Angiotensin II, interstitial inflammation, and the pathogenesis of salt-sensitive hypertension

LncTCONS_00058568 is involved in the pathophysiologic processes mediated by P2X7R in the lower thoracic spinal cord after acute kidney injury

Acute kidney injury (AKI), a prevalent clinical syndrome, involves the participation of the nervous system in neuroimmune regulation. However, the intricate molecular mechanism that governs renal function regulation by the central nervous system (CNS) is complex and remains incompletely understood. In the present study, we found that the upregulated expression of lncTCONS_00058568 in lower thoracic spinal cord significantly ameliorated AKI-induced renal tissue injury, kidney morphology, inflammation and apoptosis, and suppressed renal sympathetic nerve activity. Mechanistically, the purinergic ionotropic P2X7 receptor (P2X7R) was overexpressed in AKI rats, whereas lncTCONS_00058568 was able to suppress the upregulation of P2X7R. In addition, RNA sequencing data revealed differentially expressed genes associated with nervous system inflammatory responses after lncTCONS_00058568 was overexpressed in AKI rats. Finally, the overexpression of lncTCONS_00058568 inhibited the activation of PI3K/Akt and NF-κB signaling pathways in spinal cord. Taken together, the results from the present study show that lncTCONS_00058568 overexpression prevented renal injury probably by inhibiting sympathetic nerve activity mediated by P2X7R in the lower spinal cord subsequent to I/R-AKI.

Interaction of Angiotensin II AT1 Receptors with Purinergic P2X Receptors in Regulating Renal Afferent Arterioles in Angiotensin II-Dependent Hypertension

In angiotensin II (Ang II)-dependent hypertension, Ang II activates angiotensin II type 1 receptors (AT1R) on renal vascular smooth muscle cells, leading to renal vasoconstriction with eventual glomerular and tubular injury and interstitial inflammation. While afferent arteriolar vasoconstriction is initiated by the increased intrarenal levels of Ang II activating AT1R, the progressive increases in arterial pressure stimulate the paracrine secretion of adenosine triphosphate (ATP), leading to the purinergic P2X receptor (P2XR)-mediated constriction of afferent arterioles. Thus, the afferent arteriolar tone is maintained by two powerful systems eliciting the co-existing activation of P2XR and AT1R. This raises the conundrum of how the AT1R and P2XR can both be responsible for most of the increased renal afferent vascular resistance existing in angiotensin-dependent hypertension. Its resolution implies that AT1R and P2XR share common receptor or post receptor signaling mechanisms which converge to maintain renal vasoconstriction in Ang II-dependent hypertension. In this review, we briefly discuss (1) the regulation of renal afferent arterioles in Ang II-dependent hypertension, (2) the interaction of AT1R and P2XR activation in regulating renal afferent arterioles in a setting of hypertension, (3) mechanisms regulating ATP release and effect of angiotensin II on ATP release, and (4) the possible intracellular pathways involved in AT1R and P2XR interactions. Emerging evidence supports the hypothesis that P2X1R, P2X7R, and AT1R actions converge at receptor or post-receptor signaling pathways but that P2XR exerts a dominant influence abrogating the actions of AT1R on renal afferent arterioles in Ang II-dependent hypertension. This finding raises clinical implications for the design of therapeutic interventions that will prevent the impairment of kidney function and subsequent tissue injury.

Comparative Analysis of Hypertensive Tubulopathy in Animal Models of Hypertension and Its Relevance to Human Pathology

Assessment of hypertensive tubulopathy for more than fifty animal models of hypertension in experimental pathology employs criteria that do not correspond to lesional descriptors for tubular lesions in clinical pathology. We provide a critical appraisal of experimental hypertension with the same approach used to estimate hypertensive renal tubulopathy in humans. Four models with different pathogenesis of hypertension were analyzed-chronic angiotensin (Ang) II-infused and renin-overexpressing (TTRhRen) mice, spontaneously hypertensive (SHR), and Goldblatt two-kidney one-clip (2K1C) rats. Mouse models, SHR, and the nonclipped kidney in 2K1C rats had no regular signs of hypertensive tubulopathy. Histopathology in animals was mild and limited to variations in the volume density of tubular lumen and epithelium, interstitial space, and interstitial collagen. Affected kidneys in animals demonstrated lesion values that are significantly different compared with healthy controls but correspond to mild damage if compared with hypertensive humans. The most substantial human-like hypertensive tubulopathy was detected in the clipped kidney of 2K1C rats. For the first time, our study demonstrated the regular presence of chronic progressive nephropathy (CPN) in relatively young mice and rats with induced hypertension. Because CPN may confound the assessment of rodent models of hypertension, proliferative markers should be used to verify nonhypertensive tubulopathy.

Circ_0000284: A risk factor and potential biomarker for prehypertension and hypertension

CircRNAs have been shown to be involved in the development of certain diseases, but their application in prehypertension and hypertension remains unclear. We aimed to explore the potential role of circ_0000284 in revealing the molecular regulatory mechanisms of prehypertension and hypertension. We enrolled a total of 100 patients with normal blood pressure, 100 patients with prehypertension and 100 patients with hypertension. The expression of circ_0000284 among the groups was detected by real-time fluorescence quantitative polymerase chain reaction (qRT‒PCR). Multivariate logistic models were constructed combining conventional risk factors with circ_0000284. A receiver operating characteristic curve (ROC) was used to analyze the diagnostic value of circRNAs in the clinical model. Spearman correlation was used to analyze the correlation of circ_0000284 and the biochemical characteristics of all subjects. The results showed that circ_0000284 was differentially expressed among the normal blood pressure group, prehypertensive group and hypertensive group and showed a significantly upregulated trend in the progression to hypertension (P < 0.05). The ROC curve revealed a high diagnostic ability of circ_0000284 in hypertension in the clinical model (AUC = 0.812). Circ_0000284 also presented a certain ability for early diagnosis of prehypertension (AUC = 0.628). Spearman correlation showed that circ_0000284 was positively correlated with Na and CKMB. Our study suggested that upregulated expression of circ_0000284 was an independent risk factor for prehypertension and hypertension. Circ_0000284 was a potential fingerprint for the early diagnosis of hypertension and distinguished the intermediate stage of hypertension development. Moreover, our study provided new insight into the correlation between circ_0000284 and cardiac injury in the progression to hypertension.

Should Renal Inflammation Be Targeted While Treating Hypertension?

