Endothelin (ET)-1 inhibits nicotinamide adenine dinucleotide phosphate oxidase activity in human abdominal aortic endothelial cells: a novel function of ETB1 receptors

TNFα Induces DNA and Histone Hypomethylation and Pulmonary Artery Smooth Muscle Cell Proliferation Partly via Excessive Superoxide Formation

Objective: The level of tumor necrosis factor-α (TNF-α) is upregulated during the development of pulmonary vascular remodeling and pulmonary hypertension. A hallmark of pulmonary arterial (PA) remodeling is the excessive proliferation of PA smooth muscle cells (PASMCs). The purpose of this study is to investigate whether TNF-α induces PASMC proliferation and explore the potential mechanisms. Methods: PASMCs were isolated from 8-week-old male Sprague-Dawley rats and treated with 0, 20, or 200 ng/mL TNF-α for 24 or 48 h. After treatment, cell number, superoxide production, histone acetylation, DNA methylation, and histone methylation were assessed. Results: TNF-α treatment increased NADPH oxidase activity, superoxide production, and cell numbers compared to untreated controls. TNF-α-induced PASMC proliferation was rescued by a superoxide dismutase mimetic tempol. TNF-α treatment did not affect histone acetylation at either dose but did significantly decrease DNA methylation. DNA methyltransferase 1 activity was unchanged by TNF-α treatment. Further investigation using QRT-RT-PCR revealed that GADD45-α, a potential mediator of DNA demethylation, was increased after TNF-α treatment. RNAi inhibition of GADD45-α alone increased DNA methylation. TNF-α impaired the epigenetic mechanism leading to DNA hypomethylation, which can be abolished by a superoxide scavenger tempol. TNF-α treatment also decreased H3-K4 methylation. TNF-α-induced PASMC proliferation may involve the H3-K4 demethylase enzyme, lysine-specific demethylase 1 (LSD1). Conclusions: TNF-α-induced PASMC proliferation may be partly associated with excessive superoxide formation and histone and DNA methylation.

Endothelium-restricted endothelin-1 overexpression in type 1 diabetes worsens atherosclerosis and immune cell infiltration via NOX1

AIMS

NADPH oxidase (NOX) 1 but not NOX4-dependent oxidative stress plays a role in diabetic vascular disease, including atherosclerosis. Endothelin (ET)-1 has been implicated in diabetes-induced vascular complications. We showed that crossing mice overexpressing human ET-1 selectively in endothelium (eET-1) with apolipoprotein E knockout (Apoe-/-) mice enhanced high-fat diet-induced atherosclerosis in part by increasing oxidative stress. We tested the hypothesis that ET-1 overexpression in the endothelium would worsen atherosclerosis in type 1 diabetes through a mechanism involving NOX1 but not NOX4.

METHODS AND RESULTS

Six-week-old male Apoe-/- and eET-1/Apoe-/- mice with or without Nox1 (Nox1-/y) or Nox4 knockout (Nox4-/-) were injected intraperitoneally with either vehicle or streptozotocin (55 mg/kg/day) for 5 days to induce type 1 diabetes and were studied 14 weeks later. ET-1 overexpression increased 2.5-fold and five-fold the atherosclerotic lesion area in the aortic sinus and arch of diabetic Apoe-/- mice, respectively. Deletion of Nox1 reduced aortic arch plaque size by 60%; in contrast, Nox4 knockout increased lesion size by 1.5-fold. ET-1 overexpression decreased aortic sinus and arch plaque alpha smooth muscle cell content by ∼35% and ∼50%, respectively, which was blunted by Nox1 but not Nox4 knockout. Reactive oxygen species production was increased two-fold in aortic arch perivascular fat of diabetic eET-1/Apoe-/- and eET-1/Apoe-/-/Nox4-/- mice but not eET-1/Apoe-/-/Nox1y/- mice. ET-1 overexpression enhanced monocyte/macrophage and CD3+ T-cell infiltration ∼2.7-fold in the aortic arch perivascular fat of diabetic Apoe-/- mice. Both Nox1 and Nox4 knockout blunted CD3+ T-cell infiltration whereas only Nox1 knockout prevented the monocyte/macrophage infiltration in diabetic eET-1/Apoe-/- mice.

