Synthesis of hydroxyeicosatetraenoic acids and leukotrienes in rat nephrotoxic serum glomerulonephritis. Role of anti-glomerular basement membrane antibody dose, complement, and neutrophiles.

The basal and stimulated synthesis of immunoassayable 12- and 5-monohydroxyeicosatetraenoic acids (HETE) and leukotrienes (LT) B4 and C4 was studied in glomeruli isolated from rats with nephrotoxic serum glomerulonephritis (NSGN) induced by low (30 micrograms/g body weight) or high (105 micrograms/g) doses of anti-rat glomerular basement membrane (GBM) immunoglobulin (Ig). In the early heterologous phase of the disease, low doses of anti-GBM Ig enhanced the basal synthesis of 12-HETE but not that of 5-HETE or LT. High anti-GBM Ig doses enhanced the basal synthesis of 5-HETE and LTB4 as well. Under stimulated conditions, enhanced glomerular production of 5-HETE and LTB4 occurred at 15 min after infusion of anti-GBM Ig, peaked at 1 h, and returned toward control levels by 24 h. At 48 h, 72 h, and on day 12, the synthesis of these eicosanoids was impaired. Neutrophile depletion only partially reduced glomerular eicosanoid synthesis after induction of NSGN whereas complement depletion significantly reduced 5-HETE, 12-HETE, and LTB4. These observations indicate that in the heterologous phase of NSGN there is enhanced but short-lived glomerular 5-HETE and LTB4 synthesis. This phenomenon is mediated by complement activation and may be an important proinflammatory event leading to capillary wall injury in the early stages of the disease.

Glomerular arachidonate lipoxygenation in rat nephrotoxic serum nephritis.

Arachidonate lipoxygenation to monohydroxylated eicosatetraenoic acids (HETE) was studied in rat nephrotoxic serum nephritis (NSN). A single infusion of nephrotoxic serum enhanced conversion of [3H]arachidonic acid ([3H]C20:4) to [3H]12-HETE in glomeruli isolated from nephritic rats compared with controls. The percent conversion of [3H]arachidonic acid was 1.95 +/- 0.2% in control glomeruli and 14.2 +/- 2% in nephritic glomeruli 2 d after induction of disease. No significant changes in the conversion of [3H]C20:4 to [3H]5-, 8-, and 9-HETE were noted. Extraction of glomerular HETE by alkaline hydrolysis, to evaluate possible reacylation of HETE after their production, confirmed the presence of 12-HETE and did not provide evidence of 5-HETE synthesis. Increased glomerular 12-HETE synthesis in nephritic rats was also demonstrated by high pressure liquid chromatography-UV detection and by 12-HETE radioimmunoassay. The enhanced glomerular 12-HETE synthesis commenced as early as 3-5 h after administration of nephrotoxic serum and peaked at day 2 with 10-fold enhancement of 12-HETE production. Increments of glomerular 12-HETE persisted on day 7 and returned toward control levels by day 14. Platelet depletion, induced by antiplatelet antisera, did not decrease glomerular 12-HETE synthesis in NSN, thereby eliminating platelets as the cellular origin of 12-HETE. Glomerular epithelial and mesangial cells are the most likely sources of enhanced 12-lipoxygenase activity. The enhanced arachidonate 12-lipoxygenation in glomerular immune injury could have important proinflammatory effects in the evolution of glomerulonephritis since 12-HETE has important effects on leukocyte function.

Mesangial cell immune injury. Synthesis, origin, and role of eicosanoids.

