Enhanced expression of group IIA secreted phospholipase A2 by elevated glucose levels in cytokine-stimulated rat mesangial cells and in kidneys of diabetic rats.

BACKGROUND: Group IIA secreted phospholipase A2 (sPLA2-IIA) has been implicated in various inflammatory processes including the kidney. Previously it has been shown that potent proinflammatory cytokines such as interleukin 1beta (IL-1beta) increase sPLA2-IIA expression and secretion in rat mesangial cells. AIM: The present study examines the effects of glucose on sPLA2-IIA regulation in interleukin-1beta (IL-1beta) treated mesangial cell cultures and in diabetic kidneys of Sprague-Dawley rats. MATERIALS AND METHODS: Rat mesangial cells were grown either in low glucose (5.55 mM D-Glucose) or high glucose (25 mM) conditions followed by assessment of sPLA2-IIA transcription, expression and secretion after 24 h. The model of streptozotocin induced diabetes mellitus in Sprague-Dawley rats was used for the in vivo experiments. Diabetic kidneys where examined for sPLA2-IIA-mRNA and -protein expression as well as IL-1beta-levels at 2, 4 and 6 weeks after induction of diabetes mellitus. RESULTS: Increased concentration of glucose had a weak, but significant stimulatory effect on sPLA2-IIA expression, which was markedly up-regulated (2-3-fold) in IL-1beta treated mesangial cells compared to the levels obtained in low glucose medium. Concerning the underlying mechanism, we found that high concentration of glucose increased the activity of the rat sPLA2-IIA-promoter, whereas mRNA stability was not affected. Furthermore, the in vivo experiments revealed a marked up-regulation of sPLA2-IIA mRNA and protein in the diabetic rat kidneys 2 - 4 weeks after induction. Since the strong up-regulation of sPLA2-IIA in vitro under high glucose conditions occurred mainly in presence of cytokine, we measured the levels of IL-1beta in diabetic kidneys by ELISA. We detected rat IL-1beta only in diabetic, but not in control rat kidneys. CONCLUSIONS: The changes of sPLA2-IIA expression under increased glucose concentrations as well as in diabetic rat kidneys suggest a function of this enzyme as an acute phase protein providing lipid autacoids that may contribute to early changes in the course of diabetic nephropathy.

[An unusual cause of hepatorenal symptoms]. / Ungewöhnliche Ursache einer hepatorenalen Symptomatik.

CASE REPORT: A 65-year-old patient with normal blood pressure had an exclusive elevation of the cholestasis enzymes (alkaline phosphatase 297 U/l, gamma-GT 315 U/l) and elevated bilirubin levels (1.4 mg/dl) since August 1994. A biopsy of the liver in March 1995 showed features of a "subacute viral hepatitis"; DD drug-induced or toxic lesions. Serological tests gave no support for an acute hepatitis. Intra- or extrahepatic cholestasis could not be proved neither by ultrasound nor by an endoscopic retrograde cholangiopancreatography. Since November 1995 serum creatinine increased up to 1.7 mg/dl (March 1995 1.1 mg/dl) and proteinuria (2.1 g/d) developed. Due to worsening of renal function (serum creatinine 2.8 mg/dl) and increasing proteinuria (3.5 g/d) without nephrotic syndrome, a kidney biopsy was performed. Histologically an amyloidosis (type A lambda) was proven, involving glomerula, kidney vessels and tubules. Further biopsies from the stomach and the duodenum showed profound infiltration of the mucosa and submucosa with amyloid. Therefore, staining of the liver biopsy of March 1995 with congo red proved the diagnosis of liver amyloidosis. By a punch biopsy of the iliac crest a low-grade non-Hodgkin's lymphoma could be identified as the cause for this generalized amyloidosis. DISCUSSION: In the present case, the reason for these unusual hepatorenal symptoms with unclear cholestasis over years as the first clinical symptom and a succeeding progressive renal insufficiency with proteinuria could be found by the use of kidney biopsy and extending the analysis of a liver sample taken by biopsy 1 year ago. Immunoglobulin light chains produced by a low-grade non-Hodgkin's lymphoma caused a generalized amyloidosis type A lambda. CONCLUSION: As a consequence, by an occurrence of unusual hepatorenal symptoms with cholestasis and progressive renal failure, amyloidosis should be considered as a pathogenetic factor.

Effect of chronic therapy with proteolytic enzymes on hypertension-induced renal injury in the rat model of Goldblatt hypertension.