CONCLUSION

Endothelium ET-1 overexpression enhances the progression of atherosclerosis in type 1 diabetes, perivascular oxidative stress, and inflammation through NOX1.

Beneficial Effect of Bariatric Surgery on Abnormal MMP-9 and AMPK Activities: Potential Markers of Obesity-Related CV Risk

Bariatric surgery (BS) results in sustained weight loss and may reverse inflammation, metabolic alterations, extracellular matrix remodeling and arterial stiffness. We hypothesize that increased stiffening in omental arteries from obese patients might be associated with an increase in MMP activity and a decrease in p-AMPK, together with systemic oxidative stress and inflammation. Moreover, BS could contribute to reversing these alterations. This study was conducted with 38 patients of Caucasian origin: 31 adult patients with morbid obesity (9 men and 22 women; mean age 46 years and BMI = 42.7 ± 1.0 kg/m²) and 7 non-obese subjects (7 women; mean age 45 years and BMI = 22.7 ± 0.6 kg/m²). Seventeen obese patients were studied before and 12 months after BS. The stiffness index β, an index of intrinsic arterial stiffness, was determined in omental arteries and was significantly higher in obese patients. Levels of phosphorylated AMPK (p-AMPK^Thr-172) and SIRT-1 were significantly lower in peripheral blood mononuclear cells (PBMCs) from obese patients than those from non-obese patients (p < 0.05) and were normalized after BS. Total and active MMP-9 activities, LDH, protein carbonyls and uric acid were higher in obese patients and reduced by BS. Moreover, there was a correlation between plasmatic LDH levels and the stiffness index β. BS has a beneficial effect on abnormal MMP-9, LDH and AMPK activities that might be associated with the development of arterial stiffness in obese patients. Since these parameters are easily measured in blood samples, they could constitute potential biomarkers of cardiovascular risk in morbid obesity.

Regulation of NADPH Oxidases by G Protein-Coupled Receptors

SIGNIFICANCE

G protein-coupled receptors (GPCR) are the largest group of cell surface receptors, which link cells to their environment. Reactive oxygen species (ROS) can act as important cellular signaling molecules. The family of NADPH oxidases generates ROS in response to activated cell surface receptors. Recent Advances: Various signaling pathways linking GPCRs and activation of NADPH oxidases have been characterized.

CRITICAL ISSUES

Still, a more detailed analysis of G proteins involved in the GPCR-mediated activation of NADPH oxidases is needed. In addition, a more precise discrimination of NADPH oxidase activation due to either upregulation of subunit expression or post-translational subunit modifications is needed. Also, the role of noncanonical modulators of NADPH oxidase activation in the response to GPCRs awaits further analyses.

FUTURE DIRECTIONS

As GPCRs are one of the most popular classes of investigational drug targets, further detailing of G protein-coupled mechanisms in the activation mechanism of NADPH oxidases as well as better understanding of the link between newly identified NADPH oxidase interaction partners and GPCR signaling will provide new opportunities for improved efficiency and decreased off target effects of therapies targeting GPCRs.

Activation of SIRT1 Attenuates Klotho Deficiency-Induced Arterial Stiffness and Hypertension by Enhancing AMP-Activated Protein Kinase Activity

Arterial stiffness is an independent risk factor for stroke and myocardial infarction. This study was designed to investigate the role of SIRT1, an important deacetylase, and its relationship with Klotho, a kidney-derived aging-suppressor protein, in the pathogenesis of arterial stiffness and hypertension. We found that the serum level of Klotho was decreased by ≈45% in patients with arterial stiffness and hypertension. Interestingly, Klotho haplodeficiency caused arterial stiffening and hypertension, as evidenced by significant increases in pulse wave velocity and blood pressure in Klotho-haplodeficient (KL^+/-) mice. Notably, the expression and activity of SIRT1 were decreased significantly in aortic endothelial and smooth muscle cells in KL^+/- mice, suggesting that Klotho deficiency downregulates SIRT1. Treatment with SRT1720 (15 mg/kg/d, IP), a specific SIRT1 activator, abolished Klotho deficiency-induced arterial stiffness and hypertension in KL^+/- mice. Klotho deficiency was associated with significant decreases in activities of AMP-activated protein kinase α (AMPKα) and endothelial NO synthase (eNOS) in aortas, which were abolished by SRT1720. Furthermore, Klotho deficiency upregulated NADPH oxidase activity and superoxide production, increased collagen expression, and enhanced elastin fragmentation in the media of aortas. These Klotho deficiency-associated changes were blocked by SRT1720. In conclusion, this study provides the first evidence that Klotho deficiency downregulates SIRT1 activity in arterial endothelial and smooth muscle cells. Pharmacological activation of SIRT1 may be an effective therapeutic strategy for arterial stiffness and hypertension.

