E-value: a superior alternative to P-value and its adjustments in DNA methylation studies.

DNA methylation plays a crucial role in transcriptional regulation. Reduced representation bisulfite sequencing (RRBS) is a technique of increasing use for analyzing genome-wide methylation profiles. Many computational tools such as Metilene, MethylKit, BiSeq and DMRfinder have been developed to use RRBS data for the detection of the differentially methylated regions (DMRs) potentially involved in epigenetic regulations of gene expression. For DMR detection tools, as for countless other medical applications, P-values and their adjustments are among the most standard reporting statistics used to assess the statistical significance of biological findings. However, P-values are coming under increasing criticism relating to their questionable accuracy and relatively high levels of false positive or negative indications. Here, we propose a method to calculate E-values, as likelihood ratios falling into the null hypothesis over the entire parameter space, for DMR detection in RRBS data. We also provide the R package 'metevalue' as a user-friendly interface to implement E-value calculations into various DMR detection tools. To evaluate the performance of E-values, we generated various RRBS benchmarking datasets using our simulator 'RRBSsim' with eight samples in each experimental group. Our comprehensive benchmarking analyses showed that using E-values not only significantly improved accuracy, area under ROC curve and power, over that of P-values or adjusted P-values, but also reduced false discovery rates and type I errors. In applications using real RRBS data of CRL rats and a clinical trial on low-salt diet, the use of E-values detected biologically more relevant DMRs and also improved the negative association between DNA methylation and gene expression.

Functional NADPH oxidase 2 in T cells amplifies salt-sensitive hypertension and associated renal damage.

Infiltrating T cells in the kidney amplify salt-sensitive (SS) hypertension and renal damage, but the mechanisms are not known. Genetic deletion of T cells (SSCD247-/-) or of the p67phox subunit of NADPH oxidase 2 (NOX2; SSp67phox-/-) attenuates SS hypertension in the Dahl SS rat. We hypothesized that reactive oxygen species produced by NOX2 in T cells drive the SS phenotype and renal damage. T cells were reconstituted by adoptively transferring splenocytes (∼10 million) from the Dahl SS (SS→CD247) rat, the SSp67phox-/- rat (p67phox→CD247), or only PBS (PBS→CD247) into the SSCD247-/- rat on postnatal day 5. Animals were instrumented with radiotelemeters and studied at 8 wk of age. There were no detectable differences in mean arterial pressure (MAP) or albuminuria between groups when rats were maintained on a low-salt (0.4% NaCl) diet. After 21 days of high-salt diet (4.0% NaCl), MAP and albuminuria were significantly greater in SS→CD247 rats compared with p67phox→CD247 and PBS→CD247 rats. Interestingly, there was no difference between p67phox→CD247 and PBS→CD247 rats in albuminuria or MAP after 21 days. The lack of CD3+ cells in PBS→CD247 rats and the presence of CD3+ cells in rats that received the T cell transfer demonstrated the effectiveness of the adoptive transfer. No differences in the number of CD3+, CD4+, or CD8+ cells were observed in the kidneys of SS→CD247 and p67phox→CD247 rats. These results indicate that reactive oxygen species produced by NOX2 in T cells participates in the amplification of SS hypertension and renal damage.NEW & NOTEWORTHY Our current work used the adoptive transfer of T cells that lack functional NADPH oxidase 2 into a genetically T cell-deficient Dahl salt-sensitive (SS) rat model. The results demonstrated that reactive oxygen species produced by NADPH oxidase 2 in T cells participate in the amplification of SS hypertension and associated renal damage and identifies a potential mechanism that exacerbates the salt-sensitive phenotype.

Renal histaminergic system and acute effects of histamine receptor 2 blockade on renal damage in the Dahl salt-sensitive rat.

