cells activated by bystander macrophages showed blunted responses of NF-kappaB to subsequent macrophage exposure. It was associated with sustained levels of IkappaBbeta, but not IkappaBalpha. The tolerance observed was reversible and reproduced by conditioned media from activated macrophages (macrophage-conditioned medium (MphiCM)). In vivo priming of mesangial cells by activated glomerular macrophages also caused the tolerance of mesangial cells. The macrophage-derived tolerance inducers were heat-labile, and multiple molecules were involved. Among inflammatory cytokines produced by macrophages, TNF-alpha and IL-1beta were able to induce mesangial cell tolerance dose-dependently. The mesangial cell tolerance was also observed in activation of the MAPK-AP-1 pathway; i.e., phosphorylation of ERK, JNK, and p38 MAPK by macrophages was blunted when the cells were pre-exposed to MphiCM. Induction of c-fos and c-jun was also abrogated in mesangial cells pre-exposed to MphiCM, and the suppression was attenuated by blockade of MAPK activation during the first exposure to MphiCM. These data elucidated that mesangial cells, once exposed to macrophages, become insensitive to subsequent activation by macrophages and proinflammatory stimuli. This self defense of glomerular cells may play a role in the resolution of macrophage-mediated, acute glomerulonephritis.

In situ glomerular expression of activated NF-kappaB in human lupus nephritis and other non-proliferative proteinuric glomerulopathy

Nuclear Factor-kappaB (NF-kappaB) has been suggested to play a role in the cellular and molecular mechanisms underlying glomerular injury. We investigated the potential role of NF-kappaB activation in the pathogenesis of glomerular injury in 31 patients with class III-V lupus nephritis (LN), 14 patients with non-proliferative proteinuric glomerulopathy and six normal controls. The expression of NF-kappaB subunits p65 and p50, and the NF-kappaB regulated proinflammatory mediators tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), interleukin-6 (IL-6) and intercellular adhesion molecule-1 (ICAM-1) as well as CD68 and synaptopodin was examined by Southwestern histochemistry (SWH) or immunohistochemistry. In contrast to non-proliferative glomerulopathy and normal controls, NF-kappaB activation (both p65 and p50) was enhanced in glomerular endothelial, mesangial cells or infiltrating cells in class IV LN, along with upregulation of TNF-alpha, IL-1beta, IL-6 and ICAM-1 expression. Glomerular endothelial and mesangial activation of NF-kappaB and mesangial ICAM-1 expression correlated with disease activity and the level of glomerular macrophage infiltration. Podocyte NF-kappaB overactivation (predominantly p65) paralleled podocyte expression of TNF-alpha and IL-1beta in patients with LN and non-proliferative glomerulopathy. Podocyte staining scores of NF-kappaB and p65 were positively correlated with the severity of proteinuria in LN and non-proliferative glomerulopathy. These results suggest a pathogenic role for NF-kappaB in glomerular injury by multiple mechanisms.

Protein kinase p-JNK is correlated with the activation of AP-1 and its associated Jun family proteins in hepatocellular carcinoma

To study the role of c-Jun N-terminal kinase (JNK) and its relation to transcription factor AP-1 and Jun family proteins in hepatocellular carcinoma (HCC) with or without hepatitis B virus (HBV) infection. Immunohistochemical and in situ hybridization techniques were performed for studying phosphorylated JNK (p-JNK), c-Jun, JunB, JunD and AP-1 in 40 cases of human HCC and corresponding nontumoral tissues. Positive staining of nucleus for p-JNK, c-Jun, JunD and AP-1 was presented in 28 (70%), 29 (72.5%), 32 (80%) and 25 (62.5%) in cancer cells respectively, while 0%, 28%, 17.5% and 10% in adjacent non-tumor tissues. The expression levels of p-JNK, c-Jun, JunD and AP-1 were significantly and positively correlated with each other and with HBsAg positive rate (P<0.05). JunB was negative staining in both cancer cells and non-tumor tissues of all cases. JNK phosphorylation may correlate with AP-1 activation and the expression of c-Jun and JunD in HCC. JNK/c-Jun/JunD/AP-1 signaling pathway may play an important role in the pathogenesis of HBV-associated HCC. JunB may not be involved in the process.

Activation of transcription factors NF-kappaB and AP-1 and their relations with apoptosis-associated proteins in hepatocellular carcinoma

AIM: To study the distribution pattern of transcription factors NF-κB and AP-1 and their relations with the expression of apoptosis associated-proteins Fas/FasL and ICH-1L/S in human hepatocellular carcinoma (HCC).

METHODS: We performed in situ hybridization and immunohistochemical techniques for NF-κB, AP-1, Fas/FasL and ICH-1 in 40 cases of human HCC along with corresponding nontumoral tissues and 7 cases of normal liver tissues.

