Nintedanib-induced glomerular microangiopathy: a case report.

Nintedanib, a triple tyrosine kinase inhibitor of vascular endothelial growth factor receptor, platelet-derived growth factor receptor, and fibroblast growth factor receptor, has been used in idiopathic pulmonary fibrosis and adenocarcinoma in advanced non-small cell lung cancer. Although vascular endothelial growth factor inhibitors have been reported to cause endothelial injury and glomerular microangiopathy, nintedanib-induced glomerular microangiopathy has not been reported. A 68-year-old man with a history of primary aldosteronism, idiopathic pulmonary fibrosis, and pleomorphic carcinoma of the lung developed proteinuria and leg edema after nintedanib initiation. Kidney biopsy revealed prominent endothelial and mesangial injury. Proteinuria improved after nintedanib withdrawal. To the best of our knowledge, this is the second case report of nintedanib-induced glomerular microangiopathy. Although the incidence of nephropathy among patients receiving nintedanib is unknown at this moment, we recommend monitoring urinary protein excretion and blood pressure in patients receiving nintedanib and performing kidney biopsy to determine any histopathological change.

Association of circulatory asymmetric dimethylarginine (ADMA) with diabetic nephropathy in Asian Indians and its causative role in renal cell injury.

AIM: Asymmetric dimethylarginine (ADMA) is involved in the regulation of nitric oxide synthesis and in the maintenance of vascular tone and structure. But the role and status of ADMA in diabetes induced kidney injury is not clear. Hence this study is investigating the role of ADMA in the progression of kidney injury and its circulatory status in Asian Indians with and without diabetic nephropathy. METHODS: Recruited study subjects were divided into normal glucose tolerance (NGT), type 2 diabetes mellitus (T2DM) and T2DM with micro or macroalbuminuria. Albuminuria was calculated using urinary albumin and creatinine ratio (UACR). ADMA was measured using ELISA. Kidney cell damage in terms of fibrotic markers and ADMA metabolism in terms of DDAH activity were investigated in kidney fibroblasts and mesangial cells. RESULTS: There was a significant elevation in plasma ADMA levels in micro and macroalbuminuric diabetic patients. We found a significant positive correlation between ADMA and UACR, serum creatinine, HbA1C and fasting plasma glucose. A cut-off value of ADMA, 0.666µM/l had a sensitivity and specificity of 70.0% and 65.6%, respectively for detecting diabetic nephropathy. DDAH activity was significantly decreased and fibrotic markers such as fibronectin and α-SMA were significantly increased upon high glucose and ADMA treatment. CONCLUSION: We are suggesting a causative role of ADMA in the development of kidney injury in terms of renal fibrosis and also a cut point of 0.666µM/l of plasma ADMA level appears to be a predictive risk threshold for diabetic nephropathy in south Asian Indian population.

Restricted nutrition-induced low birth weight, low number of nephrons and glomerular mesangium injury in Japanese quail.

Insufficient nutrition during the perinatal period causes structural alterations in humans and experimental animals, leading to increased vulnerability to diseases in later life. Japanese quail, Coturnix japonica, in which partial (8-10%) egg white was withdrawn (EwW) from eggs before incubation had lower birth weights than controls (CTs). EwW birds also had reduced hatching rates, smaller glomeruli and lower embryo weight. In EwW embryos, the surface condensate area containing mesenchymal cells was larger, suggesting that delayed but active nephrogenesis takes place. In mature EwW quail, the number of glomeruli in the cortical region (mm2) was significantly lower (CT 34.7±1.4, EwW 21.0±1.2); capillary loops showed focal ballooning, and mesangial areas were distinctly expanded. Immunoreactive cell junction proteins, N-cadherin and podocin, and slit diaphragms were clearly seen. With aging, the mesangial area and glomerular size continued to increase and were significantly larger in EwW quail, suggesting compensatory hypertrophy. Furthermore, apoptosis measured by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling analysis was higher in EwWs than in CTs on embryonic day 15 and postnatal day 4 (D4). Similarly, plasma glucocorticoid (corticosterone) was higher (P<0.01) on D4 in EwW quail. These results suggest that although nephrogenic activity is high in low-nutrition quail during the perinatal period, delayed development and increased apoptosis may result in a lower number of mature nephrons. Damaged or incompletely mature mesangium may trigger glomerular injury, leading in later life to nephrosclerosis. The present study shows that birds serve as a model for 'fetal programming,' which appears to have evolved phylogenetically early.

