Renal NF-κB activation and TNF-α upregulation correlate with salt-sensitive hypertension in Dahl salt-sensitive rats

The Role of the Vascular System in Degenerative Diseases: Mechanisms and Implications

Degenerative diseases, encompassing a wide range of conditions affecting various organ systems, pose significant challenges to global healthcare systems. This comprehensive review explores the intricate interplay between the vascular system and degenerative diseases, shedding light on the underlying mechanisms and profound implications for disease progression and management. The pivotal role of the vascular system in maintaining tissue homeostasis is highlighted, as it serves as the conduit for oxygen, nutrients, and immune cells to vital organs and tissues. Due to the vital role of the vascular system in maintaining homeostasis, its dysfunction, characterized by impaired blood flow, endothelial dysfunction, and vascular inflammation, emerges as a common denominator of degenerative diseases across multiple systems. In the nervous system, we explored the influence of vascular factors on neurodegenerative diseases such as Alzheimer's and Parkinson's, emphasizing the critical role of cerebral blood flow regulation and the blood-brain barrier. Within the kidney system, the intricate relationship between vascular health and chronic kidney disease is scrutinized, unraveling the mechanisms by which hypertension and other vascular factors contribute to renal dysfunction. Throughout this review, we emphasize the clinical significance of understanding vascular involvement in degenerative diseases and potential therapeutic interventions targeting vascular health, highlighting emerging treatments and prevention strategies. In conclusion, a profound appreciation of the role of the vascular system in degenerative diseases is essential for advancing our understanding of degenerative disease pathogenesis and developing innovative approaches for prevention and treatment. This review provides a comprehensive foundation for researchers, clinicians, and policymakers seeking to address the intricate relationship between vascular health and degenerative diseases in pursuit of improved patient outcomes and enhanced public health.

Transcriptomic changes in glomeruli in response to a high salt challenge in the Dahl SS rat

Salt sensitivity impacts a significant portion of the population and is an important contributor to the development of chronic kidney disease. One of the significant early predictors of salt-induced damage is albuminuria, which reflects the deterioration of the renal filtration barrier: the glomerulus. Despite significant research efforts, there is still a gap in knowledge regarding the molecular mechanisms and signaling networks contributing to instigating and/or perpetuating salt-induced glomerular injury. To address this gap, we used 8-wk-old male Dahl salt-sensitive rats fed a normal-salt diet (0.4% NaCl) or challenged with a high-salt diet (4% NaCl) for 3 wk. At the end of the protocol, a pure fraction of renal glomeruli obtained by differential sieving was used for next-generation RNA sequencing and comprehensive semi-automatic transcriptomic data analyses, which revealed 149 differentially expressed genes (107 and 42 genes were downregulated and upregulated, respectively). Furthermore, a combination of predictive gene correlation networks and computational bioinformatic analyses revealed pathways impacted by a high salt dietary challenge, including renal metabolism, mitochondrial function, apoptotic signaling and fibrosis, cell cycle, inflammatory and immune responses, circadian clock, cytoskeletal organization, G protein-coupled receptor signaling, and calcium transport. In conclusion, we report here novel transcriptomic interactions and corresponding predicted pathways affecting glomeruli under salt-induced stress.NEW & NOTEWORTHY Our study demonstrated novel pathways affecting glomeruli under stress induced by dietary salt. Predictive gene correlation networks and bioinformatic semi-automatic analysis revealed changes in the pathways relevant to mitochondrial function, inflammatory, apoptotic/fibrotic processes, and cell calcium transport.

Brown-Norway chromosome 1 mitigates the upregulation of proinflammatory pathways in mTAL cells and subsequent age-related CKD in Dahl SS/JrHsdMcwi rats

Chronic kidney disease (CKD) has a strong genetic component; however, the underlying pathways are not well understood. Dahl salt-sensitive (SS)/Jr rats spontaneously develop CKD with age and are used to investigate the genetic determinants of CKD. However, there are currently several genetically diverse Dahl SS rats maintained at various institutions and the extent to which some exhibit age-related CKD is unclear. We assessed glomerulosclerosis (GS) and tubulointerstitial fibrosis (TIF) in 3- and 6-mo-old male and female SS/JrHsdMcwi, BN/NHsd/Mcwi [Brown-Norway (BN)], and consomic SS-Chr 1BN/Mcwi (SS.BN1) rats, in which chromosome 1 from the BN rat was introgressed into the genome of the SS/JrHsdMcwi rat. Rats were fed a 0.4% NaCl diet. GS (31 ± 3% vs. 7 ± 1%) and TIF (2.3 ± 0.2 vs. 0.5 ± 0.1) were significantly greater in 6-mo-old compared with 3-mo-old SS/JrHsdMcwi rats, and CKD was exacerbated in males. GS was minimal in 6- and 3-mo-old BN (3.9 ± 0.6% vs. 1.2 ± 0.4%) and SS.BN1 (2.4 ± 0.5% vs. 1.0 ± 0.3%) rats, and neither exhibited TIF. In SS/JrHsdMcwi and SS.BN1 rats, mean arterial blood pressure was significantly greater in 6-mo-old compared with 3-mo-old SS/JrHsdMcwi (162 ± 4 vs. 131 ± 2 mmHg) but not SS.BN1 (115 ± 2 vs. 116 ± 1 mmHg) rats. In 6-mo-old SS/JrHsdMcwi rats, blood pressure was significantly greater in females. RNA-sequencing analysis revealed that inflammatory pathways were upregulated in isolated medullary thick ascending tubules in 7-wk-old SS/JrHsdMcwi rats, before the development of tubule pathology, compared with SS.BN1 rats. In summary, SS/JrHsdMcwi rats exhibit robust age-related progression of medullary thick ascending limb abnormalities, CKD, and hypertension, and gene(s) on chromosome 1 have a major pathogenic role in such changes.NEW & NOTEWORTHY This study shows that the robust age-related progression of kidney disease in Dahl SS/JrHsdMcw rats maintained on a normal-salt diet is abolished in consomic SS.BN1 rats. Evidence that medullary thick ascending limb segments of SS/JrHsdMcw rats are structurally abnormal and enriched in proinflammatory pathways before the development of protein casts provides new insights into the pathogenesis of kidney disease in this model.

Astragalus Polysaccharide Reduces Blood Pressure, Renal Damage, and Dysfunction Through the TGF-β1-ILK Pathway

Background:Astragalus polysaccharide extract (APS) has been shown to exhibit antioxidant and anti-inflammatory potential in the treatment of several diseases. However, whether APS could protect against renal damage in hypertensive mice is unknown.

Methods: Hematoxylin and eosin staining, immunohistochemistry, real-time polymerase chain reaction, and Western blotting were used to investigate the effect of APS on the renal damage in deoxycorticosterone acetate- (DOCA) salt- and angiotensin II- (Ang II-) induced hypertensive mice and to elucidate the underlying mechanisms.

Results: Our data demonstrated that APS significantly reduced blood pressure in DOCA-salt- and Ang II-treated mice. Furthermore, APS reduced the inflammatory response and renal fibrosis, thereby improving renal function. Furthermore, the levels of serum creatinine, urea nitrogen, and uric acid increased in DOCA-salt-treated mice, alleviated by APS administration. At the molecular level, DOCA-salt and Ang II increased the mRNA levels of IL-1β, IL-6, α-SMA, collagen I, and collagen III, while APS significantly inhibited these effects. APS inhibited the TGF-β1/ILK signaling pathway, which was activated in hypertensive mice due to the administration of DOCA-salt.

Conclusion: Our results suggest that APS plays a beneficial role in improving renal dysfunction in hypertensive mice.

Cyclosporine A and Tacrolimus Induce Functional Impairment and Inflammatory Reactions in Endothelial Progenitor Cells

Immunosuppressants are a mandatory therapy for transplant patients to avoid rejection of the transplanted organ by the immune system. However, there are several known side effects, including alterations of the vasculature, which involve a higher occurrence of cardiovascular events. While the effects of the commonly applied immunosuppressive drugs cyclosporine A (CsA) and tacrolimus (Tac) on mature endothelial cells have been addressed in several studies, we focused our research on the unexplored effects of CsA and Tac on endothelial colony-forming cells (ECFCs), a subgroup of endothelial progenitor cells, which play an important role in vascular repair and angiogenesis. We hypothesized that CsA and Tac induce functional defects and activate an inflammatory cascade via NF-κB signaling in ECFCs. ECFCs were incubated with different doses (0.01 µM–10 µM) of CsA or Tac. ECFC function was determined using in vitro models. The expression of inflammatory cytokines and adhesion molecules was explored by quantitative real-time PCR and flow cytometry. NF-κB subunit modification was assessed by immunoblot and immunofluorescence. CsA and Tac significantly impaired ECFC function, including proliferation, migration, and tube formation. TNF-α, IL-6, VCAM, and ICAM mRNA expression, as well as PECAM and VCAM surface expression, were enhanced. Furthermore, CsA and Tac led to NF-κB p65 subunit phosphorylation and nuclear translocation. Pharmacological inhibition of NF-κB by parthenolide diminished CsA- and Tac-mediated proinflammatory effects. The data of functional impairment and activation of inflammatory signals provide new insight into mechanisms associated with CsA and Tac and cardiovascular risk in transplant patients.

Pharmacological inhibition of the NLRP3 inflammasome reduces blood pressure, renal damage, and dysfunction in salt-sensitive hypertension

Aims

Renal inflammation, leading to fibrosis and impaired function is a major contributor to the development of hypertension. The NLRP3 inflammasome mediates inflammation in several chronic diseases by processing the cytokines pro-interleukin (IL)-1β and pro-IL-18. In this study, we investigated whether MCC950, a recently-identified inhibitor of NLRP3 activity, reduces blood pressure (BP), renal inflammation, fibrosis and dysfunction in mice with established hypertension.