The Ins and Outs of Small GTPase Rac1 in the Vasculature

The Rho family of small GTPases forms a 20-member family within the Ras superfamily of GTP-dependent enzymes that are activated by a variety of extracellular signals. The most well known Rho family members are RhoA (Ras homolog gene family, member A), Cdc42 (cell division control protein 42), and Rac1 (Ras-related C3 botulinum toxin substrate 1), which affect intracellular signaling pathways that regulate a plethora of critical cellular functions, such as oxidative stress, cellular contacts, migration, and proliferation. In this review, we describe the current knowledge on the role of GTPase Rac1 in the vasculature. Whereas most recent reviews focus on the role of vascular Rac1 in endothelial cells, in the present review we also highlight the functional involvement of Rac1 in other vascular cells types, namely, smooth muscle cells present in the media and fibroblasts located in the adventitia of the vessel wall. Collectively, this overview shows that Rac1 activity is involved in various functions within one cell type at distinct locations within the cell, and that there are overlapping but also cell type-specific functions in the vasculature. Chronically enhanced Rac1 activity seems to contribute to vascular pathology; however, Rac1 is essential to vascular homeostasis, which makes Rac1 inhibition as a therapeutic option a delicate balancing act.

Endothelin Receptors Expressed by Immune Cells Are Involved in Modulation of Inflammation and in Fibrosis: Relevance to the Pathogenesis of Systemic Sclerosis

Endothelin-1 (ET-1) plays a pivotal role in vasoconstriction, fibrosis, and inflammation, the key features of systemic sclerosis (SSc). ET-1 receptors (ET_A and ET_B) are expressed on endothelial cells, smooth muscle cells, and fibroblasts, but their presence on immune cells has not been deeply investigated so far. Endothelin receptors antagonists such as bosentan have beneficial effects on vasoconstriction and fibrosis, but less is known about their potential anti-inflammatory effects. We studied the expression of ET-1 receptors on immune cells (T and B lymphocytes, monocytes, and neutrophils) and the link between ET-1 and inflammation in patients with SSc. We show here that ET-1 exerts a proinflammatory effect in CD4+ T cells, since it induces an increased IFN-γ production; preincubation with antagonists of both receptors reduces IFN-γ production. Moreover, following ET-1 stimulation, neutrophils produce proinflammatory mediators, thus amplifying the effects of activated CD4+ T cells. Our data indicate that ET-1 system is involved in the pathogenesis of inflammation and fibrosis typical of SSc, through the activation of T lymphocytes and neutrophils and the consequent release of proinflammatory and profibrotic cytokines. These findings suggest that dual ET-1 receptors antagonist therapy, besides its effect on vasculopathy, has a profound impact on the immune system favouring antiinflammatory and antifibrogenic effects.

Nox family NADPH oxidases: Molecular mechanisms of activation

NADPH oxidases of the Nox family are important enzymatic sources of reactive oxygen species (ROS). Numerous homologue-specific mechanisms control the activity of this enzyme family involving calcium, free fatty acids, protein-protein interactions, intracellular trafficking, and posttranslational modifications such as phosphorylation, acetylation, or sumoylation. After a brief review on the classic pathways of Nox activation, this article will focus on novel mechanisms of homologue-specific activity control and on cell-specific aspects which govern Nox activity. From these findings of the recent years it must be concluded that the activity control of Nox enzymes is much more complex than anticipated. Moreover, depending on the cellular activity state, Nox enzymes are selectively activated or inactivated. The complex upstream signaling aspects of these events make the development of "intelligent" Nox inhibitors plausible, which selectively attenuate disease-related Nox-mediated ROS formation without altering physiological signaling ROS. This approach might be of relevance for Nox-mediated tissue injury in ischemia-reperfusion and inflammation and also for chronic Nox overactivation as present in cancer initiation and cardiovascular disease.

