Klk1 as One of the Genes Contributing to Hypertension in Dahl Salt-Sensitive Rat

Evaluation of a crystallographic surrogate for kallikrein 5 in the discovery of novel inhibitors for Netherton syndrome

The inhibition of kallikrein 5 (KLK5) has been identified as a potential strategy for treatment of the genetic skin disorder Netherton syndrome, in which loss-of-function mutations in the SPINK5 gene lead to down-regulation of the endogenous inhibitor LEKTI-1 and profound skin-barrier defects with severe allergic manifestations. To aid in the development of a medicine for this target, an X-ray crystallographic system was developed to facilitate fragment-guided chemistry and knowledge-based drug-discovery approaches. Here, the development of a surrogate crystallographic system in place of KLK5, which proved to be challenging to crystallize, is described. The biochemical robustness of the crystallographic surrogate and the suitability of the system for the study of small nonpeptidic fragments and lead-like molecules are demonstrated.

P2X7 receptor is involved in lung injuries induced by ischemia-reperfusion in pulmonary arterial hypertension rats

Pulmonary arterial hypertension (PAH) is a progressive disease that ultimately leads to right heart failure and death. Current strategies are ineffective to prevent and cure PAH, especially in those who undergo cardiopulmonary bypass. P2 × 7 receptors (P2 × 7Rs) have been implied to participate in the pathogenesis of PAH and injuries induced by ischemia-reperfusion (IR). In the present study, we aimed to assess the potential therapeutic effects of anti-P2 × 7Rs on PAH and IR-induced lung injuries in rats and explore their underlying cellular and molecular mechanisms. In the present study, we have successfully established rat models with PAH and/or lung IR injuries. Immunohistochemical staining, western blot, and polymerase chain reaction were performed to detect the P2 × 7R expression in these models; P2 × 7R-specific inhibitor, Brilliant Blue G (BBG), was used to antagonize P2 × 7R, and enzyme-linked immunosorbent assay was used to help evaluate the P2 × 7R-mediated function in PAH with or without IR. Moreover, BBG, SB203580 (p38/MAPK inhibitor), and CD39 (adenosine triphosphate hydrolase) were applied to explore the inner signal pathway in vitro and in vivo. Our findings showed that P2 × 7R was involved in the development of PAH. By applying BBG, we have shown that the severity of PAH and IR was ameliorated through reducing the release of proinflammatory cytokines. Moreover, our results in vitro and in vivo indicated that P2 × 7R regulated the release of inflammatory mediators by the p38/MAPK signal pathway. Most important, CD39 showed the most dominant potential in improving inflammation in lung injuries caused by PAH and IR. In conclusion, the inhibition of P2 × 7R could effectively attenuate inflammation in lung injuries caused by PAH and IR in rats by reducing proinflammatory cytokines through regulating the p38/MAPK pathway.

Transcriptome reveals the overexpression of a kallikrein gene cluster (KLK1/3/7/8/12) in the Tibetans with high altitude-associated polycythemia

High altitude-associated polycythemia (HAPC) is a very common disease. However, it the disease is still unmanageable and the related molecular mechanisms remain largely unclear. In the present study, we aimed to explore the molecular mechanisms responsible for the development of HAPC using transcriptome analysis. Transcriptome analysis was conducted in 3 pairs of gastric mucosa tissues from patients with HAPC and healthy residents at a similar altitude. Endoscopy and histopathological analyses were used to examine the injury to gastric tissues. Molecular remodeling was performed for the interaction between different KLK members and cholesterol. HAPC was found to lead to morphological changes and pathological damage to the gastric mucosa of patients. A total of 10,304 differentially expressed genes (DEGs) were identified. Among these genes, 4,941 DEGs were upregulated, while 5,363 DEGs were downregulated in the patients with HAPC (fold change ≥2, P<0.01 and FDR <0.01). In particular, the kallikrein gene cluster (KLK1/3/7/8/12) was upregulated >17-fold. All the members had high-score binding cholesterol, particularly for the polymers of KLK7. The kallikrein gene cluster (KLK1/3/7/8/12) is on chromosome 19q13.3-13.4. The elevated levels of KLK1, KLK3, KLK7, KLK8 and KLK12 may be closely associated with the hypertension, inflammation, obesity and other gastric injuries associated with polycythemia. The interaction of KLKs and cholesterol maybe play an important role in the development of hypertension. The findings of the present study revealed that HAPC induces gastric injury by upregulating the kallikrein gene cluster (KLK1/3/7/8/12), which can bind cholesterol and result in kallikrein hypertension. These findings provide some basic information for understanding the molecular mechanisms responsible for HAPC and HAPC-related diseases.