Endothelial progenitor cell-derived extracellular vesicles protect from complement-mediated mesangial injury in experimental anti-Thy1.1 glomerulonephritis.

BACKGROUND: Endothelial progenitor cells (EPCs) are known to induce tissue repair by paracrine mechanisms including the release of growth factors and extracellular vesicles (EVs), nanoparticles able to carry proteins and genetic information to target cells. The aim of this study was to evaluate whether EVs derived from EPCs may protect from complement-mediated mesangial injury in experimental anti-Thy1.1 glomerulonephritis. METHODS: EVs were isolated by serial ultracentrifugation from supernatants of cultured human EPCs and characterized for their protein and RNA content. In vivo, EVs were injected i.v. in the experimental rat model of mesangiolytic anti-Thy1.1 glomerulonephritis evaluating renal function, proteinuria, complement activity and histological lesions. In vitro, the biological effects of EPC-derived EVs were studied in cultured rat mesangial cells incubated with anti-Thy1.1 antibody and rat or human serum as complement source. RESULTS: After i.v. injection in Thy1.1-treated rats, EVs localized within injured glomeruli and inhibited mesangial cell activation, leucocyte infiltration and apoptosis, decreased proteinuria, increased serum complement haemolytic activity (CH50) and ameliorated renal function. EV treatment decreased intraglomerular deposition of the membrane attack complex (MAC or C5b-9) and expression of smooth muscle cell actin and preserved the endothelial antigen RECA-1 and the podocyte marker synaptopodin. The protective effect of EVs was significantly reduced by pre-treatment with a high dose of RNase (1 U/mL), suggesting a key role for EV-carried RNAs in these mechanisms. Indeed, EPC-derived EVs contained different mRNAs coding for several anti-apoptotic molecules and for the complement inhibitors Factor H, CD55 and CD59 and the related proteins. The in vitro experiments aimed to investigate the mechanisms of EV protection indicated that EVs transferred to mesangial cell mRNAs coding for Factor H, CD55 and CD59 and inhibited anti-Thy1.1 antibody/complement-induced apoptosis and C5b-9/C3 mesangial cell deposition. CONCLUSIONS: EVs derived from EPCs exert a protective effect in Thy1.1 glomerulonephritis by inhibition of antibody- and complement-mediated injury of mesangial cells.

The Lipoxin A4 receptor is coupled to SHP-2 activation: implications for regulation of receptor tyrosine kinases.

Mesangial cell proliferation is pivotal to the pathology of glomerular injury in inflammation. We have previously reported that lipoxins, endogenously produced eicosanoids with anti-inflammatory and pro-resolution bioactions, can inhibit mesangial cell proliferation in response to several agents. This process is associated with elaborate receptor cross-talk involving modification receptor tyrosine kinase phosphorylation (McMahon, B., Mitchell, D., Shattock, R., Martin, F., Brady, H. R., and Godson, C. (2002) FASEB J. 16, 1817-1819). Here we demonstrate that the lipoxin A(4) (LXA(4)) receptor is coupled to activation and recruitment of the SHP-2 (SH2 domain-containing tyrosine phosphatase-2) within a lipid raft microdomain. Using site-directed mutagenesis of the cytosolic domain of the platelet-derived growth factor receptor beta (PDGFRbeta), we report that mutation of the sites for phosphatidylinositol 3-kinase (Tyr(740) and Tyr(751)) and SHP-2 (Tyr(763) and Tyr(1009)) recruitment specifically inhibit the effect of LXA(4) on the PDGFRbeta signaling; furthermore inhibition of SHP-2 expression with short interfering RNA constructs blocked the effect of LXA(4) on PDGFRbeta phosphorylation. We demonstrate that association of the PDGFRbeta with lipid raft microdomains renders it susceptible to LXA(4)-mediated dephosphorylation by possible reactivation of oxidatively inactivated SHP-2. These data further elaborate on the potential mechanisms underlying the anti-inflammatory, proresolution, and anti-fibrotic bioactions of lipoxins.

Lack of integrin alpha1beta1 leads to severe glomerulosclerosis after glomerular injury.