Histamine is involved in the regulation of immune response, vasodilation, neurotransmission, and gastric acid secretion. Although elevated histamine levels and increased expression of histamine metabolizing enzymes have been reported in renal disease, there is a gap in knowledge regarding the mechanisms of histamine-related pathways in the kidney. We report here that all four histamine receptors as well as enzymes responsible for the metabolism of histamine are expressed in human and rat kidney tissues. In this study, we hypothesized that the histaminergic system plays a role in salt-induced kidney damage in the Dahl salt-sensitive (DSS) rat, a model characterized with inflammation-driven renal lesions. To induce renal damage related to salt sensitivity, DSS rats were challenged with 21 days of a high-salt diet (4% NaCl); normal-salt diet (0.4% NaCl)-fed rats were used as a control. We observed lower histamine decarboxylase and higher histamine N-methyltransferase levels in high-salt diet-fed rats, indicative of a shift in histaminergic tone; metabolomics showed higher histamine and histidine levels in the kidneys of high-salt diet-fed rats, whereas plasma levels for both compounds were lower. Acute systemic inhibition of histamine receptor 2 in the DSS rat revealed that it lowered vasopressin receptor 2 in the kidney. In summary, we established here the existence of the local histaminergic system, revealed a shift in the renal histamine balance during salt-induced kidney damage, and provided evidence that blockage of histamine receptor 2 in the DSS rat affects water balance and urine concentrating mechanisms.NEW & NOTEWORTHY Histamine is a nitrogenous compound crucial for the inflammatory response. The knowledge regarding the renal effects of histamine is very limited. We showed that renal epithelia exhibit expression of the components of the histaminergic system. Furthermore, we revealed that there was a shift in the histaminergic tone in salt-sensitive rats when they were challenged with a high-salt diet. These data support the notion that histamine plays a role in renal epithelial physiological and pathophysiological functions.

Impact of bedding on Dahl salt-sensitive hypertension and renal damage.

Salt-sensitive hypertension, increases in blood pressure in response to increased salt intake, is associated with an increased risk of morbidity, mortality, and end-organ damage compared with salt-resistant hypertension. The Dahl salt-sensitive (SS) rat mimics the phenotypic characteristics observed in human hypertension when rats are challenged with a high-salt diet. Our previous work demonstrated that environmental factors, such as dietary protein, alter the severity of salt sensitivity in Dahl SS rats and should be an important consideration in experimental design. The present study investigated how the bedding on which animals were maintained (wood vs. corncob) could impact the SS phenotype in the Dahl SS rat. Animals that were maintained on corncob bedding exhibited a significant attenuation in blood pressure and renal end-organ damage in response to a high-salt diet compared with animals maintained on wood bedding. This attenuation was associated with an improvement in renal function and reduction in immune cell infiltration into the kidneys of Dahl SS rats maintained on corncob bedding. These results indicate that the type of bedding impacts the SS phenotype in the Dahl SS rat and that the bedding used in experiments can be a confounding factor to consider during data interpretation and experimental design.NEW & NOTEWORTHY Results from our present study demonstrate the profound effect of animal bedding on the severity of salt-sensitive hypertension, renal damage, and inflammation in Dahl salt-sensitive rats. This study highlights the important consideration that should be given to environmental factors, namely, the type of bedding in animal facilities, in experimental design and data interpretation.

Contribution of Th17 cells to tissue injury in hypertension.

PURPOSE OF REVIEW: Hypertension has been demonstrated to be a chief contributor to morbidity and mortality throughout the world. Although the cause of hypertension is multifactorial, emerging evidence, obtained in experimental studies, as well as observational studies in humans, points to the role of inflammation and immunity. Many aspects of immune function have now been implicated in hypertension and end-organ injury; this review will focus upon the recently-described role of Th17 cells in this pathophysiological response. RECENT FINDINGS: Studies in animal models and human genetic studies point to a role in the adaptive immune system as playing a contributory role in hypertension and renal tissue damage. Th17 cells, which produce the cytokine IL17, are strongly pro-inflammatory cells, which may contribute to tissue damage if expressed in chronic disease conditions. The activity of these cells may be enhanced by physiological factors associated with hypertension such as dietary salt or Ang II. This activity may culminate in the increased sodium retaining activity and exacerbation of inflammation and renal fibrosis via multiple cellular mechanisms. SUMMARY: Th17 cells are a distinct component of the adaptive immune system that may strongly enhance pathways leading to increased sodium reabsorption, elevated vascular tone and end-organ damage. Moreover, this pathway may lend itself towards specific targeting for treatment of kidney disease and hypertension.