Methods and results

C57BL6/J mice were made hypertensive by uninephrectomy and treatment with deoxycorticosterone acetate (2.4 mg/day, s.c.) and 0.9% NaCl in the drinking water (1K/DOCA/salt). Normotensive controls were uninephrectomized and received normal drinking water. Ten days later, mice were treated with MCC950 (10 mg/kg/day, s.c.) or vehicle (saline, s.c.) for up to 25 days. BP was monitored by tail-cuff or radiotelemetry; renal function by biochemical analysis of 24-h urine collections; and kidney inflammation/pathology was assessed by real-time PCR for inflammatory gene expression, flow cytometry for leucocyte influx, and Picrosirius red histology for collagen. Over the 10 days post-surgery, 1K/DOCA/salt-treated mice became hypertensive, developed impaired renal function, and displayed elevated renal levels of inflammatory markers, collagen and immune cells. MCC950 treatment from day 10 attenuated 1K/DOCA/salt-induced increases in renal expression of inflammasome subunits (NLRP3, ASC, pro-caspase-1) and inflammatory/injury markers (pro-IL-18, pro-IL-1β, IL-17A, TNF-α, osteopontin, ICAM-1, VCAM-1, CCL2, vimentin), each by 25–40%. MCC950 reduced interstitial collagen and accumulation of certain leucocyte subsets in kidneys of 1K/DOCA/salt-treated mice, including CD206⁺ (M2-like) macrophages and interferon-gamma-producing T cells. Finally, MCC950 partially reversed 1K/DOCA/salt-induced elevations in BP, urine output, osmolality, [Na⁺], and albuminuria (each by 20–25%). None of the above parameters were altered by MCC950 in normotensive mice.

Conclusion

MCC950 was effective at reducing BP and limiting renal inflammation, fibrosis and dysfunction in mice with established hypertension. This study provides proof-of-concept that pharmacological inhibition of the NLRP3 inflammasome is a viable anti-hypertensive strategy.

New Insights on the Role of Sodium in the Physiological Regulation of Blood Pressure and Development of Hypertension

A precise maintenance of sodium and fluid balance is an essential step in the regulation of blood pressure and alterations of this balance may lead to the development of hypertension. In recent years, several new advances were made in our understanding of the interaction between sodium and blood pressure regulation. The first is the discovery made possible with by new technology, such as ²³Na-MRI, that sodium can be stored non-osmotically in tissues including the skin and muscles particularly when subjects are on a high sodium diet or have a reduced renal capacity to excrete sodium. These observations prompted the refinement of the original model of regulation of sodium balance from a two-compartment model comprising the extracellular fluid within the intravascular and interstitial spaces to a three-compartment model that includes the intracellular space of some tissues, most prominently the skin. In this new model, the immune system plays a role, thereby supporting many previous studies indicating that the immune system is a crucial co-contributor to the maintenance of hypertension through pro-hypertensive effects in the kidney, vasculature, and brain. Lastly, there is now evidence that sodium can affect the gut microbiome, and induce pro-inflammatory and immune responses, which might contribute to the development of salt-sensitive hypertension.

Matrix Metalloproteinases in Renal Diseases: A Critical Appraisal

Matrix metalloproteinases (MMPs) are endopeptidases within the metzincin protein family that not only cleave extracellular matrix (ECM) components, but also process the non-ECM molecules, including various growth factors and their binding proteins. MMPs participate in cell to ECM interactions, and MMPs are known to be involved in cell proliferation mechanisms and most probably apoptosis. These proteinases are grouped into six classes: collagenases, gelatinases, stromelysins, matrilysins, membrane type MMPs, and other MMPs. Various mechanisms regulate the activity of MMPs, inhibition by tissue inhibitors of metalloproteinases being the most important. In the kidney, intrinsic glomerular cells and tubular epithelial cells synthesize several MMPs. The measurement of circulating MMPs can provide valuable information in patients with kidney diseases. They play an important role in many renal diseases, both acute and chronic. This review attempts to summarize the current knowledge of MMPs in the kidney and discusses recent data from patient and animal studies with reference to specific diseases. A better understanding of the MMPs' role in renal remodeling may open the way to new interventions favoring deleterious renal changes in a number of kidney diseases.

JYYS Granule Mitigates Renal Injury in Clinic and in Spontaneously Hypertensive Rats by Inhibiting NF-κB Signaling-Mediated Microinflammation

Introduction

Hypertensive renal damage is a chronic and life-threatening kidney disease all over the world. The traditional Chinese medicine Jiang Ya Yi Shen (JYYS) granule has been a perfect drug for patients with hypertensive renal injury in clinic for 20 years in China. However, the molecular mechanism of JYYS granule remains unknown in treatment of this disease.

Methods

The clinic data were from this study's patients. The clinical symptoms of patients were indicated by (N-Acetyl-β-D-Glucosaminidase) NAG, (albumin) Alb, and (β2-microglobin) β2-MG content in urinary of patients, and renal artery's hemodynamic parameters including (pulse index) PI, mean velocity of the arterial blood (Vm), minimum velocity of the diastolic stage (Vdmin) and peak velocity of the systolic wave (Vsmax). To further observe the effect of JYYS granule on renal damage, the rats were included in six groups: normal rats (WKY), spontaneously hypertensive rats (SHR), positive drug-treated rats (Benazepril), low dose JYYS (L), middle dose JYYS (M), and high dose JYYS (H). Then, we observed the effect of JYYS on renal function, renal tubules, inflammatory cell infiltration, and small artery thickening, and we explored the potential mechanism of JYYS in treatment of renal injury.

Results

JYYS significantly improved the clinic symptoms of patients with hypertensive nephropathy by downregulating NAG, Alb, and β2-MG content in urinary of patients and by decreasing renal artery's hemodynamic parameters including PI, Vm, Vdmin, and Vsmax. In SHR, JYYS significantly improved renal function including creatinine clearance rate, urinary albumin/creatinine, β2-MG/creatinine and arteria caudalis pressure in SHR. Secondly, light and electron microscopic examinations told that after administration of JYYS and Benazepril, the mesangial region exhibited no hyperplasia and renal capsule did not expanded, and there no abnormalities were observed in renal tubules, inflammatory cell infiltration and small artery thickening in SHR. Thirdly, JYYS exhibited its protective role by inhibiting nuclear factor kappa beta signaling-mediated micro-inflammation cytokines including interleukin 6 (IL-6), tumor necrosis factor α (TNF-α), intercellular cell adhesion molecule-1 (ICAM-1), and monocyte chemotactic protein 1 (MCP-1) in SHR.

Conclusion

JYYS is a promising prescription of Chinese medicine for patients with hypertension and hypertensive renal damage.

Candesartan targeting of angiotensin II type 1 receptor demonstrates benefits for hypertension in pregnancy via the NF‑κB signaling pathway

Hypertensive disorders may be a complication of pregnancy and are characterized by the high blood pressure. Evidence suggests that alterations in the renin-angiotensin-aldosterone system and the sympathetic nervous system are associated with gestational hypertension. Angiotensin II type 1 receptor (Ang-IITR) is a potential target in the progression of gestational hypertension. Candesartan is selective Ang-IITR antagonist that may act against vasoconstriction and reduces peripheral vascular resistance. The aim of the present study was to evaluate the efficacy of Candesartan and the underlying molecular mechanism of the nuclear factor-κB (NF-κB) signaling pathway in the progression of gestational hypertension in a mouse model. Expression and activity of Ang-IITR was evaluated in a mouse model of gestational hypertension prior to and post-treatment of Candesartan both in vitro and in vivo. It was determined whether Candesartan treatment reduces higher blood pressure activated the renal renin-angiotensin system and a prognostic marker, soluble endoglin, and its associated gene in mice with gestational hypertension. Angiotensin-converting enzyme plasma levels and activity were also evaluated in the present study. Cytoplasmic and nuclear immunostaining of NF-κB and associated proteins transforming growth factor β (TGF-β) and endoglin was enhanced in vascular endothelial cells and mice with gestational hypertension. Soluble fms-like tyrosine kinase 1 (sFlt-1), insulin resistance homeostasis model assessment score and associated cardiovascular risk factors also were measured. Results demonstrated that angiotensin and Ang-IITR expression levels were upregulated in mice with gestational hypertension and were downregulated by Candesartan treatment. Renal renin-angiotensin and soluble endoglin were also improved in mice in the Candesartan-treated group. In addition, Candesartan treatment enhanced NF-κB activity, as well as TGF-β and vascular endothelial growth factor expression which led to improved levels of sFlt-1, insulin resistance homeostasis and associated cardiovascular risk factors. Gestational hypertension was markedly improved by treatment of Candesartan compared with the control. In conclusion, the findings of the present study suggested that the NF-κB signaling pathway may be involved in with Candesartan-mediated Ang-IITR for the treatment of gestational hypertension.

Resveratrol ameliorates renal injury in spontaneously hypertensive rats by inhibiting renal micro-inflammation

Micro-inflammation plays an important role in the pathogenesis of spontaneously hypertensive rat (SHR). In the present study, we investigated the therapeutic potential of resveratrol (RSV), a polyphenol with anti-fibrosis activity in hypertensive renal damage model. In SHR renal damage model, RSV treatment blunted the increase in urine albumin excretion, urinary β2-microglobulin (β2-MG), attenuated the decrease in creatinine clearance rate (CCR). The glomerular sclerosis index (1.54±0.33 compared with 0.36±0.07) and tubulointerstitial fibrosis (1.57±0.31 compared with 0.19±0.04) were significantly higher in SHRs compared with Wistar Kyoto rats (WKYs), which were significantly lower by RSV treatment. The increases in mesangium accumulation and the expression of renal collagen type I (Col I), fibronectin (Fn), plasminogen activator inhibitor-1 (PAI-1) and transforming growth factor-β1 (TGF-β1) in SHR were also reduced by RSV treatment. Nuclear factor κB (NF-κB) expression was increased in the cytoplasm and nuclei of the SHR kidneys, which was significantly decreased by RSV treatment. Furthermore, the protein level of IκB-α significantly decreased in the kidneys of the SHR when compared with the WKYs. RSV treatment partially restored the decreased IκB-α level. In SHR kidney, increased expression of interleukin-6 (IL-6), intercellular adhesion molecule-1 (ICAM-1) and monocyte chemoattractant protein 1 (MCP-1) were observed. These changes were attenuated by RSV treatment. No changes in blood pressure were detected between SHR group and SHR + RSV group. Taken together, the present study demonstrated that RSV treatment may significantly attenuate renal damage in the SHR model of chronic kidney disease (CKD). The renal protective effect is associated with inhibition of IL-6, ICAM-1 and MCP-1 expression via the regulation of the nuclear translocation of NF-κB, which suggesting that micro-inflammation may be a potential therapeutic target of hypertensive renal damage.

