Effect of interleukin-6 receptor blockage on renal injury in apolipoprotein E-deficient mice

The role of exercise in improving hyperlipidemia-renal injuries induced by a high-fat diet: a literature review

A diet that is high in sugar and fat is a precursor to various chronic diseases, especially hyperlipidemia. Patients with hyperlipidemia have increased levels of plasma free fatty acids and an ectopic accumulation of lipids. The kidney is one of the main organs affected by this disease and, recently, there have been more studies conducted on renal injury caused by hyperlipidemia. The main pathological mechanism is closely related to renal lipotoxicity. However, in different kidney cells, the reaction mechanism varies due to the different affinities of the lipid receptors. At present, it is believed that in addition to lipotoxicity, hyperlipidemia induced-renal injury is also closely related to oxidative stress, endoplasmic reticulum stress, and inflammatory reactions, which are the result of multiple factors. Exercise plays an important role in the prevention of various chronic diseases and recently emerging researches indicated its positive effects to renal injury caused by hyperlipidemia. However, there are few studies summarizing the effects of exercise on this disease and the specific mechanisms need to be further explored. This article summarizes the mechanisms of hyperlipidemia induced-renal injury at the cellular level and discusses the ways in which exercise may regulate it. The results provide theoretical support and novel approaches for identifying the intervention target to treat hyperlipidemia induced-renal injury.

CXCL2 Impairs Functions of Bone Marrow Mesenchymal Stem Cells and Can Serve as a Serum Marker in High-Fat Diet-Fed Rats

In modern society excessive consumption of a high-fat diet (HFD) is a significant risk factor for many diseases such as diabetes, osteoarthritis and certain cancers. Resolving cellular and molecular mechanisms underlying HFD-associated disorders is of great importance to human health. Mesenchymal stem cells (MSCs) are key players in tissue homeostasis and adversely affected by prolonged HFD feeding. Low-grade systemic inflammation induced by HFD is characterized by increased levels of pro-inflammatory cytokines and alters homeostasis in many organs. However, whether, which and how HFD associated inflammatory cytokines impair MSCs remain unclear. Here we demonstrated that HFD induced serum cytokines disturbances, especially a continuous elevation of serum CXCL2 level in rats. Coincidentally, the differentially expressed genes (DEGs) of bone marrow MSCs (BMSCs) which functions were impaired in HFD rats were enriched in cytokine signaling. Further mechanism analysis revealed that CXCL2 treatment in vitro suppresses the adipogenic potential of BMSCs via Rac1 activation, and promoted BMSC migration and senescence by inducing over-production of ELMO1 and reactive oxygen species (ROS) respectively. Moreover, we found that although glycolipid metabolism indicators can be corrected, the CXCL2 elevation and BMSC dysfunctions cannot be fully rescued by diet correction and anti-inflammatory aspirin treatment, indicating the long-lasting deleterious effects of HFD on serum CXCL2 levels and BMSC functions. Altogether, our findings identify CXCL2 as an important regulator in BMSCs functions and may serve as a serum marker to indicate the BMSC dysfunctions induced by HFD. In addition, our findings underscore the intricate link among high-fat intake, chronic inflammation and BMSC dysfunction which may facilitate development of protective strategies for HFD associated diseases.

A Plant-Centered Diet and Markers of Early Chronic Kidney Disease during Young to Middle Adulthood: Findings from the Coronary Artery Risk Development in Young Adults (CARDIA) Cohort

BACKGROUND

Few studies have evaluated whether plant-centered diets prevent progression of early stage chronic kidney disease (CKD).

OBJECTIVES

We examined the association between plant-centered diet quality and early CKD markers.

METHODS

We prospectively examined 2869 black and white men and women in the Coronary Artery Risk Development in Young Adults Study free of diagnosed kidney failure in 2005-2006 [examination year 20 (Y20); mean age: 45.3 ± 3.6  y]. CKD marker changes from Y20 to 2015-2016 (Y30) were considered, including estimated glomerular filtration rate (eGFR; serum creatinine), urinary albumin-to-creatinine ratio (ACR), and both. Diet was assessed through interviewer-administered diet histories at Y0, Y7, and Y20, and plant-centered diet quality was quantified with the A Priori Diet Quality Score (APDQS). Linear regression models were used to examine the association of APDQS and subsequent 10-y changes in CKD markers.

RESULTS

After adjustment for sociodemographic, behavioral, and diet factors, we found that higher APDQS was related to less adverse changes in CKD markers in the subsequent 10-y period. Compared with the lowest APDQS quintile, the highest quintile was associated with an attenuated increase in lnACR (-0.25 mg/g; 95% CI: -0.37, -0.13 mg/g; P-trend < 0.001), whereas the highest quintile was associated with an attenuated decrease in eGFR (4.45 mL·min-1·1.73 m-2; 95% CI: 2.46, 6.43 mL·min-1·1.73 m-2). There was a 0.50 lower increase in combined CKD markers [ln(ACR) z score - eGFR z score] when comparing the extreme quintiles. Associations remained similar after further adjustment for hypertension, diabetes, and obesity as potential mediating factors. The attenuated worsening CKD marker changes associated with higher APDQS strengthened across increasing initial CKD category; those with the best diet and microalbuminuria in Y10-Y20 returned to high normal albuminuria (all P-interaction < 0.001).