Despite extensive research and a plethora of therapeutic options, hypertension continues to be a global burden. Understanding of the pathological roles of known and underexplored cellular and molecular pathways in the development and maintenance of hypertension is critical to advance the field. Immune system overactivation and inflammation in the kidneys are proposed alternative mechanisms of hypertension, and resistant hypertension. Consideration of the pathophysiology of hypertension in chronic inflammatory conditions such as autoimmune diseases, in which patients present with autoimmune-mediated kidney inflammation as well as hypertension, may reveal possible contributors and novel therapeutic targets. In this review, we 1) summarize current therapies used to control blood pressure and their known effects on inflammation; 2) provide evidence on the need to target renal inflammation, specifically, and especially when first-line and combinatory treatment efforts fail; and 3) discuss the efficacy of therapies used to treat autoimmune diseases with a hypertension/renal component. We aim to elucidate the potential of targeting renal inflammation in certain subsets of patients resistant to current therapies.

Immunity and Hypertension

Hypertension is the primary cause of cardiovascular mortality. Despite multiple existing treatments, only half of those with the disease achieve adequate control. Therefore, understanding the mechanisms causing hypertension is essential for the development of novel therapies. Many studies demonstrate that immune cell infiltration of the vessel wall, kidney and central nervous system, as well as their counterparts of oxidative stress, the renal renin-angiotensin system (RAS) and sympathetic tone play a critical role in the development of hypertension. Genetically modified mice lacking components of innate and/or adaptive immunity confirm the importance of chronic inflammation in hypertension and its complications. Depletion of immune cells improves endothelial function, decreases oxidative stress, reduces vascular tone and prevents renal interstitial infiltrates, sodium retention and kidney damage. Moreover, the ablation of microglia or central nervous system perivascular macrophages reduces RAS-induced inflammation and prevents sympathetic nervous system activation and hypertension. Therefore, understanding immune cell functioning and their interactions with tissues that regulate hypertensive responses may be the future of novel antihypertensive therapies.

Differential effects of low-dose sacubitril and/or valsartan on renal disease in salt-sensitive hypertension

Diuretics and renin-angiotensin system blockers are often insufficient to control the blood pressure (BP) in salt-sensitive (SS) subjects. Abundant data support the proposal that the level of atrial natriuretic peptide may correlate with the pathogenesis of SS hypertension. We hypothesized here that increasing atrial natriuretic peptide levels with sacubitril, combined with renin-angiotensin system blockage by valsartan, can be beneficial for alleviation of renal damage in a model of SS hypertension, the Dahl SS rat. To induce a BP increase, rats were challenged with a high-salt 4% NaCl diet for 21 days, and chronic administration of vehicle or low-dose sacubitril and/or valsartan (75 μg/day each) was performed. Urine flow, Na+ excretion, and water consumption were increased on the high-salt diet compared with the starting point (0.4% NaCl) in all groups but remained similar among the groups at the end of the protocol. Upon salt challenge, we observed a mild decrease in systolic BP and urinary neutrophil gelatinase-associated lipocalin levels (indicative of alleviated tubular damage) in the valsartan-treated groups. Sacubitril, as well as sacubitril/valsartan, attenuated the glomerular filtration rate decline induced by salt. Alleviation of protein cast formation and lower renal medullary fibrosis were observed in the sacubitril/valsartan- and valsartan-treated groups, but not when sacubitril alone was administered. Interestingly, proteinuria was mildly mitigated only in rats that received sacubitril/valsartan. Further studies of the effects of sacubitril/valsartan in the setting of SS hypertension, perhaps involving a higher dose of the drug, are warranted to determine if it can interfere with the progression of the disease.

The Role of P2X7 Purinergic Receptors in the Renal Inflammation Associated with Angiotensin II-induced Hypertension

Purinergic receptors play a central role in the renal pathophysiology of angiotensin II-induced hypertension, since elevated ATP chronically activates P2X7 receptors in this model. The changes induced by the P2X antagonist Brilliant blue G (BBG) in glomerular hemodynamics and in tubulointerstitial inflammation resulting from angiotensin II infusion were studied. Rats received angiotensin II (435 ng·kg^-1·min^-1, 2 weeks) alone or in combination with BBG (50 mg/kg/day intraperitoneally). BBG did not modify hypertension (214.5 ± 1.4 vs. 212.7 ± 0.5 mmHg), but restored to near normal values afferent (7.03 ± 1.00 to 2.97 ± 0.27 dyn.s.cm^-5) and efferent (2.62 ± 0.03 to 1.29 ± 0.09 dyn.s.cm^-5) arteriolar resistances, glomerular plasma flow (79.23 ± 3.15 to 134.30 ± 1.11 nl/min), ultrafiltration coefficient (0.020 ± 0.002 to 0.036 ± 0.003 nl/min/mmHg) and single nephron glomerular filtration rate (22.28 ± 2.04 to 34.46 ± 1.54 nl/min). Angiotensin II induced overexpression of P2X7 receptors in renal tubular cells and in infiltrating T and B lymphocytes and macrophages. All inflammatory cells were increased by angiotensin II infusion and reduced by 20% to 50% (p < 0.05) by BBG administration. Increased IL-2, IL-6, TNFα, IL-1β, IL-18 and overexpression of NLRP3 inflammasome were induced by angiotensin II and suppressed by BBG. These studies suggest that P2X7 receptor-mediated renal vasoconstriction, tubulointerstitial inflammation and activation of NLRP3 inflammasome are associated with angiotensin II-induced hypertension.

The role of pericytes in brain disorders: from the periphery to the brain

It is becoming increasingly apparent that disorders of the brain microvasculature contribute to many neurological disorders. In recent years it has become clear that a major player in these events is the capillary pericyte which, in the brain, is now known to control the blood-brain barrier, regulate blood flow, influence immune cell entry and be crucial for angiogenesis. In this review we consider the under-explored possibility that peripheral diseases which affect the microvasculature, such as hypertension, kidney disease and diabetes, produce central nervous system (CNS) dysfunction by mechanisms affecting capillary pericytes within the CNS. We highlight how cellular messengers produced peripherally can act via signalling pathways within CNS pericytes to reshape blood vessels, restrict blood flow or compromise blood-brain barrier function, thus causing neuronal dysfunction. Increased understanding of how renin-angiotensin, Rho-kinase and PDGFRβ signalling affect CNS pericytes may suggest novel therapeutic approaches to reducing the CNS effects of peripheral disorders.