RESULTS: Twenty-two (55%) and 25 (62.5%) of 40 cases for NF-κB and AP-1 were presented for nuclear or both nuclear and cytoplastic staining respectively, while less cases were presented for only cytoplastic staining for NF-κB (18%) and AP-1 (10%) in adjacent nontumoral tissues and negative staining in normal liver tissues. There was no statistically significant difference of NF-κB or AP-1 activation between well differentiated tumors and poorly differentiated tumors (P > 0.05). NF-κB activity is positively corresponded to AP-1 activation. The expression of ICH-1L/S was associated with the activation of NF-κB and AP-1 (P < 0.05), but no significant relationship was found between Fas/FasL and NF-κB or AP-1(P > 0.05).

CONCLUSION: Activation of both NF-κB and AP-1 may be required for ICH-1L/S-induced apoptosis in HCC, but not for Fas/FasL-mediated apoptosis. NF-κB and AP-1 may play important roles in the pathogenesis of human HCC.

Heterozygous mice for TGF-betaIIR gene are resistant to the progression of streptozotocin-induced diabetic nephropathy

BACKGROUND

Transforming growth factor-beta (TGF-beta) receptor complex and its downstream Smad signaling intermediates constitute an extracellular matrix (ECM) accumulation pathway.

METHODS

In the present study, we examined whether decreased expression of the TGF-beta type II receptor (TGF-betaIIR) in TGF-betaIIR gene heterozygous (TGF-betaIIR+/-) (HT) mice could inhibit the Smad signaling pathway and subsequent progression of renal lesions when streptozotocin (STZ) diabetes is induced.

RESULTS

At the end of the 28-week experiment after STZ injections, wild-type diabetic mice showed severe glomerular hypertrophy and mesangial matrix accumulation occasionally featuring nodular glomerulosclerosis. In contrast, mean glomerular area and mesangial volume density were significantly decreased in the HT diabetic mice as compared with the wild-type diabetic mice. Immunostaining for phosphorylated Smad2/Smad3 and TGF-betaIIR in the glomerular cells was also significantly reduced in the HT diabetic mice. Southwestern histochemistry using digoxigenin-labeled CAGA sequence probes showed that localization of labeled probes to the nuclei of glomerular cells in the HT diabetic mice was significantly less frequent than that in the wild-type diabetic animals. Northern blot analysis showed that alpha1(IV) collagen mRNA levels were significantly reduced in the kidney tissue of HT diabetic mice as compared with the wild-type diabetic mice.

CONCLUSION

These results suggest that decreased expression of TGF-betaIIR in the HT diabetic mice can inhibit the progression of diabetic renal injury by inhibiting the downstream Smad signaling pathway and subsequent ECM gene expression. Thus, TGF-betaIIR appears to play an important role in the progression of diabetic nephropathy by mediating intracellular Smad signaling.

Activation of nuclear factor-kappa B and macrophage invasion in cyclosporin A- and tacrolimus-treated renal transplants

This retrospective study was designed to compare the efficacy of cyclosporin A (CyA) and tacrolimus (FK506) on chronic rejection (CR) associated with nuclear factor-kappa B (NF-kappaB) activation and macrophage invasion. Non-episodic day 50 protocol renal biopsy was performed in 63 consecutive patients with renal transplants from living donors, treated with either CyA or FK506. Southwestern histochemistry for NF-kappaB, immunostaining for CD68, and Banff classification were performed, and these findings were compared with outcome over 34 +/- 13 months. Compared with specimens from FK506-treated patients (n = 20), specimens from CyA-treated patients (n = 43) showed a significant increase in tubulointerstitial CD68-positive cells (1.5 +/- 0.9 vs. 0.9 +/- 0.8, p < 0.01), although no significant differences were observed in NF-kappaB activation. Specimens with Banff acute rejection (AR) grade > or = 1A (n = 20) showed increased macrophages (p < 0.01) compared with specimens with AR < 1A (n = 43). Specimens from patients with clinical AR prior to day 50 biopsy (n = 23) also showed increased macrophage invasion (p < 0.01) compared with specimens from patients without prior clinical AR (n = 40). The cumulative well-functioning (serum creatinine < 1.5 mg/dL) graft survival rate was significantly lower in patients with increased tubulointerstitial CD68-positive cells (n = 63, p < 0.05). Our findings suggest that tacrolimus is more effective than CyA against CR with respect to macrophage invasion and AR.

NF-kappaB activation and Fas ligand overexpression in blood and plaques of patients with carotid atherosclerosis: potential implication in plaque instability

BACKGROUND AND PURPOSE

Apoptosis is present in human atherosclerotic lesions. Nuclear factor-kappaB (NF-kappaB) is involved in the transcriptional regulation of the proapoptotic protein Fas ligand (FasL). We have analyzed NF-kappaB activation and FasL expression in atherosclerotic plaques and peripheral blood mononuclear cells (PBMCs) of patients with carotid stenosis.