The synthesis, cell origin, and physiologic role of eicosanoids were investigated in a model of mesangial cell immune injury induced by a monoclonal antibody against the rat thymocyte antigen Thy 1.1 also expressed in rat mesangial cells. A single intravenous injection of the antibody resulted in enhanced glomerular synthesis of thromboxane (Tx)B2, leukotriene (LT)B4, and 12-hydroxyeicosatetraenoic acid (HETE), whereas that of PGE2 and PGF2 alpha was either unaltered or impaired. The enhanced eicosanoid synthesis was associated with decrements in glomerular filtration rate (GFR) and renal blood flow (RBF). Complement activation mediated both the increments in TxB2, LTB4, and 12-HETE and the decrements in GFR and RBF. The decrements in GFR were abolished by the TxA2 receptor antagonist SQ-29,548. Although both neutrophiles and Ia (+) leukocytes infiltrated glomeruli, glomerular LTB4 originated mainly from the latter. Platelets entirely accounted for the enhanced 12-HETE synthesis in isolated glomeruli and to a lesser extent for that of LTB4 and TxB2. Glomerular PGE2 and PGF2 alpha originated from mesangial cells as their impaired synthesis coincided with extensive mesangial cell lysis. The observations indicate that in mesangial cell immune injury vasoactive and proinflammatory eicosanoids originate from recruited or activated Ia (+) leukocytes and platelets and may exert paracrine effects on mesangial cells.

Glomerular prostaglandin and thromboxane synthesis in rat nephrotoxic serum nephritis. Effects on renal hemodynamics.

Glomerular arachidonate cyclooxygenation by isolated rat glomeruli was assessed in vitro in antiglomerular basement membrane (anti-GBM) antibody-induced glomerulonephritis by radioimmunoassay for prostaglandins (PG) and thromboxane. After a single intravenous injection of rabbit anti-rat GBM serum, we observed enhancement of glomerular thromboxane B2 (TxB2) synthesis as early as 2 to 3 h with smaller increments in PGF2 alpha, PGE2 and 6-keto-PGF1 alpha synthetic rates. On day 2 of the disease, the glomerular synthesis of TxB2 and, to a lesser extent, PGF2 alpha and PGE2 remained enhanced, whereas on days 8, 11, and 14, TxB2 was the only prostanoid synthesized at increased rates. Glomerular TxB2 synthesis correlated with the presacrifice 24-h protein excretion. 60 min after intravenous infusion of anti-GMB serum, glomerular filtration rate (GFR) decreased (0.66 +/- 0.04 to 0.44 +/- 0.03 ml/min per 100 g, P less than 0.05), without a significant change in renal plasma flow (RPF): 1.97 +/- 0.23 to 1.80 +/- 0.23 ml/min per 100 g) and without a change in glomerular PG synthetic rates. At 2 h, GFR and RPF reached a nadir (0.25 +/- 0.04 and 1.3 +/- 0.1 ml/min per 100 g, respectively) coinciding with a fivefold increment in glomerular TxB2. By 3 h GFR and RPF partially recovered to 0.43 +/- 0.07 and 1.77 +/- 0.20 ml/min per 100 g, respectively, P less than 0.05, despite further increments in TxB2 synthesis. This recovery of GFR and RPF coincided with increments in vasodilatory PG, (PGE2 and PGI2). The thromboxane synthetase inhibitor OKY-1581 markedly inhibited platelet and glomerular TxB2 synthesis and preserved GFR at 1, 2, and 3 h. Another thromboxane synthetase inhibitor, UK-38485, also completely inhibited platelet and glomerular TxB2 synthesis and prevented decrements of GFR at 2 and 3 h. A cyclooxygenase inhibitor, ibuprofen, inhibited platelet TxB2 and PGE2 synthesis and significantly reduced glomerular PGE2 but not TxB2 synthesis. In the ibuprofen-treated rats, the partial recoveries of GFR and RPF at 3 h were attenuated. The in vitro glomerular TxB2 synthesis correlated inversely with the presacrifice GFR and filtration fraction. These observations indicate that in anti-GBM nephritis there is enhanced synthesis of TxA2 and PG in the glomerulus that mediate changes in renal hemodynamics.

Leukotriene D4 is a mediator of proteinuria and glomerular hemodynamic abnormalities in passive Heymann nephritis.