Integration of purinergic and angiotensin II receptor function in renal vascular responses and renal injury in angiotensin II-dependent hypertension

Glomerular arteriolar vasoconstriction and tubulointerstitial injury are observed before glomerular damage occurs in models of hypertension. High interstitial ATP concentrations, caused by the increase in arterial pressure, alter renal mechanisms involved in the long-term control of blood pressure, autoregulation of glomerular filtration rate and blood flow, tubuloglomerular feedback (TGF) responses, and sodium excretion. Elevated ATP concentrations and augmented expression of P2X receptors have been demonstrated under a genetic background or induction of hypertension with vasoconstrictor peptides. In addition to the alterations of the microcirculation in the hypertensive kidney, the vascular actions of elevated intrarenal angiotensin II levels may be mitigated by the administration of broad purinergic P2 antagonists or specific P2Y12, P2X1, and P2X7 receptor antagonists. Furthermore, the prevention of tubulointerstitial infiltration with immunosuppressor compounds reduces the development of salt-sensitive hypertension, indicating that tubulointerstitial inflammation is essential for the development and maintenance of hypertension. Inflammatory cells also express abundant purinergic receptors, and their activation by ATP induces cytokine and growth factor release that in turn contributes to augment tubulointerstitial inflammation. Collectively, the evidence suggests a pathophysiological activation of purinergic P2 receptors in angiotensin-dependent hypertension. Coexistent increases in intrarenal angiotensin II and activates Ang II AT1 receptors, which interacts with over-activated purinergic receptors in a complex manner, suggesting convergence of their post-receptor signaling processes.

Reno-Cerebral Reflex Activates the Renin-Angiotensin System, Promoting Oxidative Stress and Renal Damage After Ischemia-Reperfusion Injury

AIMS

A kidney-brain interaction has been described in acute kidney injury, but the mechanisms are uncertain. Since we recently described a reno-cerebral reflex, we tested the hypothesis that renal ischemia-reperfusion injury (IRI) activates a sympathetic reflex that interlinks the renal and cerebral renin-angiotensin axis to promote oxidative stress and progression of the injury.

RESULTS

Bilateral ischemia-reperfusion activated the intrarenal and cerebral, but not the circulating, renin-angiotensin system (RAS), increased sympathetic activity in the kidney and the cerebral sympathetic regulatory regions, and induced brain inflammation and kidney injury. Selective renal afferent denervation with capsaicin or renal denervation significantly attenuated IRI-induced activation of central RAS and brain inflammation. Central blockade of RAS or oxidative stress by intracerebroventricular (ICV) losartan or tempol reduced the renal ischemic injury score by 65% or 58%, respectively, and selective renal afferent denervation or reduction of sympathetic tone by ICV clonidine decreased the score by 42% or 52%, respectively (all p < 0.05). Ischemia-reperfusion-induced renal damage and dysfunction persisted after controlling blood pressure with hydralazine.

INNOVATION

This study uncovered a novel reflex pathway between ischemic kidney and the brain that sustains renal oxidative stress and local RAS activation to promote ongoing renal damage.

CONCLUSIONS

These data suggest that the renal and cerebral renin-angiotensin axes are interlinked by a reno-cerebral sympathetic reflex that is activated by ischemia-reperfusion, which contributes to ischemia-reperfusion-induced brain inflammation and worsening of the acute renal injury. Antioxid. Redox Signal. 27, 415-432.

Immunohistochemical expression of intrarenal renin angiotensin system components in response to tempol in rats fed a high salt diet

AIM

To determine the effect of tempol in normal rats fed high salt on arterial pressure and the balance between antagonist components of the renal renin-angiotensin system.

METHODS

Sprague-Dawley rats were fed with 8% NaCl high-salt (HS) or 0.4% NaCl (normal-salt, NS) diet for 3 wk, with or without tempol (T) (1 mmol/L, administered in drinking water). Mean arterial pressure (MAP), glomerular filtration rate (GFR), and urinary sodium excretion (UVNa) were measured. We evaluated angiotensin II (Ang II), angiotensin 1-7 (Ang 1-7), angiotensin converting enzyme 2 (ACE2), mas receptor (MasR), angiotensin type 1 receptor (AT1R) and angiotensin type 2 receptor (AT2R) in renal tissues by immunohistochemistry.

RESULTS

The intake of high sodium produced a slight but significant increase in MAP and differentially regulated components of the renal renin-angiotensin system (RAS). This included an increase in Ang II and AT1R, and decrease in ACE-2 staining intensity using immunohistochemistry. Antioxidant supplementation with tempol increased natriuresis and GFR, prevented changes in blood pressure and reversed the imbalance of renal RAS components. This includes a decrease in Ang II and AT1R, as increase in AT2, ACE2, Ang (1-7) and MasR staining intensity using immunohistochemistry. In addition, the natriuretic effects of tempol were observed in NS-T group, which showed an increased staining intensity of AT2, ACE2, Ang (1-7) and MasR.

CONCLUSION

These findings suggest that a high salt diet leads to changes in the homeostasis and balance between opposing components of the renal RAS in hypertension to favour an increase in Ang II. Chronic antioxidant supplementation can modulate the balance between the natriuretic and antinatriuretic components of the renal RAS.

Mycophenolate mofetil prevents cerebrovascular injury in stroke-prone spontaneously hypertensive rats

Stroke-prone spontaneously hypertensive rats (SHR-A3) develop strokes and progressive kidney disease as a result of naturally occurring genetic variations. We recently identified genetic variants in immune signaling pathways that contribute to end-organ injury. The present study was designed to test the hypothesis that a dysregulated immune response promotes stroke susceptibility. We salt-loaded 20 wk old male SHR-A3 rats and treated them with the immunosuppressant mycophenolate mofetil (MMF, 25 mg/kg/day po) (n = 8) or vehicle (saline) (n = 9) for 8 wk. Blood pressure (BP) was measured weekly by telemetry. Compared with vehicle-treated controls, MMF-treated SHR-A3 rats had improved survival and lower neurological deficit scores (1.44 vs. 0.125; P < 0.02). Gross morphology of the brain revealed cerebral edema in 8 of 9, and microbleeds and hemorrhages in 5 of 9 vehicle-treated rats. These lesions were absent in MMF-treated rats. Brain CD68 expression, indicating macrophage/microglial activation, was upregulated in vehicle-treated rats with microbleeds and hemorrhages but was undetectable in the brains of MMF-treated rats. MMF also prevented renal injury in SHR-A3 rats, evidenced by reduced proteinuria (albumin:creatinine) from 7.52 to 1.05 mg/mg (P < 0.03) and lower tubulointerstitial injury scores (2.46 vs. 1.43; P < 0.01). Salt loading resulted in a progressive increase in BP, which was blunted in rats receiving MMF. Our findings provide evidence that abnormal immune activation predisposes to cerebrovascular and renal injury in stroke-prone SHR-A3 rats.