METHODS

NF-kappaB activation and FasL and active caspase-3 expression were analyzed in 32 human carotid plaques. NF-kappaB activation and FasL mRNA were tested in PBMCs of patients and healthy volunteers. We analyzed whether the NF-kappaB inhibitor parthenolide regulates FasL expression and cytotoxicity in human T cells.

RESULTS

The inflammatory region of plaques showed an increase in NF-kappaB activation (3393+/-281 versus 1029+/-100 positive nuclei per mm(2), P<0.001) and FasL (16+/-1.4% versus 13+/-1.8%, P<0.05) and active caspase-3 (3.3+/-0.6 versus 1.5+/-0.3%, P<0.05) expression compared with the fibrous area. Activated NF-kappaB and FasL protein were colocalized in plaque cells. In PBMCs obtained from those patients the day of endarterectomy, NF-kappaB activation and FasL expression were significantly increased compared with healthy controls (1.5+/-0.1 versus 0.5+/-0.1 and 2.1+/-0.1 versus 1.2+/-0.1 arbitrary units, respectively; P<0.001). There was a significant correlation between NF-kappaB activation and FasL expression. In activated T cells, parthenolide decreased NF-kappaB activation, FasL promoter activity, and mRNA expression. Parthenolide also decreased cytotoxicity of activated Jurkat cells on FasL-sensitive cells.

CONCLUSIONS

NF-kappaB activation and FasL overexpression occur in PBMCs and atherosclerotic lesions of patients with carotid stenosis. The NF-kappaB-FasL pathway could be involved in the mechanisms underlying plaque instability in humans.

Pre-existing glomerular immune complexes induce polymorphonuclear cell recruitment through an Fc receptor-dependent respiratory burst: potential role in the perpetuation of immune nephritis

In immune complex (IC) diseases, FcR are essential molecules facilitating polymorphonuclear cell (PMN) recruitment and effector functions at the IC site. Although FcR-dependent initial tethering and FcR/integrin-dependent PMN accumulation were postulated, their underlying mechanisms remain unclear. We here addressed potential mechanisms involved in PMN recruitment in acute IC glomerulonephritis (nephrotoxic nephritis). Since some renal cells may be recruited from bone marrow (BM) lineages, reconstitution studies with BM chimeras and PMN transfer between wild-type (WT) and FcR-deficient mice (gamma(-/-)) were performed. Severe glomerular damage was induced in WT and W gamma chimeras (BM from WT to irradiated gamma(-/-)), while it was absent in gamma(-/-) and gamma W chimeras (gamma(-/-) BM to WT). Moreover, WT PMN transfer, but not gamma(-/-) PMN, reconstituted the disease in gamma(-/-), indicating that FcR on resident cells is not a prerequisite for PMN recruitment in this disease. Surprisingly, transferred WT PMN were recruited coincidentally with NF-kappa B activation and TNF-alpha overexpression even in glomeruli with preformed IC (nephrotoxic Ab administered 3 days previously), suggesting that PMN can initially be recruited via its own FcR without previous chemoattractant release. Furthermore, H(2)O(2) inhibition by catalase attenuated the acute WT PMN recruitment and the induction of NF-kappa B and TNF-alpha much more than integrin (CD18) blockade, indicating a role for the respiratory burst before integrin-dependent accumulation. In coculture experiments with IC-stimulated PMN and glomeruli, PMN caused acute glomerular TNF-alpha expression predominantly via FcR-mediated H(2)O(2) production. In conclusion, glomerular IC, even preformed, can cause PMN recruitment and injury through PMN FcR-mediated respiratory burst during initial PMN tethering to IC.

Nitric oxide production in renal cells by immune complexes: Role of kinases and nuclear factor-kappaB

BACKGROUND

Interaction of deposited immune complexes (IC) with Fc receptors (FcR) on tissue cells elicits the release of inflammatory mediators leading to tissue damage. Nitric oxide (NO) radicals generated by inducible NO synthase (iNOS) are important mediators in inflammatory processes. To analyze the role of NO in IC-mediated glomerular inflammation, we studied the in vitro and in vivo expression of iNOS in renal cells [resident mesangial cells (MC), and infiltrating monocytes] induced by IC, and the possible intermediate steps between FcR occupancy and iNOS induction.

METHODS

MC and monocytes were stimulated with IgG- and IgA-containing IC, and NO production (nitrite accumulation), iNOS transcription (luciferase assay) and their expression was measured by RT-PCR and Western blot. The involvement of FcR, transcription factor nuclear factor-kappaB (NF-kappaB), and protein kinases was assessed by using Fc fragments and specific inhibitors. Immune glomerulonephritis was induced in rats, and iNOS expression and NF-kappaB activation were analyzed.