CONCLUSIONS

Individuals who consumed plant-centered, high-quality diets were less likely to experience deterioration of kidney function through midlife, especially among participants with initial stage characterized as mild CKD.

Effect of meloxicam (cyclooygenase-2 inhibitor) versus vitamin D3 (cholecalciferol) as ameliorating agents of progressive doxorubicin-induced nephrotoxicity in rats

Doxorubicin (DOX)-induced nephropathy hampered its antineoplastic efficiency. The objective of the current work is to assess the prospective ameliorating effects of meloxicam versus vitamin D3 (Vit D3, cholecalciferol) against progressive DOX-induced nephropathy in rats trying to ascertain the possible mechanism underlying such amelioration. Ninety Male Wistar rats were randomly distributed to five experimental groups for 3 weeks, with saline, meloxicam (daily), DOX (single dose), Vit D3+DOX, or both meloxicam and DOX. We measured levels of urinary protein, serum creatinine, malondialdehyde (MDA) and renal reduced glutathione (GSH). In addition, tumor necrosis factor-alpha (TNF-α) expression and renal histopathology were assessed. Meloxicam alone treated group revealed no significant difference in urinary protein and serum creatinine. It also presented non-significant reduction in the MDA content while an increase in the reduced GSH content in contrast to the control group, which is more evident after the first week. Renal sections of rats received meloxicam only showed no significant histological changes and negative immunoreactivity compared to the control group. DOX induced a significant increase in urinary protein, serum creatinine, decrease reduced GSH, increased renal MDA and disrupted renal morphometric parameters and histology with increased TNF-α expression. Combination groups of Vit D3+DOX and meloxicam+DOX showed improvement of all DOX disturbed parameters. Meloxicam showed better results most likely due to anti-inflammatory and antioxidant activities superimposing the immune-modulatory effect of Vit D3. So, it is recommended to use meloxicam in patients receiving DOX as a renoprotective agent in addition to its analgesic effects required by cancer patients.

Effects of endothelial progenitor cells transplantation on hyperlipidemia associated kidney damage in ApoE knockout mouse model

Background

Hyperlipidaemia causes kidney damage over the long term. We investigated the effect of the administration of endothelial progenitor cells (EPCs) on the progression of kidney damage in a mouse model of hyperlipidaemia.

Methods

Apolipoprotein E-knockout (ApoE^−/−) mice were treated with a high-cholesterol diet after spleen resection. Twenty-four weeks later, the mice were divided into two groups and intravenously injected with PBS or EPCs. Six weeks later, the recruitment of EPCs to the kidney was monitored by immunofluorescence. The lipid, endothelial cell, and collagen contents in the kidney were evaluated by specific immunostaining. The protein expression levels of transforming growth factor-β (TGF-β), Smad2/3, and phospho-Smad3 (p-smad3) were detected by western blot analysis.

Results

ApoE^−/− mice treated with a high-fat diet demonstrated glomerular lipid deposition, enlargement of the glomerular mesangial matrix, endothelial cell enlargement accompanied by vacuolar degeneration and an area of interstitial collagen in the kidney. Six weeks after EPC treatment, only a few EPCs were detected in the kidney tissues of ApoE^−/− mice, mainly in the kidney interstitial area. No significant differences in TGF-β, p-smad3 or smad2/3 expression were found between the PBS group and the EPC treatment group (TGF-β expression, PBS group: 1.06 ± 0.09, EPC treatment group: 1.09 ± 0.17, P = 0.787; p-smad3/smad2/3 expression: PBS group: 1.11 ± 0.41, EPC treatment group: 1.05 ± 0.33, P = 0.861).

Conclusions

Our findings demonstrate that hyperlipidaemia causes basement membrane thickening, glomerulosclerosis and the vascular degeneration of endothelial cells. The long-term administration of EPCs substantially has limited effect in the progression of kidney damage in a mouse model of hyperlipidaemia.

Lipid Metabolism Disorder and Renal Fibrosis

Since the lipid nephrotoxicity hypothesis was proposed in 1982, increasing evidence has supported the hypothesis that lipid abnormalities contributed to the progression of glomerulosclerosis. In this chapter, we will discuss the general promises of the original hypothesis, focusing especially on the role of lipids and metabolic inflammation accompanying CKD in renal fibrosis and potential new strategies of prevention.

Inflammatory Links Between High Fat Diets and Diseases

In recent years, chronic overnutrition, such as consumption of a high-fat diet (HFD), has been increasingly viewed as a significant modifiable risk factor for diseases such as diabetes and certain types of cancer. However, the mechanisms by which HFDs exert adverse effects on human health remains poorly understood. Here, this paper will review the recent scientific literature about HFD-induced inflammation and subsequent development of diseases and cancer, with an emphasis on mechanisms involved. Given the expanding global epidemic of excessive HFD intake, understanding the impacts of a HFD on these medical conditions, gaining great insights into possible underlying mechanisms, and developing effective therapeutic strategies are of great importance.