Endoplasmic reticulum stress in bone marrow-derived cells prevents acute cardiac inflammation and injury in response to angiotensin II

Inflammation plays an important role in hypertensive cardiac injury. The endoplasmic reticulum (ER) stress pathway is involved in the inflammatory response. However, the role of ER stress in elevated angiotensin II (Ang II)-induced cardiac injury remains unclear. In this study, we investigated the role of ER stress in Ang II-induced hypertensive cardiac injury. Transcriptome analysis and quantitative real-time PCR showed that Ang II infusion in mice increased ER stress-related genes expression in the heart. C/EBP homologous protein (CHOP) deficiency, a key mediator of ER stress, increased infiltration of inflammatory cells, especially neutrophils, the production of inflammatory cytokines, chemokines in Ang II-infused mouse hearts. CHOP deficiency increased Ang II-induced cardiac fibrotic injury: (1) Masson trichrome staining showed increased fibrotic areas, (2) immunohistochemistry staining showed increased expression of α-smooth muscle actin, transforming growth factor β1 and (3) quantitative real-time PCR showed increased expression of collagen in CHOP-deficient mouse heart. Bone marrow transplantation experiments indicated that CHOP deficiency in bone marrow cells was responsible for Ang II-induced cardiac fibrotic injury. Moreover, TUNEL staining and flow cytometry revealed that CHOP deficiency decreased neutrophil apoptosis in response to Ang II. Taken together, our study demonstrated that hypertension induced ER stress after Ang II infusion. ER stress in bone marrow-derived cells protected acute cardiac inflammation and injury in response to Ang II.

Th-17 cell activation in response to high salt following acute kidney injury is associated with progressive fibrosis and attenuated by AT-1R antagonism

Exposure of rats to elevated dietary salt following recovery from acute kidney injury (AKI) accelerates the transition to chronic kidney disease (CKD), and is dependent on lymphocyte activity. Here we tested whether high salt diet triggers lymphocyte activation in postischemic kidneys to worsen renal inflammation and fibrosis. Male Sprague-Dawley rats on a 0.4% salt diet were subjected to left unilateral ischemia-reperfusion and allowed to recover for 5 weeks. This resulted in a mild elevation of CD4(+) T cells relative to sham animals. Contralateral unilateral nephrectomy and elevated dietary salt (4%) for 4 extra weeks hastened CKD and interstitial fibrosis. Activated T cells were increased in the kidney threefold after 4 weeks of elevated dietary salt exposure relative to post-AKI rats before salt feeding. The T cell subset was largely positive for IL-17, indicative of Th-17 cells. Because angiotensin II activity may influence lymphocyte activation, injured rats were given the AT1R antagonist, losartan, along with high salt diet. This significantly reduced the number of renal Th-17 cells to levels of sham rats, and significantly reduced the salt-induced increase in fibrosis to about half. In vitro studies in AKI-primed CD4(+) T cells indicated that angiotensin II and extracellular sodium enhanced, and losartan inhibited, IL-17 expression. Thus, dietary salt modulates immune cell activity in postischemic recovering kidneys because of the activity of local RAS, suggesting the participation of these cells in CKD progression post-AKI.

Renal autoregulation in health and disease

Intrarenal autoregulatory mechanisms maintain renal blood flow (RBF) and glomerular filtration rate (GFR) independent of renal perfusion pressure (RPP) over a defined range (80-180 mmHg). Such autoregulation is mediated largely by the myogenic and the macula densa-tubuloglomerular feedback (MD-TGF) responses that regulate preglomerular vasomotor tone primarily of the afferent arteriole. Differences in response times allow separation of these mechanisms in the time and frequency domains. Mechanotransduction initiating the myogenic response requires a sensing mechanism activated by stretch of vascular smooth muscle cells (VSMCs) and coupled to intracellular signaling pathways eliciting plasma membrane depolarization and a rise in cytosolic free calcium concentration ([Ca(2+)]i). Proposed mechanosensors include epithelial sodium channels (ENaC), integrins, and/or transient receptor potential (TRP) channels. Increased [Ca(2+)]i occurs predominantly by Ca(2+) influx through L-type voltage-operated Ca(2+) channels (VOCC). Increased [Ca(2+)]i activates inositol trisphosphate receptors (IP3R) and ryanodine receptors (RyR) to mobilize Ca(2+) from sarcoplasmic reticular stores. Myogenic vasoconstriction is sustained by increased Ca(2+) sensitivity, mediated by protein kinase C and Rho/Rho-kinase that favors a positive balance between myosin light-chain kinase and phosphatase. Increased RPP activates MD-TGF by transducing a signal of epithelial MD salt reabsorption to adjust afferent arteriolar vasoconstriction. A combination of vascular and tubular mechanisms, novel to the kidney, provides for high autoregulatory efficiency that maintains RBF and GFR, stabilizes sodium excretion, and buffers transmission of RPP to sensitive glomerular capillaries, thereby protecting against hypertensive barotrauma. A unique aspect of the myogenic response in the renal vasculature is modulation of its strength and speed by the MD-TGF and by a connecting tubule glomerular feedback (CT-GF) mechanism. Reactive oxygen species and nitric oxide are modulators of myogenic and MD-TGF mechanisms. Attenuated renal autoregulation contributes to renal damage in many, but not all, models of renal, diabetic, and hypertensive diseases. This review provides a summary of our current knowledge regarding underlying mechanisms enabling renal autoregulation in health and disease and methods used for its study.

Signaling pathways involved in renal oxidative injury: role of the vasoactive peptides and the renal dopaminergic system

The physiological hydroelectrolytic balance and the redox steady state in the kidney are accomplished by an intricate interaction between signals from extrarenal and intrarenal sources and between antinatriuretic and natriuretic factors. Angiotensin II, atrial natriuretic peptide and intrarenal dopamine play a pivotal role in this interactive network. The balance between endogenous antioxidant agents like the renal dopaminergic system and atrial natriuretic peptide, by one side, and the prooxidant effect of the renin angiotensin system, by the other side, contributes to ensuring the normal function of the kidney. Different pathological scenarios, as nephrotic syndrome and hypertension, where renal sodium excretion is altered, are associated with an impaired interaction between two natriuretic systems as the renal dopaminergic system and atrial natriuretic peptide that may be involved in the pathogenesis of renal diseases. The aim of this review is to update and comment the most recent evidences about the intracellular pathways involved in the relationship between endogenous antioxidant agents like the renal dopaminergic system and atrial natriuretic peptide and the prooxidant effect of the renin angiotensin system in the pathogenesis of renal inflammation.

