Effect of angiotensin II receptor blocker on glucose-induced mRNA expressions of matrix metalloproteinase-9 and tissue inhibitor of metalloproteinase-1 in rat mesangial cells.

BACKGROUND: The decreased degradation of extra-cellular matrix proteins plays an important role in the onset of diabetic nephropathy. Matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of metalloproteinase-1 (TIMP-1), which are members of the matrix metalloproteinase family, are associated with this process. Angiotensin II (AII) plays an important role in the development of diabetic nephropathy also. This research aimed to investigate the effect of angiotensin II receptor blocker on glucose-induced mRNA expressions of MMP-9 and TIMP-1 in rat mesangial cells. METHODS: Rat mesangial cells were cultured and divided into 5 groups: normal glucose (group NG), high glucose (group HG), group NG + AII, NG + AII + saralasin (group NG + AII + S, saralasin is the AII receptor blocker) and HG + saralasin (group HG + S). After the cells were incubated for 24 hours, AII concentrations in the supernatant were measured by radioimmunoassay and the expression of MMP-9 and TIMP-1 mRNA was assayed by reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: AII concentrations were higher in group HG ((56.90 +/- 13.54) pg/ml) and group HG + S ((51.30 +/- 5.96) pg/ml) than in group NG ((37.89 +/- 8.62) pg/ml, P < 0.05), whereas there was no significant difference between group HG and group HG + S. The expression of MMP-9 mRNA and MMP-9/TIMP-1 mRNA ratio in group NG + AII (MMP-9, 0.33 +/- 0.04; MMP-9/TIMP-1, 0.40 +/- 0.06) and group HG (MMP-9, 0.36 +/- 0.02; MMP-9/TIMP-1, 0.45 +/- 0.03) were decreased more significantly than those in group NG (MMP-9, 0.72 +/- 0.02; MMP-9/TIMP-1, 1.21 +/- 0.07). These values in group NG + AII + S (MMP-9, 0.71 +/- 0.02; MMP-9/TIMP-1, 1.18 +/- 0.05) were higher than those in group NG + AII, and the values in group HG + S (MMP-9, 0.71 +/- 0.02; MMP-9/TIMP-1, 1.16 +/- 0.05) were higher than those in group HG (all were P < 0.05). TIMP-1 mRNA expression was increased more significantly in group NG + AII (0.81 +/- 0.03) and group HG (0.80 +/- 0.03) than in group NG (0.59 +/- 0.02), but it was lower in group NG + AII + S (0.60 +/- 0.01) than in group NG + AII and also lower in group HG + S (0.61 +/- 0.01) than in group HG (all were P < 0.05). CONCLUSIONS: High glucose stimulates AII production. Both high glucose and AII induce a decrease in MMP-9 mRNA expression and MMP-9/TIMP-1 mRNA ratio as well as an increase in TIMP-1 mRNA expression, which can be reversed by saralasin, suggesting that high glucose can aggravate impaired matrix degradation by altering gene expression of MMP-9 and TIMP-1 and that the effect of high glucose may be mediated by AII.

[Effects of losartan on the levels of angiotensin II and its type-1 receptor in diabetic rat kidney].

OBJECTIVE: To investigate the effect of losartan, an angiotensin II type-1 receptor (AT1R) antagonist, on the levels of angiotensin II (Ang II) and AT1R in diabetic rat kidney. METHODS: Male Wistar rats were divided into 3 groups, group A (n=11) served as the control group, group B (n=11) included the diabetic rats (induced by intraperitoneal injection of streptozotocin) without any therapy, and group C (n=9) diabetic rats treated with losartan. After 18 weeks of treatment, the kidneys were taken from all the rats to measure the expression of AT1R mRNA by RT-PCR and detect the Ang II level. Blood was also drawn from the heart to measure Ang II level, and 24-hour urine was collected to measure albumin level (urine albumin excretion, UAE) with rat albumin enzyme immunoassay kit. RESULTS: The blood and renal Ang II levels showed no significant difference between the 3 groups. The expression of renal AT1R mRNA in group B (0.62-/+0.17) was significantly lower than that in group A (1.13-/+0.82, P<0.01) and group C (1.13-/+0.62,P<0.01). UAE in group B (2.18-/+1.98 mg) was significantly higher than that in group A (0.41-/+0.47 mg/d, P<0.01) and C (0.65 -/+0.89 mg/d, P<0.01). CONCLUSION: Losartan can increase the expression of AT1R mRNA in diabetic rat kidneys without altering the blood and renal Ang II levels.

Effect of losartan on the mRNA expressions of MT3-MMP and TIMP-2 in diabetic kidneys.

BACKGROUND AND OBJECTIVES: The renin-angiotensin system plays a critical role in circulatory homoeostasis. Evidence has emerged that suggests a pathologic role for angiotensin II in patients with kidney disease. Losartan is an antagonist of angiotensin II and blocks the angiotensin II type-1 receptor. Thus it may reduce proteinuria and delay the progression of renal disease in diabetic nephropathy. We investigated the effects of losartan on the mRNA expressions of membrane-type3 matrix metalloproteinases (MT3-MMP) and the tissue inhibitor of metalloproteinase-2 (TIMP-2) in diabetic kidneys in order to evaluate degradation and remodeling of the extracellular matrix. METHODS: Male Wistar rats were divided into 3 groups. Group A was the control group containing healthy rats (n = 11), group B comprised diabetic rats without any therapy (n = 11), and group C consisted of diabetic rats treated with losartan (n = 9). 24-hr urine samples were collected in order to measure urinary albumin excretion (UAE). After a period of 18 weeks, the kidneys were extracted from all rats in order to measure the mRNA expressions of MT3-MMP, TIMP-2 and transforming growth factor-beta1 (TGF-beta1) by RT-PCR. We also examined the glomerular basement membrane thickening and the mesangial matrix (MM) density (MM area/mesangial area). RESULTS: The expression of renal MT3-MMP mRNA in group B (1.37 +/- 0.96) was significantly higher than that in group A (0.75 +/- 0.34, p < 0.05), but also significantly higher than in group C (0.75 +/- 0.30, p < 0.05). Similarly, the mRNA expression of renal TIMP-2 in group B (0.73 +/- 0.37) was significantly increased compared to that in group A (0.32 +/- 0.19, p < 0.05), but also higher than in group C (0.34 +/- 0.17, p < 0.05). In addition, subjects in group B showed abundant TGF-beta1 mRNA expression and UAE compared to groups A and C, as well as significantly higher glomerular basement membrane thickening and MM density (all p < 0.05). CONCLUSIONS: We conclude that MT3-MMP and TIMP-2 production in the renal cortex of diabetic kidneys is increased. Losartan can prevent the development of diabetic nephropathy by decreasing MT3-MMP and TIMP2 production in diabetic kidneys.