Protective Effect of Taurine on Mice with Doxorubicin-induced Acute Kidney Injury

Nephrotic syndrome is still a therapeutic challenge because an effective treatment has not been developed. Evidence suggests that multidrug therapy is more effective than monotherapy in amelioration of renal injury. Therefore, we examined if taurine exerts a protective effect on doxorubicin-induced acute kidney injury in mice. Eight-week-old male Balb/c nude mice were used in this study. Taurine was orally administered at a dose of 50 mg/kg and 100 mg/kg body weight for 5 days. In the meantime, the mice were administered intraperitoneal injections of doxorubicin at 15 mg/kg body weight. At 24 h after the doxorubicin challenge, the response in the taurine-treated mice was compared with that in the vehicle-treated control mice. The doxorubicin-induced acute kidney injury model displayed a significant increase in the renal expression of apoptosis-related proteins (p53, phospho-p53, caspase 9, and caspase 3), whereas in the taurine-treated mice, the augmented expression of renal inflammation-related mRNAs such as NF-kB, COX-2, and iNOS was down-regulated. These results suggest that taurine acts as a renoprotective agent by inhibiting apoptosis and inflammation in the kidney of mice with doxorubicin-induced renal injury.

Coptidis Rhizoma inhibits NLRP3 inflammasome activation and alleviates renal damage in early obesity-related glomerulopathy

BACKGROUND

Obese subjects have been considered to be in a state of chronic, low-grade systemic inflammation. Excess fat accumulation and persistent inflammation may promote renal dysfunction, to cause chronic kidney disease (CKD) and even end-stage kidney failure. Coptidis Rhizoma is a classical traditional Chinese herb well known for its hypoglycemic and hypolipidemic properties. The mechanism is partially associated with its anti-inflammatory effect. However, this effect is rarely investigated in obesity and obesity-related glomerulopathy (ORG).

PURPOSE

The current study was designed to evaluate the effect of Coptidis Rhizoma on ORG. It also aimed to determine whether this renal protection effect of Coptidis Rhizoma was related to the inhibition of NLRP3 inflammasome in ORG.

METHODS

Coptidis Rhizoma concentrated granules were prepared and the main components were identified by 3D-High Performance Liquid Chromatography (3D-HPLC) assay. The animal model of early stage ORG was established in obesity-prone (OP) rats by high protein and high fat diet feeding for 12 weeks. The treatment with Coptidis Rhizoma at different dosages was administered by intragastric infusion simultaneously. Then body weight, kidney weight, plasma lipid profiles, 24 h urine protein/albumin content and kidney histology were measured. Inflammatory biomarkers were examined both in the rat plasma and renal cortex. The gene expressions of NLRP3 inflammasome complex and NF-κB in renal tissues were also measured.

RESULTS

Coptidis Rhizoma alleviated dyslipidemia and reduced the renal weight of the rats with ORG. Meanwhile, urinary albumin to creatinine ratio and creatinine clearance rate were significantly improved. Coptidis Rhizoma also attenuated glomerular hypertrophy, mesangial hyperplasia, and effacement of podocyte foot in renal tissues of ORG rats. In addition, Coptidis Rhizoma intervention decreased the levels of proinflammatory cytokines (TNF-α, IL-1β, IL-6, and IL-18) both in plasma and renal tissue. The gene expression of NLRP3 inflammasome was down-regulated and NF-κB activity was also inhibited by Coptidis Rhizoma in renal tissues of ORG rats.

CONCLUSION

Coptidis Rhizoma can ameliorate early renal damage in ORG rats and the mechanisms appear to be related to the inhibition of NLRP3 inflammasome complex.

Osteopontin deficiency reduces kidney damage from hypercholesterolemia in Apolipoprotein E-deficient mice

Hypercholesterolemia is a well-established risk factor for kidney injury, which can lead to chronic kidney disease (CKD). Osteopontin (OPN) has been implicated in the pathology of several renal conditions. This study was to evaluate the effects of OPN on hypercholesterolemia induced renal dysfunction. Eight-week-old male mice were divided into 4 groups: apolipoprotein E knockout (ApoE^−/−) and ApoE/OPN knockout (ApoE^−/−/OPN^−/−) mice fed a normal diet (ND) or high cholesterol diet (HD). After 4 weeks, Periodic acid-Schiff (PAS) and oil red O staining revealed excessive lipid deposition in the glomeruli of ApoE^−/−HD mice, however, significantly suppressed in ApoE^−/−/OPN^−/−HD mice. Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) expression was lower in the glomeruli of ApoE^−/−/OPN^−/−HD mice than ApoE^−/−HD mice. In vitro study, primary mesangial cells were incubated with recombinant mouse OPN (rmOPN). RmOPN induced LOX-1 mRNA and protein expression in primary mesangial cells. Pre-treatment with an ERK inhibitor suppressed the LOX-1 gene expression induced by rmOPN. These results indicate that OPN contributes to kidney damage in hypercholesterolemia and suggest that inhibition of OPN may provide a potential therapeutic target for the prevention of hypercholesterolemia.