We assessed the role of leukotrienes (LTs) in Munich-Wistar rats with passive Heymann nephritis (PHN), an animal model of human membranous nephropathy. 10 d after injection of anti-Fx1A antibody, urinary protein excretion rate (Upr) in PHN was significantly higher than that of control. Micropuncture studies demonstrated reduced single nephron plasma flow and glomerular filtration rates, increased transcapillary hydraulic pressure difference, pre- and postglomerular resistances, and decreased ultrafiltration coefficient in PHN rats. Glomerular LTB4 generation from PHN rats was increased. Administration of the 5-LO activating protein inhibitor MK886 for 10 d markedly blunted proteinuria and normalized glomerular hemodynamic abnormalities in PHN rats. An LTD4 receptor antagonist SK&F 104353 led to an immediate reduction in Upr and to reversal of glomerular hemodynamic impairment. Ia(+) cells/glomerulus were increased in PHN rats. In x-irradiated PHN rats, which developed glomerular macrophage depletion, augmented glomerular LT synthesis was abolished. Thus, in the autologous phase of PHN, LTD4 mediates glomerular hemodynamic abnormalities and a hemodynamic component of the accompanying proteinuria. The synthesis of LTD4 likely occurs directly from macrophages or from macrophage-derived LTA4, through LTC4 synthase in glomerular cells.

Mechanism of action of glucocorticosteroids. Inhibition of T cell proliferation and interleukin 2 production by hydrocortisone is reversed by leukotriene B4.

The mechanism whereby glucocorticosteroids are immunosuppressive is unknown. One potential mechanism of action of these compounds is inhibition of arachidonic acid metabolism. We found that the inhibition of lymphocyte proliferation by hydrocortisone or dexamethasone was mimicked by nonspecific lipoxygenase inhibitors and also by a specific 5-lipoxygenase inhibitor, but not by a specific cyclooxygenase inhibitor. Mitogen-stimulated cultures of T cells produce approximately 5 X 10(-9) M leukotriene B4 (LTB4) in 24 h. This production of LTB4 is completely inhibited by concentrations of hydrocortisone or lipoxygenase inhibitors that inhibit mitogen-induced [3H]thymidine incorporation. The inhibition of lymphocyte proliferation by either hydrocortisone or by the 5-lipoxygenase inhibitor was totally reversed by LTB4 but not by leukotriene C4 or leukotriene D4. LTB4 had no effect on the inhibition of lymphocyte proliferation by noncorticosteroids such as prostaglandin E2, histamine, or gamma-interferon. The inhibition of interleukin 2 (IL-2) production by hydrocortisone or dexamethasone was also completely reversed by exogenous LTB4. LTB4 alone did not cause IL-2 production or cell proliferation when added to resting lymphocytes. Thus, endogenous LTB4 production appears to be necessary but not sufficient for phytohemagglutinin-induced IL-2 production and lymphocyte proliferation. Glucocorticosteroids inhibit IL-2 production and lymphocyte proliferation by inhibiting endogenous LTB4 production.

Mesangial cell immune injury. Hemodynamic role of leukocyte- and platelet-derived eicosanoids.