RESULTS

In MC and monocytes, IC enhanced iNOS transcription/expression and NO generation, which were attenuated by specific inhibitors of NF-kappaB. In addition, mitogen-activated protein kinase (MAPK) inhibitors decreased NO production, but did not interfere with NF-kappaB activity, suggesting that both pathways may converge downstream in the induction of iNOS. In experimental immune glomerulonephritis, increased iNOS expression correlated with proteinuria levels, and appeared colocalized with NF-kappaB in glomerular and infiltrating cells. Treatment of animals and cells with Fc fragments prevented iNOS induction and NF-kappaB activation by IC.

CONCLUSIONS

These results indicate that IC, through activation of FcR, induce iNOS expression in renal resident and recruited cells by mechanisms involving MAPK and NF-kappaB, and support the idea of the important role of local NO generation in IC-mediated glomerular injury.

Transcriptional regulation of a mesangium-predominant gene, megsin

The cDNA of a new human mesangium-predominant gene, megsin, a novel member of the serpin superfamily, has recently been cloned. This study investigates the regulatory mechanisms of megsin gene expression. A genomic clone of the human megsin gene was obtained by screening bacterial artificial chromosome (BAC) library with the megsin cDNA. The analysis for exon-intron junctions of megsin genomic DNA demonstrated that the gene contained 8 exons and 7 introns, spanned 20 kbp, and that the genomic structure of the serpin superfamily was highly conserved. Fluorescence in situ hybridization (FISH) revealed that the megsin gene is localized in chromosome 18q21.3, close to the other serpin genes. The transcriptional start site, located by primer extension analysis, was 391 bp upstream from the start codon. The sequence and reporter analyses on 4021-bp-long 5'-flanking region of megsin gene demonstrated a consensus promoter segment within this region and a relatively strong promoter activity in human mesangial cells and A431, a human tumor cell line recently reported to express a novel serpin identical with megsin. Moreover, this study utilized site-directed and deletion mutagenesis analyses, and electrophoretic mobility shift assay identified one positive regulatory motif, an incomplete activator protein-1 (AP-1) binding motif (CTGATTCAC) within the -120 to -112 region. This cis-acting element in the 5'-flanking region of megsin is involved in the activation of the megsin gene in mesangial cells.

Susceptibility to T cell-mediated injury in immune complex disease is linked to local activation of renin-angiotensin system: the role of NF-AT pathway

FcR provides a critical link between ligands and effector cells in immune complex diseases. Emerging evidence reveals that angiotensin (Ang)II exerts a wide variety of cellular effects and contributes to the pathogenesis of inflammatory diseases. In anti-glomerular basement membrane Ab-induced glomerulonephritis (GN), we have previously noted that FcR-deficient mice (gamma(-/-)) surviving from lethal initial damage still developed mesangial proliferative GN, which was drastically prevented by an AngII type 1 receptor (AT1) blocker. We further examined the mechanisms by which renin-Ang system (RAS) participates in this immune disease. Using bone marrow chimeras between gamma(-/-) and AT1(-/-) mice, we found that glomerular injury in gamma(-/-) mice was associated with CD4(+) T cell infiltration depending on renal AT1-stimulation. Based on findings in cutaneous delayed-type hypersensitivity, we showed that AngII-activated renal resident cells are responsible for the recruitment of effector T cells. We next examined the chemotactic activity of AngII-stimulated mesangial cells, as potential mechanisms coupling RAS and cellular immunity. Chemotactic activity for T cells and Th1-associated chemokine (IFN-gamma-inducible protein-10 and macrophage-inflammatory protein 1alpha) expression was markedly reduced in mesangial cells from AT1(-/-) mice. Moreover, this activity was mainly through calcineurin-dependent NF-AT. Although IFN-gamma-inducible protein-10 was NF-kappaB-dependent, macrophage-inflammatory protein 1alpha was dominantly regulated by NF-AT. Furthermore, AT1-dependent NF-AT activation was observed in injured glomeruli by Southwestern histochemistry. In conclusion, our data indicate that local RAS activation, partly via the local NF-AT pathway, enhances the susceptibility to T cell-mediated injury in anti-glomerular basement membrane Ab-induced GN. This novel mechanism affords a rationale for the use of drugs interfering with RAS in immune renal diseases.