Renal Tumor Necrosis Factor α Contributes to Hypertension in Dahl Salt-Sensitive Rats

Tumor necrosis factor α (TNFα) is a major proinflammatory cytokine and its level is elevated in hypertensive states. Inflammation occurs in the kidneys during the development of hypertension. We hypothesized that TNFα specifically in the kidney contributes to the development of hypertension and renal injury in Dahl salt-sensitive (SS) rats, a widely used model of human salt-sensitive hypertension and renal injury. SS rats were chronically instrumented for renal interstitial infusion and blood pressure measurement in conscious, freely moving state. Gene expression was measured using real-time PCR and renal injury assessed with histological analysis. The abundance of TNFα in the renal medulla of SS rats, but not the salt-insensitive congenic SS.13^BN26 rats, was significantly increased when rats had been fed a high-salt diet for 7 days (n = 6 or 9, p < 0.01). The abundance of TNFα receptors in the renal medulla was significantly higher in SS rats than SS.13^BN26 rats. Renal interstitial administration of Etanercept, an inhibitor of TNFα, significantly attenuated the development of hypertension in SS rats on a high-salt diet (n = 7–8, p < 0.05). Glomerulosclerosis and interstitial fibrosis were also significantly ameliorated. These findings indicate intrarenal TNFα contributes to the development of hypertension and renal injury in SS rats.

Differential role of afferent and efferent renal nerves in the maintenance of early- and late-phase Dahl S hypertension

Clinical data suggest that renal denervation (RDNX) may be an effective treatment for human hypertension; however, it is unclear whether this therapeutic effect is due to ablation of afferent or efferent renal nerves. We have previously shown that RDNX lowers arterial pressure in hypertensive Dahl salt-sensitive (S) rats to a similar degree observed in clinical trials. In addition, we have recently developed a method for selective ablation of afferent renal nerves (renal-CAP). In the present study, we tested the hypothesis that the antihypertensive effect of RDNX in the Dahl S rat is due to ablation of afferent renal nerves by comparing the effect of complete RDNX to renal-CAP during two phases of hypertension in the Dahl S rat. In the early phase, rats underwent treatment after 3 wk of high-NaCl feeding when mean arterial pressure (MAP) was ∼ 140 mmHg. In the late phase, rats underwent treatment after 9 wk of high NaCl feeding, when MAP was ∼ 170 mmHg. RDNX reduced MAP ∼ 10 mmHg compared with sham surgery in both the early and late phase, whereas renal-CAP had no antihypertensive effect. These results suggest that, in the Dahl S rat, the antihypertensive effect of RDNX is not dependent on pretreatment arterial pressure, nor is it due to ablation of afferent renal nerves.

Depressor effect of chymase inhibitor in mice with high salt-induced moderate hypertension

The aim of the present study was to determine whether long-term high salt intake in the drinking water induces hypertension in wild-type (WT) mice and whether a chymase inhibitor or other antihypertensive drugs could reverse the increase of blood pressure. Eight-week-old male WT mice were supplied with drinking water containing 2% salt for 12 wk (high-salt group) or high-salt drinking water plus an oral chymase inhibitor (TPC-806) at four different doses (25, 50, 75, or 100 mg/kg), captopril (75 mg/kg), losartan (100 mg/kg), hydrochlorothiazide (3 mg/kg), eplerenone (200 mg/kg), or amlodipine (6 mg/kg). Control groups were given normal water with or without the chymase inhibitor. Blood pressure and heart rate gradually showed a significant increase in the high-salt group, whereas a dose-dependent depressor effect of the chymase inhibitor was observed. There was also partial improvement of hypertension in the losartan- and eplerenone-treated groups but not in the captopril-, hydrochlorothiazide-, and amlodipine-treated groups. A high salt load significantly increased chymase-dependent ANG II-forming activity in the alimentary tract. In addition, the relative contribution of chymase to ANG II formation, but not actual average activity, showed a significant increase in skin and skeletal muscle, whereas angiotensin-converting enzyme-dependent ANG II-forming activity and its relative contribution were reduced by high salt intake. Plasma and urinary renin-angiotensin system components were significantly increased in the high-salt group but were significantly suppressed in the chymase inhibitor-treated group. In conclusion, 2% salt water drinking for 12 wk caused moderate hypertension and activated the renin-angiotensin system in WT mice. A chymase inhibitor suppressed both the elevation of blood pressure and heart rate, indicating a definite involvement of chymase in salt-sensitive hypertension.

IL-1β and IL-18: inflammatory markers or mediators of hypertension?

Chronic inflammation in the kidneys and vascular wall is a major contributor to hypertension. However, the stimuli and cellular mechanisms responsible for such inflammatory responses remain poorly defined. Inflammasomes are crucial initiators of sterile inflammation in other diseases such as rheumatoid arthritis and gout. These pattern recognition receptors detect host-derived danger-associated molecular patterns (DAMPs), such as microcrystals and reactive oxygen species, and respond by inducing activation of caspase-1. Caspase-1 then processes the cytokines pro-IL-1β and pro-IL-18 into their active forms thus triggering inflammation. While IL-1β and IL-18 are known to be elevated in hypertensive patients, no studies have examined whether this occurs downstream of inflammasome activation or whether inhibition of inflammasome and/or IL-1β/IL-18 signalling prevents hypertension. In this review, we will discuss some known actions of IL-1β and IL-18 on leukocyte and vessel wall function that could potentially underlie a prohypertensive role for these cytokines. We will describe the major classes of inflammasome-activating DAMPs and present evidence that at least some of these are elevated in the setting of hypertension. Finally, we will provide information on drugs that are currently used to inhibit inflammasome/IL-1β/IL-18 signalling and how these might ultimately be used as therapeutic agents for the clinical management of hypertension.

Decrease in IL-10 and increase in TNF-α levels in renal tissues during systemic inhibition of nitric oxide in anesthetized mice

Earlier, we demonstrated that the inhibition of nitric oxide synthase (NOS) by nitro‐l‐arginine methyl ester (l‐NAME) infusion increases the endogenous production of proinflammatory cytokine, tumor necrosis factor (TNF‐α). In the present study, we examined the hypothesis that inhibition of nitric oxide (NO) production leads to the suppression of interleukin (IL)‐10 (anti‐inflammatory cytokine) generation which facilitates the enhancement of TNF‐α production endogenously. Using appropriate enzyme‐linked immunosorbent assay kits and immunohistochemical staining, the levels of IL‐10 and TNF‐α in plasma (P) and in renal tissues (R) were measured in anesthetized mice (C57BL/6; ~10 weeks age; n = 6/group) infused with or without l‐NAME (200 μg/min/kg; i.v. for 2 h). Compared to vehicle‐treated control mice, l‐NAME‐treated mice had a lower level of IL‐10 (P, 0.3 ± 0.1 vs. 2.6 ± 0.6 ng/mL; R, 0.5 ± 0.1 vs. 3 ± 0.1 ng/mg protein) and a higher level of TNF‐α (P, 432 ± 82 vs. undetected pg/mL; R, 58 ± 7 vs. 6 ± 5 pg/mg protein). IL‐10 protein expression, present mostly in the distal nephron segments in control mice, was markedly downregulated in l‐NAME‐treated mice. Compared to control mice, TNF‐α expression increased 2.5‐fold in renal cortical sections (mostly in the distal nephron segments) in l‐NAME‐treated mice. Coinfusion of a NO donor, S‐nitroso‐N‐acetyl‐penicillamine (SNAP; 25 μg/min/kg) with l‐NAME in a separate group of mice prevented these changes in IL‐10 and TNF‐α induced by l‐NAME. IL‐10 infusion (0.075 ng/min/g) in l‐NAME‐treated mice markedly attenuated l‐NAME‐induced increments in TNF‐α. Thus, these results demonstrate that NOS inhibition decreases endogenous IL‐10 generation and thus, minimizes its immune downregulating action on the TNF‐α production in the kidney.

In this study in mice, we examined the hypothesis that NOS inhibition reduces the endogenous production of anti‐inflammatory cytokine, IL‐10 which facilitates enhanced production of TNF‐α in the kidney. Using appropriate enzyme‐linked immunosorbent assay kits and immunohistochemical staining, levels of IL‐10 and TNF‐α in renal tissue were measured in anesthetized mice infused with or without l‐NAME (200 μg/min/kg) in the presence or absence of a NO donor, S‐nitroso‐N‐acetyl‐penicillamine (SNAP; 25 μg/min/kg) or IL‐10 infusion (0.075 ng/min/g). These results demonstrate that NOS inhibition decreases endogenous IL‐10 generation and thus, minimizes its immune downregulating action on the TNF‐α production in the kidney.