The role of leukocytes and platelets and of leukocyte- and platelet-derived eicosanoids in mediating acute changes in renal and glomerular hemodynamics was assessed in a model of antibody-induced mesangial cell injury in the rat. After a single intravenous injection (6 mg/kg) of the monoclonal antibody (ER4) against the mesangial cell membrane antigen Thy 1, significant decrements in glomerular filtration rate (GFR) and renal blood flow (RBF) were observed at 1 h, and were associated with increments in glomerular LC (+) leukocyte counts and in the synthesis of thromboxane (Tx)B2, leukotriene (LT)B4, and 12-hydroxyeicosatetraenoic acid (HETE). In rats with immune leukopenia, the rise in glomerular LC (+) leukocytes and in eicosanoid synthesis were abolished and the fall in GFR and RBF after administration of ER4 were completely ameliorated. Likewise, pretreatment of rats with both a thromboxane synthase and a 5-lipoxygenase inhibitor also blocked the fall in GFR and RBF and the rise in glomerular synthesis of TxB2 and LTB4 produced by ER4 without changing glomerular LC (+) leukocyte counts. Selective inhibition of thromboxane or 5-lipoxygenase alone only partially ameliorated the decrements in GFR and RBF produced by ER4. In animals with immune thrombocytopenia, the elevated glomerular synthesis of 12-HETE and fall in RBF but not GFR was ameliorated after administration of ER4. The ER4 antibody-induced fall in GFR was mainly caused by a marked decrement in the ultrafiltration coefficient, Kf, which was dependent on TxA2 and 5-lipoxygenase products, since pretreatment of animals with a thromboxane receptor antagonist or with a 5-lipoxygenase inhibitor partially ameliorated this decrement. Structural changes such as infiltration of glomerular capillaries by leukocytes and endothelial cell damage may also have accounted for the fall in Kf. These observations indicate that in antibody-mediated mesangial cell injury, infiltrating leukocytes and platelets mediate the changes in renal hemodynamics via synthesis of thromboxane and arachidonate 5-lipoxygenation products.

Activation of extracellular signal-regulated kinase in proliferative glomerulonephritis in rats.

Multiple extracellular mitogens are involved in the pathogenesis of proliferative forms of glomerulonephritis (GN). In vitro studies demonstrate the pivotal role of extracellular signal-regulated kinase (ERK) in the regulation of cellular proliferation in response to extracellular mitogens. In this study, we examined whether this kinase, as a convergence point of mitogenic stimuli, is activated in proliferative GN in vivo. Two different proliferative forms of anti-glomerular basal membrane (GBM) GN in rats were induced and whole cortical tissue as well as isolated glomeruli examined using kinase activity assays and Western blot analysis. Administration of rabbit anti-rat GBM serum to rats, preimmunized with rabbit IgG, induced an accelerated crescentic anti-GBM GN. A significant increase in cortical, and more dramatically glomerular ERK activity was detected at 1, 3, and 7 d after induction of GN. Immunization of Wistar-Kyoto rats with bovine GBM also induced a crescentic anti-GBM GN with an increase of renal cortical ERK activity after 4, 6, and 8 wk. ERK is phosphorylated and activated by the MAP kinase/ERK kinase (MEK). We detected a significant increase in the expression of glomerular MEK in the accelerated form of anti-GBM GN, providing a possible mechanism of long-term activation of ERK in this disease model. In contrast to ERK, activation of stress-activated protein kinase was only detectable at early stages of proliferative GN, indicating these related kinases to serve distinct roles in the pathogenesis of GN. Our observations point to ERK as a putative mediator of the proliferative response to immune injury in GN and suggest that upregulation of MEK is involved in the long-term regulation of ERK in vivo.

The biological activity of acetylated sphingosylphosphorylcholine derivatives.