Vascular Smooth Muscle Cell Signaling Mechanisms for Contraction to Angiotensin II and Endothelin-1

Vasoactive peptides, such as endothelin-1 and angiotensin II are recognized by specific receptor proteins located in the cell membrane of target cells. Following receptor recognition, the specificity of the cellular response is achieved by G-protein coupling of ligand binding to the regulation of intracellular effectors. These intracellular effectors will be the subject of this brief review on contractile activity initiated by endothelin-1 and angiotensin II.Activation of receptors by endothelin-1 and angiotensin II in smooth muscle cells results in phopholipase C (PLC) activation leading to the generation of the second messengers insitol trisphosphate (IP(3)) and diacylglycerol (DAG). IP(3) stimulates intracellular Ca(2+) release from the sarcoplasmic reticulum and DAG causes protein kinase C (PKC) activation. Additionally, different Ca(2+) entry channels, such as voltage-operated (VOC), receptor-operated (ROC), and store-operated (SOC) Ca(2+) channels, as well as Ca(2+)-permeable nonselective cation channels (NSCC), are involved in the elevation of intracellular Ca(2+) concentration. The elevation in intracellular Ca(2+) is transient and initiates contractile activity by a Ca(2+)-calmodulin interaction, stimulating myosin light chain (MLC) phosphorylation. When the Ca(2+) concentration begins to decline, Ca(2+)-sensitization of the contractile proteins is signaled by the RhoA/Rho-kinase pathway to inhibit the dephosphorylation of MLC phosphatase (MLCP) thereby maintaining force generation. Removal of Ca(2+) from the cytosol and stimulation of MLCP initiates the process of smooth muscle relaxation. In pathological conditions such as hypertension, alterations in these cellular signaling components can lead to an over stimulated state causing maintained vasoconstriction and blood pressure elevation.

Normal IgG downregulates the intracellular superoxide level and attenuates migration and permeability in human aortic endothelial cells isolated from a hypertensive patient

The normal IgG, a circulating antibody, is maintained at a constant level in humans. However, little is known regarding whether normal IgG has effects on the function of vascular endothelial cells. The purpose of this study was to investigate whether IgG affects superoxide (O(2)(·-)) generation and cell permeability in human aortic endothelial cells (HAECs) isolated from a hypertensive patient. The effect of normal human IgG on endothelial cell function was investigated in cultured HAECs isolated from a hypertensive patient who died of stroke. The results demonstrated, for the first time, that normal IgG attenuated the intracellular O(2)(·-) level and decreased cell migration, cell permeability, and stress fiber formation in HAECs. IgG significantly decreased Rac1 activity and NADPH oxidase activity but upregulated Mn superoxide dismutase expression in HAECs, which may contribute to the IgG-induced decrease in O(2)(·-) level. It is noted that AMP-activated protein kinase (AMPK) was activated by IgG, as evidenced by increased phosphorylation of AMPK. Interestingly, inhibition of AMPK by an AMPK inhibitor abolished IgG-induced decreases in Rac1 and NADPH oxidase activities and IgG-induced increases in Mn superoxide dismutase expression, suggesting that AMPK is an important mediator of the IgG-induced regulation of these enzymes. Importantly, inhibition of AMPK activity also prevented the IgG-induced decrease in O(2)(·-) levels, cell migration, cell permeability, and stress fiber formation. Therefore, normal human IgG may protect HAECs via activation of AMPK and subsequent decreases in intracellular O(2)(·-). These findings reveal a previously unidentified role of normal IgG in regulating AMPK and endothelial cell function.