Protective role of the endothelial isoform of nitric oxide synthase in ANG II-induced inflammatory responses in the kidney

In the present study, we examine the hypothesis that the nitric oxide (NO) produced by endothelial NO synthase (eNOS) plays a protective role in the development of ANG II-induced hypertension and renal injury by minimizing oxidative stress and the inflammation induced by TNF-α. Systolic blood pressure (SBP) and renal injury responses to chronic infusions of ANG II (via implanted minipumps) were evaluated for 2 wk in wild-type (WT) and in eNOS knockout mice (KO) cotreated with or without a superoxide (O2(-)) scavenger, tempol (400 mg/l in the drinking water), or a TNF-α receptor blocker, etanercept (5 mg/kg/day ip). In study 1, when ANG II was given at a dose of 25 ng/min, it increased mean SBP in WT mice (Δ36 ± 3 mmHg; n = 7), and this effect was attenuated in mice pretreated with tempol (Δ24 ± 3 mmHg; n = 6). In KO mice (n = 9), this dose of ANG II resulted in severe renal injury associated with high mortality. To avoid this high mortality in KO, study 2 was conducted with a lower dose of ANG II (10 ng/min) that increased SBP slightly in WT (Δ17 ± 7 mmHg; n = 6) but exaggeratedly in KO (Δ48 ± 12 mmHg, n = 6) associated with severe renal injury. Cotreatment with either tempol (n = 6) or etanercept (n = 6) ameliorated the hypertensive, as well as the renal injury responses in KO compared with WT. These data demonstrate a protective role for eNOS activity in preventing renal inflammatory injury and hypertension induced by chronic increases in ANG II.

Age-dependent salt hypertension in Dahl rats: fifty years of research

Fifty years ago, Lewis K. Dahl has presented a new model of salt hypertension - salt-sensitive and salt-resistant Dahl rats. Twenty years later, John P. Rapp has published the first and so far the only comprehensive review on this rat model covering numerous aspects of pathophysiology and genetics of salt hypertension. When we summarized 25 years of our own research on Dahl/Rapp rats, we have realized the need to outline principal abnormalities of this model, to show their interactions at different levels of the organism and to highlight the ontogenetic aspects of salt hypertension development. Our attention was focused on some cellular aspects (cell membrane function, ion transport, cell calcium handling), intra- and extrarenal factors affecting renal function and/or renal injury, local and systemic effects of renin-angiotensin-aldosterone system, endothelial and smooth muscle changes responsible for abnormal vascular contraction or relaxation, altered balance between various vasoconstrictor and vasodilator systems in blood pressure maintenance as well as on the central nervous and peripheral mechanisms involved in the regulation of circulatory homeostasis. We also searched for the age-dependent impact of environmental and pharmacological interventions, which modify the development of high blood pressure and/or organ damage, if they influence the salt-sensitive organism in particular critical periods of development (developmental windows). Thus, severe self-sustaining salt hypertension in young Dahl rats is characterized by pronounced dysbalance between augmented sympathetic hyperactivity and relative nitric oxide deficiency, attenuated baroreflex as well as by a major increase of residual blood pressure indicating profound remodeling of resistance vessels. Salt hypertension development in young but not in adult Dahl rats can be attenuated by preventive increase of potassium or calcium intake. On the contrary, moderate salt hypertension in adult Dahl rats is attenuated by superoxide scavenging or endothelin-A receptor blockade which do not affect salt hypertension development in young animals.

Significance of estimated salt excretion as a possible predictor of the efficacy of concomitant angiotensin receptor blocker (ARB) and low-dose thiazide in patients with ARB resistance

The purpose of this study was to assess the factors affecting the efficacy of combination therapy with losartan and thiazide, with a focus on the significance of salt excretion, via a multicenter observational study. Adult patients with essential hypertension showing therapy resistance to angiotensin receptor blocker (ARB) as a monotherapy or in combination with Ca channel blockers (CCB) were enrolled, and their previously administered ARBs were replaced with the combination tablet containing losartan (50 mg per day) and hydrochlorothiazide (12.5 mg per day). Blood pressure and biochemical parameters were monitored for a year. The baseline blood pressure (153.4±14.8/86.4±11.3 mm Hg) was significantly lowered at the 3rd month (137.3±17.4/78.2±11.1 mm Hg, n=93) and was maintained at this lower level until the 12th month (135.3±14.0/76.4±11.1 mm Hg, n=74). The baseline value of estimated salt excretion (eSE), calculated using Tanaka's formula, differed significantly between the high and low treatment response groups, which were defined by the average change in mean blood pressure (MBP-C, -11.3 mm Hg; eSE=10.8±2.9 g per day in high responders vs. 9.2±2.3 g per day in low responders, P=0.004). Univariate and multivariate analyses showed a significant correlation between eSE and MBP-C (R=-0.288, P=0.007) and indicated the clinical effectiveness of eSE as a possible predictor for MBP-C (P=0.021). In addition, the urine Na-to-Cr ratio (NCR) demonstrated significant correlations with eSE (R=0.848, P<0.001) and MBP-C (R=-0.344, P<0.001). These results suggest that eSE or NCR could, to a certain extent, predict the efficacy of combination therapy with losartan and low-dose thiazide in patients demonstrating ARB resistance. Combination therapy with losartan and thiazide might thus be suitable for patients with a large amount of salt excretion.

TNF-α type 2 receptor mediates renal inflammatory response to chronic angiotensin II administration with high salt intake in mice

Tumor necrosis factor-alpha (TNF-α) has been implicated in salt-sensitive hypertension and renal injury (RI) induced by angiotensin II (ANG II). To determine the receptor type of TNF-α involved in this mechanism, we evaluated the responses to chronic ANG II infusion (25 ng/min by implanted minipump) given with high-salt diet (HS; 4% NaCl) for 2 wk in gene knockout mice for TNF-α receptor type 1 (TNFR1KO; n = 6) and type 2 (TNFR2KO; n = 6) and compared the responses with those in wild-type (WT; C57BL/6; n = 6) mice. Blood pressure in these mice was measured by implanted radiotelemetry as well as by tail-cuff plethysmography. RI responses were assessed by measuring macrophage cell infiltration (CD68(+) immunohistochemistry), glomerulosclerosis (PAS staining), and interstitial fibrosis (Gomori's trichrome staining) in renal tissues at the end of the treatment period. The increase in mean arterial pressure induced by ANG II + HS treatment was not different in these three groups of mice (TNFR1KO, 114 ± 1 to 161 ± 7 mmHg; TNFR2KO, 113 ± 1 to 161 ± 3 mmHg; WT, 110 ± 3 to 154 ± 3 mmHg). ANG II + HS-induced RI changes were similar in TNFR1KO mice but significantly less in TNFR2KO mice (macrophage infiltration, 0.02 ± 0.01 vs. 1.65 ± 0.45 cells/mm(2); glomerulosclerosis, 26.3 ± 2.6 vs. 35.7 ± 2.2% area; and interstitial fibrosis, 5.2 ± 0.6 vs. 8.1 ± 1.1% area) compared with the RI changes in WT mice. The results suggest that a direct activation of TNF-α receptors may not be required in inducing hypertensive response to chronic ANG II administration with HS intake, but the induction of inflammatory responses leading to renal injury are mainly mediated by TNF-α receptor type 2.

NKCC2A and NFAT5 regulate renal TNF production induced by hypertonic NaCl intake

Pathways that contribute to TNF production by the kidney are not well defined. Mice given 1% NaCl in the drinking water for 3 days exhibited a 2.5-fold increase in urinary, but not plasma, TNF levels compared with mice given tap water. Since furosemide attenuated the increase in TNF levels, we hypothesized that hypertonic NaCl intake increases renal TNF production by a pathway involving the Na(+)-K(+)-2Cl(-) cotransporter (NKCC2). A 2.5-fold increase in NKCC2A mRNA accumulation was observed in medullary thick ascending limb (mTAL) tubules from mice given 1% NaCl; a concomitant 2-fold increase in nuclear factor of activated T cells 5 (NFAT5) mRNA and protein expression was observed in the outer medulla. Urinary TNF levels were reduced in mice given 1% NaCl after an intrarenal injection of a lentivirus construct designed to specifically knockdown NKCC2A (EGFP-N2A-ex4); plasma levels of TNF did not change after injection of EGFP-N2A-ex4. Intrarenal injection of EGFP-N2A-ex4 also inhibited the increase of NFAT5 mRNA abundance in the outer medulla of mice given 1% NaCl. TNF production by primary cultures of mTAL cells increased approximately sixfold in response to an increase in osmolality to 400 mosmol/kgH2O produced with NaCl and was inhibited in cells transiently transfected with a dnNFAT5 construct. Transduction of cells with EGFP-N2A-ex4 also prevented increases in TNF mRNA and protein production in response to high NaCl concentration and reduced transcriptional activity of a NFAT5 promoter construct. Since NKCC2A expression is restricted to the TAL, NKCC2A-dependent activation of NFAT5 is part of a pathway by which the TAL produces TNF in response to hypertonic NaCl intake.

Interleukin-17 causes Rho-kinase-mediated endothelial dysfunction and hypertension

AIMS

Elevated levels of pro-inflammatory cytokine interleukin-17A (IL-17) are associated with hypertensive autoimmune diseases; however, the connection between IL-17 and hypertension is unknown. We hypothesized that IL-17 increases blood pressure by decreasing endothelial nitric oxide production.

METHODS AND RESULTS

Acute treatment of endothelial cells with IL-17 caused a significant increase in phosphorylation of the inhibitory endothelial nitric oxide (NO) synthase residue threonine 495 (eNOS Thr495). Of the kinases known to phosphorylate eNOS Thr495, only inhibition of Rho-kinase prevented the IL-17-induced increase. IL-17 caused a threefold increase in the Rho-kinase activator RhoA, and this was prevented by an IL-17 neutralizing antibody. In isolated mouse aortas, IL-17 significantly increased eNOS Thr495 phosphorylation, induced RhoA expression, and decreased NO-dependent relaxation responses, all of which were prevented by either an IL-17 neutralizing antibody or inhibition of Rho-kinase. In mice, IL-17 treatment for 1 week significantly increased systolic blood pressure and this was associated with decreased aortic NO-dependent relaxation responses, increased eNOS Thr495 phosphorylation, and increased RhoA expression. Inhibition of Rho-kinase prevented the hypertension caused by IL-17.