Early kidney damage induced by subchronic exposure to PM2.5 in rats

BACKGROUND

Particulate matter exposure is associated with respiratory and cardiovascular system dysfunction. Recently, we demonstrated that fine particles, also named PM_2.5, modify the expression of some components of the angiotensin and bradykinin systems, which are involved in lung, cardiac and renal regulation. The endocrine kidney function is associated with the regulation of angiotensin and bradykinin, and it can suffer damage even as a consequence of minor alterations of these systems. We hypothesized that exposure to PM_2.5 can contribute to early kidney damage as a consequence of an angiotensin/bradykinin system imbalance, oxidative stress and/or inflammation.

RESULTS

After acute and subchronic exposure to PM_2.5, lung damage was confirmed by increased bronchoalveolar lavage fluid (BALF) differential cell counts and a decrease of surfactant protein-A levels. We observed a statistically significant increment in median blood pressure, urine volume and water consumption after PM_2.5 exposure. Moreover, increases in the levels of early kidney damage markers were observed after subchronic PM_2.5 exposure: the most sensitive markers, β-2-microglobulin and cystatin-C, increased during the first, second, sixth and eighth weeks of exposure. In addition, a reduction in the levels of specific cytokines (IL-1β, IL-6, TNF-α, IL-4, IL-10, INF-γ, IL-17a, MIP-2 and RANTES), and up-regulated angiotensin and bradykinin system markers and indicators of a depleted antioxidant response, were also observed. All of these effects are in concurrence with the presence of renal histological lesions and an early pro-fibrotic state.

CONCLUSION

Subchronic exposure to PM_2.5 induced an early kidney damage response that involved the angiotensin/bradykinin systems as well as antioxidant and immune imbalance. Our study demonstrates that PM_2.5 can induce a systemic imbalance that not only affects the cardiovascular system, but also affects the kidney, which may also overall contribute to PM-related diseases.

Pex11a deficiency is associated with a reduced abundance of functional peroxisomes and aggravated renal interstitial lesions

Although proteinuria is known to be associated with the deterioration of chronic kidney disease, the molecular basis of this mechanism is not fully understood. We previously found that Pex11a deficiency was associated with a reduction of functional peroxisomes and impaired fatty acid metabolism in hepatocytes and resulted in steatosis. Proximal tubule cells are rich in peroxisomes. We assessed whether Pex11a deficiency might result in the derangement of peroxisome systems in proximal tubule cells and the aggravation of tubulointerstitial lesions in chronic kidney disease. Histological analyses showed that the number of functional peroxisomes in proximal tubule cells was reduced in Pex11a knockout (Pex11a(-/-)) mice. To clarify whether a decrease in the number of tubular peroxisomes might aggravate interstitial lesions, we assessed 2 models in which proximal tubule cells are overloaded with fatty acids (ie, deoxycorticosterone acetate and salt hypertension and the overload of fatty acid-bound albumin). Deoxycorticosterone acetate -salt-treated Pex11a(-/-) mice exhibited greater interstitial lesions than deoxycorticosterone acetate-salt-treated wild-type mice in terms of tubular lipid accumulation, blood pressure, urinary albumin, urinary N-acetyl-β-d-glucosaminidase, urinary 8-iso-prostane, and the histological evaluation of fibrosis and inflammation. An overload of fatty acid-bound albumin also resulted in more severe tubulointerstitial lesions in Pex11a(-/-) mice than in wild-type mice. Fenofibrate, a peroxisome proliferator-activated receptor-α agonist, restored the abundance of peroxisomes and reduced the tubulointerstitial lesions induced by deoxycorticosterone acetate-salt hypertension. In conclusion, our results indicate that proximal tubule peroxisomes play an important role in proteinuria-induced interstitial lesions. The activation of tubular peroxisomes might be an excellent therapeutic strategy against chronic kidney disease.