T Cell Immunometabolism and Redox Signaling in Hypertension.

PURPOSE OF REVIEW: In this article, we summarize the current literature supporting metabolic and redox signaling pathways as important mechanisms underlying T cell activation in the context of hypertension. RECENT FINDINGS: T cell immunometabolism undergoes dramatic remodeling in order to meet the demands of T cell activation, differentiation, and proliferation. Recent evidence demonstrates that the T cell oxidation-reduction (redox) system also undergoes significant changes upon activation, which can itself modulate metabolic processes and T cell function. Dysregulation of these signaling pathways can lead to aberrant T cell activation and inappropriate ROS production, both of which are linked to pathological conditions like hypertension. While the contribution of T cells to the progression of hypertension has been thoroughly investigated, how T cell metabolism and redox signaling changes, both separately and together, is an area of study that remains largely untouched. This review presents evidence from our own laboratory as well as others to highlight the importance of these two mechanisms in the study of hypertension.

Inflammatory macrophages in the kidney contribute to salt-sensitive hypertension.

This review will highlight recent studies that have investigated the relationship between Na+, renal macrophage polarization, and renal damage. A hyperosmotic environment drives the macrophage toward a proinflammatory phenotype and away from an anti-inflammatory phenotype. Animal models of salt-sensitive hypertension demonstrate a characteristic infiltration of macrophages into the kidney that is greatly reduced when blood pressure is lowered. Because general immunosuppression or macrophage depletion leads to a host of adverse side effects, more recent studies have modulated the interaction of specific signaling molecules, including NOD-like receptor family pyrin domain-containing 3, chemokine (C-X-C motif) ligand 16, and VEGF, to prevent the end-organ renal damage that accumulates in salt-sensitive disease.

CCL2 mediates early renal leukocyte infiltration during salt-sensitive hypertension.

Studies examining mechanisms of Dahl salt-sensitive (SS) hypertension have implicated the infiltration of leukocytes in the kidneys, which contribute to renal disease and elevated blood pressure. However, the signaling pathways by which leukocytes traffic to the kidneys remain poorly understood. The present study nominated a signaling pathway by analyzing a kidney RNA sequencing data set from SS rats fed either a low-salt (0.4% NaCl) diet or a high-salt (4.0% NaCl) diet. From this analysis, chemokine (C-C motif) ligand 2 (CCL2) and chemokine (C-C motif) receptor 2 (CCR2) were nominated as a potential pathway modifying renal leukocyte infiltration and contributing to SS hypertension. The functional role of the CCL2/CCR2 pathway was tested by daily administration of CCR2 antagonist (RS-102895 at 5 mg·kg-1·day-1 in DMSO) or DMSO vehicle for 3 or 21 days by intraperitoneal injections during the high salt challenge. Blood pressure, renal leukocyte infiltration, and renal damage were evaluated. The results demonstrated that RS-102895 treatment ameliorated renal damage (urinary albumin excretion; 43.4 ± 5.1 vs. 114.7 ± 15.2 mg/day in vehicle, P < 0.001) and hypertension (144.3 ± 2.2 vs. 158.9 ± 4.8 mmHg in vehicle, P < 0.001) after 21 days of high-salt diet. It was determined that renal leukocyte infiltration was blunted by day 3 of the high-salt diet (1.4 ± 0.1 vs. 1.9 ± 0.2 in vehicle × 106 CD45+ cells/kidney, P = 0.034). An in vitro chemotaxis assay validated the effect of RS-102895 on leukocyte chemotaxis toward CCL2. The results suggest that increased CCL2 in SS kidneys is important in the early recruitment of leukocytes, and blockade of this recruitment by administering RS-102895 subsequently blunted the renal damage and hypertension.