Nuclear factor-kappa B inhibitors as potential novel anti-inflammatory agents for the treatment of immune glomerulonephritis

Nuclear factor (NF)-kappa B regulates several genes implicated in the inflammatory response and represents an interesting therapeutic target. We examined the effects of gliotoxin (a fungal metabolite) and parthenolide (a plant extract), which possess anti-inflammatory activities in vitro, on the progression of experimental glomerulonephritis. In the anti-Thy 1.1 rat model, gliotoxin (75 micro g/rat/day, 10 days, n = 18 rats) markedly reduced proteinuria, glomerular lesions, and monocyte infiltration. In anti-mesangial cell nephritis in mice, parthenolide (70 micro g/mouse/day, 7 days, n = 17 mice) significantly decreased proteinuria, hematuria, and glomerular proliferation. NF-kappa B activity, localized in glomerular and tubular cells, was attenuated by either gliotoxin or parthenolide, in association with diminished renal expression of monocyte chemoattractant protein-1 and inducible nitric oxide synthase. In cultured mesangial cells and monocytes, gliotoxin and parthenolide inhibited NF-kappa B activation and expression of inflammatory genes induced by lipopolysaccharide and cytokines, by blocking the phosphorylation/degradation of the I kappa B(alpha) subunit. In summary, gliotoxin and parthenolide prevent proteinuria and renal lesions by inhibiting NF-kappa B activation and expression of regulated genes. This may represent a novel approach for the treatment of immune and inflammatory renal diseases.

Smad pathway is activated in the diabetic mouse kidney and Smad3 mediates TGF-beta-induced fibronectin in mesangial cells

Activation of the transforming growth factor-beta (TGF-beta) system has been implicated in the pathological changes of diabetic nephropathy such as renal hypertrophy and accumulation of extracellular matrix. Streptozotocin-induced diabetic mice were used to examine whether the Smad pathway, which transduces the TGF-beta signal, is activated in the diabetic kidney, employing Southwestern histochemistry with labeled Smad-binding element (SBE) oligonucleotides and immunoblotting of nuclear protein extracts for Smad3. Mouse mesangial cells were used to study the role of Smads in mediating the effects of high glucose and TGF-beta on fibronectin expression, using transient transfections of Smad expression vectors and TGF-beta-responsive reporter assays. By Southwestern histochemistry, the binding of nuclear proteins to labeled SBE increased in both glomeruli and tubules at 1, 3, and 6 weeks of diabetes. Likewise, immunoblotting demonstrated that nuclear accumulation of Smad3 was increased in the kidney of diabetic mice. Both increases were prevented by insulin treatment. In mesangial cells, high glucose potentiated the effect of low-dose TGF-beta1 (0.2ng/ml) on the following TGF-beta-responsive constructs: 3TP-Lux (containing AP-1 sites and PAI-1 promoter), SBE4-Luc (containing four tandem repeats of SBE sequence), and the fibronectin promoter. Additionally, Smad3 overexpression increased fibronectin promoter activity, an effect that was enhanced by high ambient glucose or treatment with TGF-beta1 (2ng/ml). The TGF-beta-stimulated activity of the fibronectin promoter was prevented by transfection with either a dominant-negative Smad3 or the inhibitory Smad7. We conclude that hyperglycemia activates the intrarenal TGF-beta/Smad signaling pathway, which then promotes mesangial matrix gene expression in diabetic nephropathy.

Atorvastatin reduces the expression of cyclooxygenase-2 in a rabbit model of atherosclerosis and in cultured vascular smooth muscle cells

Inflammation is involved in the genesis and rupture of atherosclerotic plaques. We assessed the effect of atorvastatin (ATV) on the expression of cyclooxygenase-2 (COX-2) and other proinflammatory molecules in a rabbit model of atherosclerosis. Fourteen animals underwent injury of femoral arteries and 2 weeks of atherogenic diet. Afterwards, they were randomized to receive either 5 mg/kg per day of ATV (n=8) or no treatment (NT, n=6) during 4 weeks, and were finally killed. ATV reduced lipid levels, neointimal size (0.13 (0.03-0.29) mm(2) vs 0.65 (0.14-1.81) mm(2), P=0.005) and the percentage of neointimal area positive for macrophages (1% (0-3) vs 19% (5-32), P=0.001), COX-2 (32% (23-39) vs 60% (37-81) P=0.019), interleukin-8 (IL-8) (23% (3-63) vs 63% (25-88) P=0.015), and metalloproteinase-3 (19% (12-34) vs 42% (27-93), P=0.010), without significant differences in COX-1 expression (immunohistochemistry). In situ hybridization confirmed a decreased expression of COX-2 mRNA (22% (5-40) vs 43% (34-59) P=0.038). The activity of nuclear factor-kappaB, which controls many proinflammatory genes including COX-2, was reduced in atherosclerotic lesions (3538 (2663-5094) vs 8696 (5429-11312)) positive nuclei per mm(2), P=0.001) and circulating mononuclear cells (2966 vs 17130 arbitrary units). In cultured vascular smooth muscle cells, ATV reduced the expression of COX-2 mRNA induced by IL-1beta and TNF-alpha without affecting COX-1 expression. In conclusion, ATV, besides decreasing a number of inflammatory mediators in the atherosclerotic lesion, significantly downregulates COX-2 both in vivo and in vitro. These anti-inflammatory actions could partially account for the reduction of acute coronary events achieved by statins.