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.

Identification of hypertension susceptibility loci on rat chromosome 12

Previous studies have identified multiple blood pressure and renal disease quantitative trait loci located on rat chromosome 12. In the present study, we narrowed blood pressure loci using a series of overlapping Dahl salt-sensitive/Mcwi (SS)-12 Brown Norway (BN) congenic lines. We found that transferring 6.1 Mb of SS chromosome 12 (13.4-19.5 Mb) onto the consomic SS-12BN background significantly elevated blood pressure on 1% NaCl (146±6 versus 127±1 mm Hg; P<0.001) and 8% NaCl diets (178±7 versus 144±2 mm Hg; P<0.001). Compared with the SS-12BN consomic, these animals also had significantly elevated albumin (218±31 versus 104±8 mg/d; P<0.001) and protein excretion (347±41 versus 195±12 mg/d; P<0.001) on a 1% NaCl diet. Elevated blood pressure, albuminuria, and proteinuria coincided with greater renal and cardiac damage, demonstrating that SS allele(s) within the 6.1 Mb congenic interval are associated with strong cardiovascular disease phenotypes. Sequence analysis of the 6.1 Mb congenic region revealed 12 673 single nucleotide polymorphisms between SS and BN rats. Of these polymorphisms, 293 lie within coding regions, and 18 resulted in nonsynonymous changes in conserved genes, of which 5 were predicted to be potentially damaging to protein function. Syntenic regions in human chromosome 7 have also been identified in multiple linkage and association studies of cardiovascular disease, suggesting that genetic variants underlying cardiovascular phenotypes in this congenic strain can likely be translated to a better understanding of human hypertension.

P2X7 deficiency attenuates hypertension and renal injury in deoxycorticosterone acetate-salt hypertension

The P2X(7) receptor is a ligand-gated ion channel, and genetic variations in the P2X(7) gene significantly affect blood pressure. P2X(7) receptor expression is associated with renal injury and inflammatory diseases. Uninephrectomized wild-type (WT) and P2X(7)-deficient (P2X(7) KO) mice were subcutaneously implanted with deoxycorticosterone acetate (DOCA) pellets and fed an 8% salt diet for 18 days. Their blood pressure was assessed by a telemetry system. The mice were placed in metabolic cages, and urine was collected for 24 h to assess renal function. After 18 days of DOCA-salt treatment, P2X(7) mRNA and protein expression increased in WT mice. Blood pressure in P2X(7) KO mice was less than that of WT mice (mean systolic blood pressure 133 ± 3 vs. 150 ± 2 mmHg). On day 18, urinary albumin excretion was lower in P2X(7) KO mice than in WT mice (0.11 ± 0.07 vs. 0.28 ± 0.07 mg/day). Creatinine clearance was higher in P2X(7) KO mice than in WT mice (551.53 ± 65.23 vs. 390.85 ± 32.81 μl·min(-1)·g renal weight(-1)). Moreover, renal interstitial fibrosis and infiltration of immune cells (macrophages, T cells, B cells, and leukocytes) were markedly attenuated in P2X(7) KO mice compared with WT mice. The levels of IL-1β, released by macrophages, in P2X(7) KO mice had decreased dramatically compared with that in WT mice. These results strongly suggest that the P2X(7) receptor plays a key role in the development of hypertension and renal disease via increased inflammation, indicating its potential as a novel therapeutic target.

P2X(7) receptor antagonism attenuates the hypertension and renal injury in Dahl salt-sensitive rats