Severity of fibrosis after injury is determined by the nature of the injury and host genetic susceptibility. Metabolism of collagen, the major component of fibrotic lesions, is, in part, regulated by integrins. Using a model of glomerular injury by adriamycin, which induces reactive oxygen species (ROS) production, we demonstrated that integrin alpha1-null mice develop more severe glomerulosclerosis than wild-type mice. Moreover, primary alpha1-null mesangial cells produce more ROS both at baseline and after adriamycin treatment. Increased ROS synthesis leads to decreased cell proliferation and increased glomerular collagen IV accumulation that is reversed by antioxidants both in vivo and in vitro. Thus, we have identified integrin alpha1beta1 as a modulator of glomerulosclerosis. In addition, we showed a novel pathway where integrin alpha1beta1 modulates ROS production, which in turn controls collagen turnover and ultimately fibrosis. Because integrin alpha1beta1 is expressed in many cell types this may represent a generalized mechanism of controlling matrix accumulation, which has implications for numerous diseases characterized by fibrosis.

Inhibition of cyclooxygenases reduces complement-induced glomerular epithelial cell injury and proteinuria in passive Heymann nephritis.

In the passive Heymann nephritis (PHN) model of rat membranous nephropathy, complement induces glomerular epithelial cell injury and proteinuria, which is partially mediated by eicosanoids. Glomerular cyclooxygenase (COX)-1 and -2 are up-regulated in PHN and contribute to prostanoid generation. In the current study, we address the role of COX isoforms in proteinuria, using the nonselective COX inhibitor indomethacin and the COX-2-selective inhibitor 5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulphonyl)phenyl-2(5H)-furanone (DFU). Four groups of rats with PHN were treated twice daily, from day 7 through 14 with vehicle, 1 mg/kg DFU, 10 mg/kg DFU, or 2 mg/kg indomethacin. Vehicle-treated rats with PHN showed significant proteinuria on day 14 (163 +/- 15 mg/d, n = 19), compared with normal rats (10 +/- 4 mg/d, n = 3, p < 0.001). Treatment with DFU (1 or 10 mg/kg) reduced proteinuria significantly (by ~33%), compared with vehicle, but to a lesser extent than indomethacin (56% reduction). Glomerular eicosanoid generation was reduced significantly in the DFU and indomethacin groups, compared with vehicle. There were no significant differences among vehicle- or DFU-treated groups in [(3)H]inulin clearance, or in glomerular expression of COX-1 and -2. DFU did not affect the autologous immune response. In cultured rat glomerular epithelial cells, COX inhibition reduced complement-induced cytotoxicity, and this reduction was reversed by the thromboxane A(2) analog 9,11-dideoxy-9alpha,11alpha-methanoepoxyprostaglandin F(2alpha) (U46619). Thus, in experimental membranous nephropathy, selective inhibition of COX-2 reduces proteinuria, without adversely affecting renal function. However, inhibition of both COX-1 and -2 is required to achieve a maximum cytoprotective and antiproteinuric effect.

In vitro evidence for differential involvement of CTGF, TGFbeta, and PDGF-BB in mesangial response to injury.

BACKGROUND: Connective tissue growth factor (CTGF) is a profibrotic growth factor, which is upregulated in wound healing and renal fibrosis, including anti-Thy-1.1 nephritis. The kinetics of CTGF mRNA expression in anti-Thy-1.1 nephritis suggested that CTGF regulation might contribute to glomerular response to injury downstream of transforming growth factor-beta (TGFbeta). In anti-Thy-1.1 nephritis the initial damage is followed by mesangial repair and limited sclerosis, which involves mesangial cell (MC) activation (alpha-smooth-muscle actin (alphaSMA) expression), proliferation, migration, and extracellular matrix production. The present in vitro study addresses the possible role of CTGF in these different aspects of mesangial response to injury, and how CTGF activity might relate to effects of TGFbeta and platelet-derived growth factor-BB (PDGF-BB). METHODS AND RESULTS: Immunostaining and ELISA showed that alphaSMA expression and transformation of MC into myofibroblast-like cells was induced by TGFbeta, but not affected by PDGF-BB, CTGF, or neutralizing anti-CTGF antibodies. [(3)H]thymidine incorporation and Ki67 staining demonstrated that, unlike PDGF-BB, neither CTGF nor TGFbeta induced the proliferation of MC. In contrast, both CTGF and TGFbeta induced MC migration, as evidenced by approximation of wound edges in scrape-wounded, non-proliferating rat MC monolayers. In addition, fibronectin expression was upregulated by both CTGF and TGFbeta, as measured by dot-blot analysis. Anti-CTGF completely blocked the effect of added CTGF. Moreover, anti-CTGF significantly reduced TGFbeta-induced increase in fibronectin. CONCLUSION: It thus appears that CTGF is specifically involved in a subset of the adaptive changes of MC involved in mesangial repair and sclerosis, which makes it an interesting candidate target for future intervention strategies.