CONCLUSION

These data demonstrate that IL-17 activates RhoA/Rho-kinase leading to endothelial dysfunction and hypertension. Inhibitors of IL-17 or Rho-kinase may prove useful as anti-hypertensive drugs in IL-17-associated autoimmune diseases.

Tumor necrosis factor-α receptor type 1, not type 2, mediates its acute responses in the kidney

Acute administration of tumor necrosis factor-α (TNF-α) resulted in decreases in renal blood flow (RBF) and glomerular filtration rate (GFR) but induced diuretic and natriuretic responses in mice. To define the receptor subtypes involved in these renal responses, experiments were conducted to assess the responses to human recombinant TNF-α (0.3 ng·min(-1)·g body wt(-1) iv infusion for 75 min) in gene knockout (KO) mice for TNF-α receptor type 1 (TNFαR1 KO, n = 5) or type 2 (TNFαR2 KO, n = 6), and the results were compared with those obtained in corresponding wild-type [WT (C57BL/6), n = 6] mice. Basal levels of RBF (PAH clearance) and GFR (inulin clearance) were similar in TNFαR1 KO, but were lower in TNFαR2 KO, than WT mice. TNF-α infusion in WT mice decreased RBF and GFR but caused a natriuretic response, as reported previously. In TNFαR1 KO mice, TNF-α infusion failed to cause such vasoconstrictor or natriuretic responses; rather, there was an increase in RBF and a decrease in renal vascular resistance. Similar responses were also observed with infusion of murine recombinant TNF-α in TNFαR1 KO mice (n = 5). However, TNF-α infusion in TNFαR2 KO mice caused changes in renal parameters qualitatively similar to those observed in WT mice. Immunohistochemical analysis in kidney slices from WT mice demonstrated that while both receptor types were generally located in the renal vascular and tubular cells, only TNFαR1 was located in vascular smooth muscle cells. There was an increase in TNFαR1 immunoreactivity in TNFαR2 KO mice, and vice versa, compared with WT mice. Collectively, these functional and immunohistological findings in the present study demonstrate that the activation of TNFαR1, not TNFαR2, is mainly involved in mediating the acute renal vasoconstrictor and natriuretic actions of TNF-α.

Prevention of salt-induced renal injury by activation of NAD(P)H:quinone oxidoreductase 1, associated with NADPH oxidase

NADPH oxidase (NOX) is a predominant source of reactive oxygen species (ROS), and the activity of NOX, which uses NADPH as a common rate-limiting substrate, is upregulated by prolonged dietary salt intake. β-Lapachone (βL), a well-known substrate of NAD(P)H:quinone oxidoreductase 1 (NQO1), decreases the cellular NAD(P)H/NAD(P)(+) ratio via activation of NQO1. In this study, we evaluated whether NQO1 activation by βL modulates salt-induced renal injury associated with NOX-derived ROS regulation in an animal model. Dahl salt-sensitive (DS) rats fed a high-salt (HS) diet were used to investigate the renoprotective effect of NQO1 activation. βL treatment significantly lowered the cellular NAD(P)H:NAD(P)(+) ratio and dramatically reduced NOX activity in the kidneys of HS diet-fed DS rats. In accordance with this, total ROS production and expression of oxidative adducts also decreased in the βL-treated group. Furthermore, HS diet-induced proteinuria and glomerular damage were markedly suppressed, and inflammation, fibrosis, and apoptotic cell death were significantly diminished by βL treatment. This study is the first to demonstrate that activation of NQO1 has a renoprotective effect that is mediated by NOX activity via modulation of the cellular NAD(P)H:NAD(P)(+) ratio. These results provide strong evidence that NQO1 might be a new therapeutic target for the prevention of salt-induced renal injury.

Autocrine modulation of glucose transporter SGLT2 by IL-6 and TNF-α in LLC-PK(1) cells

We determined in cultured kidney epithelial cells (LLC-PK(1)) the effects of high glucose, interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) on mRNA and protein expression of the renal glucose transporters SGLT1 and SGLT2. Cultured monolayers were incubated with similar concentrations of IL-6 and TNF-α to those produced by LLC-PK(1) in the presence of 20 mM glucose. Confluent monolayers with either 5 (controls, C) or 20 mM glucose (high glucose, HG) were incubated in the presence of 5 mM glucose, 20 mM glucose, 10 pg/ml IL-6, or TNF-α alone or in combination. Separate groups with IL-6 and TNF-α were incubated with antibodies to their respective receptors. HG induced an increased SGLT1 mRNA at 48 h (p<0.05 vs. C) and protein expression in 120 h (p<0.05 vs. C). HG also induced an increased SGLT2 mRNA at 72 and 96 h (P<0.05 vs. C) and SGLT2 protein expression at 120 h (p<0.05 vs. C). In C, 10 pg/ml IL-6 or TNF-α did not modify SGLT1 mRNA (n.s vs. in the absence of cytokines). In contrast, cytokines induced an increased expression of SGLT1 protein at 120 h (p<0.05 vs. in the absence of cytokines), and SGLT2 mRNA and protein were increased at 96 and 120 h, respectively (p<0.05 vs. in absence of cytokines). No changes were observed when cells were incubated with cytokines and HG (n.s vs. C). In conclusion, this study showed that SGLT2 increased in the presence of IL-6 and TNF-α, indicating an autocrine modulation of the expression of this transporter by cytokines.

Activation of IKK/NF-κB provokes renal inflammatory responses in guanylyl cyclase/natriuretic peptide receptor-A gene-knockout mice

The present study was aimed at determining the consequences of the disruption of guanylyl cyclase/natriuretic peptide receptor-A (GC-A/NPRA) gene (Npr1) on proinflammatory responses of nuclear factor kappa B, inhibitory kappa B kinase, and inhibitory kappa B alpha (NF-κB, IKK, IκBα) in the kidneys of mutant mice. The results showed that the disruption of Npr1 enhanced the renal NF-κB binding activity by 3.8-fold in 0-copy (-/-) mice compared with 2-copy (+/+) mice. In parallel, IKK activity and IκBα protein phosphorylation were increased by 8- and 11-fold, respectively, in the kidneys of 0-copy mice compared with wild-type mice. Interestingly, IκBα was reduced by 80% and the expression of proinflammatory cytokines and renal fibrosis were significantly enhanced in 0-copy mice than 2-copy mice. Treatment of 0-copy mice with NF-κB inhibitors andrographolide, pyrrolidine dithiocarbamate, and etanercept showed a substantial reduction in renal fibrosis, attenuation of proinflammatory cytokines gene expression, and significantly reduced IKK activity and IkBα phosphorylation. These findings indicate that the systemic disruption of Npr1 activates the renal NF-κB pathways in 0-copy mice, which transactivates the expression of various proinflammatory cytokines to initiate renal remodeling; however, inhibition of NF-κB pathway repairs the abnormal renal pathology in mutant mice.

High salt intake fails to enhance plasma adiponectin in normotensive salt-sensitive subjects

OBJECTIVE

Evidence shows that salt can modulate adiponectin and inflammation levels in normal individuals. Therefore, we hypothesized that abnormalities in adiponectin and inflammation might be the potential mechanism of salt sensitivity. The aim of this study was to investigate whether different alterations of adiponectin and inflammation levels in response to a high-salt intake were exhibited between normotensive salt-sensitive and salt-resistant subjects.

METHODS

Thirty normotensive subjects (25 to 50 y old) were selected from a rural community of northern China. They were sequentially maintained on a normal diet for 3 d at baseline, a low-salt diet for 7 d (NaCl 3 g/d), and then a high-salt diet for 7 d (18 g/d).

RESULTS

Salt sensitivity was diagnosed in 10 subjects who exhibited an increase of at least 10% in mean blood pressure from the low-salt to the high-salt periods. Plasma adiponectin was significantly higher with the high-salt intake than with the low-salt intake (6.1 ± 1.3 versus 7.1 ± 1.7 μg/mL, P = 0.047) in normotensive salt-resistant subjects but not in the normotensive salt-sensitive subjects (6.4 ± 2 versus 5.9 ± 2.1 μg/mL, P = 0.481). The high-salt intake markedly increased plasma tumor necrosis factor-α (P < 0.0001) and monocyte chemoattractant protein-1 (P < 0.0001) in normotensive salt-sensitive and salt-resistant subjects. No significant change in plasma high-sensitivity C-reactive protein was observed.

CONCLUSIONS

Our data indicate that the disturbance of adiponectin exists in normotensive salt-sensitive subjects during a high-salt diet, which may be a novel underlying mechanism of salt sensitivity.

Physiological stress increases renal injury in eNOS-knockout mice

African Americans have a fourfold greater likelihood of developing end-stage renal disease (ESRD) compared with Caucasians. It has been proposed that the increased prevalence may be explained by non-traditional factors such as environmental stress and psychosocial factors. In this study, we used infrequent running to exhaustion as a physiological stressor to mimic real life experiences, such walking up stairs when an elevator is malfunctioning or running to catch a bus, to study its effect on renal injury in a hypertensive mouse model (endothelial nitric oxide synthase-deficient mice; eNOS(-/-)). This model has previously been shown to have renal injury comparable to that observed in African Americans. The effect of physiological stress on renal injury was examined in the setting of low (0.12%), control (0.45%) and high (8%) dietary salt. Following bouts of physiological stress, eNOS(-/-) mice had significantly greater interstitial inflammation compared with unstressed eNOS(-/-) mice (two-way analysis of variance (2-ANOVA), Holm-Sidak; P<0.01). Interestingly, eNOS(-/-) mice on a high-salt diet had greater interstitial inflammation compared with similarly stressed eNOS(-/-) mice on a low- or control-salt diet (2-ANOVA, Holm-Sidak; P<0.03). These effects of stress were independent of systolic blood pressure (141±7, 143±4, and 158±8 vs. 141±4, 138±5, 150±4 mm Hg; end of study vs. baseline, respectively). There was no significant effect of stress or dietary salt on renal injury in control wild-type mice (eNOS(+)/(+)). These data demonstrate that physiological stress exacerbates the renal injury associated with hypertension and that high-salt compounds this effect of stress. These results provide support for the idea that psychosocial and environmental factors contribute to the increased prevalence of ESRD in hypertensive African Americans.