The P2X(7) receptor is a ligand-gated ion channel activated by extracellular ATP, and a common genetic variation in the P2X(7) gene significantly affects blood pressure. P2X(7) receptor expression is associated with renal injury and some inflammatory diseases. Brilliant blue G (BBG) is a selective rat P2X(7) receptor antagonist. In this study, to test whether BBG has protective effects on salt-sensitive hypertension and renal injury, Dahl salt-sensitive (DS) rats fed an 8% NaCl diet were i.p. injected with BBG (50 mg kg(-1) per day) for 4 weeks. We also tested another P2X(7) receptor antagonist, namely A-438079 (100 mg kg(-1) per day), for 7 days. We found that P2X(7) antagonism markedly attenuated salt-sensitive hypertension, urinary protein or albumin excretion, renal interstitial fibrosis and macrophage and T-cell infiltration in the DS rats, and significantly improved creatinine clearance. In an in vitro experiment using macrophages, we showed that lipopolysaccharide (LPS)-primed macrophages from the DS rats released more interleukin-1 beta in response to BzATP, a P2X(7) receptor agonist, than the macrophages from Lewis rats, possibly due to higher P2X(7) expression in the DS rats. In conclusion, in vivo blockade of P2X(7) receptors attenuated salt-sensitive hypertension and renal injury in the DS rats. Thus, P2X(7) appears to be responsible for a vicious cycle of salt-sensitive hypertension and renal injury in the DS rats, through higher expression in the immune cells. Furthermore, P2X(7) antagonists can prevent the development of salt-sensitive hypertension and renal injury, thus confirming that the P2X(7) receptor is an important therapeutic target.

Serious limitations of the QTL/microarray approach for QTL gene discovery

BACKGROUND

It has been proposed that the use of gene expression microarrays in nonrecombinant parental or congenic strains can accelerate the process of isolating individual genes underlying quantitative trait loci (QTL). However, the effectiveness of this approach has not been assessed.

RESULTS

Thirty-seven studies that have implemented the QTL/microarray approach in rodents were reviewed. About 30% of studies showed enrichment for QTL candidates, mostly in comparisons between congenic and background strains. Three studies led to the identification of an underlying QTL gene. To complement the literature results, a microarray experiment was performed using three mouse congenic strains isolating the effects of at least 25 biometric QTL. Results show that genes in the congenic donor regions were preferentially selected. However, within donor regions, the distribution of differentially expressed genes was homogeneous once gene density was accounted for. Genes within identical-by-descent (IBD) regions were less likely to be differentially expressed in chromosome 2, but not in chromosomes 11 and 17. Furthermore, expression of QTL regulated in cis (cis eQTL) showed higher expression in the background genotype, which was partially explained by the presence of single nucleotide polymorphisms (SNP).

CONCLUSIONS

The literature shows limited successes from the QTL/microarray approach to identify QTL genes. Our own results from microarray profiling of three congenic strains revealed a strong tendency to select cis-eQTL over trans-eQTL. IBD regions had little effect on rate of differential expression, and we provide several reasons why IBD should not be used to discard eQTL candidates. In addition, mismatch probes produced false cis-eQTL that could not be completely removed with the current strains genotypes and low probe density microarrays. The reviewed studies did not account for lack of coverage from the platforms used and therefore removed genes that were not tested. Together, our results explain the tendency to report QTL candidates as differentially expressed and indicate that the utility of the QTL/microarray as currently implemented is limited. Alternatives are proposed that make use of microarray data from multiple experiments to overcome the outlined limitations.

Tissue kallikrein deficiency and renovascular hypertension in the mouse

The kallikrein kinin system (KKS) is involved in arterial and renal functions. It may have an antihypertensive effect in both essential and secondary forms of hypertension. The role of the KKS in the development of two-kidneys, one-clip (2K1C) hypertension, a high-renin model, was investigated in mice rendered deficient in tissue kallikrein (TK) and kinins by TK gene inactivation (TK−/−) and in their wild-type littermates (TK+/+). Four weeks after clipping the renal artery, blood flow was reduced in the clipped kidney (2K1C-TK+/+: −90%, 2K1C-TK−/−: −93% vs. sham-operated mice), and the kidney mass had also decreased (2K1C-TK+/+: −65%, 2K1C-TK−/−: −66%), whereas in the unclipped kidney, blood flow (2K1C-TK+/+: +19%, 2K1C-TK−/−: +17%) and kidney mass (2K1C-TK+/+: +32%, 2K1C-TK−/−: +30%) had both increased. The plasma renin concentration (2K1C-TK+/+: +78%, 2K1C-TK−/−: +65%) and renal renin content of the clipped kidney (2K1C-TK+/+: +58%, 2K1C-TK−/−: +65%) had increased significantly. There was no difference for these parameters between 2K1C-TK+/+ and 2K1C-TK−/− mice. Blood pressure monitored by telemetry and by plethysmography, rose immediately after clipping in both genotypes, and reached similar levels (2K1C-TK+/+: +24%, 2K1C-TK−/−: +21%). 2K1C-TK+/+ and 2K1C-TK−/− mice developed similar concentric left ventricular hypertrophy (+24% and +17%, respectively) with normal cardiac function. These findings suggest that in the context of chronic unilateral reduction in renal blood flow, TK and kinins do not influence the trophicity of kidneys, the synthesis and secretion of renin, blood pressure increase, and cardiac remodeling due to renin angiotensin system activation.