Deletion of Rac1GTPase in the Myeloid Lineage Protects against Inflammation-Mediated Kidney Injury in Mice

Macrophage-mediated inflammation has been implicated in various kidney diseases. We previously reported that Rac1, a Rho family small GTP-binding protein, was overactivated in several chronic kidney disease models, and that Rac1 inhibitors ameliorated renal injury, in part via inhibition of inflammation, but the detailed mechanisms have not been clarified. In the present study, we examined whether Rac1 in macrophages effects cytokine production and the inflammatory mechanisms contributing to kidney derangement. Myeloid-selective Rac1 flox control (M-Rac1 FC) and knockout (M-Rac1 KO) mice were generated using the cre-loxP system. Renal function under basal conditions did not differ between M-Rac1 FC and KO mice. Accordingly, lipopolysaccharide (LPS)-evoked kidney injury model was created. LPS elevated blood urea nitrogen and serum creatinine, enhanced expressions of kidney injury biomarkers, Kim-1 and Ngal, and promoted tubular injury in M-Rac1 FC mice. By contrast, deletion of myeloid Rac1 almost completely prevented the LPS-mediated renal impairment. LPS triggered a marked induction of macrophage-derived inflammatory cytokines, IL-6 and TNFα, in M-Rac1 FC mice, which was accompanied by Rac1 activation, stimulation of reduced nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase, and reactive oxygen species overproduction. These changes were inhibited in M-Rac1 KO mice. LPS evoked F4/80-positive macrophages accumulation in the kidney, which was not affected by myeloid Rac1 deficiency. We further tested the role of Rac1 signaling in cytokine production using macrophage cell line, RAW264.7. Exposure to LPS increased IL-6 and TNFα mRNA expression. The LPS-driven cytokine induction was dose-dependently blocked by the Rac1 inhibitor EHT1864, NADPH oxidase inhibitor diphenyleneiodonium, and NF-κB inhibitor BAY11-7082. In conclusion, genetic ablation of Rac1 in the myeloid lineage protected against LPS-induced renal inflammation and injury, by suppressing macrophage-derived cytokines, IL-6 and TNFα, without blocking recruitment. Our data suggest that Rac1 in macrophage is a novel target for the treatment of kidney disease through inhibition of cytokine production.

Anti-Inflammatory Effects of Ang-(1-7) in Ameliorating HFD-Induced Renal Injury through LDLr-SREBP2-SCAP Pathway

The angiotensin converting enzyme 2-angiotensin-(1–7)-Mas axis (ACE2-Ang-(1–7)-Mas axis) is reported to participate in lipid metabolism in kidney, but its precise effects and underlying mechanisms remain unknown. We hypothesized that Ang-(1–7) reduces lipid accumulation and improves renal injury through the low density lipoprotein receptor–sterol regulatory element binding proteins 2–SREBP cleavage activating protein (LDLr-SREBP2-SCAP) system by suppressing inflammation in high fat diet (HFD)-fed mice. In this study, male C57BL/6 mice were randomized into four groups: STD (standard diet)+saline, HFD+saline, HFD+Ang-(1–7) and STD+Ang-(1–7). After 10 weeks of feeding, mice were administered Ang-(1–7) or saline for two weeks. We found that high inflammation status induced by HFD disrupted the LDLr-SREBP2-SCAP feedback system. Treatment of mice fed a high-fat diet with Ang-(1–7) induced significant improvement in inflammatory status, following the downregulation of LDLr, SREBP2 and SCAP, and then, decreased lipid deposition in kidney and improved renal injury. In conclusion, the anti-inflammatory effect of Ang-(1–7) alleviates renal injury triggered by lipid metabolic disorders through a LDLr- SREBP2-SCAP pathway.

IL-6 Trans-Signaling Drives Murine Crescentic GN

The role of IL-6 signaling in renal diseases remains controversial, with data describing both anti-inflammatory and proinflammatory effects. IL-6 can act via classic signaling, engaging its two membrane receptors gp130 and IL-6 receptor (IL-6R). Alternatively, IL-6 trans-signaling requires soluble IL-6R (sIL-6R) to act on IL-6R-negative cells that express gp130. Here, we characterize the role of both pathways in crescentic nephritis. Patients with crescentic nephritis had significantly elevated levels of IL-6 in both serum and urine. Similarly, nephrotoxic serum-induced nephritis (NTN) in BALB/c mice was associated with elevated serum IL-6 levels. Levels of serum sIL-6R and renal downstream signals of IL-6 (phosphorylated signal transducer and activator of transcription 3, suppressor of cytokine signaling 3) increased over time in this model. Simultaneous inhibition of both IL-6 signaling pathways using anti-IL-6 antibody did not have a significant impact on NTN severity. In contrast, specific inhibition of trans-signaling using recombinant sgp130Fc resulted in milder disease. Vice versa, specific activation of trans-signaling using a recombinant IL-6-sIL-6R fusion molecule (Hyper-IL-6) significantly aggravated NTN and led to increased systolic BP in NTN mice. This correlated with increased renal mRNA synthesis of the Th17 cell cytokine IL-17A and decreased synthesis of resistin-like alpha (RELMalpha)-encoding mRNA, a surrogate marker of lesion-mitigating M2 macrophage subtypes. Collectively, our data suggest a central role for IL-6 trans-signaling in crescentic nephritis and offer options for more effective and specific therapeutic interventions in the IL-6 system.