Chronic antagonism of the mineralocorticoid receptor ameliorates hypertension and end organ damage in a rodent model of salt-sensitive hypertension

We investigated the effects of chronic mineralocorticoid receptor blockade with eplerenone on the development and progression of hypertension and end organ damage in Dahl salt-sensitive rats. Eplerenone significantly attenuated the progressive rise in systolic blood pressure (SBP) (204 ± 3 vs. 179±3 mmHg, p < 0.05), reduced proteinuria (605.5 ± 29.6 vs. 479.7 ± 26.1 mg/24h, p < 0.05), improved injury scores of glomeruli, tubules, renal interstitium, and vasculature in Dahl salt-sensitive rats fed a high-salt diet. These results demonstrate that mineralocorticoid receptor antagonism provides target organ protection and attenuates the development of elevated blood pressure (BP) in a model of salt-sensitive hypertension.

Salt sensitivity, insulin resistance, and public health in India

OBJECTIVE

To provide a current overview of the worldwide prevalence and pattern of cardiovascular disease and discuss the role of sodium intake and salt sensitivity, with a focus on the Asian Indian population.

METHODS

An extensive search of the literature from PubMed and the Cochrane Library was undertaken. Moreover, the pathophysiologic basis of the relationship between sodium intake and insulin sensitivity in various populations was reviewed.

RESULTS

High blood pressure is the most common cause of cardiovascular disease and mortality globally. Although salt sensitivity is a frequent determinant of hypertension, a strong link between salt sensitivity and cardiovascular disease associated with insulin resistance has not received adequate attention. This may be particularly relevant to the public health challenges of increasing prevalences of obesity, diabetes, and cardiometabolic syndrome in India where, according to recent estimates, approximately 60% of the world's cases of cardiovascular disease occur and the salt consumption is among the highest in any large population.

CONCLUSION

There is evidence for a strong link between increased salt sensitivity and insulin resistance leading to metabolic syndrome and cardiovascular disease. This relationship may be particularly relevant to the escalating epidemic of cardiovascular disease in the southern Asian Indian population. A broad-based community action to achieve at least a modest restriction of salt intake can yield important health benefits and is urgently needed.

Long-term high salt diet causes hypertension and alters renal cytokine gene expression profiles in Sprague-Dawley rats

OBJECTIVE

The present study examines whether a long-term high salt diet causes hypertension and renal injury in normal subjects [Sprague-Dawley (SD) rats] and alters renal cytokine-related gene expression profiles.

METHODS

Four 10 week old male SD rats received a high salt diet (HS, 8%) and the other 4 SD rats received a normal salt diet (NS, 0.5%) for 8 weeks. Mean arterial pressure (MAP) and renal damages such as albuminuria and histological renal injury were determined. The relative mRNA levels of 514 cytokine-related genes (normalized by beta-actin) in rat kidneys following NS or HS were determined quantitatively through analysis of 4 sets of gene expression profiles using the mouse cDNA membrane microarrays.

RESULTS

We demonstrated that 8 weeks of HS diet increased MAP [(140.0+/-5.3) vs (112.0+/-2.2) mmHg; 1 mmHg=0.133 kPa, P<0.01], albuminuria [(41.4+/-3.2) vs (20.1+/-4.5) mg/d; P<0.01], and caused histological renal injury in SD rats, compared to NS group. Of the 514 genes in the array, there were 27 (5.25%) genes with significantly different expression in the kidney of SD rats with HS compared to those of SD rats with NS. Functional clustering analysis indicated the following functional pathways related to high salt diet-induced hypertension: (1) pro-inflammatory response ( upward arrowIL-17, CCL28; downward arrow NFkappabib); (2) endothelial dysfunction ( downward arrowVEGF-A, VEGF-B, endoglin); (3) pro-matrix formation ( upward arrowosteopontin, IGFBP-5; downward arrow IFN-gamma); and (4) attenuated cell survival and differentiation ( downward arrowCNTF, IGF-II R, ephrin-B1). Northern blot confirmed that 8 weeks of HS diet significantly decreased renal expression of VEGF mRNA, compared to NS group (P<0.01). ELISA showed that HS diet significantly decreased renal protein levels of VEGF and CCL28.

CONCLUSION

These findings support the hypothesis that hypertension can be induced in normal rats by a long-term high salt diet, which is associated with increased renal injury and marked changes in renal cytokine gene expression profiles that are closely related to the pro-inflammatory response, pro-matrix formation, endothelial dysfunction, and attenuated cell survival and differentiation.

Mechanisms and consequences of salt sensitivity and dietary salt intake

PURPOSE OF REVIEW

Investigation into the underlying mechanisms of salt sensitivity has made important advances in recent years. This review examines in particular the effects of sodium and potassium on vascular function.

RECENT FINDINGS

Sodium chloride (salt) intake promotes cutaneous lymphangiogenesis mediated through tissue macrophages and directly alters endothelial cell function, promoting increased production of transforming growth factor-β (TGF-β) and nitric oxide. In the setting of endothelial dysfunction, such as occurs with aging, diminished nitric oxide production exacerbates the vascular effects of TGF-β, promoting decreased arterial compliance and hypertension. Dietary potassium intake may serve as an important countervailing influence on the effects of salt in the vasculature.

SUMMARY

There is growing appreciation that, independently of alterations in blood pressure, dietary intake of sodium and potassium promotes functional changes in the vasculature and lymphatic system. These changes may protect against development of salt-sensitive hypertension. While salt sensitivity cannot be ascribed exclusively to these factors, perturbation of these processes promotes hypertension during high-salt intake. These studies add to the list of genetic and environmental factors that are associated with salt sensitivity, but in particular provide insight into adaptive mechanisms during high salt intake.

High-salt diet and hypertension: focus on the renin-angiotensin system

A high-salt diet is one of the major risk factors in the development and maintenance of hypertension. Numerous experimental and observational studies have confirmed the association of sodium intake with blood pressure levels. The effects of a high-salt diet are related to the function of the renin-angiotensin system, which is normally suppressed by a high-salt diet. Endothelial dysfunction probably plays an important role in the influence of high sodium intake on blood pressure, although the exact mechanisms remain elusive. Genetic factors are known to be very important, and various consomic and congenic rat strains as animal models have proven to be very useful in bringing us a step closer to understanding the interaction between salt intake and hypertension. In this article, experimental data obtained in studies on animals and humans, as well as epidemiological data are reviewed.

Captopril reduces cardiac inflammatory markers in spontaneously hypertensive rats by inactivation of NF-kB

Background

Captopril is an angiotensin-converting enzyme (ACE) inhibitor widely used in the treatment of arterial hypertension and cardiovascular diseases. Our objective was to study whether captopril is able to attenuate the cardiac inflammatory process associated with arterial hypertension.

Methods

Left ventricle mRNA expression and plasma levels of pro-inflammatory (interleukin-1β (IL-1β) and IL-6) and anti-inflammatory (IL-10) cytokines, were measured in spontaneously hypertensive rats (SHR) and their control normotensive, Wistar-Kyoto (WKY) rats, with or without a 12-week treatment with captopril (80 mg/Kg/day; n = six animals per group). To understand the mechanisms involved in the effect of captopril, mRNA expression of ACE, angiotensin II type I receptor (AT1R) and p22phox (a subunit of NADPH oxidase), as well as NF-κB activation and expression, were measured in the left ventricle of these animals.

Results

In SHR, the observed increases in blood pressures, heart rate, left ventricle relative weight, plasma levels and cardiac mRNA expression of IL-1β and IL-6, as well as the reductions in the plasma levels and in the cardiac mRNA expression of IL-10, were reversed after the treatment with captopril. Moreover, the mRNA expressions of ACE, AT1R and p22phox, which were enhanced in the left ventricle of SHR, were reduced to normal values after captopril treatment. Finally, SHR presented an elevated cardiac mRNA expression and activation of the transcription nuclear factor, NF-κB, accompanied by a reduced expression of its inhibitor, IκB; captopril administration corrected the observed changes in all these parameters.

Conclusion

These findings show that captopril decreases the inflammation process in the left ventricle of hypertensive rats and suggest that NF-κB-driven inflammatory reactivity might be responsible for this effect through an inactivation of NF-κB-dependent pro-inflammatory factors.

Involvement of tumor necrosis factor-alpha in natriuretic response to systemic infusion of nitric oxide synthase inhibitor in anesthetized mice

Systemic infusion of TNF-alpha exerts renal vasoconstriction but caused marked natriuresis in mice. Similar renal responses were also observed during systemic infusion of nitric oxide (NO) synthase inhibitors as opposed to their usual antinatriuretic responses when administered intrarenally. In the present study, we examined the hypothesis that acute NO blockade systemically induces TNF-alpha generation. which induces this natriuretic response. Renal responses to intravenous infusion of the NO synthase inhibitor nitro-L-arginine methyl ester (L-NAME; 0.2 microg x min(-1) x g body wt(-1) for 85 min) and its impact on the plasma level of TNF-alpha were evaluated in anesthetized mice. Plasma TNF-alpha was undetected in untreated mice (n = 7) but was elevated in L-NAME-treated mice (109 +/- 22 pg/ml; P < 0.01 vs. untreated group; n = 7) along with an increase in TNF-alpha protein expression in kidney tissue. L-NAME infusion caused a usual increase in mean arterial pressure (MAP; 98 +/- 3 to 122 +/- 3 mmHg; P < 0.01) and decreases in renal blood flow (RBF; 8.6 +/- 0.3 to 4.4 +/- 0.2 ml x min(-1) x g(-1); P < 0.01) and glomerular filtration rate (GFR; 1.14 +/- 0.07 to 0.77 +/- 0.04 ml x min(-1) x g(-1); P < 0.01) with a marked increase in sodium excretion (U(Na)V; 0.48 +/- 0.10 to 3.52 +/- 0.85 micromol x min(-1) x g(-1); P < 0.01). Interestingly, in mice (n = 7) pretreated with the TNF-alpha blocker etanercept (5 mg/kg sc), the U(Na)V response to l-NAME infusion was markedly blunted (0.58 +/- 0.08 to 1.22 +/- 0.28 micromol x min(-1) x g(-1); P = NS) although responses for MAP, RBF, and GFR were mostly unchanged. However, pretreatment with the superoxide scavenger tempol in mice (n = 7) did not alter the U(Na)V response to L-NAME. These data demonstrate that L-NAME-induced natriuresis is mediated, at least in part, by concomitant generation of TNF-alpha during NO blockade.