This study investigated the possible beneficial effect of intraperitoneal proteolytic enzyme administration on the development of hypertension-induced renal injury in the rat model of 2-kidney 1-clip (2K1C) Goldblatt hypertension. Male Wistar rats (120-150 g) underwent either sham surgery (control, n = 5) or clipping of the left renal artery. From day one 2K1C rats were randomized into 2 groups, placebo treatment (n = 7), and proteolytic enzyme treatment (n = 9). To the verum group a fixed mixture of trypsin (2.42 mg), bromelain (4.54 mg), and rutin (5.04 mg) dissolved in 2 ml of sterile 0.9% NaCl was administered intraperitoneally daily, while the placebo group received only vehicle. Rats were pair-fed. The duration of the study was 7 weeks. All 2K1C rats developed hypertension and the mean values of systolic blood pressure (SBP) did not differ significantly between the groups at any time recorded (SBP at sacrifice: controls 122.0 +/- 8.5 mm Hg; placebo 191.4 +/- 7. 6 mm Hg; enzyme 180.5 +/- 6.5 mm Hg). Enzyme treatment prevented the rise in proteinuria (controls 12.4 +/- 2.6 mg/24 h; placebo 19.7 +/- 3.9 mg/24 h; enzyme 12.2 +/- 1.3 mg/24 h; p < 0.05) and ameliorated the increase in serum urea concentrations. Histomorphologically, signs of malignant nephrosclerosis were not found in control rats, while they were present in 4/7 (57%) of placebo-treated rats, but only in 1/9 (11%) of the enzyme-treated group. The volume fraction of renocortical interstitium was increased in both 2K1C groups in comparison with controls; however, enzyme treatment decreased the accumulation of interstitial tissue significantly (-22%) compared to placebo treatment. Cellular infiltration with mononuclear cells was also lower in the protease-treated group. To summarize, in the rat model of 2K1C hypertension, systemic treatment with proteases ameliorates the severity of nephrosclerosis and tubulointerstitial fibrosis in the non-clipped kidney, as well as proteinuria, without affecting high blood pressure.

Effects of early and late antihypertensive treatment on extracellular matrix proteins and mononuclear cells in uninephrectomized SHR.

The efficacy of an early and late treatment with the angiotensin converting enzyme inhibitor lisinopril or the angiotensin II receptor blocker ICI D8731 was investigated in uninephrectomized spontaneously hypertensive rats (SHR). Rats that underwent uninephrectomy (UNX) at six weeks of age were randomly assigned to receive no treatment, lisinopril shortly after UNX, lisinopril starting 16 weeks after UNX, ICI D8731 shortly after UNX, and ICI D8731 starting 16 weeks after UNX. Blood pressure was normalized with both treatments. After six months inulin clearance was not significant different, while proteinuria and prevalence of interstitial fibrosis were significantly reduced in all treatment groups. Immunohistochemical studies revealed an interstitial, periglomerular and perivascular increase of extracellular matrix proteins in all rats, but a markedly reduced expression of collagen I, IV and fibronectin after early and late treatment compared to untreated controls. We found a significant reduction of infiltrating macrophages and T-lymphocytes in all treated animals compared to untreated controls after 2, 4 and 6 months. Especially early treatment was associated with lower numbers of infiltrating cells. Both treatments reduced proliferation of tubular and interstitial cells. There were no striking differences with regard to nephroprotection between the ACE inhibitor and angiotensin II receptor blocker. These findings show that both treatments have beneficial effects on kidney structure and function. They suggest that both ACE inhibition and angiotensin II blockade decrease renal cell proliferation and suppress the infiltration of mononuclear cells that may trigger expression of extracellular matrix proteins and progressive nephrosclerosis.

Subthreshold stimulation of a serotonin 5-HT3 reflex attenuates cardiovascular reflexes.

Volume-sensitive and chemosensitive cardiopulmonary reflexes modulate volume homeostasis via renal sympathetic nerve activity (RSNA). Blunting of volume-sensitive cardiopulmonary reflexes is associated with volume retention, e.g., in hypertension, whereas the role of chemosensitive cardiopulmonary reflexes is largely unknown. To elucidate the possible role of chemosensitive cardiopulmonary reflexes in control of volume homeostasis, we investigated whether subthreshold stimulation of 5-HT3 receptors modulates the control of RSNA by volume-sensitive cardiopulmonary reflexes or the arterial baroreceptor reflex in rats. Phenyl biguanide (PBG) was infused intravenously to stimulate 5-HT3 receptors. Higher doses of PBG lowered RSNA, but a dose of 6 micrograms/min, given as a background infusion throughout the experiment, did not change arterial pressure, heart rate (HR), or RSNA. Ten minutes after beginning the 6 micrograms/min PBG infusion, a 15-min volume expansion (0.9% saline, 5 or 10% body weight) was started to stimulate volume-sensitive cardiopulmonary reflexes. In separate experiments, 5-min ramp infusions of methoxamine and nitroglycerin to stimulate the arterial baroreceptor reflex (evaluated by a 4-parameter logistic regression) were performed 15 min after beginning the PBG background infusion (6 micrograms/min). During PBG infusion, the RSNA responses to volume expansions were significantly impaired (5% body weight: PBG -6 +/- 6%, n = 7 vs. control -39 +/- 9%, n = 6, P < 0.001; 10% body weight: PBG -33 +/- 6%, n = 8 vs. control -52 +/- 5%, n = 7, P < 0.05). The 5-HT3 receptor antagonist odansetron (GR-38032F) abolished these effects of PBG. The maximum HR gain of the arterial baroreceptor reflex was impaired but the arterial baroreceptor control of RSNA was unaffected by PBG background infusion. We conclude that 5-HT3-serotonergic cardiopulmonary chemoreceptors blunt the RSNA decrease to volume loading. This mechanism may facilitate volume retention when cardiac serotonin is increased.