Impaired pressure natriuresis resulting in salt-sensitive hypertension is caused by tubulointerstitial immune cell infiltration in the kidney

Immune cell infiltration of the kidney is a constant feature in salt-sensitive hypertension (SSHTN). We evaluated the relationship between the renal inflammation and pressure natriuresis in the model of SSHTN that results from transient oral administration of N(ω)-nitro-L-arginine methyl ester (L-NAME). Pressure natriuresis was determined in Wistar rats that received 4 wk of a high-salt (4% NaCl) diet, starting 1 wk after stopping L-NAME, which was administered alone (SSHTN group, n = 17) or in association with mycophenolate mofetil (MMF; MMF group, n = 15). The administration of MMF in association with L-NAME is known to prevent the subsequent development of SSHTN. Control groups received a high (n = 12)- and normal (0.4%)-salt diet (n = 20). Rats with SSHTN had increased expression of inflammatory cytokines and oxidative stress. The severity of hypertension correlated directly (P < 0.0001) with the number of tubulointerstitial immune cells and angiotensin II-expressing cells. Pressure natriuresis was studied at renal arterial pressures (RAPs) of 90, 110, 130, and 150 mmHg. Glomerular filtration rate was similar and stable in all groups, and renal blood flow was decreased in the SSHTN group. Significantly decreased natriuresis (P < 0.05) was found in the SSHTN group at RAPs of 130 and 150 mmHg, and there was an inverse correlation (P < 0.01) between the urinary sodium excretion and the number of tubulointerstitial inflammatory cells (lymphocytes and macrophages) and cells expressing angiotensin II. We conclude that tubulointerstitial inflammation plays a key role in the impairment of pressure natriuresis that results in salt-dependent hypertension in this experimental model.

Immunosuppression preserves renal autoregulatory function and microvascular P2X(1) receptor reactivity in ANG II-hypertensive rats

Autoregulation is critical for protecting the kidney against arterial pressure elevation and is compromised in some forms of hypertension. Evidence indicates that activated lymphocytes contribute importantly to cardiovascular injury in hypertension. We hypothesized that activated lymphocytes contribute to renal vascular dysfunction by impairing autoregulation and P2X(1) receptor signaling in ANG II-infused hypertensive rats. Male Sprague-Dawley rats receiving ANG II infusion were treated with a lymphocyte proliferation inhibitor, mycophenolate mofetil (MMF) for 2 wk. Autoregulation was assessed in vitro and in vivo using the blood-perfused juxtamedullary nephron preparation and anesthetized rats, respectively. ANG II-treated rats exhibited impaired autoregulation. At the single vessel level, pressure-mediated afferent arteriolar vasoconstriction was significantly blunted (P < 0.05 vs. control rats). At the whole kidney level, renal blood flow passively decreased as renal perfusion pressure was reduced. MMF treatment did not alter the ANG II-induced hypertensive state; however, MMF did preserve autoregulation. The autoregulatory profiles in both in vitro or in vivo settings were similar to the responses from control rats despite persistent hypertension. Autoregulatory responses are linked to P2X(1) receptor activation. Accordingly, afferent arteriolar responses to ATP and the P2X(1) receptor agonist β,γ-methylene ATP were assessed. ATP- or β,γ-methylene ATP-induced vasoconstriction was significantly attenuated in ANG II-infused hypertensive rats but was normalized by MMF treatment. Moreover, MMF prevented elevation of plasma transforming growth factor-β1 concentration and lymphocyte and macrophage infiltration in ANG II-infused kidneys. These results suggest that anti-inflammatory treatment with MMF prevents lymphocyte infiltration and preserves autoregulation in ANG II-infused hypertensive rats, likely by normalizing P2X(1) receptor activation.

Role of the immune system in hypertension: modulation by dietary antioxidants

Hypertension is a major health problem worldwide. Individuals with hypertension are at an increased risk for stroke, heart disease, and kidney failure. Although the etiology of essential hypertension has a genetic component, lifestyle factors such as diet play an important role. Insulin resistance is a common feature of hypertension in both humans and animal models affecting glucose and lipid metabolism producing excess aldehydes including methylglyoxal. These aldehydes react with proteins to form conjugates called advanced glycation end products (AGEs). This alters protein structure and function and can affect vascular and immune cells leading to their activation and secretion of inflammatory cytokines. AGEs also act via receptors for advanced glycation end products on these cells altering the function of antioxidant and metabolic enzymes, and ion channels. This results in an increase in cytosolic free calcium, decrease in nitric oxide, endothelial dysfunction, oxidative stress, peripheral vascular resistance, and infiltration of vascular and kidney tissue with inflammatory cells leading to hypertension. Supplementation with dietary antioxidants including vitamins C, E, or B(6), thiols such as cysteine and lipoic acid, have been shown to lower blood pressure and plasma inflammatory cytokines in animal models and humans with essential hypertension. A well-balanced diet rich in antioxidants that includes vegetables, fruits, low fat dairy products, low salt, and includes whole grains, poultry, fish and nuts, lowers blood pressure and vascular inflammation. These antioxidants may achieve their antihypertensive and anti-inflammatory/immunomodulatory effects by reducing AGEs and improving insulin resistance and associated alterations. Dietary supplementation with antioxidants may be a beneficial, inexpensive, front-line alterative treatment modality for hypertension.

Intrarenal Angiotensin ii is associated with inflammation, renal damage and dysfunction in dahl salt-sensitive hypertension

BACKGROUND

The goal of this study was to test the hypothesis that intrarenal Ang II has a proinflammatory effect leading to renal damage and dysfunction in Dahl S rats on high Na intake.

METHODS

Forty-six 7-to 8-week old Dahl S or R/Rapp strain rats were maintained for 5 weeks on high sodium (8%) with or without candesartan cilexetil in daily doses of 10-15 mg/kg/day. Arterial catheters were implanted at day 28.

RESULTS

By day 35 in the high Na S + candesartan rats, renal tissue Ang II concentration, renal monocytes/macrophages, TNFalpha, and MCP-1 significantly decreased. Plasma Ang II remained at very low levels in all groups. Reduced renal damage in candesartan-treated Dahl S rats was demonstrated by marked decreases in urinary protein excretion and renal glomerular and interstitial damage. After 5 weeks of high Na, compared to high Na Dahl S rats, arterial pressure was unchanged in candesartan S rats, but creatinine clearance was increased.

CONCLUSIONS

Therefore, candesartan reduced renal tissue Ang II, renal damage, infiltration of immune cells, cytokines, chemokines, and improved renal hemodynamics. These data suggest that intrarenal Ang II plays an important role in causing renal inflammation which leads to renal cortical damage, proteinuria, and decreases in renal hemodynamics.

Dietary salt intake is related to inflammation and albuminuria in primary hypertensive patients

BACKGROUND/OBJECTIVES

In this study, we hypothesized that dietary salt intake may be related with inflammation and albuminuria independently from blood pressure (BP) in non-diabetic hypertensive patients.