Taking into account their stereochemical similarity with 1-O-alkyl-2-acetyl-sn-glycerol-3-phosphorylcholine (PAF), which is known to exhibit a diverse spectrum of biological actions, including platelet aggregating and glycogenolytic activity, the acetylated derivatives of sphingosylphosphorylcholine and sphingomyelin were synthesized and tested for their ability to promote washed rabbit platelet aggregation and glycogenolysis in Tetrahymena pyriformis cells. Sphingomyelin (SPM) and sphingosylphosphorylcholine (SPC) were subjected to acetylation, following chromatographic purification and physicochemical characterization. The synthesized compounds N-acetyl, O-acetyl SPC (NAc, OAc SPC), N-acetyl SPC (NAc SPC) and O-acetyl SPM (OAc, SPM) were tested for their biological activity in the washed rabbit platelets and washed Tetrahymena pyriformis cell systems. These derivatives induced [3H]serotonin and ATP release and a monophasic aggregation of washed rabbit platelets in the concentration range 10(-8)-10(-6) M. However, authentic PAF-induced washed rabbit platelet aggregation was inhibited at higher concentrations of the acetylated sphingophospholipid compounds ( > 10(-6) M) and by the PAF-specific receptor(s) antagonists kadsurenone and triazolam. Platelet desensitization and crossed desensitization experiments with authentic PAF and the acetylated sphingophospholipids, suggested interaction with the same receptor(s) as PAF and different from the ADP or thrombin receptor. The involvement of calmodulin and protein kinase C in the biological activity of the prepared analogues was also demonstrated. Besides their action on rabbit platelets, the PAF-like activity of the acetylated sphingophospholipids was also demonstrated in a platelet-independent system, by showing that they stimulate glycogenolysis in washed Tetrahymena pyriformis cells. These observations indicate that a new class of compounds with PAF-like activity were synthesized but their role in the cellular metabolism remains to be shown. The existence of acetylated sphingophospholipids with PAF-like activity has so far been reported only in Urtica dioica.

Regulation of human P2X1 promoter activity by beta helix-loop-helix factors in smooth muscle cells.

We isolated and characterized genomic clones of the human P2X1 receptor (hP2X1) gene in an effort to understand its tissue specific expression. The hP2X1 gene contains 12 exons spanning 20 kb, with exon sizes ranging from 59 to 143 bp. A 385 bp upstream fragment promoted hP2X1 gene expression in smooth muscle (A7R5 and primary trachealis) and fibroblast (NIH3T3) cell lines, and mutation of a consensus E box sequence (CACCTG) within this fragment (-340 to -345) did not alter basal promoter activity. However, co-transfected bHLH factors regulated activity of the 385 bp minimal P2X1 promoter in a tissue-specific manner. E12 expression inhibited and ITF2b augmented activity in A7R5 cells, but had no effect in NIH3T3 cells. ITF2a, Myo-D, and Id1 proteins had no effect on either cell line, but co-expression of ITF2a blocked E12 inhibition in A7R5 cells, while ITF2b failed to reverse the inhibition. Northern analysis of A7R5 RNA identified high levels of E12 and ITF2b transcripts, and gel shift assays using A7R5 and NIH3T3 nuclear extracts indicated the formation of a protein-DNA complex with an oligonucleotide corresponding to -330 and -348, which was abolished by base substitutions within the E box motif. Our results identify a critical E box response element in the hP2X1 promoter that binds bHLH factors and demonstrate smooth muscle specific transcriptional regulation by E proteins.

Induction of heme oxygenase 1 in radiation nephropathy: role of angiotensin II.

Datta, P. K., Moulder, J. E., Fish, B. L., Cohen, E. P. and Lianos, E. A. Induction of Heme Oxygenase 1 in Radiation Nephropathy: Role of Angiotensin II. Radiat. Res. 155, 734-739 (2001). In a rat model of radiation-induced nephropathy, we investigated changes in expression of heme oxygenase 1 (Hmox1, also known as HO-1), an enzyme that catalyzes conversion of heme into biliverdin, carbon monoxide and iron. The study explored whether radiation induces Hmox1 expression in the irradiated kidney and whether angiotensin II (AII) mediates Hmox1 expression in glomeruli isolated from irradiated kidneys. To assess the effects of radiation on Hmox1 expression, rats received 20 Gy bilateral renal irradiation and were randomized to groups receiving an AII type 1 (AT(1)) receptor antagonist (L-158,809) or no treatment. Drug treatment began 9 days prior to bilateral renal irradiation and continued for the duration of the study. Estimation of Hmox1 levels in glomerular protein lysates assessed by Western blot analysis revealed a significant increase in Hmox1 protein at 50 and 65 days postirradiation. In animals treated with the AT(1) receptor antagonist, there was no induction of Hmox1, suggesting that AII may be a mediator of Hmox1 induction. To confirm that AII stimulates Hmox1 expression, animals were infused with 200, 400 or 800 ng/kg min(-1) of AII for 18-19 days, and Hmox1 protein levels in glomeruli were assessed. There was a significant induction of Hmox1 in glomeruli of animals infused with 800 ng/kg min(-1) of AII. These studies demonstrate that glomerular Hmox1 expression is elevated in the middle phase of radiation nephropathy and that AII can increase glomerular Hmox1 levels.