The contribution of mesangial cell proliferation to progressive glomerular injury.

Mesangial cell proliferation is a general characteristic of a variety of glomerular diseases. Therefore, an understanding of the regulatory mechanism is important for treatment of glomerular diseases. The present review shows that the growth arrest gene 6 (Gas 6) is a new autocrine growth factor of mesangial cells and that warfarin inhibits mesangial cell proliferation by inhibiting the gamma-carboxylation of Gas 6 in vitro and in vivo. The present findings also show that a vitamin D analog (22-oxa-calcitriol) is a new growth regulator of mesangial cells in vitro and in vivo. These findings indicate that these compounds have considerable potential for therapeutic use in the treatment of progressive glomerular disease.

Overexpression of Crry protects mesangial cells from complement-mediated injury.

Crry is a membrane-associated complement regulatory protein expressed on glomerular mesangial, endothelial, and epithelial cells, which reduces C3/C5 convertase activity. This study utilized an overexpression strategy to determine the functional significance of Crry in cultured rat mesangial cells. A Crry expression vector was constructed and was tagged with a c-myc epitope that allowed transfected Crry to be distinguished from the constitutively expressed protein. In stable clones, overexpressed Crry was clearly detected immunocytochemically both by anti-c-myc and anti-Crry antibody in a membrane localization. The overexpression of Crry was also confirmed by Western blotting and immunoprecipitation. To determine if overexpression of Crry by mesangial cells confers a protective effect from complement attack, complement-mediated cell lysis assays were performed. Crry-transfected mesangial cells demonstrated complete resistance to complement-mediated cell lysis, which was reversed by neutralization of Crry with both monoclonal antibody and F(ab')2 fragments of the antibody. This study also investigated the role of Crry in protecting cells from the effects of sublytic complement attack. Overexpressed Crry suppressed antibody/complement induced production of superoxide, one of the inflammatory mediators induced by sublytic complement attack. Immunocytochemical staining confirmed a reduction in C3 and C5b-9 deposition in Crry-transfected cells. These results demonstrate directly that transfected Crry functions as a potent protector of mesangial cells against complement-mediated injury. Crry may play an important role in modulating the glomerular response to immune injury in vivo.

Participation of glomerular endothelial cells in the capillary repair of glomerulonephritis.

In many glomerular diseases severe injury to the mesangium may occur, leading to matrix dissolution and damage to the glomerular capillaries. Although the destruction of glomerular architecture may lead to permanent injury, in some cases spontaneous recovery occurs. The mechanisms that mediate this recovery are unknown. In this study we provide evidence for glomerular capillary repair (angiogenesis) in the adult injured glomerulus. Injection of anti-Thy 1 antibody into rats results in severe mesangiolysis with capillary ballooning, microaneurysm formation, and loss of endothelial cells in addition to mesangial cells. Although mesangial proliferation is a major response to injury, proliferation of endothelial cells also can be documented from days 2 to 14 in association with repair of the capillaries. The endothelial cell proliferation peaks on days 2 and 7, when it is seven- to ninefold greater than normal. Many of the endothelial cells display morphological features of angiogenesis. The initial wave of endothelial cell proliferation can be reduced by 40% with neutralizing anti-basic fibroblast growth factor antibodies (P < 0.001). The later glomerular endothelial cell proliferation is associated with upregulated expression of vascular permeability factor/endothelial cell growth factor (VPF/VEGF) and an increase of flk, a VPF/VEGF receptor. Although PDGF is expressed in this model, anti-PDGF antibody treatment did not affect the endothelial cell proliferative response. In summary, glomerular endothelial cells have an active role in the glomerular response to injury. Glomeruli are capable of healing microaneurysms, and the mechanism involves basic fibroblast growth factor- and VPF/VEGF-mediated endothelial proliferative responses.

Pathophysiologic role of eicosanoids in mesangial cell immune injury.