SUBJECTS/METHODS

A total of 224 patients with primary hypertension were included in the study. Serum C-reactive protein (CRP) levels, 24-h urine sodium and albumin excretion were measured in all patients. The subjects were divided into tertiles according to the level of 24-h urinary sodium excretion: low-salt-intake group (n = 76, mean urine sodium: 111.7 ± 29.1 mmol/24 h), medium-salt-intake group (n = 77, mean urine sodium: 166.1 ± 16.3 mmol/24 h) and high-salt-intake group (n = 71, mean urine sodium: 263.6 ± 68.3 mmol/24 h).

RESULTS

Systolic and diastolic BP measurements of patients were similar in the three salt-intake groups. CRP and urinary albumin levels were significantly higher in high-salt-intake group compared with medium- and low-salt-intake groups (P = 0.0003 and P = 0.001, respectively). CRP was positively correlated with 24-h urinary sodium excretion (r = 0.28, P = 0.0008) and albuminuria, whereas albuminuria was positively correlated with 24-h urinary sodium excretion (r = 0.21, P = 0.0002). Multiple regression analysis revealed that urinary sodium excretion was an independent predictor of both CRP and albuminuria.

CONCLUSIONS

These findings suggest that high salt intake is associated with enhanced inflammation and target organ damage reflected by increased albuminuria in treated hypertensive patients independent of any BP effect.

Adverse consequences of accelerated neonatal growth: cardiovascular and renal issues

Epidemiological and experimental studies show that the risk of cardiovascular and metabolic diseases at adulthood is inversely related to the weight at birth. Although with less evidence, low birth weight has been suggested to increase the risk of chronic kidney disease (CKD). It is well established that the developmental programming of arterial hypertension and of renal disease involves in particular renal factors, especially nephron endowment, which is reduced in low birth weight and maternal diabetes situations. Experimental studies, especially in rodents, have demonstrated the long-term influence of postnatal nutrition and/or postnatal growth on cardiovascular, metabolic and renal functions, while human data are scarce on this issue. Vascular and renal diseases appear to have a "multihits" origin, with reduced nephron number the initial hit and rapid postnatal growth the second hit. This review addresses the current understanding of the role of the kidney, both as a mechanism and as a target, in the developmental origins of adult disease theory, with a particular focus on the long-term effects of postnatal growth and nutrition.

P2X1 receptor-mediated vasoconstriction of afferent arterioles in angiotensin II-infused hypertensive rats fed a high-salt diet

Experiments tested the hypothesis that P2 receptor reactivity is impaired in angiotensin (Ang) II hypertensive rats fed an 8%NaCl diet (Ang II+HS). Juxtamedullary afferent arteriolar autoregulatory behavior was determined over a pressure range of 65 to 200 mm Hg. Arteriolar responsiveness to P2X1 (β,γ-methylene ATP) or P2Y2 receptor (uridine triphosphate) activation was determined in vitro. Systolic blood pressure averaged 126±3 and 225±4 mm Hg in control and Ang II+HS rats, respectively (P<0.05). In control kidneys, β,γ-methylene ATP (10(-8) to 10(-4) mol/L) reduced arteriolar diameter by 8±3%, 13±5%, 19±5%, 22±6%, and 24±9%, respectively, whereas uridine triphosphate reduced diameter by 2±1%, 2±2%, 9±3%, 37±7%, and 58±7%. Autoregulation was markedly blunted in Ang II+HS kidneys, with arteriolar diameter remaining essentially unchanged when perfusion pressure increased to 200 mm Hg compared with a 40±2% decline in diameter observed in normal kidneys over the same pressure range (P<0.05). P2X1 receptor-mediated vasoconstriction was significantly attenuated in Ang II+HS kidneys. β,γ-Methylene ATP reduced arteriolar diameter by 1±1%, 3±2%, 6±1%, 9±3%, and 7±1%, respectively (P<0.05), versus control rats. Similar patterns were noted when hypertensive perfusion pressures were used. Uridine triphosphate-mediated responses were unchanged in Ang II+HS rats compared with control, indicating preservation of P2Y2 receptor function. Ang II+HS blunted P2X1-mediated increases in intracellular Ca2+ concentration in preglomerular smooth muscle cells. Therefore, Ang II+HS rats exhibit attenuated afferent arteriolar responses to P2X1 receptor stimulation. These data support the hypothesis that P2X1 receptors are important for pressure-mediated autoregulatory responses. Impairment of P2X1 receptor function may explain the hypertension-induced decline in renal autoregulatory capability.

Transient induction of ANG II-dependent malignant hypertension causes sustained elevation of blood pressure and augmentation of the pressor response to ANG II in CYP1A1-REN2 transgenic rats

INTRODUCTION

Transgenic rats with inducible expression of the mouse Ren2 renin gene [strain name: TGR(Cyp1a1Ren2)] allow induction of various degrees of ANG II-dependent hypertension. Dietary administration of the aryl hydrocarbon indole-3-carbinol (I3C) at a dose of 0.15% induces a slowly developing form of ANG II-dependent hypertension, whereas dietary administration of a higher dose (0.3%) of I3C results in the development of ANG II-dependent malignant hypertension. Cessation of administration of 0.15% I3C results in the normalization of blood pressure, indicating the reversibility of hypertension induced by this dose of I3C. The present study was performed to determine if ANG II-dependent malignant hypertension is similarly reversible following cessation of dietary administration of 0.3% I3C.

METHODS

Cyp1a1-Ren2 rats (n = 6) were fed a normal diet containing 0.3% I3C for 11 days to induce malignant hypertension.

RESULTS

Cyp1a1-Ren2 rats induced with I3C exhibited pronounced increases in systolic blood pressure (SBP) (132 +/- 3-229 +/- 11 mm Hg, P < 0.001) and marked decreases in body weight (303 +/- 4-222 +/- 2 g, P < 0.001). When I3C administration was terminated, SBP decreased to 167 +/- 4 mm Hg (P < 0.01) and body weight increased to normal levels (309 +/- 2 g, P < 0.01) within 12 days. However, SBP remained significantly elevated (172 +/- 1 mm Hg, P < 0.01) for up to 3 weeks after termination of dietary administration of 0.3% I3C. In addition, the magnitude of the blood pressure response to intravenous bolus administration of 50 ng of ANG II (50 microL in volume) 3 weeks after cessation of dietary I3C administration was substantially higher than that observed in normotensive control rats (134 +/- 1 mm Hg, n = 6) not previously induced with 0.3% I3C (53 +/- 2 versus 38 +/- 3 mm Hg, P < 0.05).

CONCLUSIONS

The present findings demonstrate that transient induction of ANG II-dependent malignant hypertension results in prolonged elevations of arterial blood pressure and marked augmentation of the magnitude of the pressor response to ANG II in Cyp1a1-Ren2 transgenic rats.