Different activation of mitogen-activated protein kinases in experimental proliferative glomerulonephritis.

Mitogen-activated protein (MAP) kinases are critical for cell signaling goals such as cellular proliferation and induction of apoptosis. We examined whether MAP kinases, as a point of convergence for multiple extracellular stimuli, are activated in proliferative glomerulonephritis (GN) in vivo. Accelerated crescentic anti-glomerular basement membrane (GBM) GN was induced in rats preimmunized with rabbit IgG by administration of rabbit anti-rat GBM serum. Whole cortical tissue and isolated glomeruli were then subjected to kinase activity assays and Western blot analysis. Cortical activity of the archetypal MAP kinase, extracellular signal-regulated kinase (ERK), was increased significantly one, three, and seven days after induction of GN. In contrast, activation of MAP kinases with antiproliferative actions, stress-activated protein kinase, and p38 MAP kinase was detectable only in the early stages of proliferative GN (days one and three), implying that different MAP kinases serve distinct roles in the pathogenesis of GN.

Plasma renin activity as a marker of renovascular injury in patients with rheumatoid arthritis.

OBJECTIVES: To assess whether plasma renin activity (PRA) in patients with rheumatoid arthritis (RA) and evidence of renal involvement (microhematuria) can serve as potential marker of renovascular injury. METHODS: PRA was measured at rest and following exercise. All nonsteroidal antiinflammatory drugs or other medications that might affect renin release were stopped at least ten days prior to PRA measurements. PRA was correlated with the number of dysmorphic erythrocytes present in the urine sediment as indicators of glomerular capillary injury (microhematuria). RESULTS: All patients with RA had a higher mean PRA than controls. Moreover, all patients with RA in whom microhematuria was present had a higher PRA than those without microhematuria. Simple and multiple regression analysis revealed a significant correlation between: a) PRA and rheumatoid factor levels; b) rheumatoid factor levels and the number of erythrocytes in the urine sediment; and c) PRA levels and the number of erythrocytes in the urine sediment. CONCLUSIONS: The observations indicate that increased PRA may occur in normotensive patients with RA and no clinical or biochemical evidence of renal involvement. This may reflect activation of the renin-angiotensin system. The positive correlation between enhanced PRA, rheumatoid factor levels and microhematuria in RA patients may indicate inflammatory injury of the glomerular microvasculature involving the juxtaglomerular apparatus.

TGF-beta 1 production in radiation nephropathy: role of angiotensin II.

PURPOSE: Angiotensin II receptor antagonists are effective in the prophylaxis of radiation nephropathy. Studies were designed to determine whether TGF-beta 1, a fibrogenic cytokine, plays a role in mediating the protective effect of AII antagonism. These studies explored the time-course of glomerular TGF-beta 1 production in the irradiated kidney, and whether AII mediates TGF-beta 1 production in glomeruli isolated from irradiated rats. MATERIALS AND METHODS: Rats received 20 Gy of bilateral renal irradiation in five fractions and were randomized to receive an AII type 1 receptor antagonist (L-158,809) at 20mg/l in their drinking water, or no treatment. Drug therapy began 9 days prior to irradiation and continued for the duration of the study. RESULTS: Analysis of renal function showed a significant increase in urinary proteinuria and blood urea nitrogen by 37 days and 63 days after irradiation, respectively. Estimation of glomerular TGF-beta1 levels by quantitative sandwich enzyme immunoassay technique revealed a significant increase in latent but not active TGF-beta 1 levels at 50 days and 63 days after irradiation. In animals treated with the AT1 receptor antagonist, there was a complete elimination in the rise of TGF-beta 1. CONCLUSIONS: These studies demonstrate that glomerular TGF-beta 1 production is elevated in the course of radiation nephropathy, and that AII mediates this induction of TGF-beta 1.