Klotho gene delivery suppresses Nox2 expression and attenuates oxidative stress in rat aortic smooth muscle cells via the cAMP-PKA pathway

Klotho is a recently discovered anti-aging gene. The purpose of this study was to investigate whether klotho gene transfer attenuates superoxide production and oxidative stress in rat aorta smooth muscle (RASM) cells. RASM cells were transfected with AAV plasmids carrying mouse klotho full-length cDNA (mKL) or LacZ as a control. Klotho gene transfer increased klotho expression in RASM cells. Notably, klotho gene expression decreased Nox2 NADPH oxidase protein expression but did not affect Nox2 mRNA expression, suggesting that the inhibition may occur at the posttranscriptional level. Klotho gene transfer decreased intracellular superoxide production and oxidative stress in RASM cells. Klotho gene expression also significantly attenuated the angiotensin II (AngII)-induced superoxide production, oxidative damage, and apoptosis. Interestingly, klotho gene delivery dose dependently increased the intracellular cAMP level and PKA activity in RASM cells. Rp-cAMP, a competitive inhibitor of cAMP, abolished the klotho-induced increase in PKA activity, indicating that klotho activated PKA via cAMP. Notably, inhibition of cAMP-dependent PKA activity by RP-cAMP abolished klotho-induced inhibition of Nox2 protein expression, suggesting an important role of cAMP-dependent PKA in this process. This finding revealed a previously unidentified role of klotho in regulating Nox2 protein expression in RASM cells. Klotho not only downregulated Nox2 protein expression and intracellular superoxide production but also attenuated AngII-induced superoxide production, oxidative damage, and apoptosis. The klotho-induced suppression of Nox2 protein expression may be mediated by the cAMP-PKA pathway.

Biochemistry, physiology, and pathophysiology of NADPH oxidases in the cardiovascular system

The NADPH oxidase (Nox) enzymes are critical mediators of cardiovascular physiology and pathophysiology. These proteins are expressed in virtually all cardiovascular cells, and regulate such diverse functions as differentiation, proliferation, apoptosis, senescence, inflammatory responses and oxygen sensing. They target a number of important signaling molecules, including kinases, phosphatases, transcription factors, ion channels, and proteins that regulate the cytoskeleton. Nox enzymes have been implicated in many different cardiovascular pathologies: atherosclerosis, hypertension, cardiac hypertrophy and remodeling, angiogenesis and collateral formation, stroke, and heart failure. In this review, we discuss in detail the biochemistry of Nox enzymes expressed in the cardiovascular system (Nox1, 2, 4, and 5), their roles in cardiovascular cell biology, and their contributions to disease development.

Genetic interleukin-10 deficiency causes vascular remodeling via the upregulation of Nox1

BACKGROUND AND HYPOTHESIS

Interleukin (IL)-10 is an anti-inflammatory cytokine. Nox1 is a mitogenic oxidase (p65-mox). The objective of this study was to test a hypothesis that IL-10 deficiency would cause vascular remodeling via the upregulation of Nox1.

METHODS AND RESULTS

Recombinant adeno-associated virus (AAV) carrying short hairpin small interference RNA for Nox1 (AAV.Nox1shRNA) was constructed for in-vivo-specific inhibition of Nox1. Three groups of IL-10 gene knockout (IL-10KO) mice and three groups of wild-type mice were used. Three groups of each strain received intravenous delivery of AAV.Nox1shRNA, AAV with scrambled shRNA, and PBS, respectively. Animals were euthanized at 3 weeks after gene delivery. IL-10KO increased Nox1 protein expression, NADPH oxidase activity, and superoxide production in aortas. IL-10KO also resulted in a significant decrease in aortic medial thickness, a loss of smooth muscle cells (SMCs), and an increase in vascular collagen deposition, indicating vascular remodeling. The IL-10KO induced increases in NADPH oxidase activity and superoxide production, and vascular remodeling were abolished by silencing of Nox1 (p65-mox), suggesting that these effects may be mediated by the upregulation of Nox1. In addition, IL-10KO increased endothelin-1 levels in plasma and aortas, and this effect was partially blocked by silencing of Nox1. RNA interference silencing of Nox1 obliterated the IL-10KO-induced increases in IL-6 expression in aortas, superoxide production, and matrix metalloproteinase-9 activity in aortic SMCs, and SMC migration.

CONCLUSION

IL-10 is essential for the maintenance of normal vasculature, as IL-10 deficiency resulted in vascular damage and remodeling. The IL-10KO-induced vascular structure damage may be mediated by the upregulation of Nox1.