Influences of environmental factors during preeclampsia.

Preeclampsia is a pregnancy-specific disorder that impacts 5-8% of pregnancies and has long-term cardiovascular and metabolic implications for both mother and fetus. The mechanisms are unclear; however, it is believed that preeclampsia is characterized by abnormal vascularization during placentation resulting in the manifestation of clinical signs such as hypertension, proteinuria, and endothelial dysfunction. Although there is no current cure to alleviate the clinical signs, an emerging area of interest in the field is the influence of environmental factors including diet on the risk of preeclampsia. Because preeclampsia has serious cardiovascular implications to both the mother and fetus and most antihypertensive medications are contraindicated in pregnancy, it is important to investigate other potential therapeutic options such as dietary manipulation. The emerging field of nutrigenomics links diet with the gene expression of known pathways such as oxidative stress and inflammation via microbiome-mediated metabolites and could serve as one potential avenue of therapeutic targets for preeclampsia. Although the exact role of nutrition in the pathogenesis of preeclampsia is unknown, this review will focus on known pathways involved in the development of preeclampsia and how dietary intake modulates the microbiome, oxidative stress, and inflammation with an emphasis on nutrigenomics as a potential avenue of further investigation to better understand this pathology.

Splenocyte transfer exacerbates salt-sensitive hypertension in rats.

NEW FINDINGS: What is the central question of this study? Recruitment of immune cells to the kidney potentiates hypertensive pathology, but more refined methods are needed to assess these cells functionally. Adoptive transfer studies of immune cells have been limited in rat models and especially in the study of salt-sensitive hypertension. We tested the hypothesis that splenocyte transfer into T-cell-deficient rats is sufficient to exacerbate salt-sensitive hypertension. What is the main finding and its importance? We demonstrate that transfer of splenocytes into T-cell-deficient animals exacerbates salt-sensitive hypertension, and an enrichment in the CD4+ compartment specifically induces this phenomenon. ABSTRACT: Increasing evidence of immune system activation during the progression of hypertension and renal injury has led to a need for new methods to study individual cell types. Transfer of immune cells serves as a powerful tool to isolate effects of specific subsets. Transfer studies in Rag1-/- mice have demonstrated an important role of T-cell activation in hypertension, but this approach has yielded limited success in rat models. Using the T-cell-deficient Dahl salt-sensitive (SS) rat, SSCD247-/- , we hypothesized that splenocyte transfer from SS wild-type animals into SSCD247-/- animals would populate the T-cell compartment. The Dahl SS background provides a model for studying salt-sensitive hypertension; therefore, we also tested whether the dietary salt content of the donor would confer differential salt sensitivity in the recipient. To test this, donors were maintained on either a low-salt or a high-salt diet, and at postnatal day 5 the recipients received splenocyte transfer from one of these groups before a high-salt diet challenge. We showed that splenocyte transfer elevated blood pressures while rats were fed low salt and exacerbated the salt-sensitive increase in pressure when they were fed fed high salt. Furthermore, transfer of splenocytes conferred exacerbated renal damage. Lastly, we confirmed the presence of T cells in the circulation and in the spleen, and that infiltration of immune cells, including T cells, macrophages and B cells, into the kidney was elevated in those receiving the transfer. Interestingly, the source of the splenocytes, from donors fed either a low-salt or a high-salt diet, did not significantly affect these salt-sensitive phenotypes.

Salt-sensitive increase in macrophages in the kidneys of Dahl SS rats.