Increased pulmonary activation of nuclear factor-kappaB (NF-kappaB) in foals inoculated with Rhodococcus equi is associated with increased expression of inflammatory cytokines

Previous studies revealed that foals inoculated with virulent Rhodococcus equi had significantly higher pulmonary levels of interleukin-1beta, interleukin-12 p40, interferon-gamma, and tumor necrosis factor-alpha mRNA compared to foals inoculated with an avirulent plasmid-cured derivative. The purpose of this study was to determine if the increases in cytokine expression were associated with increased pulmonary activation of nuclear factor-kappaB (NF-kappaB). Electrophoretic mobility shift assays were performed on pulmonary nuclear protein extracted from foals treated with phosphate-buffered saline, or inoculated with either virulent or avirulent R. equi. NF-kappaB activation was increased in the nuclear extracts from foals inoculated with virulent R. equi at 14 days after inoculation when increased cytokine expression was also observed. Southwestern histochemistry revealed activated NF-kappaB in multinucleated giant cells that often contained bacteria. These results indicate that the cytokine response to R. equi is at least partially mediated by NF-kappaB activation.

Tubular NF-kappaB and AP-1 activation in human proteinuric renal disease

BACKGROUND

Nuclear factor-kappaB (NF-kappaB) and activated protein-1 (AP-1) are transcription factors that regulate many genes involved in the progression of renal disease. Recent data have shown that NF-kappaB is activated in tubules and glomeruli in various experimental models of renal injury. In vitro studies also suggest that proteinuria could be an important NF-kappaB activator. We therefore approached the idea that NF-kappaB may be an indicator of renal damage progression.

METHODS

Paraffin-embedded renal biopsy specimens from 34 patients with intense proteinuria [14 with minimal change disease (MCD) and 20 with idiopathic membranous nephropathy (MN)] and from 7 patients with minimal or no proteinuria (IgA nephropathy) were studied by Southwestern histochemistry for the in situ detection of activated transcription factors NF-kappaB and AP-1. In addition, by immunohistochemistry, we performed staining for the NF-kappaB subunits (p50 and p65) and AP-1 subunits (c-fos, c-jun). By immunohistochemistry and/or in situ hybridization, the expression of some chemokines [monocyte chemoattractant protein-1 (MCP-1), RANTES, osteopontin (OPN)] and profibrogenic cytokines [transforming growth factor-beta (TGF-beta)], whose genes are regulated by NF-kappaB and/or AP-1, were studied further.

RESULTS

NF-kappaB was detected mainly in the tubules of proteinuric patients, but rarely in nonproteinuric IgA nephropathy (IgAN) patients. In addition, there was a significant relationship between the intensity of proteinuria and NF-kappaB activation in MCD (r = 0.64, P = 0.01) and MN patients (r = 0.64, P < 0.01). Unexpectedly, patients with MCD had a significantly higher NF-kappaB tubular activation than those with MN (P < 0.01). To assess whether there was a different composition of NF-kappaB protein components, immunostaining was performed for the NF-kappaB subunits p50 and p65. However, no differences were noted between MCD and MN patients. In those patients, there was a lower tubular activation of AP-1 compared with NF-kappaB. Moreover, a strong correlation in the expression of both transcription factors was observed only in MN (r = 0.7, P = 0.004). Patients with progressive MN had an overexpression of MCP-1, RANTES, OPN, and TGF-beta, mainly in the proximal tubules, while no significant expression was found in MCD patients.

CONCLUSIONS

On the whole, our results show that a tubular overactivation of NF-kappaB and AP-1 and a simultaneous up-regulation of certain proinflammatory and profibrogenic genes are markers of progressive renal disease in humans. Increased activation of solely NF-kappaB and/or AP-1 may merely indicate the response of tubular renal cells to injury.

