Chieko Ihoriya

Selective estrogen receptor modulation attenuates proteinuria-induced renal tubular damage by modulating mitochondrial oxidative status.

Proteinuria is an independent risk factor for progressive renal diseases because it initiates or aggravates tubulointerstitial injury. Clinically, females are less susceptible to progression of chronic kidney disease; however, the mechanisms underlying the renoprotective effect of estrogen receptor stimulation have yet to be clarified. Recently, inflammasome-dependent inflammatory responses were shown to be triggered by free fatty acids, and mitochondria-derived reactive oxygen species were shown to be required for this response. Albumin-bound free fatty acids trigger inflammasome activation through mitochondrial reactive oxygen species production in human proximal tubule epithelial cells in vitro, an effect inhibited by raloxifene. Female ICR-derived glomerulonephritic mice (mice with hereditary nephritic syndrome) were ovariectomized and treated with raloxifene, a selective estrogen receptor modulator. Ovariectomized mice showed activation of tubular inflammasomes and elevated levels of inflammasome-dependent cytokines. Raloxifene attenuated these changes ameliorating tubulointerstitial damage, reduced production of reactive oxygen species, averted morphological changes, and improved respiratory function in mitochondria. The expression of genes that encode rate-limiting enzymes in the mitochondrial β-oxidation pathway was reduced by ovariectomy but enhanced by raloxifene. Thus, inflammasomes may be a novel and promising therapeutic target for proteinuria-induced renal injury.

Relationship between vascular function indexes, renal arteriolosclerosis, and renal clinical outcomes in chronic kidney disease

Hypertension contributes critically to the development of renal arteriolosclerosis in chronic kidney disease (CKD), but the impact of vascular function indexes including central blood pressure on renal arteriolosclerosis has not been investigated. We determined whether vascular function indexes were related to renal arteriolosclerosis and renal clinical outcomes in CKD.

Angiostatin production increases in response to decreased nitric oxide in aging rat kidney

The development of interstitial fibrosis occurs with aging. Impaired angiogenesis, associated with progressive loss of the renal microvasculature, is thought to be a cause of age-related nephropathy. However, the mechanism of capillary loss in aging kidney has not been fully elucidated. Angiostatin is a kringle-containing fragment of plasminogen and is a potent inhibitor of angiogenesis in vivo. Whether angiostatin generation is increased in the aging kidney has not been investigated. We examined 4, 10, 16, and 24-month-old Sprague-Dawley rats for angiostatin production and found that angiostatin generation was increased in aged rats. The protein expression and the activity of cathepsin D—the enzyme for angiostatin production—were increased in aged rats. In the aging kidney, nitric oxide (NO) availability is decreased. To investigate the role of NO in angiostatin production, human umbilical vein endothelial cells were treated with L-NG-nitroarginine methyl ester (L-NAME). L-NAME-treated cells showed increased cathepsin D activity and angiostatin production. For in vivo experiments, 16- to 18-month-old rats were treated with L-NAME or molsidomine for 3 months. Angiostatin production was increased in L-NAME-treated kidney, accompanied by increased cathepsin D activity. In contrast, angiostatin production was decreased in molsidomine-treated kidney, accompanied by decreased cathepsin D activity. In conclusion, angiostatin generation by cathepsin D was increased in the aging rat kidney. Decreased NO production activated cathepsin D activity. Increased angiostatin production may be related to capillary loss and interstitial damage in the aging rat kidney.

Angiotensin II regulates islet microcirculation and insulin secretion in mice.

Angiotensin II causes potent increases in systemic and local pressure through its vasoconstrictive effect. Despite the importance of angiotensin II for local blood flow regulation, whether angiotensin II regulates the pancreatic islet microcirculation remains incompletely understood. We hypothesized that angiotensin II directly regulates the pancreatic islet microcirculation and thereby regulates insulin secretion. The aims of this study were to develop a new technique to visualize pancreatic islet hemodynamic changes in vivo and to analyze changes in islet circulation induced by angiotensin II or an angiotensin type 1 receptor blocker.