The pathophysiologic role of thromboxane and of arachidonate 5-lipoxygenation products in mediating changes in glomerular filtration rate (GFR) and renal blood flow (RBF) was investigated in a rat model of mesangial cell immune injury induced by a monoclonal antibody (ER4) directed against the mesangial cell membrane antigen, Thy 1. Following a single intravenous dose of the ER4 antibody acute decrements in GFR and RBF occurred at 1 h and were associated with enhanced glomerular leukocyte infiltration and synthesis of thromboxane A2, 12-HETE and LTB4. Pretreatment of animals with the thromboxane synthase inhibitor, Furegrelate, or the thromboxane receptor antagonist SQ-29,548 ameliorated or completely abolished the decrements in GFR and RBF without reducing glomerular leukocyte infiltration. Pretreatment with the arachidonate 5-lipoxygenase inhibitor MK-886 partially ameliorated the decrements in GFR and RBF, reduced the glomerular leukocyte infiltration and completely inhibited the glomerular LTB4 synthesis. Combined treatment with Furegrelate and MK-886 completely abolished the decrements in GFR and RBF as well as the glomerular synthesis of thromboxane, LTB4 and 12-HETE without altering glomerular leukocyte infiltration. These observations indicate that in mesangial cell immune injury thromboxane A2 and arachidonate 5-lipoxygenation products originating from infiltrating inflammatory cells mediate the decrements in GFR and RBF. Selective inhibition of these eicosanoids could be of benefit in clinical forms of mesangial nephritis.

Enhanced in vitro growth of glomerular cells derived from rats with immune-mediated mesangial injury.

In order to evaluate whether in vivo immune-mediated lesions in the glomerulus might affect growth of glomerular cells in vitro, we developed a combined in vivo-in vitro approach. An immune-mediated mesangial cell injury was induced in rats by intravenous injection of a rabbit anti-rat thymocyte antiserum (ATS). Beginning at day 1 up to 12 days after ATS, glomeruli were isolated for glomerular cell culture and evaluation of cell growth. Compared with control rats cell growth from nephritic glomeruli was significantly higher at all time points studied. Immunohistologic studies performed revealed that the proliferating cells had characteristics of glomerular mesangial cells. These data demonstrate that mesangial cells derived from nephritic glomeruli have increased growth in vitro compared with cells from normal glomeruli.

Glomerular NO synthase activity in mesangial cell immune injury.

Ex vivo synthesis of nitrite (NO2-) by nephritic glomeruli provides evidence of induction of nitric oxide (NO) in glomerulonephritis (GN). In macrophage-associated GN, the major source is infiltrating macrophages. As induction of NO synthesis has now been shown in cultured mesangial cells, we have examined whether in vivo mesangial proliferation is a source of NO2-. Mesangial proliferative GN was induced by intravenous anti-Thy1.1 (monoclonal antibody ER4). Isolated glomeruli were assayed for NO2- synthesis and macrophage infiltration on day 4 (mesangiolytic phase) and on day 7 (mesangial proliferation). On day 4, but not on day 7, basal NO2- was increased (8.3 +/- 1.8, controls 0.7 +/- 0.1 nmol/2,000 glomeruli/48 h; p = 0.05) and there was macrophage infiltration (60 +/- 15; controls 14 macrophages/glomerulus). At both times NO2- was elevated by exogenous IL1 or LPS, more significantly on day 4 than on day 7. Thus, mesangial proliferative lesions are not a source of basal NO2-, and macrophages are the most likely source. However, NO2- can be induced in mesangial proliferative glomeruli by exogenous stimuli, findings similar to those reported in cultured mesangial cells. Irradiation experiments in normal rats show that stimulated NO2- synthesis is inhibited by macrophage depletion. Therefore in neither normal nor proliferative glomeruli is there evidence for mesangial cell production of NO2-.

Mesangial cell killing by leukocytes: role of leukocyte oxidants and proteolytic enzymes.