AT1 receptor blockade prevents the increase in blood pressure and the augmentation of intrarenal ANG II levels in hypertensive Cyp1a1-Ren2 transgenic rats fed with a high-salt diet

INTRODUCTION

This study was performed to determine the effects of high-salt diet on the magnitude of the increases in systolic blood pressure (SBP) and kidney tissue angiotensin (ANG) II levels that occur after induction of ANG II-dependent malignant hypertension in Cyp1a1-Ren2 transgenic rats with inducible expression of the mouse Ren2 renin gene [strain name: TGR(Cyp1a1Ren2)].

METHODS

Cyp1a1-Ren2 rats (n = 6) were fed a normal diet containing 0.3% indole-3-carbinol (I3C) for 10 days to induce ANG II-dependent malignant hypertension.

RESULTS

Rats induced with I3C exhibited increases in SBP and elevations of ANG II levels in kidney cortex and medulla. In a second group of rats (n = 6), high-salt intake alone did not alter basal SBP; however, subsequent dietary administration of 0.3% I3C during continued high-salt intake elicited a substantially greater increase in SBP than observed in rats fed a normal salt diet. ANG II levels in kidney cortex and medulla of rats induced with I3C and fed a high-salt diet were elevated similarly to those in rats induced with I3C alone. Chronic administration of the AT1 receptor antagonist, losartan (100 mg/L in drinking water, n = 6), markedly attenuated the I3C-induced increase in SBP and prevented the augmentation of ANG II levels in kidney cortex and medulla in rats induced with I3C and maintained on a high-salt diet.

CONCLUSIONS

Activation of AT1 receptors contributes to the augmented blood pressure and elevated kidney tissue ANG II levels that occur in Cyp1a1-Ren2 transgenic rats with malignant hypertension maintained on a high-salt diet.

The Soluble Epoxide Hydrolase Inhibitor AR9281 Decreases Blood Pressure, Ameliorates Renal Injury and Improves Vascular Function in Hypertension

Soluble epoxide hydrolase inhibitors (sEHIs) are demonstrating promise as potential pharmaceutical agents for the treatment of cardiovascular disease, diabetes, inflammation, and kidney disease. The present study determined the ability of a first-inclass sEHI, AR9281, to decrease blood pressure, improve vascular function, and decrease renal inflammation and injury in angiotensin hypertension. Rats were infused with angiotensin and AR9281 was given orally during the 14-day infusion period. Systolic blood pressure averaged 180 ± 5 mmHg in vehicle treated and AR9281 treatment significantly lowered blood pressure to 142 ± 7 mmHg in angiotensin hypertension. Histological analysis demonstrated decreased injury to the juxtamedullary glomeruli. Renal expression of inflammatory genes was increased in angiotensin hypertension and two weeks of AR9281 treatment decreased this index of renal inflammation. Vascular function in angiotensin hypertension was also improved by AR9281 treatment. Decreased afferent arteriolar and mesenteric resistance endothelial dependent dilator responses were ameliorated by AR9281 treatment of angiotensin hypertensive rats. These data demonstrate that the first-in-class sEHI, AR9281, lowers blood pressure, improves vascular function and reduces renal damage in angiotensin hypertension.

Pathogenesis of essential hypertension: historical paradigms and modern insights

Since its first identification in the late 1800s, a variety of etiologies for essential hypertension have been proposed. In this paper we review the primary proposed hypotheses in the context of both the time in which they were proposed as well as the subsequent studies performed over the years. From these various insights, we propose a current paradigm to explain the renal mechanisms underlying the hypertension epidemic today. Specifically, we propose that hypertension is initiated by agents that cause systemic and intrarenal vasoconstriction. Over time intrarenal injury develops with microvascular disease, interstitial T cell and macrophage recruitment with the induction of an autoimmune response, with local angiotensin II formation and oxidant generation. These changes maintain intrarenal vasoconstriction and hypoxia with a change in local vasoconstrictor-vasodilator balance favoring sodium retention. Both genetic and congenital (nephron number) mechanisms have profound influence on this pathway. As blood pressure rises, renal ischemia is ameliorated and sodium balance restored completely (in salt-resistant) or partially (in salt-sensitive) hypertension, but at the expense of a rightward shift in the pressure natriuresis curve and persistent hypertension.

Renal response to angiotensin II is blunted in sodium-sensitive normotensive men

BACKGROUND

In hypertension, sodium sensitivity (SS) of blood pressure is associated with renal hemodynamic abnormalities related to increased activity of the renal renin-angiotensin aldosterone system (RAAS). The renal mechanisms of SS in normotensives are unknown. Therefore, we studied whether SS is related to renal hemodynamics and renal responsiveness to angiotensin II (AngII) in young healthy adults.

METHODS

Blood pressure (mean arterial pressure (MAP)) and renal function were measured in 34 healthy men after 1-week low-sodium diet (LS; 50 mmol Na(+)/24 h), 1-week high-sodium diet (HS; 200 mmol Na(+)/24h), and 1-week HS-ACEi (enalapril 20 mg/day). The responses of effective renal plasma flow (ERPF; (131)I-Hippuran clearance) to graded infusion of AngII were assessed during each condition.

RESULTS

The sodium-induced change in MAP ranged from -7 to +14 mm Hg. SS (a sodium-induced increase in MAP >3 mm Hg) was present in 13 subjects. ERPF was lower in SS subjects during LS and during HS-ACEi. The AngII-induced decrease in ERPF was blunted in SS on LS (-25 +/- 6 vs. -29 +/- 7% in sodium-resistant (SR) subjects, P < 0.05) and on HS (-30 +/- 5 vs. -35 +/- 6%, P < 0.05). The blunting was corrected by angiotensin-converting enzyme inhibitors (ACEi) (-36 +/- 6 vs. -37 +/- 7%).

CONCLUSION

SS normotensive subjects have a blunted renal response to exogenous AngII. This is ameliorated by ACEi, supporting a role for inappropriately high intrarenal RAAS activity. As these findings cannot be attributed to subclinical renal hypertensive damage, high intrarenal RAAS activity and altered renal hemodynamics may be primary phenomena underlying SS.