Studies of Dahl salt-sensitive (SS) rats have shown that renal CD3+ T cells and ED-1+ macrophages are involved in the development of salt-sensitive hypertension and renal damage. The present study demonstrated that the increase in renal immune cells, which accompanies renal hypertrophy and albuminuria in high-salt diet-fed Dahl SS rats, is absent in Sprague-Dawley and SSBN13 rats that are protected from the SS disease phenotype. Flow cytometric analysis demonstrated that >70% of the immune cells in the SS kidney are M1 macrophages. PCR profiling of renal myeloid cells showed a salt-induced upregulation in 9 of 84 genes related to Toll-like receptor signaling, with notable upregulation of the Toll-like receptor 4/CD14/MD2 complex. Because of the prominent increase in macrophages in the SS kidney, we used liposome-encapsulated clodronate (Clod) to deplete macrophages and assess their contribution to salt-sensitive hypertension and renal damage. Dahl SS animals were administered either Clod-containing liposomes (Clod-Lipo), Clod, or PBS-containing liposomes as a vehicle control. Clod-Lipo treatment depleted circulating and splenic macrophages by ∼50%; however, contrary to our hypothesis, Clod-Lipo-treated animals developed an exacerbated salt-sensitive response with respect to blood pressure and albuminuria, which was accompanied by increased renal T and B cells. Interestingly, those treated with Clod also demonstrated an exacerbated phenotype, but it was less severe than Clod-Lipo-treated animals and independent of changes to the number of renal immune cells. Here, we have shown that renal macrophages in Dahl SS animals sustain a M1 proinflammatory phenotype in response to increased dietary salt and highlighted potential adverse effects of Clod-Lipo macrophage depletion.

Renal nerves and leukocyte infiltration in the kidney during salt-sensitive hypertension.

Based on previous studies suggesting a role of renal nerves in renal inflammation, the present studies were performed to test the hypothesis that renal nerves mediate renal damage in Dahl salt-sensitive (SS) hypertension by increasing renal leukocyte infiltration. Experiments were performed in Dahl SS rats with bilateral renal denervation (RDN) and bilateral sham operation (n = 10 or 11 per group) and with unilateral RDN and contralateral sham operation (n = 10). After denervation, rats were switched from a low-salt 0.4% NaCl (LS) diet to a high-salt 4% NaCl (HS) diet and maintained on HS diet for 21 days. Bilateral RDN reduced the magnitude of hypertension assessed by radiotelemetry in Dahl SS rats compared with sham-operated rats (mean arterial pressure 140.9 ±4.8 mmHg and 159.7 ± 3.5 mmHg, respectively) and reduced proteinuria at day 21 of HS diet. However, assessment of renal leukocyte infiltration demonstrated no significant effect of bilateral RDN on the number of infiltrating leukocytes (RDN 3.6 ± 0.5 × 106 vs. sham operated 4.3 ± 0.3 × 106 CD45+ cells) or any of the subsets examined by flow cytometry. The unilateral RDN experiment showed no effect of RDN on the renal infiltration of leukocytes (RDN 6.5 ± 0.9 × 106 vs. sham operated 6.1 ± 1.1 × 106 CD45+ cells/kidney) or renal damage in RDN vs. sham-operated kidney after 21 days of HS diet. This work investigated the relationship between renal nerves and renal inflammation during Dahl SS hypertension. Contrary to our hypothesis, the results of this work suggest that immune cell infiltration in the kidney of Dahl SS rats is not mediated by the renal nerves.

Influence of dietary protein on Dahl salt-sensitive hypertension: a potential role for gut microbiota.

High blood pressure affects 1.39 billion adults across the globe and is the leading preventable cause of death worldwide. Hypertension is a multifaceted disease with known genetic and environmental factors contributing to its progression. Our studies utilizing the Dahl salt-sensitive (SS) rat have demonstrated the remarkable influence of dietary protein and maternal environment on the development of hypertension and renal damage in response to high salt. There is growing interest in the relationship between the microbiome and hypertension, with gut dysbiosis being correlated to a number of pathologies. This review summarizes the current literature regarding the interplay among dietary protein, the gut microbiota, and hypertension. These studies may provide insight into the effects we have observed between diet and hypertension in Dahl SS rats and, we hope, lead to new perspectives where potential dietary interventions or microbiota manipulations could serve as plausible therapies for hypertension.