Mesangial cells from human and rat kidney were examined for sensitivity to killing by neutrophils. Cells from both species were sensitive to killing by phorbol myristate acetate-stimulated neutrophils. Catalase was highly protective while superoxide dismutase was less protective and a number of protease inhibitors were not protective. Strong protection was also observed with the iron chelators, deferoxamine and phenanthroline, and with the hydroxyl radical scavengers, dimethylthiourea and 5,5-dimethyl-1-pyrroline N-oxide. Pretreatment of the mesangial cells with deferoxamine followed by washing also provided protection. Mesangial cells were also killed by reagent hydrogen peroxide (H2O2) but were much less sensitive to injury by direct application of proteolytic enzymes. The ability of H2O2 to injure mesangial cells was prevented by pre-incubation of the H2O2 with human leukocyte myeloperoxidase. These data suggest that killing is due primarily to the generation of H2O2 by the stimulated neutrophils and its further reduction in an iron-catalyzed reaction. The hydroxyl radical may be the reduction product that actually mediates lethal injury but lack of scavenger specificity prevents definitively concluding this. Mesangial cell killing by activated neutrophils could be significantly inhibited by monoclonal antibodies to CD11/CD18 molecules, suggesting that close contact between the target and effector cells is required for cytotoxicity. Although qualitatively similar to endothelial cells, the mesangial cells appeared to be quantitatively more oxidant sensitive than previously examined human and rat endothelial cells. Taken together, these data show that mesangial cells from rat and human are sensitive to leukocyte-induced injury and that injury results via an oxidant pathway.(ABSTRACT TRUNCATED AT 250 WORDS)

Chemoattractants provoke monocyte adhesion to human mesangial cells and mesangial cell injury.

Infiltration of glomerular mesangium by monocytes/macrophages is a prominent pathologic finding in many forms of glomerulonephritis (GN). While the mechanism(s) by which infiltration occurs is incompletely understood, monocyte adhesion to glomerular endothelial cells, provoked by inflammatory mediators, appears to be an important early step. In the present study, we assessed the influence of chemotactic peptides (C5a) and lipids (LTB4 and PAF) on adhesion of human monocytes and mesangial cells, to determine if mesangial cells (glomerular pericytes with smooth muscle properties) represent potential targets for adhesion of chemoattractant-activated monocytes following their diapedesis from the intravascular space. C5a and LTB4 provoked rapid (onset less than 1 min) monocyte-mesangial cell adhesion at nanomolar concentrations via actions with monocytes, while PAF was less potent in this regard. Monoclonal antibodies (mAb) were used to define the monocyte and mesangial cell adhesion molecules involved in these interactions. C5a- and LTB4-induced monocyte adhesion was inhibited (approximately 54%) by mAb against the common beta CD18 subunit of CD11/CD18 leukocyte integrins, while mAb against monocyte L-selectin was without effect. MAb against unique CD11 subunits were used to determine the relative contributions of different CD11/CD18 integrins. In this regard, adhesion was inhibited by mAb against CD11b (approximately 41%), and CD11c (approximately 23%), but not CD11a. MAb against mesangial cell ICAM-1 afforded approximately 27% reduction in adhesion, while mAb against VCAM-1, E-selectin, and P-selectin were without effect. GM-CSF, a cytokine generated by monocytes and mesangial cells, also provoked CD11/CD18-dependent adhesion, and primed monocytes to the actions of chemoattractants.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased oxygen radical and eicosanoid formation in immune-mediated mesangial cell injury.

To evaluate whether monocytes/macrophages derived from glomeruli could be a source of increased eicosanoid and free oxygen radical formation in glomerular disease, monocytes/macrophage (M/M) were isolated from nephritic glomeruli and their in vitro generation of eicosanoids and superoxides were measured. Glomerular immune injury was induced by i.v. injection of a rabbit-anti-rat thymocyte antiserum (ATS). Kidneys were removed two, five, and 24 hours, and three and eight days after ATS. Adhesive glomerular macrophages were obtained by isolation of glomeruli, enzymatic digestion and incubation of the single cell suspensions in culture dishes. O2-production was evaluated by superoxide dismutase (SOD)-inhibitable reduction of ferricytochrome C; PGE2 and TxB2 release was assessed by direct RIA. Glomerular macrophage infiltration was maximal 24 hours after intravenous antibody (35.9 +/- 5.1 M/M per glomerulus). In vitro production of superoxide was significantly enhanced (P less than 0.001) five hours after ATS administration (51.6 +/- 4.4 nmol O2/10(6) MM/hr), when compared with M/M from controls (30.4 +/- 2.0 nmol O2/10(6) MM/hr). TxB2 formation of glomerular M/M was increased (P less than 0.001) two hours and five hours after ATS administration (1056 +/- 75 and 1182 +/- 112 pg TxB2/10(6) MM/hr) compared with controls (390 +/- 34 pg TxB2/10(6) MM/hr). PGE2 synthesis, however, was decreased (P less than 0.01) at five hours after ATS (629 +/- 43 pg PGE2/10(6) MM/hr) compared with controls (950 +/- 125 pg PGE2/10(6) MM/hr). Furthermore, there was release of leukotriene B4 (LTB4) in monocytes of nephritic glomeruli five hours after ATS administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Immune damage to the mesangium: antibody- and complement-mediated stimulation and destruction of mesangial cells.