Endothelial dysfunction and the development of renal injury in spontaneously hypertensive rats fed a high-fat diet

Obesity and hypertension have been identified as cardiovascular risk factors that contribute to the progression of end-stage renal disease. To examine the mechanisms by which a high-fat diet and hypertension contribute to endothelial dysfunction and renal injury, 8-week-old male spontaneously hypertensive rats and Wistar rats were fed a high-fat (36% fat) or a normal-fat (7% fat) diet for 10 weeks. The high-fat diet increased body weight in Wistar and hypertensive rats by 25 and 31 g, respectively. Systolic blood pressure was higher in the hypertensive rats compared with Wistar rats; however, blood pressure was unaltered by the high-fat diet. Afferent arteriole response to acetylcholine was impaired in the high-fat groups after just 3 weeks. Renal macrophage infiltration was increased in the hypertensive high-fat group compared with others, and monocyte chemoattractant protein-1 excretion was increased in both of the high-fat-fed groups. Renal PCR arrays displayed significant increases in 2 inflammatory genes in hypertensive rats fed a normal diet, 1 gene was increased in high-fat-fed Wistar rats, whereas 12 genes were increased in high-fat-fed hypertensive rats. Urinary albumin excretion was increased in the hypertensive rats compared with the Wistar rats, which was further exacerbated by the high-fat diet. Glomerular nephrin expression was reduced and desmin was increased by the high-fat diet in the hypertensive rats. Our results indicate that endothelial dysfunction precedes renal injury in normotensive and spontaneously hypertensive rats fed a high-fat diet, and hypertension with obesity induces a powerful inflammatory response and disruption of the renal filtration barrier.

Persistent hypertension and progressive renal injury induced by salt overload after short term nitric oxide inhibition

INTRODUCTION

Administration of the NO inhibitor N(wdelta)-nitro-L-arginine methyl ester (NAME) and a high-salt diet (HS) promotes severe albuminuria and renal injury, which regresses upon discontinuation of treatments.

OBJECTIVE

We investigated whether these changes reappear after reinstitution of HS, and whether they are prevented by treatment with the antilymphocyte agent mycophenolate mofetil (MMF) or the AT-1 receptor blocker losartan (L). Adult male Munich-Wistar rats received NAME and HS. A control Group (C) received only HS. After 20 days, rats receiving HS and NAME exhibited severe hypertension and albuminuria. After a 30-day recovery period, hypertension was attenuated and albuminuria had virtually disappeared.

MATERIAL AND METHODS

Rats were then distributed among the following groups: HS, receiving HS; NS, receiving a normal salt (NS) diet; HS-MMF, receiving HS and MMF; HS-LOS, receiving HS and L; HS-HDZ, receiving HS and hydralazine (HDZ). Sixty days later, NS rats showed only slight albuminuria and renal damage or inflammation. In contrast, HS rats developed severe hypertension, marked glomerulosclerosis with interstitial expansion and renal infiltration by macrophages and angiotensin II-positive cells. The group treated with losartan had lowered blood pressure and a lack of albuminuria or renal injury. MMF provided similar protection without altering blood pressure, suggesting a nonhemodynamic effect, a hypothesis reinforced by the finding that HDZ lowered blood pressure without preventing renal injury.

RESULTS

These results indicate that treatment with HS and NAME predisposes to the development of hypertension and renal injury upon salt overload, characterizing a new model of chronic nephropathy.

CONCLUSION

The response to MMF or L, but not HDZ, suggests a key role for inflammatory rather than hemodynamic factors.

Pathophysiological Mechanisms of Salt-Dependent Hypertension

Changes in salt intake are associated in general with corresponding changes in arterial blood pressure. An exaggerated increment in blood pressure driven by a salt load is characteristic of salt-sensitive hypertension, a condition affecting more than two thirds of individuals with essential hypertension who are older than 60 years. In the last decade, significant insight was gained about the role of the kidney in the increment in blood pressure induced by sodium retention. The present review focuses on the pathophysiological characteristics of the blood pressure increase driven by expansion of extracellular fluid and the increment in plasma sodium concentration. In addition, we discuss systemic and renal conditions that result in decreased urinary sodium excretion and were implicated in the development of salt-sensitive hypertension.

Mycophenolate mofetil administration reduces renal inflammation, oxidative stress, and arterial pressure in rats with lead-induced hypertension

Hypertension is a likely consequence of chronic lead exposure in humans, especially in association with reduced renal function and in high risk populations. Numerous studies have demonstrated that oxidative stress plays an important role in the pathogenesis of experimental lead-induced hypertension and we have shown recently that tubulointerstitial immune cell infiltration is a feature of chronic low-dose lead exposure. Since oxidative stress, renal inflammation, and angiotensin activity are closely linked characteristics in experimental models of hypertension, we decided to investigate whether lead-induced hypertension would be ameliorated by suppressing renal inflammation with the immunosuppressive drug mycophenolate mofetil (MMF). We studied rats exposed for 14 wk to lead acetate (100 ppm in the drinking water) that, in addition, received either MMF, 20 mg.kg(-1).day(-1) by gastric gavage (Pb.MMF group, n = 12) or vehicle (Pb group, n = 12). Control rats received MMF alone (n = 5) or neither lead nor MMF (n = 6). All rats were killed at the end of the experiment. Low-dose lead exposure resulted in mild to moderate tubular cell damage and a progressive increment in blood pressure, oxidative stress, interstitial accumulation of lymphocytes and macrophages, NF-kappaB activation, and increased renal angiotensin II level. The administration of MMF suppressed the tubulointerstitial accumulation of lymphocytes and macrophages and prevented the hypertension, oxidative stress, and NF-kappaB activation and reduced the heightened renal angiotensin content associated with chronic lead exposure. We conclude that interstitial inflammation plays an important role in lead-induced hypertension.

Renal angiotensin II concentration and interstitial infiltration of immune cells are correlated with blood pressure levels in salt-sensitive hypertension

Renal immune cell infiltration and cells expressing angiotensin II (AII) in tubulointerstitial areas of the kidney are features of experimental models of salt-sensitive hypertension (SSHTN). A high-salt intake tends to suppress circulating AII levels, but intrarenal concentrations of AII have not been investigated in SSHTN. This study explored the relationship between these features to gain insight into the pathophysiology of SSHTN. Plasma angiotensin II (AII) and renal interstitial AII (microdialysis technique) and the infiltration of macrophages, lymphocytes, and AII-positive cells were determined in SSHTN induced by 5 wk of a high-salt diet (HSD) after short-term infusion of AII in rats with (n = 10) and without (n = 11) treatment with mycophenolate mofetil (MMF) and in control rats fed a high- (n = 7) and normal (n = 11) salt diet. As in previous studies, MMF did not affect AII-associated hypertension but reduced the interstitial inflammation and the SSHTN in the post-AII-period. During the HSD period, the AII group untreated with MMF had mean +/- SD) low plasma (2.4 +/- 1.4 pg/ml) and high interstitial AII concentration (1,310 +/- 208 pg/ml); MMF treatment resulted in a significantly lower interstitial AII (454 +/- 128 pg/ml). Renal AII concentration and the number of tubulointerstitial AII-positive cells were correlated. Blood pressure correlated positively with interstitial AII and negatively with plasma AII, thus giving compelling evidence of the paramount role of the AII within the kidney in the AII-induced model of salt-driven hypertension.