Systemic infusion of angiotensin II into normal rats activates nuclear factor-kappaB and AP-1 in the kidney: role of AT(1) and AT(2) receptors

Recent studies have pointed out the implication of angiotensin II (Ang II) in various pathological settings. However, the molecular mechanisms and the AngII receptor (AT) subtypes involved are not fully identified. We investigated whether AngII elicited the in vivo activation of nuclear transcription factors that play important roles in the pathogenesis of renal and vascular injury. Systemic infusion of Ang II into normal rats increased renal nuclear factor (NF)-kappaB and AP-1 binding activity that was associated with inflammatory cell infiltration and tubular damage. Interestingly, infiltrating cells presented activated NF-kappaB complexes, suggesting the involvement of AngII in inflammatory cell activation. When rats were treated with AT(1) or AT(2) receptor antagonists different responses were observed. The AT(1) antagonist diminished NF-kappaB activity in glomerular and tubular cells and abolished AP-1 in renal cells, improved tubular damage and normalized the arterial blood pressure. The AT(2) antagonist diminished mononuclear cell infiltration and NF-kappaB activity in glomerular and inflammatory cells, without any effect on AP-1 and blood pressure. These data suggest that AT(1) mainly mediates tubular injury via AP-1/NF-kappaB, whereas AT(2) receptor participates in the inflammatory cell infiltration in the kidney by NF-kappaB. Our results provide novel information on AngII receptor signaling and support the recent view of Ang II as a proinflammatory modulator.

Increased glomerular and tubular expression of transforming growth factor-beta1, its type II receptor, and activation of the Smad signaling pathway in the db/db mouse

Activation of the renal transforming growth factor-beta (TGF-beta) system likely mediates the excess production of extracellular matrix in the diabetic kidney. To establish the role of the TGF-beta system in type 2 diabetic nephropathy, we examined the intrarenal localization and expression of the TGF-beta1 isoform, the TGF-beta type II receptor, and the Smad signaling pathway in the 16-week-old db/db mouse, a genetic model of type 2 diabetes that exhibits mesangial matrix expansion, glomerular basement membrane thickening, and renal insufficiency that closely resemble the human disease. Compared with its nondiabetic db/m littermate, the db/db mouse showed significantly increased TGF-beta1 mRNA expression by in situ hybridization in both glomerular and tubular compartments. Likewise, TGF-beta1 protein, by immunohistochemical staining, was increased in both renal compartments, but the fractional expression of TGF-beta1 protein was less than that of the mRNA in the glomerulus. In situ hybridization and immunohistochemical staining for the TGF-beta type II receptor revealed concordant and significant increases of both mRNA and protein in the glomerular and tubular compartments of diabetic animals. Finally, immunohistochemistry showed preferential accumulation of Smad3 in the nuclei of glomerular and tubular cells in diabetes. The complementary technique of Southwestern histochemistry using a labeled Smad-binding element demonstrated increased binding of nuclear proteins to Smad-binding element, indicating active signaling downstream of the TGF-beta stimulus. We therefore propose that the TGF-beta system is up-regulated at the ligand, receptor, and signaling levels throughout the renal cortex in this animal model of type 2 diabetes. Our findings suggest that the profibrotic effects of TGF-beta may underlie the progression to glomerulosclerosis and tubulointerstitial fibrosis that characterize diabetic nephropathy.

Activation of NF-kappaB in tubular epithelial cells of rats with intense proteinuria: role of angiotensin II and endothelin-1

The mechanisms by which persistent proteinuria induces interstitial inflammation and fibrosis are not well known, although nuclear factor-kappaB (NF-kappaB), which regulates the transcription of many genes involved in renal injury, could be implicated. In rats with intense proteinuria, we studied the renal activation of NF-kappaB as well as the potential involvement of the vasoactive hormones angiotensin II (Ang II) and endothelin-1 (ET-1). Uninephrectomized Wistar-Kyoto rats receiving 1 g/d of BSA had proteinuria but no renal morphological lesions at day 1. By contrast, tubular atrophy and/or dilation and mononuclear cell infiltration were observed after 8 or 28 days of BSA administration, coinciding with maximal proteinuria. In relation to control uninephrectomized rats, the renal cortex of nephritic rats showed an increment in the activation of NF-kappaB at all time periods studied. By in situ Southwestern histochemistry, NF-kappaB activity was mainly localized in proximal tubules, interstitial mononuclear cells, and, to a lesser extent, the glomeruli. The administration of the ACE inhibitor quinapril plus the ET(A)/ET(B) receptor antagonist bosentan during 28 days to BSA-overloaded animals diminished proteinuria, renal lesions, and NF-kappaB activity more markedly than single drugs. Cultured tubular epithelial cells exposed to BSA revealed an intense NF-kappaB activation in a time- and dose-dependent manner. Incubation of cells with receptor antagonists of Ang II (AT(1): losartan and AT(2): PD-123,319) or ET-1 (ET(A): BQ123 and ET(B): IRL1038) inhibited significantly the BSA-induced NF-kappaB activity (90%, 75%, 90%, and 60% of inhibition versus basal, respectively). Our results show that overload proteinuria causes NF-kappaB activation in tubular epithelial cells both in vivo and in vitro. The vasoactive peptides Ang II and ET-1 appear to be implicated in this effect. The results reveal a novel mechanism of perpetuation of renal damage induced by persistent proteinuria.