Klotho gene delivery suppresses Nox2 expression and attenuates oxidative stress in rat aortic smooth muscle cells via the cAMP-PKA pathway

Klotho is a recently discovered anti-aging gene. The purpose of this study was to investigate whether klotho gene transfer attenuates superoxide production and oxidative stress in rat aorta smooth muscle (RASM) cells. RASM cells were transfected with AAV plasmids carrying mouse klotho full-length cDNA (mKL) or LacZ as a control. Klotho gene transfer increased klotho expression in RASM cells. Notably, klotho gene expression decreased Nox2 NADPH oxidase protein expression but did not affect Nox2 mRNA expression, suggesting that the inhibition may occur at the posttranscriptional level. Klotho gene transfer decreased intracellular superoxide production and oxidative stress in RASM cells. Klotho gene expression also significantly attenuated the angiotensin II (AngII)-induced superoxide production, oxidative damage, and apoptosis. Interestingly, klotho gene delivery dose dependently increased the intracellular cAMP level and PKA activity in RASM cells. Rp-cAMP, a competitive inhibitor of cAMP, abolished the klotho-induced increase in PKA activity, indicating that klotho activated PKA via cAMP. Notably, inhibition of cAMP-dependent PKA activity by RP-cAMP abolished klotho-induced inhibition of Nox2 protein expression, suggesting an important role of cAMP-dependent PKA in this process. This finding revealed a previously unidentified role of klotho in regulating Nox2 protein expression in RASM cells. Klotho not only downregulated Nox2 protein expression and intracellular superoxide production but also attenuated AngII-induced superoxide production, oxidative damage, and apoptosis. The klotho-induced suppression of Nox2 protein expression may be mediated by the cAMP-PKA pathway.

Aging-related kidney damage is associated with a decrease in klotho expression and an increase in superoxide production

The purpose of this study was to determine changes in klotho, endothelin (ET) receptors, and superoxide production in kidneys of aged rats and whether these changes are exacerbated in aged rats with cognitive impairment. Twenty aged rats (male, 27 months) were divided into an Old Impaired group (n=9) and an Old Intact group (n=11) according to a cognitive function test. A group of 12-month-old rats (n=10) was used as a Young Intact group. Serum creatinine was increased significantly in the Old Impaired group, suggesting impaired renal function. Aged rats showed glomerulosclerosis and tubulointerstitialfibrosis. These pathological changes were markedly aggravated in the old cognitively impaired than in the old cognitively intact animals. Notably, aged rats demonstrated a significant decrease in klotho protein expression in renal cortex and medulla. Protein expression of IL-6, Nox2, ETa receptors and superoxide production were increased whereas mitochondrial SOD (MnSOD) and ETb receptors expression were decreased in kidneys of the aged rats. Interestingly, these changes were more pronounced in the old impaired than in the old intact rats. In conclusion, the aging-related kidney damage was exacerbated in aged rats with cognitive impairment. Klotho, ETB, and MnSOD were downregulated but ETa, IL-6, Nox2, and superoxide production were upregulated in the aging-related kidney damage. These changes were more pronounced in rats with cognitive impairment.

Differential regulation of Nox1, Nox2 and Nox4 in vascular smooth muscle cells from WKY and SHR

The functional significance and regulation of NAD(P)H oxidase (Nox) isoforms by angiotensin II (Ang II) and endothelin-1 (ET-1) in vascular smooth muscle cells (VSMCs) from normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) was studied. Expression of Nox1, Nox2, and Nox4 (gene and protein) and NAD(P)H oxidase activity were increased in SHR. Basal NAD(P)H oxidase activity was blocked by GKT136901 (Nox1/4 inhibitor) and by Nox1 siRNA in WKY cells and by siNOX1 and siNOX2 in SHR. Whereas Ang II increased expression of all Noxes in WKY, only Nox1 was influenced in SHR. Ang II-induced NAD(P)H activity was inhibited by siNOX1 in WKY and by siNOX1 and siNOX2 in SHR. ET-1 upregulated Nox expression only in WKY and increased NAD(P)H oxidase activity, an effect inhibited by siNOX1 and siNOX2. Nox1 co-localized with Nox2 but not with Nox4, implicating association between Nox1 and Nox2 but not between Nox1 and Nox4. These data highlight the complexity of Nox biology in VSMCs, emphasising that more than one Nox member, alone or in association, may be involved in NAD(P)H oxidase-mediated •O(2)(-) production. Nox1 regulation by Ang II, but not by ET-1, may be important in •O(2)(-) formation in VSMCs from SHR.