The deposition of immune complexes in the tissue results in complement activation leading to the formation of the lytic C5b-9 complex. Tissue cells are relatively resistant to complement attack due to cellular mechanisms such as removing C5b-9 from the surface and the expression of membrane proteins, which regulate complement activation and attack on the cell surface. Hence, cell killing is not an important consequence of complement activation on nucleated cells. On the other hand, the sublethal C5b-9-membrane interaction leads to various cellular responses, among them the synthesis of eicosanoids, cytokines, matrix-degrading proteases, and extracellular matrix, resulting in the modification of cell proliferation, leukocyte function, matrix degradation, and the formation of scar tissue. Thus, the complement-dependent immune damage is caused by secondary mediators, either derived from leukocytes or mesangial cells, rather than by a direct C5b-9-mediated killing.

Morphologic and functional consequences of immune-mediated mesangiolysis: development of chronic glomerular sclerosis.

The i.v. injection of a rabbit anti-rat thymocyte serum (ATS) induces mesangiolysis in rats, followed by a mesangioproliferative glomerulonephritis (4 to 7 days after antibody). This proliferative lesion disappears 4 to 6 wks after antibody. In order to induce an antibody-mediated sclerotic glomerular disease, uninephrectomized rats received ATS twice at 6-wk interval. At 6 months after the first antibody injection, albuminuria, arterial blood pressure, and inulin clearances were evaluated and renal morphologic studies were performed. At the time of evaluation, mean arterial blood pressure and inulin clearances were not different between animals that received the antibody and uninephrectomized controls. Rats that were injected with antibody, however, had significantly higher albuminuria compared with that of controls. Glomeruli of rats with ATS revealed expansion of the glomerular mesangial matrix and focal sclerosis. A semiquantitative morphologic analysis revealed an increased incidence of glomerular lesions and a higher glomerular damage index in kidneys of nephritic rats. These data demonstrate that the repetitive injection of ATS to unilaterally nephrectomized rats induces a model of chronic glomerular sclerosis.

The platelet activating factor receptor antagonist WEB 2170 improves glomerular hemodynamics and morphology in a proliferative model of mesangial cell injury.

Rats were treated with the platelet activating factor receptor antagonist WEB 2170 (15 mg/kg/day) in three different protocols to evaluate a possible role of platelet activating factor in an experimental proliferative model of glomerular disease. The glomerular immune injury was initiated by the i.v. administration of a rabbit anti-rat thymocyte antiserum. Anti-rat thymocyte antiserum induces a proliferative glomerulonephritis with reduction of glomerular filtration rate (614 +/- 94) compared with controls (1,120 +/- 192 microL/min/100 g body wt) when studied at day 7. Treatment of rats with WEB 2170 over 8 days (starting at day -1; protocol 1) ameliorated the loss in glomerular filtration rate (936 +/- 82 microL/min/100 g body wt) in nephritic rats at day 7; however, it had no effect on controls (1,142 +/- 104 microL/min/100 g body wt). Interventional treatment with WEB 2170 (starting at day 4 after anti-rat thymocyte antiserum; protocol 2) also improved glomerular function when glomerular filtration rate was already reduced (410 +/- 41 microL/min/100 g body wt) at day 4. The platelet activating factor receptor antagonist given at day 7 after induction of disease (protocol 3) did not improve impaired glomerular filtration rate. Preinterventional and interventional treatment with WEB 2170 reduced the infiltration of polymorphonuclear granulocytes in glomeruli. Interventional treatment with WEB 2170 also reduced glomerular morphologic damage in nephritic glomeruli. The data demonstrate a beneficial effect of the platelet activating factor receptor antagonist in this animal model of proliferative glomerulonephritis which suggests that platelet activating factor might play an important role in the mediation of this disease.