Involvement of prolylcarboxypeptidase in the effect of rutaecarpine on the regression of mesenteric artery hypertrophy in renovascular hypertensive rats

1. Previous studies indicate that rutaecarpine blocks increases in blood pressure and inhibits vascular hypertrophy in experimentally hypertensive rats. The aim of the present study was to determine whether the effects of rutaecarpine are related to activation of prolylcarboxypeptidase (PRCP). 2. Renovascular hypertensive rats (Goldblatt two-kidney, one-clip (2K1C)) were developed using male Sprague-Dawley rats. Chronic treatment with rutaecarpine (10 or 40 mg/kg per day) or losartan (20 mg/kg per day) for 4 weeks to the hypertensive rats caused a sustained dose-dependent attenuation of increases in blood pressure, increased lumen diameter and decreased media thickness, which was accompanied by a similar reduction in the media cross-sectional area : lumen area ratio in mesenteric arteries compared with untreated hypertensive rats. 3. Angiotensin (Ang) II expression was significantly increased in mesenteric arteries of hypertensive rats compared with sham-operated rats. No significant differences in plasma AngII levels were observed between untreated hypertensive and sham-operated rats. Hypertensive rats treated with high-dose rutaecarpine had significantly decreased Ang II levels in both the plasma and mesenteric arteries. 4. Expression of PRCP protein or kallikrein mRNA was significantly inhibited in the right kidneys and mesenteric arteries of hypertensive rats. However, expression of PRCP protein and kallikrein mRNA was significantly increased after treatment with rutaecarpine or losartan (20 mg/kg per day). 5. The data suggest that the repression of increases in systolic blood pressure and reversal of mesenteric artery remodelling by rutaecarpine may be related to increased expression of PRCP in the circulation and small arteries in 2K1C hypertensive rats.

Inhalation exposure to carbon black induces inflammatory response in rats

BACKGROUND

A link between exposure to fine particulate matter and cardiovascular events has been established. Inhaled nanoparticles are thought to pass through the lungs to reach other tissues via systemic circulation and to induce cell or tissue injuries. It was recently shown that long-term exposure to intra-tracheal dispersion of nano-sized carbon black (CB) exacerbates atherosclerotic lesions in low-density lipoprotein receptor-deficient mice. Because intra-tracheal dispersion of CB may be associated with aggregate formation and may not be an ideal method for CB exposure, whole-body inhalation exposure was used in the present study, the aim of which was to examine whether exposure of rats to nano-sized CB particles by inhalation leads to translocation of these particles into the circulation, exerting direct adverse effects on extrapulmonary tissues.

METHODS AND RESULTS

Sprague-Dawley rats were exposed to a high dose of CB or filtered air for 6 h/day, 5 days a week for a total of 4 weeks. Although the presence of CB was confirmed in pulmonary macrophages, electron microscopic survey did not detect CB in other tissues including liver, spleen and aorta. CB exposure raised blood pressure levels in an exposure-time dependent manner. Levels of circulating inflammatory marker proteins, including monocyte chemoattractant protein-1, interleukin-6, and C-reactive protein, were higher in the CB-treated group than in the controls.

CONCLUSION

Evidence of translocation of inhaled CB was not obtained. It is likely that inhaled nano-sized CB particles form aggregations in the lung and do not exert direct adverse effects on extrapulmonary tissues. Air-pollution-mediated cardiovascular events appear to be induced by the low-grade inflammatory response to the accumulation of aggregated nano-sized particles in the lung.