Transcription factor-kappa B (NF-kappa B) and renal disease

Transcription factor-kappa B (NF-kappa B) and renal disease. Nuclear factor-kappa B (NF-kappa B) comprises a family of dimeric transcription factors that regulate the expression of numerous genes involved in inflammation and cell proliferation. Although NF-kappa B was initially identified in lymphocytes, it has been found to be a transcription factor present in virtually all cell types. In resting cells, NF-kappa B dimers remain in the cytoplasm in an inactive form bound to the inhibitory subunit I kappa B. Upon stimulation, I kappa B is phosphorylated, ubiquitinylated, and ultimately degraded by proteolytic cleavage by the proteasome system. As a result, NF-kappa B dimers are translocated into the nucleus and activate the transcription of target genes. Increasing data suggest a pivotal role for NF-kappa B in a variety of pathophysiological conditions in which either inflammation or cell number control are critical events. NF-kappa B has been found to be activated in experimental renal disease. Importantly, both in vivo and in vitro, NF-kappa B activation can be modulated by pharmacological maneuvers. Indeed, it is now widely acknowledged that the anti-inflammatory action of steroids is basically obtained through the inhibition of the transactivation of NF-kappa B-dependent genes. In addition, some of the beneficial effects of angiotensin-converting enzyme inhibitors and statins may, at least in part, be mediated by an inhibition of NF-kappa B activation. A better understanding of the mechanisms involved in NF-kappa B regulation and its modulation may provide new tools to improve the treatment of renal diseases with a better sound pathophysiological approach.

Chlamydia pneumoniae activates nuclear factor kappaB and activator protein 1 in human vascular smooth muscle and induces cellular proliferation

BACKGROUND

Observational data strongly suggest an association between Chlamydia pneumoniae and atherosclerotic cardiovascular disease. However, few studies have mechanistically linked C. pneumoniae to vascular remodeling. The purpose of the present study was to examine the mechanistic relationship between C. pneumoniae and human vascular smooth muscle cell (VSMC) physiology. We sought to determine the influence of human VSMC infection by C. pneumoniae on (1) VSMC proliferation and (2) activation of the proinflammatory and proliferative transcription factors nuclear factor kappaB (NF-kappaB) and activator protein 1 (AP-1).

MATERIALS AND METHODS

C. pneumoniae was grown and isolated from Hep 2 cells. Human aortic VSMCs were inoculated with C. pneumoniae in the presence and absence of the azalide antibiotic azithromycin. Cell proliferation was assayed by direct cell counting 48 h following infection. Two hours following infection, nuclear extracts were isolated, and activation of both NF-kappaB and AP-1 was assessed by electrophoretic mobility shift assay.

RESULTS

Compared with control, C. pneumoniae infection stimulated VSMC proliferation (P < 0.05) and induced both NF-kappaB and AP-1 DNA binding activity. These effects were eliminated by concurrent treatment with azithromycin.

CONCLUSIONS

VSMC infection with C. pneumoniae activates proliferative intracellular signals and stimulates cell growth. These data implicate C. pneumoniae as a pathogenic mediator and a potential therapeutic target in the prevention of atherosclerotic disease.

Administration of IgG Fc fragments prevents glomerular injury in experimental immune complex nephritis

Most human nephritis is due to glomerular deposition and/or formation of immune complexes (IC). In cultured mesangial cells, Fc receptor stimulation induces proliferation, matrix synthesis, and release of several mediators implicated in the initiation and progression of glomerular injury. Since Ig Fc fragments in vitro modified these phenomena, we studied the effects of systemic administration of IgG Fc fragments on the evolution of experimental IC nephritis. Fc fragment injection (1 mg/day i.p.) to rats with ongoing nephritis (proteinuria 20-50 mg/24 h vs 9 +/- 0.2 mg/24 h in controls) markedly ameliorates proteinuria, renal function, and morphological renal lesions. This was accompanied by a reduction in the renal synthesis of chemokines (monocyte chemoattractant protein-1, IFN-inducible protein-10, and cytokine-induced neutrophil chemoattractant-1), matrix proteins, and growth factors (platelet-derived growth factor, and TGF-beta), and in the activity of transcription factors. The treatment did not affect the glomerular deposition of IgG IC and complement C1q. In contrast, a decrease in the renal expression and production of C3 was observed without changes in serum complement levels. In vitro, very low complement consumption and no C3b covalent interaction were observed with Fc fragments, confirming that they did not modify systemic complement activity. These results indicate that the administration of Fc fragments prevents the development of glomerular damage in an aggressive model of proliferative glomerulonephritis through mechanisms involving a reduced local generation of complement, chemokines and growth factors. Modulation of IC-mesangial cell interaction by Fc fragment administration could represent a new approach to the treatment of severe immune nephritis.