Enhanced expression of the cytoskeletal-associated protein, paxillin, in experimental nephrotic syndrome.

BACKGROUND: In the model of aminonucleoside of Puromycin (PAN)-induced nephrotic syndrome we assessed changes in glomerular expression of three proteins that regulate cell adhesion to extracellular matrix: paxillin, focal adhesion kinase (FAK), and Rho. METHODS: Following a single intravenous injection of PAN in Sprague-Dawley rats, proteinuria ensued and glomeruli were isolated at three stages: prior to onset of proteinuria (days 1 and 2), and when proteinuria peaked (day 9), subsided (day 29) or resolved (day 35). Glomerular protein lysates were analyzed by Western blot for expression of paxillin, FAK, and Rho. RESULTS: There was a progressive increase in glomerular paxillin level that peaked concomitantly with heavy proteinuria (day 9). Paxillin remained increased during the recovery phase of PAN-induced injury and when proteinuria resolved. Expression of FAK and Rho remained unchanged at all time points. To explore whether the increase in paxillin expression following administration of PAN was due to a direct effect on glomerular epithelial cells (GEC), cultured rat GECs were incubated with PAN for 3, 6, and 24 hours, and expression of paxillin was assessed in GEC lysates by Western blot analysis. No change in paxillin levels was observed. CONCLUSIONS: In PAN-induced nephrotic syndrome there is a preferential increase in paxillin expression that cannot be accouted for by an effect of PAN on GEC paxillin synthesis. We propose that the enhanced paxillin synthesis in the course of PAN-induced GEC injury reflects perturbations in contact between GEC and the GBM and may play a role in regulating adherence of GEC to the GBM.

Cytokine inhibition preserves renal hemodynamic function following mesangial cell immune injury.

BACKGROUND: We assessed the effect of a cytokine inhibitor, compound SKF 86002 (a bicyclic imidazole), on changes in renal hemodynamics (renal blood flow and glomerular filtration rate) that occur acutely following immune injury of glomerular mesangial cells. METHODS: Injury was induced in Munich-Wistar rats by the administration of a monoclonal antibody against the mesangial cell membrane antigen Thy 1.1. An acute drop in renal blood flow (RBF) and glomerular filtration rate (GFR) occurred within one hour of injury. RESULTS: Pretreatment of animals with the cytokine inhibitor SKF 86002 prevented this drop. SKF 86002 had no effect on glomerular synthesis of vasoconstrictor eicosanoids. CONCLUSIONS: The observations indicate that in mesangial cell immune injury, cytokines mediate renal hemodynamic impairment.

Effects of all-trans-retinoic acid (atRA) on inducible nitric oxide synthase (iNOS) activity and transforming growth factor beta-1 production in experimental anti-GBM antibody-mediated glomerulonephritis.