A coding polymorphism of the kallikrein 1 gene is associated with essential hypertension: a tagging SNP-based association study in a Chinese Han population

OBJECTIVE

The aim of this study was to investigate the association between common variants in the human tissue kallikrein 1 (KLK1) gene and susceptibility to essential hypertension in Chinese Han.

METHODS

A tagging single nucleotide polymorphism (tSNP) approach was used for a case-control study in 2411 patients with essential hypertension and 2348 controls. All DNA samples and clinical data were collected from the International Collaborative Study of Cardiovascular Disease in Asia (InterASIA).

RESULTS

Based on the HapMap data of Han Chinese in Beijing (CHB) population, two non-synonymous polymorphisms, namely rs5517 (Glu162Lys) and rs5516 (Gln121Glu), were selected as tSNPs which could efficiently tag eight SNPs of the KLK1 gene with R larger than 90% for both haplotypes and single locus. Significant differences were found between groups for frequencies of rs5517 A allele (42.48% in cases versus 39.32% in controls, P=0.0019) and AA genotype [adjusted odds ratio (OR)=1.25 for AA versus AG/GG, P=0.0067]. The haplotype composed of the rs5517 A and rs5516 G allele significantly increased the risk of hypertension, with adjusted OR of 1.12 [95% confidence interval (CI), 1.04-1.28, P=0.0377] when compared with the common haplotype G-C. Diplotype analysis also showed a significant association between the diplotype of AG-AC and essential hypertension (OR=1.34, 95% CI, 1.07-1.68, P=0.0096).

CONCLUSIONS

The present study suggested that rs5517 in the KLK1 gene was significantly associated with essential hypertension in a Chinese Han population.

Congenic interval mapping of RNO10 reveals a complex cluster of closely-linked genetic determinants of blood pressure

Genetic dissection of the rat genome for identifying alleles that cause abnormalities in blood pressure (BP) resulted in the mapping of a significant number of BP quantitative trait loci (QTLs). In this study we mapped at least one such BP QTL on rat chromosome 10 (RNO10) as being within the introgressed segment of a S.LEW congenic strain S.LEWx12x2x3x8 spanning 1.34 Mb from 70,725,437 bp to 72,063,232 bp. BP of 3 congenic strains that span shorter segments of this region was additionally examined. Results obtained indicate that LEW alleles that comprise a 375-kb introgressed segment of the congenic strain S.LEWx12x2x3x5 (70,725,437 bp to 71,100,513 bp) increase BP. The magnitude of change in BP exhibited by the 2 strains, S.LEWx12x2x3x8 and S.LEWx12x2x3x5, is the net phenotypic effect of the underlying genetic determinants of BP. In this respect, the current data are superior to previous QTL localization of BP QTL1, which was hypothesized based on differential congenic segments. Genetic dissection using these 2 congenic strains as tools is expected to facilitate further dissection of the regions. Meanwhile, differential congenic segments were used to predict and thereby prioritize regions for candidate gene analysis. Using this approach, 2 distinct regions of 401 kb and 409 kb within S.LEWx12x2x3x8 and a 104 kb region within S.LEWx12x2x3x5 were prioritized for further consideration. Because all of these genetic elements are located within a 1.06-Mb region of RNO10, our study has revealed a remarkable insight into a genomic module comprising very closely-linked, opposing genetic determinants of BP.

Amadori-glycated albumin-induced vascular smooth muscle cell proliferation and expression of inhibitor of apoptosis protein-1 and nerve growth factor-gamma

We investigated the effects of Amadori-glycated serum albumin (GSA) on cell proliferation as well as expressions of antioxidant enzyme genes and marker genes associated with signal transduction pathways in rat aortic vascular smooth muscle cells (VSMCs). Quiescent VSMCs treated with GSA (0-500 microg/mL, 48 h) exhibited a dose-dependent increase in proliferation that was prevented by PD98059 (25 microM), suggesting a MAPK-dependent signaling pathway. Compared with bovine serum albumin (BSA)-treated cells, the GSA (500 microg/mL, 24~h)-treated VSMCs showed a higher superoxide dismutase 2 gene expression in quantitative RT-PCR, suggesting the involvement of oxidative stress. In a focused oligonucleotide array containing 96 signal transduction-related genes, expression of inhibitor of apoptosis protein-1 (IAP-1), nerve growth factor-gamma (NGF-gamma), and c-jun genes was significantly higher in the GSA-treated VSMCs. These results suggest that induction of antiapoptotic proteins like IAP-1 and strong mitogens like NGF-gamma by GSA might further contribute to the VSMC proliferation and accelerated vascular remodeling in diabetes.