Imbalanced gp130 signalling in ApoE-deficient mice protects against atherosclerosis

OBJECTIVE

Interleukin (IL)-6 is a key modulator of the acute phase response (APR), and while both are implicated in atherosclerosis, the pathological role of specific IL-6 signalling cascades is ill-defined. Since IL-6 employs the cytokine receptor gp130 to primarily activate the STAT3 pathway, here we evaluate whether gp130-dependent STAT3 activation modulates atherosclerosis.

METHODS

High-fat diet-induced atherosclerosis was established in ApoE(-/-) mice crossed with gp130(F/F) knock-in mice displaying elevated gp130-dependent STAT3 activation and production of the APR protein, serum amyloid A (SAA). Also generated were gp130(F/F):Stat3(-/+):ApoE(-/-) mice displaying genetically-normalised STAT3 activation and SAA levels, and bone marrow chimeras involving ApoE(-/-) and gp130(F/F):ApoE(-/-) mice. At 10 weeks post high-fat diet, aortic atherosclerotic lesions, including the presence of CD68(+) macrophages, and plasma lipid and SAA profiles, were assessed.

RESULTS

Aortic plaque development and plasma triglyceride levels in gp130(F/F):ApoE(-/-) mice were significantly reduced (3-fold, P < 0.001) compared to ApoE(-/-) littermates. By contrast, in gp130(F/F):ApoE(-/-) mice, atherosclerotic plaques contained augmented CD68(+) macrophage infiltrates, and plasma SAA levels were elevated, compared to ApoE(-/-) mice. Atherosclerotic lesion development and plasma triglyceride levels in gp130(F/F):ApoE(-/-) and gp130(F/F):Stat3(-/+):ApoE(-/-) mice were comparable, despite a significant (P < 0.05) reduction in macrophage numbers in lesions, and also plasma SAA levels, in gp130(F/F):Stat3(-/+):ApoE(-/-) mice. Aortic plaque development and plasma triglyceride levels were comparable in ApoE(-/-) mice reconstituted with gp130(F/F):ApoE(-/-) (ApoE(F/F:ApoE)) or ApoE(-/-) (ApoE(ApoE)) bone marrow cells.

CONCLUSIONS

Deregulation of gp130/STAT3 signalling augments the APR and macrophage infiltration during atherosclerosis without impacting on the development of aortic plaques.

Adipokines promote chronic kidney disease

The rapid growth in obesity worldwide contributes to an increase in metabolic syndrome and obesity-related kidney disease with an enhanced increased risk for chronic kidney disease, finally progressing to end-stage renal disease. Adipose tissue is a highly active endocrine organ secreting numerous factors that contribute to renal and cardiovascular complications. In renal damage, various adipokines are involved through mediating endothelial dysfunction, inducing oxidative stress and inflammation as well as stimulating renal sympathetic nervous activity, and it reduces cancellous bone but conversely increases cortical bone. Adipokines may also be involved in the development of renal anaemia. A balance exists between more protective adipokines (adiponectin) and factors mediating pathophysiological effects (angiotensin II, TNFα). Obesity may cause a disruption of this delicate balance, thereby inducing renal disease. Consequently, weight reduction and lifestyle changes affecting all components of the metabolic syndrome are essential to disrupt this vicious cycle.

Obesity in kidney disease: A heavyweight opponent

Obesity is an important worldwide challenge that must be faced in most developed and developing countries because of unhealthy nutritional habits. The consequences of obesity and being overweight are observed in different organs, but the kidney is one of the most affected. Excess adipose tissue causes hemodynamic alterations in the kidney that can result in renal disease. However, obesity is also commonly associated with other comorbidities such as chronic inflammation, hypertension and diabetes. This association of several aggravating factors is still a matter of concern in clinical and basic research because the pathophysiologic mechanisms surrounding chronic kidney disease development in obese patients remain unclear. This review will discuss the consequences of obesity in the context of renal injury.

Obesity and diabetic kidney disease

Obesity and diabetes are major causes of CKD and ESRD, and are thus enormous health concerns worldwide. Both obesity and diabetes, along with other elements of the metabolic syndrome including hypertension, are highly interrelated and contribute to the development and progression of renal disease. Studies show that multiple factors act in concert to initially cause renal vasodilation, glomerular hyperfiltration, and albuminuria, leading to the development of glomerulopathy. The coexistence of hypertension contributes to the disease progression, which, if not treated, may lead to ESRD. Although early intervention and management of body weight, hyperglycemia, and hypertension are imperative, novel therapeutic approaches are also necessary to reduce the high morbidity and mortality associated with both obesity-related and diabetes-related renal disease.