Role of immune factors in angiotensin II-induced hypertension and renal damage in Dahl salt-sensitive rats.

The present study assessed the importance of immunity in angiotensin (ANG) II (5 ng·kg-1·min-1 iv)-mediated hypertension in Dahl salt-sensitive (SS) rats and SS rats deficient in T and B lymphocytes (SSRag1-/-) fed a 0.4% NaCl diet. Baseline mean arterial blood pressure (MAP) was not different between groups. ANG II infusion significantly increased MAP in both groups, although MAP increased more rapidly in SS rats, and the maximal MAP achieved was significantly greater in SS than SSRag1-/- rats (190 ± 3 vs. 177 ± 3 mmHg) after 12 days. Renal damage, as assessed by albumin excretion rate, was significantly increased after 12 days of ANG lI infusion in SS (from 32 ± 4 to 81 ± 9 mg/day) and SSRag1-/- (from 12 ± 2 to 51 ± 8 mg/day) rats; albumin excretion rate was significantly different between SS and SSRag1-/- rats at all points measured. After 9 days of recovery from ANG II, MAP was decreased to a greater extent in SSRag1-/- than SS rats (143 ± 5 vs. 157 ± 8 mmHg) compared with the peak MAP during ANG II infusion. At this same time point, albumin excretion rate was significantly lower in SSRag1-/- than SS rats (42 ± 8 vs. 66 ± 7 mg/day). Further studies demonstrated an increase in CD45+ total leukocytes, CD11b/c+ macrophages/monocytes, and CD3+ T cells in kidneys of ANG II- compared with vehicle-treated SS rats. The present data suggest that infiltrating T cells in the kidney exacerbate renal damage in ANG II-induced hypertension in SS rats maintained on a 0.4% NaCl diet, similar to results observed with a salt stimulus in SS rats.

Rag1-null Dahl SS rats reveal that adaptive immune mechanisms exacerbate high protein-induced hypertension and renal injury.

The present study, performed in Dahl salt-sensitive (SS) and SS- Rag1-/- rats lacking T and B lymphocytes, tested the hypothesis that immune cells amplify salt-sensitive hypertension and kidney damage in response to a high-protein diet. After being weaned, SS and SS- Rag1-/- rats were placed on an isocaloric, 0.4% NaCl diet containing normal (18%) or high (30%) protein. At 9 wk of age, rats were switched to a 4.0% NaCl diet containing the same amount of dietary protein and maintained on the high-salt diet for 3 wk. After being fed the high-salt diet, SS rats fed high protein had amplified hypertension and albumin excretion (158.7 ± 2.6 mmHg and 140.8 ± 16.0 mg/day, respectively, means ± SE) compared with SS rats fed normal protein (139.4 ± 3.6 mmHg and 69.4 ± 11.3 mg/day). When compared with the SS rats, SS- Rag1-/- rats fed high protein were protected from exacerbated hypertension and albuminuria (142.9 ± 5.8 mmHg and 66.2 ± 10.8 mg/day). After 3 wk of the high-salt diet, there was a corresponding increase in total leukocyte infiltration (CD45+) in the kidneys of both strains fed high-protein diet. The SS- Rag1-/- rats fed high-protein diet had 74-86% fewer CD3+ T lymphocytes and CD45R+ B lymphocytes infiltrating the kidney versus SS rats, but there was no difference in the infiltration of CD11b/c+ monocytes and macrophages, suggesting that the protective effects observed in the SS- Rag1-/- rats are specific to the reduction of lymphocytes. With the SS- Rag1-/- rats utilized as a novel tool to explore the effects of lymphocyte deficiency, these results provide evidence that adaptive immune mechanisms contribute to the exacerbation of salt-induced hypertension and renal injury mediated by increased dietary protein intake.

Novel adaptive and innate immunity targets in hypertension.