Exclusion of the Catechol-O-Methyltransferase Gene from Genes Contributing to Salt-Sensitive Hypertension in Dahl Salt-Sensitive Rats

Catechol-O-methyltransferase (COMT) is an enzyme that inactivates catecholamines. Several studies have suggested that this enzyme may play a role in blood pressure regulation. We previously reported that the expression levels of Comt mRNA in Dahl salt-sensitive (DS) rats were lower than those in Lewis (LEW) rats. However, the physiological significance of this phenomenon has not been investigated. The purpose of the present study was to evaluate the significance of lower expression of Comt in Dahl salt-sensitive hypertension. The Comt gene in DS rats has a palindromic insertion in 3'-untranslated region, which appears to be responsible for reduced mRNA stability. A genome-wide quantitative trait loci (QTL) analysis of blood pressure using 107 F2 rats indicated that a statistically significant QTL for pulse pressure was located at the Comt locus in chromosome 11. Microarray analysis confirmed that Comt was the only gene differentially expressed between DS and LEW rats in this chromosomal region. However, COMT inhibitors had no significant effects on blood pressure in either DS or LEW rats. Thus, Comt was excluded from the candidate genes contributing to salt-sensitive hypertension in DS rats. A true gene responsible for pulse pressure in this chromosome 11 region remains to be determined.

The Monocyte Chemotactic Protein-1 Gene May Contribute to Hypertension in Dahl Salt-Sensitive Rats

In a previous study, we performed a genome-wide quantitative trait loci (QTLs) analysis for blood pressure using F2 rats derived from Dahl salt-sensitive (DS) and Lewis (LEW) rats and identified two QTLs that influenced blood pressure levels. Although we determined that one of the causative genes in the chromosome (Ch) 1 region seemed to be Klk1, we did not perform detailed analyses on the Ch10 QTL region. The purpose of the present study was to identify candidate genes that influence blood pressure in the Ch10 QTL region. Using microarray analysis, we compiled a list of the genes that are differentially expressed between the two strains and that were localized to the Ch10 QTL region. Subsequent reverse transcription-polymerase chain reaction (RT-PCR) and Northern blot analysis identified that, while the expression levels of Ccl2 mRNA were not different between the kidneys of DS and LEW rats fed a normal diet, those in DS were 10-fold higher than those in LEW under a high-salt diet. Although the promoter reporter assay failed to identify causative nucleotide changes that led to the differential expression, monocyte chemotactic protein-1 (MCP-1) release from isolated monocytes were significantly higher in DS than in LEW. Intriguingly, this Ch10 QTL for blood pressure was also a possible QTL for urinary albumin excretion. Since Ccl2 is well known to be involved in various types of renal injury, it is likely that a higher expression of Ccl2 might aggravate macrophage infiltration, which in turn could aggravate tubulointerstitial injury, and thereby accelerate salt-sensitive hypertension. Thus, Ccl2 appears to be a interesting candidate gene for salt-sensitive hypertension in DS.

Assessment of the microRNA system in salt-sensitive hypertension

Most animal microRNAs are imperfectly complementary to their mRNA targets and inhibit protein synthesis through an unknown mechanism. MicroRNAs have been reported to play important roles in a number of biological processes. We assessed the microRNA system in Dahl salt-sensitive rats in order to investigate possible roles of microRNA in salt-sensitive hypertension. We constructed microRNA libraries from the kidneys of Dahl salt-sensitive and Lewis rats taking normal or high-salt diets (4 groups), and identified 91 previously reported and 12 new microRNAs expressed in the kidney. We then used Northern blotting to assess the expression levels of 118 microRNAs in the kidneys and heart ventricles. No significant differences in microRNA expression profiles were observed among the 4 groups. Thus, the microRNA system seemed to be unlikely to contribute to salt-sensitive hypertension in Dahl salt-sensitive rats.