Obesity-induced renal impairment is exacerbated in interleukin-6-knockout mice

AIM

Interleukin-6 (IL-6) is secreted from adipose tissue and thought to contribute to obesity-related disorders. The aim of this study was to assess if IL-6-knockout (IL-6-/-) mice would develop obesity-induced renal impairment.

METHODS

Wild-type (WT) and IL-6-/- mice were high-fat fed (HFF) for 16 weeks to induce obesity. At the end of the study, renal function was measured via albumin/creatinine ratio and serum creatinine levels, using enzyme-linked immunosorbent assay (ELISA) and high-performance liquid chromatography (HPLC). Glomerulosclerotic index (GSI) was scored in periodic acid Schiff-stained sections and collagen IV accumulation was assessed by immunohistochemistry. Renal cortical tumour growth factor beta (TGF-β(1) ) activity and monocyte chemotactic protein-1 (MCP-1) levels were measured via ELISA.

RESULTS

Renal IL-6 concentrations were increased with obesity. Although both WT HFF and IL-6-/- HFF mice exhibited renal impairment as measured by increased serum creatinine and urinary albumin/creatinine ratios, this was exacerbated in IL-6-/- mice. Obese mice had renal activation of cortical TGF-β(1) , which was also higher in IL-6-/- mice. Collagen IV staining was not affected by obesity. GSI was increased with obesity in both WT and IL-6-/- mice.

CONCLUSION

Obese IL-6-/- mice demonstrated renal functional and structural abnormalities above that seen in obese WT mice. We suggest that absence or low IL-6 levels may be an important accelerating factor implicated in the development and progression of obesity-induced renal disease.

Concordance of preclinical and clinical pharmacology and toxicology of therapeutic monoclonal antibodies and fusion proteins: cell surface targets

Monoclonal antibodies (mAbs) and fusion proteins directed towards cell surface targets make an important contribution to the treatment of disease. The purpose of this review was to correlate the clinical and preclinical data on the 15 currently approved mAbs and fusion proteins targeted to the cell surface. The principal sources used to gather data were: the peer reviewed Literature; European Medicines Agency 'Scientific Discussions'; and the US Food and Drug Administration 'Pharmacology/Toxicology Reviews' and package inserts (United States Prescribing Information). Data on the 15 approved biopharmaceuticals were included: abatacept; abciximab; alefacept; alemtuzumab; basiliximab; cetuximab; daclizumab; efalizumab; ipilimumab; muromonab; natalizumab; panitumumab; rituximab; tocilizumab; and trastuzumab. For statistical analysis of concordance, data from these 15 were combined with data on the approved mAbs and fusion proteins directed towards soluble targets. Good concordance with human pharmacodynamics was found for mice receiving surrogates or non-human primates (NHPs) receiving the human pharmaceutical. In contrast, there was poor concordance for human pharmacodynamics in genetically deficient mice and for human adverse effects in all three test systems. No evidence that NHPs have superior predictive value was found.

Anti-IL-6 receptor antibody does not ameliorate radiation pneumonia in mice

We previously showed that early administration of monoclonal anti-interleukin-6 receptor antibody (IL-6RA) does not prevent radiation-induced lung injury in mice. The purpose of this study was to investigate whether a higher dose and longer course of IL-6RA treatment was effective in ameliorating radiation pneumonia. C57Bl/6J mice received thoracic irradiation of 12 Gy, and were intraperitoneally injected with the IL-6RA, namely MR16-1, or with control rat IgG 4 times, once immediately following exposure and then weekly from 1 to 3 weeks after irradiation. Enzyme-linked immunosorbent assays were used to analyze the plasma levels of IL-6 and serum amyloid A (SAA). Lung injury was assessed by histological staining with haematoxylin and eosin (H&E) and by measuring wet lung weight. We observed marked upregulation of IL-6 in IL-6RA-treated mice compared to the IgG-treated control group, whereas IL-6RA did not increase the production of SAA in the group receiving irradiation. However, radiation pneumonia, as evaluated by H&E staining and lung weight showed no differences between the IL-6RA-treated mice and the controls. Long-term treatment with high-dose IL-6RA does not ameliorate radiation pneumonia.

Inflammation and oxidative stress in obesity-related glomerulopathy

Obesity-related glomerulopathy is an increasing cause of end-stage renal disease. Obesity has been considered a state of chronic low-grade systemic inflammation and chronic oxidative stress. Augmented inflammation in adipose and kidney tissues promotes the progression of kidney damage in obesity. Adipose tissue, which is accumulated in obesity, is a key endocrine organ that produces multiple biologically active molecules, including leptin, adiponectin, resistin, that affect inflammation, and subsequent deregulation of cell function in renal glomeruli that leads to pathological changes. Oxidative stress is also associated with obesity-related renal diseases and may trigger the initiation or progression of renal damage in obesity. In this paper, we focus on inflammation and oxidative stress in the progression of obesity-related glomerulopathy and possible interventions to prevent kidney injury in obesity.