Hypertension is a worldwide epidemic and global health concern as it is a major risk factor for the development of cardiovascular diseases. A relationship between the immune system and its contributing role to the pathogenesis of hypertension has been long established, but substantial advancements within the last few years have dissected specific causal molecular mechanisms. This review will briefly examine these recent studies exploring the involvement of either innate or adaptive immunity pathways. Such pathways to be discussed include innate immunity factors such as antigen presenting cells and pattern recognition receptors, adaptive immune elements including T and B lymphocytes, and more specifically, the emerging role of T regulatory cells, as well as the potential of cytokines and chemokines to serve as signaling messengers connecting innate and adaptive immunity. Together, we summarize these studies to provide new perspective for what will hopefully lead to more targeted approaches to manipulate the immune system as hypertensive therapy.

The function of SH2B3 (LNK) in the kidney.

Recent evidence indicates the adaptor protein SH2B3 has a major role in the progression of renal diseases. SH2B3 is highly expressed by hematopoietic cells and regulates cytokine signaling, inducing cell-specific effects. Additionally, its expression in other cell types suggests that SH2B3 may have a more extensive role within the kidney. Ex vivo studies have determined targets of SH2B3 cell-specific signaling, while in vivo studies have observed the SH2B3 overall affects in the progression of renal diseases. This mini-review covers the function of SH2B3-expressing cell types that contribute to renal pathologies and their regulation by SH2B3.

Interleukin-6 inhibition attenuates hypertension and associated renal damage in Dahl salt-sensitive rats.

Immune cells in the kidney are implicated in the development of hypertension and renal damage in the Dahl salt-sensitive (SS) rat. Interestingly, interleukin 6 (IL-6) mRNA is 54-fold higher in T-lymphocytes isolated from the kidney compared with circulating T-lymphocytes. The present experiments assessed the role of IL-6 in the development of SS hypertension by treating rats (n = 13-14/group) with an IL-6 neutralizing antibody or normal IgG during an 11-day period of high-salt (4.0% NaCl chow) intake. The mean arterial pressure (MAP) and urine albumin excretion rates (Ualb) were not different between the groups fed low salt (0.4% NaCl). Following 11 days of drug treatment and high salt, however, the rats receiving anti-IL-6 demonstrated a 47% reduction of IL-6 in the renal medulla compared with control SS. Moreover, the increase in MAP following 11 days of high-NaCl intake was significantly attenuated in SS administered anti-IL-6 compared with the control group (138 ± 3 vs. 149 ± 3 mmHg) as was the salt-induced increase in Ualb and glomerular and tubular damage. To investigate potential mechanisms of action, a flow cytometric analysis of immune cells in the kidney (n = 8-9/group) demonstrated that the total number of monocytes and macrophages was significantly lower in the treatment vs. the control group. The total number of T- and B-lymphocytes in the kidneys was not different between groups. These studies indicate that IL-6 production may participate in the development of SS hypertension and end-organ damage by mediating increased infiltration or proliferation of macrophages into the kidney.

Role of immune cells in salt-sensitive hypertension and renal injury.

PURPOSE OF REVIEW: Immune mechanisms exacerbate the severity of hypertension in humans and animal models of disease. This review summarizes recent mechanistic studies exploring the pathways whereby immunity influences salt-sensitive hypertension and renal disease. RECENT FINDINGS: Emphasis is placed on the role of T cell subtypes, the mechanisms of T-cell activation, and the identification of potential antigens or neoantigens. SUMMARY: Significant advancements have occurred in the search for pathways which activate the adaptive immune response. An enhanced understanding of the factors contributing to hypertension can lead to better therapies.

Candidate genes for hypertension: insights from the Dahl S rat.

Human genetic linkage and association studies have nominated many genes as possible contributors to disease. Mutating or deleting these genes in a relevant disease model can validate their association with disease and potentially uncover novel mechanisms of pathogenesis. Targeted genetic mutagenesis has only recently been developed in the rat, and this technique has been applied in the Dahl salt-sensitive (S) rat to investigate human candidate genes associated with hypertension. This mini-review communicates the findings of these studies and displays how targeted genetic mutagenesis may contribute to the discovery of novel therapies for patients.