Ultrastructural analysis and electron microscopic localization of Nox4 in healthy and atherosclerotic human aorta

During diverse pathological conditions, vascular smooth muscle cells (SMCs) characteristically change from a quiescent, contractile phenotype to a proliferative, synthetic state, migrate toward the intima, and synthesize excess extracellular matrix. Although reactive oxygen species (ROS) are generally considered to be toxic to cells, recent evidence suggests that they may also modulate multiple signaling pathways. The vascular system contains several sources of ROS, among which NADPH oxidases (NOXes) have been shown to take an important part in the regulation of cell function, with effects on growth and proliferation. In the present study, the authors investigate the ultrastructural features of SMCs and the expression profile of Nox4 in healthy and atherosclerotic human aorta to explore the possibility of a relationship between Nox4 and SMCs differentiation state. The data extend at the level of immunoelectron microscopy previous observations, demonstrating for the first time the precise distribution and the differential expression of Nox4 in the morphologically distinct SMC types of healthy and diseased human aorta.

Endothelin in pulmonary fibrosis

The endothelin receptor-ligand system includes a family of polypeptides and G-protein-coupled receptors, which, in addition to their classic activity in the regulation of vascular tone (both directly and through the control of nitric oxide), were implicated in a wide variety of other key biological processes. In this regard, the endothelins are potent mitogens and motogens for mesenchymal cells, and can induce cell differentiation, increasing both the synthesis and deposition of extracellular matrix components and contractile ability. The endothelins are produced as inactive pre-pro-polypeptides, with gene transcription (as well as the proteolytic processing to mature active forms) under the influence of many factors, including cytokines, hypoxia, biomechanical and shear stress, pathogen products, and many growth factors. These complex regulatory events underlie the association and potential role of endothelins in a number of human diseases affecting many different target organs, including the vasculature (atherosclerosis and hypertension), kidney (renal crisis and chronic kidney disease), heart (coronary heart disease), and lungs (pulmonary fibrosis and pulmonary hypertension). This review focuses on the biochemistry of endothelin and the pathobiology of endothelin in lung fibrosis, with particular emphasis on idiopathic pulmonary fibrosis, and examines the antifibrotic potential of endothelin receptor antagonism.

Klotho gene delivery prevents the progression of spontaneous hypertension and renal damage

Klotho is a recently discovered antiaging gene. The objective of this study was to test the hypothesis that klotho gene delivery attenuates the progression of spontaneous hypertension and renal damage in spontaneous hypertensive rats (SHRs). An adeno-associated virus (AAV) carrying mouse klotho full-length cDNA (AAV.mKL) was constructed for in vivo expression of klotho. Four groups of male SHRs and 1 group of sex- and age-matched Wistar-Kyoto rats (5 rats per group) were used. Blood pressure was measured twice in all of the animals before gene delivery. Four groups of SHRs received an IV injection of AAV.mKL, AAV.LacZ, AAV.GFP, and PBS, respectively. The Wistar-Kyoto group received PBS and served as a control. AAV.mKL stopped the further increase in blood pressure in SHRs, whereas blood pressures continued to increase in other SHR groups. One single dose of AAV.mKL prevented the progression of spontaneous hypertension for at least 12 weeks (length of the study). Klotho expression and production were suppressed in SHRs, which were reverted by AAV.mKL. AAV.mKL increased plasma interleukin 10 levels but decreased Nox2 expression, NADPH oxidase activity, and superoxide production in kidneys and aortas in SHRs. AAV.mKL abolished renal tubular atrophy and dilation, tubular deposition of proteinaceous material, glomerular collapse, and collagen deposition seen in SHRs, indicating that klotho gene delivery attenuated renal damage. Therefore, the suppressed klotho expression may play a role in the progression of spontaneous hypertension and renal damage in SHRs. AAV delivery of klotho may offer a new approach for the long-term control of hypertension and for renoprotection.