Efficacy of tocilizumab, a humanized neutralizing antibody against interleukin-6 receptor, in progressive renal injury associated with Castleman's disease

Castleman's disease is a benign lymphoproliferative disorder in which interleukin-6 (IL-6), a pleiotropic proinflammatory cytokine, is thought to play a pathogenetic role. Presented is the case of a 72-year-old man with Castleman's disease who exhibited progressive renal dysfunction with proteinuria. Renal biopsy revealed mesangial hypercellularity and matrix expansion in most glomeruli and peritubular inflammatory cell infiltration. Immunofluorescence studies showed intense deposition of IgG in a granular pattern along the glomerular basement membrane. Histological features were compatible with membranoproliferative glomerulonephritis accompanied by interstitial inflammatory cell infiltration. Immunohistological analysis showed that IL-6 was abundantly expressed by tubular cells and interstitial macrophages, suggesting involvement of IL-6 in the renal injury. As a result of administration of tocilizumab, a humanized anti-IL-6 receptor antibody, the patient experienced clinical and biochemical improvement of Castleman's disease, including marked reduction of proteinuria and stabilization of renal function. These findings suggest the efficacy of tocilizumab against Castleman's disease and its renal complications.

Obesity-related glomerulopathy and podocyte injury: a mini review

Obesity-related glomerulopathy (ORG) is morphologically defined as focal segmental glomerulosclerosis and glomerulomegaly. Podocyte hypertrophy and reduced density are related to proteinuria which in a portion of patients is in the nephrotic range and evolvs towards renal failure. This article reviews the pathogenetic mechanisms of podocyte injury or dysfunction and lists new possible antiproteinuric strategies based on pharmaceutical targeting of the reported pathogenetic mechanisms. The pathogenetic mechnisms discussed include: renin angiotensin system, plasminogen activation inhibitor-1 (PAI-1), lipid metabolism, adiponectin, macrophages and proinflammatory cytokines, oxidative stress. The proposed antiproteinuric strategies include: AT2 receptor blockers; adipokine complement C19 TNF-related protein-1 blocker; selective PAI-1 inhibitor; farnesoid x receptor activation; increase of circulating adiponectin; selective antiinflammatory drugs; more potent antioxidants (Heme oxigenase, NOX4 inhibitors). However, because ORG is a rare disease, the need for a long term pharmaceutical approach in obese proteinuric patients should be carefully evaluated and limited to the cases with progressive loss of renal function.

The Western-style diet: a major risk factor for impaired kidney function and chronic kidney disease

The Western-style diet is characterized by its highly processed and refined foods and high contents of sugars, salt, and fat and protein from red meat. It has been recognized as the major contributor to metabolic disturbances and the development of obesity-related diseases including type 2 diabetes, hypertension, and cardiovascular disease. Also, the Western-style diet has been associated with an increased incidence of chronic kidney disease (CKD). A combination of dietary factors contributes to the impairment of renal vascularization, steatosis and inflammation, hypertension, and impaired renal hormonal regulation. This review addresses recent progress in the understanding of the association of the Western-style diet with the induction of dyslipidemia, oxidative stress, inflammation, and disturbances of corticosteroid regulation in the development of CKD. Future research needs to distinguish between acute and chronic effects of diets with high contents of sugars, salt, and fat and protein from red meat, and to uncover the contribution of each component. Improved therapeutic interventions should consider potentially altered drug metabolism and pharmacokinetics and be combined with lifestyle changes. A clinical assessment of the long-term risks of whole-body disturbances is strongly recommended to reduce metabolic complications and cardiovascular risk in kidney donors and patients with CKD.

RNA interference-mediated silencing of Foxo3 in antigen-presenting cells as a strategy for the enhancement of DNA vaccine potency

The transcription factor Forkhead box O3 (Foxo3) has a critical role in suppressing the expansion of antigen-specific effector T-cell populations; hence, Foxo3 is a potential target for enhancing the antitumor immunity of cancer vaccines. In this report, we evaluated the potential of RNA interference (RNAi)-mediated silencing of Foxo3 in antigen-presenting cells as an adjuvant for HER2/neu DNA cancer vaccines. Bicistronic plasmids expressing the N-terminal extracellular domain of human HER-2/neu and the Foxo3 short hairpin RNA (hN'-neu-Foxo3 shRNA) or the scrambled control (hN'-neu-scramble shRNA) were subcutaneously injected into mice by gene gun administration to elicit antitumor immunity against p185neu-overexpressing MBT-2 bladder tumor cells. We found that mice treated with hN'-neu-Foxo3 shRNA showed greater reductions in tumor growth and longer survival times than mice treated with hN'-neu-scramble shRNA, indicating that the silencing of Foxo3 enhanced the antitumor efficacy of the HER-2/neu cancer vaccine. Cytotoxicity analyses further revealed that the Foxo3 shRNA-enhanced antitumor effect was associated with significant increases in the number of functional CD8(+) T cells and in the levels of cytotoxic T lymphocytes activity. Interleukin-6 was induced by hN'-neu-Foxo3 shRNA treatment but did not have a critical role in the antitumor effect of the hN'-neu-Foxo3 shRNA vaccine. Moreover, in vivo lymphocyte depletion analyses confirmed that the antitumor efficacy of the hN'-neu-Foxo3 shRNA vaccine depended on functional CD8(+) T cells. Finally, Foxo3 suppression was shown to markedly improve the effect of the HER-2/neu DNA vaccine in limiting the growth and lung metastases of MBT-2 cells. Overall, these results support RNAi-mediated silencing of Foxo3 as an effective strategy to enhance the therapeutic antitumor effect of HER-2/neu DNA vaccines against p185neu-positive tumors.