Sustained high output release of Nitric oxide (NO) as result of activation of inducible nitric oxide synthase (iNOS), and increased production of the antiproliferative/profibrotic cytokine transforming growth factor-beta1 (TGF-beta1) are well documented in glomerulonephritis. Modulation of iNOS activity and of TGF-beta1 production can therefore be viewed as anti-inflammatory strategies. The present study employed all-trans retinoic acid (atRA) which is known to have anti-inflammatory effects and to modulate expression of iNOS and TGF-beta1, in order to explore its effect on iNOS enzyme activity and TGF-beta1 production in anti-GBM antibody induced glomerulonephritis. Glomerulonephritis was induced in Lewis rats by injection of anti-GBM antibody. A group of nephritic rats were given daily administration of atRA for 14-16 days. Extent of proteinuria was assessed by measuring urine protein and creatinine excretion. iNOS enzyme activity was measured by calculating conversion of L[14C]arginine to L-[14C]citrulline in glomerular protein lysates. Levels of TGF-beta1 in glomerular protein lysates were measured by quantitative ELISA. Levels of proliferating nuclear antigen (PCNA), TGF-beta receptor II (TGFbeta-RII), and fibronectin were assessed by Western blot analysis. Glomerular iNOS activity in atRA treated nephritic animals was attenuated in comparison to that in nephritic controls that were not. Glomerular expression of PCNA was also reduced. Levels of TGF-beta1 were increased in glomeruli of atRA treated nephritic animals. In these animals, there was no change in glomerular levels of TGF-beta receptor II (TGFbeta-RII) or fibronectin. and there was no reduction in urine protein excretion. These results suggest that atRA attenuates iNOS activity and proliferation in glomeruli of nephritic animals. The failure of atRA treatment to reduce proteinuria could be due to the increase in TGF-beta1 levels and to inhibition of iNOS-driven NO production.

Glomerular expression and cell origin of transforming growth factor-beta 1 in anti-glomerular basement membrane disease.

The glomerular expression (mRNA levels) of transforming growth factor-beta 1 (TGF-beta 1) was assessed in two forms of rat anti-glomerular basement membrane (GBM) disease, a macrophage-independent and a macrophage-dependent variant. After a single intravenous injection of rabbit anti-rat GBM immune serum, significant proteinuria and histopathologic changes developed in both variants. Increased TGF-beta 1 mRNA levels were found in isolated glomeruli of the macrophage-dependent variant only in which glomerular infiltration by macrophages also occurred. Macrophages isolated from glomeruli of animals with this variant demonstrated TGF-beta 1 mRNA levels comparable to those found in glomeruli isolated at the same time point after injection of the anti-GBM serum. The observations indicate that in anti-GBM disease, enhanced glomerular TGF-beta 1 expression occurs in the macrophage-dependent variant and suggest that infiltrating macrophages account for this event.

Hypertension in the elderly.

Successful control of blood pressure through drug therapy can reduce morbidity and mortality in the elderly population. However, age-related factors also make this group prone to adverse side effects. A cautious approach is therefore recommended in the effort to achieve ideal control of blood pressure.

Expression of Ser729 phosphorylated PKCepsilon in experimental crescentic glomerulonephritis: an immunohistochemical study.

PKCε, a DAG-dependent, Ca2+- independent kinase attenuates extent of fibrosis following tissue injury, suppresses apoptosis and promotes cell quiescence. In crescentic glomerulonephritis (CGN), glomerular epithelial cells (GEC) contribute to fibro-cellular crescent formation while they also transdifferentiate to a mesenchymal phenotype. The aim of this study was to assess PKCε expression in CGN. Using an antibody against PKC-ε phosphorylated at Ser729, we assessed its localization in rat model of immune-mediated rapidly progressive CGN. In glomeruli of control animals, pPKCε was undetectable. In animals with CGN, pPKCε was expressed exclusively in glomerular epithelial cells (GEC) and in GEC comprising fibrocellular crescents that had acquired a myofibroblast-type phenotype. In non-immune GEC injury induced by puromycin aminonucleoside and resulting in proteinuria of similar magnitude as in CGN, pPKCε expression was absent. There was constitutive pPKCε expression in distal convoluted tubules, collecting ducts and thick segments of Henley's loops in both control and experimental animals. We propose that pPKCε expression occurring in GEC and in fibrocellular crescentic lesions in CGN may facilitate PKCε dependent pathologic processes.