Infiltration of M1, but not M2, macrophages is impaired after unilateral ureter obstruction in Nrf2-deficient mice

Chronic inflammation can be a major driver of the failure of a variety of organs, including chronic kidney disease (CKD). The NLR family pyrin domain-containing 3 (NLRP3) inflammasome has been shown to play a pivotal role in inflammation in a mouse kidney disease model. Nuclear factor erythroid 2-related factor 2 (Nrf2), the master transcription factor for anti-oxidant responses, has also been implicated in inflammasome activation under physiological conditions. However, the mechanism underlying inflammasome activation in CKD remains elusive. Here, we show that the loss of Nrf2 suppresses fibrosis and inflammation in a unilateral ureter obstruction (UUO) model of CKD in mice. We consistently observed decreased expression of inflammation-related genes NLRP3 and IL-1β in Nrf2-deficient kidneys after UUO. Increased infiltration of M1, but not M2, macrophages appears to mediate the suppression of UUO-induced CKD symptoms. Furthermore, we found that activation of the NLRP3 inflammasome is attenuated in Nrf2-deficient bone marrow–derived macrophages. These results demonstrate that Nrf2-related inflammasome activation can promote CKD symptoms via infiltration of M1 macrophages. Thus, we have identified the Nrf2 pathway as a promising therapeutic target for CKD.

Hypertension promotes islet morphological changes with vascular injury on pre-diabetic status in SHRsp rats.

Abstract Hypertensive patients have a higher incidence of new-onset diabetic mellitus than normotensive subjects, and we hypothesized that hypertension induces morphological changes in islets via vascular injury. To test our hypothesis, we administrated hydralazine or irbesartan to spontaneously hypertensive stroke-prone (SHRsp) rats. A greater islet fibrosis was observed in SHRsp rats compared with controls, and irbesartan significantly ameliorated the fibrosis. High fat diet induced glucose intorelance in SHRsp rats and irbesartan but not hydralazine improved glucose torelance. We demonstrate islet morphological changes in hypertensive rats, and our data suggest that angiotensin receptor blockers have the potential to prevent islet injury.

Nuclear Factor Erythroid 2-Related Factor 2 is Activated by Rosuvastatin via p21cip1 Upregulation in Endothelial Cells

Oxidative stress is a key component in the development of cardiovascular diseases and chronic kidney diseases. Statins have cardio-protective activity, and previous reports have indicated that they activate nuclear factor erythroid 2-related factor 2 (Nrf2), although their molecular mechanism is unknown. Nrf2 is an oxidative stress-responsive transcription factor with a crucial role in cellular defense against oxidative stress. We investigated the molecular mechanisms of Nrf2 activation by rosuvastatin. Nrf2 activity and Nrf2-mediated antioxidant gene expression were upregulated by rosuvastatin in human umbilical vein endothelial cells. Rosuvastatin increased Nrf2 protein levels by reducing Nrf2 degradation and upregulating the interaction between Nrf2 and p21Cip1, which was inhibited by p21Cip1- targeted siRNA. Rosuvastatin-mediated activation of endothelial Nrf2 provides a possible therapeutic alternative for cardiovascular diseases.

[PS 01-17] HYPERTENSION PROMOTES ISLET MORPHOLOGICAL CHANGES WITH VASCULAR INJURY ON PRE-DIABETIC STATUS IN SHR-SP RATS

Objective: Type 2 diabetes causes not only insulin resistance but also failure of insulin producing &bgr; cells resulting in insufficient insulin secretion. Hypertensive patients have a higher incidence of new-onset diabetic mellitus than normotensive subjects, and we hypothesized that hypertension induces morphological changes in islets via vascular injury. To test our hypothesis, we administrated hydralazine or irbesartan to spontaneously hypertensive stroke-prone (SHRsp)/Izm male rats. Design and Method: SHRsp rats were randomly divided into three groups (SHRsp, SHRsp+Hyd, and SHRsp+Irb). The SHRsp+Hyd group was administrated hydralazine (5.0 mg body–1 d–1) by the gavage method, and the SHRsp+Irb group was similarly administrated irbesartan (50 m g body–1 d–1) from the age of 6 weeks until 20 weeks. Systolic blood pressure (SBP) and heart rate were measured weekly by the tail-cuff method. Blood samples were obtained via cardiac puncture to measure serum creatinine levels, and the pancreas was excised and fixed in 4% paraformaldehyde after sacrificing the rats with Azan staining. Results: A marked increase in systolic blood pressure was observed in SHRsp rats compared with controls (224 ± 12 mmHg vs. 120 ± 8 mmHg, respectively), which was significantly reduced by hydralazine and irbesartan administration (SHRsp+Hyd, 166 ± 12 mmHg; SHRsp+Irb, 180 ± 9 mmHg). There was no significant change in oral glucose tolerance test results in any groups. However, a greater Azan staining area was seen in SHRsp rats compared with controls, and irbesartan significantly decreased the Azan staining of islets in SHRsp rats. Irbesartan also decreased the number of ED1-positive islet cells compared with SHRsp and SHRsp+Hyd rats. Conclusions: We demonstrate islet morphological changes in hypertensive rats, and our data suggest that angiotensin receptor blockers have the potential to prevent islet injury through independent blood pressure-lowering effects.