Tumor necrosis factor-alpha: a possible priming agent for the polymorphonuclear leukocyte-reduced nicotinamide-adenine dinucleotide phosphate oxidase in hypertension

In the Sabra rat, oxidative stress (OS) and inflammation precede the development of hypertension. Inhibition of the phagocytic NADPH oxidase attenuates the rise in blood pressure. The present study was set to identify possible priming agents for this enzyme and to test the hypothesis that the phagocytic NADPH oxidase contributes to OS and inflammation. Sabra salt-sensitive and Sabra salt-resistant rats were salt loaded or provided regular chow for 60 days with or without apocynin to inhibit NADPH oxidase. Levels of interleukin 6, tumor necrosis factor-alpha, and interferon-gamma served as indices of inflammation. Extracellular and intracellular levels of the polymorphonuclear leukocyte tumor necrosis factor-alpha receptors (p55 and p75) were assessed by flow cytometry in young and adult rats. NADPH oxidase activity and expression of p47phox were measured in polymorphonuclear leukocytes and aortic rings. Malondialdehyde and carbonylated fibrinogen served as indices of OS. Inflammatory and OS indices excluding interferon-gamma were higher in the hypertensive state and reduced by apocynin. Levels of malondialdehyde and tumor necrosis factor-alpha were elevated already in the prehypertensive state. No differences were found in the levels of p75. The extracellular expression of p55 was higher in adult Sabra salt-resistant compared with Sabra salt-sensitive rats (7.46+/-2.2% versus 2.1+/-0.5%; P<0.05), whereas levels of the intracellular p55 were higher in adult Sabra salt-sensitive rats (3.2+/-2% versus 1.1+/-0.5%; P<0.05). In young normotensive rats, the extracellular levels of p55 were higher in Sabra salt-sensitive compared with Sabra salt-resistant rats (10.6+/-5.2% versus 2.9+/-1.5%; P<0.01). Tumor necrosis factor-alpha plays a role in activation of the polymorphonuclear leukocyte NADPH oxidase, thereby contributing to systemic OS, inflammation, and the development of hypertension in this model.

Effects of a high-salt diet on adipocyte glucocorticoid receptor and 11-beta hydroxysteroid dehydrogenase 1 in salt-sensitive hypertensive rats

High-salt diets decrease insulin sensitivity in salt-sensitive hypertensive rats, and glucocorticoids promote adipocyte growth and may have pathophysiological roles in the metabolic syndrome. The aim of this study was to clarify the relationship between high-salt diet and the adipocyte glucocorticoid hormones in salt-sensitive hypertensive rats. Six-week-old Dahl salt-sensitive (DS) hypertensive rats and salt-resistant (DR) rats were fed a high-salt diet or a normal-salt diet for 4 weeks. Fasting blood glucose (FBG), serum adiponectin, plasma insulin, and corticosterone in plasma and in visceral adipose tissues, 11beta-hydroxysteroid dehydrogenase 1 (11beta-HSD1) activities in adipose tissues and glucose uptake in isolated muscle were measured. Animals underwent an oral glucose tolerance test (OGTT). The expression of mRNA for glucocorticoid receptor (GR), 11beta-HSD1 and tumor necrosis factor-alpha (TNF-alpha) in adipose tissues were measured using a real-time PCR. A high-salt diet did not influence FBG; however, decreased 2-deoxy glucose uptake and plasma insulin during OGTT in DS rats. The high-salt diet increased significantly adipose tissue corticosterone concentration and 11beta-HSD1 activities, gene expression for GR, 11beta-HSD1 and TNF-alpha in adipose tissues in DS rats compared with DR rats (p<0.05). The high-salt diet did not influence plasma corticosterone and serum adiponectin concentration in DS and DR rats. These results suggest that changes in GR and 11beta-HSD1 in adipose tissue may contribute to insulin sensitivity in salt-sensitive hypertensive rats.

Aggravated renal inflammatory responses in TRPV1 gene knockout mice subjected to DOCA-salt hypertension

To test the hypothesis that deletion of the transient receptor potential vanilloid type 1 (TRPV1) channel exaggerates hypertension-induced renal inflammatory response, wild-type (WT) or TRPV1-null mutant (TRPV1(-/-)) mice were subjected to uninephrectomy and deoxycorticosterone acetate (DOCA)-salt treatment for 4 wk. Mean arterial pressure (MAP) determined by radiotelemetry increased in DOCA-salt-treated WT or TRPV1(-/-) mice, whereas there was no difference in MAP between two strains at the baseline or after DOCA-salt treatment. DOCA-salt treatment increased urinary excretion of albumin and 8-isoprostane in both WT and TRPV1(-/-) mice, and the increases were greater in magnitude in the latter strain. Periodic acid-Schiff and Mason's trichrome staining showed that kidneys of DOCA-salt-treated TRPV1(-/-) mice exhibited more severe glomerulosclerosis and tubulointerstitial injury compared with DOCA-salt-treated WT mice. NF-kappaB assay showed that DOCA-salt treatment increased renal activated NF-kappaB concentrations in TRPV1(-/-) mice compared with WT mice. Immunostaining and ELISA assay revealed that DOCA-salt-treated TRPV1(-/-) mice had enhanced renal infiltration of monocyte/macrophage and lymphocyte, as well as increased renal levels of proinflammatory cytokine (TNF-alpha, IL-6) and chemokine (MCP-1) compared with DOCA-salt-treated WT mice. Renal ICAM-1 but not VCAM-1 expression was also greater in DOCA-salt-treated TRPV1(-/-) than WT mice. Dexamethasone (DEXA), an immunosuppressive drug, conveyed a renoprotective effect that was greater in DOCA-salt-treated TRPV1(-/-) compared with WT mice. These data show that renal inflammation is exacerbated in DOCA-salt hypertension when TRPV1 gene is deleted and that the deterioration is ameliorated by DEXA treatment, indicating that TRPV1 may act as a potential regulator of the inflammatory process to lessen renal injury in DOCA-salt hypertension.

Vascular endothelial growth factor receptor inhibitor enhances dietary salt-induced hypertension in Sprague-Dawley rats

Clinical evidence links the inhibition of VEGF to hypertension. However, the mechanisms by which VEGF affects the pathogenesis of hypertension remain in question. We determined 1) whether administration of VEGF receptor inhibitor SU5416 enhances dietary salt-induced hypertension in Sprague-Dawley (SD) rats, and 2) whether VEGF or SU5416 directly affects proliferation of cultured human renal proximal tubular epithelial cells (HRPTEC) and endothelial nitric oxide synthase (eNOS) expression in cultured human glomerular microvessel endothelial cells (HGMEC). Ten 10-wk-old male SD rats received a high sodium diet (HS; 8%) and the other 10 SD rats received a normal sodium diet (NS; 0.5%) for 4 wks. After 2 wks of the dietary program, five rats were administered with SU5416 at 10 mg x kg(-1) x day(-1) ip or DMSO (vehicle) for 14 days in HS and NS groups. Mean arterial pressure was significantly higher in rats treated with SU5416, as opposed to those treated with DMSO and fed with HS for 4 wk (157.6 +/- 3.9 vs. 125.9 +/- 4.3 mmHg, P < 0.01). Increased proteinuria and albuminuria were associated with marked renal histological abnormalities in HS group with SU5416 administration, compared with those in the vehicle HS group. 3H-thymidine incorporation assay showed that SU5416 blocked the actions of both exogenous and endogenous VEGF on the proliferation of HRPTEC. VEGF (10 ng/ml) significantly increased eNOS protein levels by 29% in cultured HGMEC, but its action was completely abolished by SU5416. These results suggest that VEGF receptor inhibition enhances dietary salt-induced hypertension and kidney injury, possibly by direct damage on renal cells and decreasing NO production by eNOS.

Vascular consequences of dietary salt intake

Animal and human studies support an untoward effect of excess dietary NaCl (salt) intake on cardiovascular and renal function and life span. Recent work has promoted the concept that the endothelium, in particular, reacts to changes in dietary salt intake through a complex series of events that are independent of blood pressure and the renin-angiotensin-aldosterone axis. The cellular signaling events culminate in the intravascular production of transforming growth factor-beta (TGF-beta) and nitric oxide in response to increased salt intake. Plasticity of the endothelium is integral in the vascular remodeling consequences associated with excess salt intake, because nitric oxide serves as a negative regulator of TGF-beta production. Impairment of nitric oxide production, such as occurs with endothelial dysfunction in a variety of disease states, results in unopposed excess vascular TGF-beta production, which promotes reduced vascular compliance and augmented peripheral arterial constriction and hypertension. Persistent alterations in vascular function promote the increase in cardiovascular events and reductions in renal function that reduce life span during increased salt intake.