Scope and mechanisms of obesity-related renal disease

PURPOSE OF REVIEW

Obesity is established as an important contributor of increased diabetes mellitus, hypertension, and cardiovascular disease, all of which can promote chronic kidney disease (CKD). Recently, there is a growing appreciation that, even in the absence of these risks, obesity itself significantly increases CKD and accelerates its progression.

RECENT FINDINGS

Experimental and clinical studies reveal that adipose tissue, especially visceral fat, elaborates bioactive substances that contribute to the pathophysiologic renal hemodynamic and structural changes leading to obesity-related nephropathy. Adipocytes contain all the components of the renin-angiotensin-aldosterone system, plasminogen activator inhibitor, as well as adipocyte-specific metabolites such as free fatty acids, leptin, and adiponectin, which affect renal function and structure. In addition, fat is infiltrated by macrophages that can alter their phenotype and foster a proinflammatory milieu, which advances pathophysiologic changes in the kidney associated with obesity.

SUMMARY

Obesity is an independent risk factor for development and progression of renal damage. Although the current therapies aimed at slowing progressive renal damage include reduction in weight and rely on inhibition of the renin-angiotensin system, the approach will likely be supplemented by interventions aimed at obesity-specific targets including adipocyte-driven cytokines and inflammatory factors.

Antibody against interleukin-6 receptor attenuates left ventricular remodelling after myocardial infarction in mice

AIMS

The plasma level of interleukin-6 (IL-6) has been reported to be associated with left ventricular (LV) remodelling after myocardial infarction (MI). The present study was designed to examine whether anti-IL-6 receptor antibody (MR16-1) prevents the development of LV remodelling after MI.

METHODS AND RESULTS

Balb/c male mice were subjected to MI by ligating the left anterior descending coronary artery. The mice were then treated with an intraperitoneal injection of MR16-1 (500 microg/body) or control IgG. MR16-1 decreased the myocardial myeloperoxidase activity and monocyte chemoattractant protein-1 concentration in the infarct region, concomitant with decreases in neutrophil and macrophage infiltration 3 days after ligation, while infarct size was comparable between the control IgG- and MR16-1-treated mice. At 7 days after ligation, MR16-1 significantly suppressed matrix metalloproteinase-2 activity in the infarct region. Furthermore, the MR16-1-treated mice demonstrated a reduction in LV dilatation and an improvement in LV contractile function compared with the control IgG-treated mice at 7 and 28 days after surgery, leading to an improvement in survival rate (80.6 vs. 59.5%, P < 0.05) at 28 days after surgery. The beneficial effects of MR16-1 were accompanied by histological suppression of cardiomyocyte hypertrophy and interstitial fibrosis in the non-infarct region.

CONCLUSION

Administration of MR16-1 after MI suppressed myocardial inflammation, resulting in the amelioration of LV remodelling. Neutralization of the IL-6 receptor is a potentially useful strategy for protecting hearts from LV remodelling after MI.

An update on the lipid nephrotoxicity hypothesis

When the 'lipid nephrotoxicity hypothesis' was proposed in 1982, it brought together several disparate experimental findings in hyperlipidemia and renal disease to suggest that concomitant hyperlipidemia and proteinuria would cause self-perpetuating renal disease once the initial glomerular insult was no longer present. This process would be analogous to atherosclerosis. Since 1982, increasing evidence has supported the hypothesis that lipid abnormalities contribute to both atherosclerosis and glomerulosclerosis. In this Review, we discuss research developments that are relevant to the lipid nephrotoxicity hypothesis. We describe how inflammatory stress accompanying chronic kidney disease modifies lipid homeostasis by increasing cholesterol uptake mediated by lipoprotein receptors, inhibiting cholesterol efflux mediated by the ATP-binding cassette transporter 1 and impairing cholesterol synthesis in peripheral cells. As a result of these events, cholesterol relocates to and accumulates in renal, vascular, hepatic and possibly other tissues. The combination of increased cellular cholesterol influx and reduced efflux causes injury in some tissues and lowers the plasma cholesterol level. In addition, inflammatory stress causes a degree of statin resistance via unknown mechanisms. These phenomena alter traditional understanding of the pathogenesis of lipid-mediated renal and vascular injury and could influence the clinical evaluation of renal and cardiovascular risk and the role of lipid-lowering treatment in affected patients.