Tumor necrosis factor-alpha induces renal vasoconstriction as well as natriuresis in mice

Tumor necrosis factor-α (TNF-α) has been implicated in the pathogenesis of hypertension and renal injury. However, the direct effects of TNF-α on renal hemodynamic and excretory function are not yet clearly defined. We examined the renal responses to infusion of TNF-α (0.33 ng·g⁻¹·min⁻¹) in anesthetized mice. Renal blood flow (RBF) and glomerular filtration rate (GFR) were determined by PAH and inulin clearance. The urine was collected from a cannula inserted into the bladder. Following the 60-min control clearance period, TNF-α infusion was initiated and 15 min were given for stabilization followed by another 60-min clearance period. TNF-α alone (n = 7) caused decreases in RBF (7.9 ± 0.3 to 6.4 ± 0.3 ml·min⁻¹·g⁻¹) and GFR (1.04 ± 0.06 to 0.62 ± 0.08 ml·min⁻¹·g⁻¹) as well as increases in absolute (0.8 ± 0.3 to 1.4 ± 0.3 μmol·min⁻¹·g⁻¹) and fractional excretion of sodium (0.5 ± 0.2 to 1.5 ± 0.4%) without affecting arterial pressure. TNF-α also increased 8-isoprostane excretion (8.10 ± 1.09 to 11.13 ± 1.34 pg·min⁻¹·g⁻¹). Pretreatment with TNF-α blocker etanercept (5 mg/kg sc; 24 and 3 h before TNF-α infusion; n = 6) abolished these responses. However, TNF-α induced an increase in RBF and caused attenuation of the GFR reduction in mice pretreated with superoxide (O₂⁻) scavenger tempol (2 μg·g⁻¹·min⁻¹; n = 6). Pretreatment with nitric oxide (NO) synthase inhibitor nitro-l-arginine methyl ester (0.1 μg·g⁻¹·min⁻¹; n = 6) resulted in further enhancement in vasoconstriction while natriuresis remained unaffected in response to TNF-α. These data suggest that TNF-α induces renal vasoconstriction and hypofiltration via enhancing the activity of O₂⁻ and thus reducing the activity of NO. The natriuretic response to TNF-α is related to its direct effects on tubular sodium reabsorption.

Macro- and micronutrient dyshomeostasis in the adverse structural remodelling of myocardium

Hypertension and heart failure are worldwide health problems of ever-increasing proportions. A failure of the heart, during either systolic and/or diastolic phases of the cardiac cycle, has its origins rooted in an adverse structural, biochemical, and molecular remodelling of myocardium that involves its cellular constituents, extracellular matrix, and intramural coronary vasculature. Herein we focus on the pathogenic role of a dyshomeostasis of several macro- (i.e. Ca(2+) and Mg(2+)) and micronutrients (i.e. Zn(2+), Se(2+), and vitamin D) in contributing to adverse remodelling of the myocardium and its failure as a pulsatile muscular pump. An improved understanding of how these macro- and micronutrients account for the causes and consequences of adverse myocardial remodelling carries with it the potential of identifying new biomarkers predictive of risk, onset and progression, and response to intervention(s), which could be monitored non-invasively and serially over time. Moreover, such incremental knowledge will serve as the underpinning to the development of novel strategies aimed at preventing and/or regressing the ongoing adverse remodelling of myocardium. The time is at hand to recognize the importance of macro- and micronutrient dyshomeostasis in the evaluation and management of hypertension and heart failure.

Long-term effects of renin-angiotensin system-blocking therapy and a low blood pressure goal on progression of hypertensive chronic kidney disease in African Americans

BACKGROUND

Antihypertensive drugs that block the renin-angiotensin system (angiotensin-converting enzyme inhibitors [ACEIs] or angiotensin receptor blockers) are recommended for patients with chronic kidney disease (CKD). A low blood pressure (BP) goal (BP, <130/80 mm Hg) is also recommended. The objective of this study was to determine the long-term effects of currently recommended BP therapy in 1094 African Americans with hypertensive CKD.

METHODS

Multicenter cohort study following a randomized trial. Participants were 1094 African Americans with hypertensive renal disease (glomerular filtration rate, 20-65 mL/min/1.73 m2). Following a 3x2-factorial trial (1995-2001) that tested 3 drugs used as initial antihypertensive therapy (ACEIs, calcium channel blockers, and beta-blockers) and 2 levels of BP control (usual and low), we conducted a cohort study (2002-2007) in which participants were treated with ACEIs to a BP lower than 130/80 mm Hg. The outcome measures were a composite of doubling of the serum creatinine level, end-stage renal disease, or death.

RESULTS

During each year of the cohort study, the annual use of an ACEI or an angiotensin receptor blocker ranged from 83.7% to 89.0% (vs 38.5% to 49.8% during the trial). The mean BP in the cohort study was 133/78 mm Hg (vs 136/82 mm Hg in the trial). Overall, 567 participants experienced the primary outcome; the 10-year cumulative incidence rate was 53.9%. Of 576 participants with at least 7 years of follow-up, 33.5% experienced a slow decline in kidney function (mean annual decline in the estimated glomerular filtration rate, <1 mL/min/1.73 m2).

CONCLUSION

Despite the benefits of renin-angiotensin system-blocking therapy on CKD progression, most African Americans with hypertensive CKD who are treated with currently recommended BP therapy continue to progress during the long term.

Important genetic checkpoints for insulin resistance in salt-sensitive (S) Dahl rats

Despite the marked advances in research on insulin resistance (IR) in humans and animal models of insulin resistance, the mechanisms underlying high salt-induced insulin resistance remain unclear. Insulin resistance is a multifactorial disease with both genetic and environmental factors (such as high salt) involved in its pathogenesis. High salt triggers insulin resistance in genetically susceptible patients and animal models of insulin resistance. One of the mechanisms by which high salt might precipitate insulin resistance is through its ability to enhance an oxidative stress-induced inflammatory response that disrupts the insulin signaling pathway. The aim of this hypothesis is to discuss two complementary approaches to find out how high salt might interact with genetic defects along the insulin signaling and inflammatory pathways to predispose to insulin resistance in a genetically susceptible model of insulin resistance. The first approach will consist of examining variations in genes involved in the insulin signaling pathway in the Dahl S rat (an animal model of insulin resistance and salt-sensitivity) and the Dahl R rat (an animal model of insulin sensitivity and salt-resistance), and the putative cellular mechanisms responsible for the development of insulin resistance. The second approach will consist of studying the over-expressed genes along the inflammatory pathway whose respective activation might be predictive of high salt-induced insulin resistance in Dahl S rats.

Variations in genes encoding the insulin receptor substrates -1 and/or -2 (IRS-1, -2) and/or genes encoding the glucose transporter (GLUTs) proteins have been found in patients with insulin resistance. To better understand the combined contribution of excessive salt and genetic defects to the etiology of the disease, it is essential to investigate the following question:

Question 1: Do variations in genes encoding the IRS -1 and -2 and/or genes encoding the GLUTs proteins predict high salt-induced insulin resistance in Dahl S rats?

A significant amount of evidence suggested that salt-induced oxidative stress might predict an inflammatory response that upregulates mediators of inflammation such as the nuclear factor- kappa B (NF-kappa B), the tumor necrosis factor-alpha (TNF-α) and the c-Jun Terminal Kinase (JNK). These inflammatory mediators disrupt the insulin signaling pathway and predispose to insulin resistance. Therefore, the following question will be thoroughly investigated:

Question 2: Do variations in genes encoding the NF-kappa B, the TNF-α and the JNK, independently or in synergy, predict an enhanced inflammatory response and subsequent insulin resistance in Dahl S rats in excessive salt environment?

Finally, to better understand the combined role of these variations on glucose metabolism, the following question will be addressed:

Question 3: What are the functional consequences of gene variations on the rate of glucose delivery, the rate of glucose transport and the rate of glucose phosphorylation in Dahl S rats?

The general hypothesis is that "high-salt diet in combination with defects in candidate genes along the insulin signaling and inflammatory pathways predicts susceptibility to high salt-induced insulin resistance in Dahl S rats".

Signaling pathways modulated by fish oil in salt-sensitive hypertension

Although many studies have indicated that fish oil (FO) improves cardiovascular risk factors and reduces histopathological manifestations of injury in experimental renal injury models, potential mechanisms underlying this protective effect have not been adequately defined. The objective of this study was to identify potential signaling pathways that confer protection in the Dahl rat model of salt-sensitive hypertension. Male Dahl salt-sensitive rats (n = 10/group) were provided with formulated diets containing 8% NaCl, 20% protein, and 25% FO or 25% corn oil (CO) for 28 days. FO reduced blood pressure (-11% at 4 wk; P < 0.05), urine protein excretion (-45% at 4 wk; P < 0.05), plasma cholesterol and triglyceride levels (-54%, P < 0.001; and -58%, P < 0.05), and histopathological manifestations of renal injury, including vascular hypertrophy, segmental and global glomerular sclerosis, interstitial fibrosis, and tubular atrophy. Interstitial inflammation was significantly reduced by FO (-32%; P < 0.001), as assessed by quantitative analysis of ED1-positive cells in sections of the renal cortex. FO reduced tubulointerstitial proliferative activity, as assessed by Western blot analysis of cortical homogenates for PCNA (-51%; P < 0.01) and quantitative analysis of Mib-1-stained sections of the renal cortex (-42%; P < 0.001). Decreased proliferative activity was associated with reduced phospho-ERK expression (-37%; P < 0.005) and NF-kappaB activation (-42%; P < 0.05). FO reduced cyclooxygenase (COX)-2 expression (-63%; P < 0.01) and membrane translocation of the NADPH oxidase subunits p47(phox) and p67(phox) (-26 and -34%; P < 0.05). We propose that FO ameliorates renal injury in Dahl salt-sensitive rats through the inhibition of ERK, decreased NF-kappaB activation, inhibition of COX-2 expression, and decreased NADPH oxidase activation.