Biomedical subjects

M R Daha

Publications and source records attributed to M R Daha.

At least 91 records · Page 5Linked to original sources

PubMed1998

Histomorphometric correlates of renal failure in IgA nephropathy.

It is generally accepted that the severity of renal insufficiency in patients correlates with the severity of tubulointerstitial abnormalities, but not with the severity of glomerular abnormalities in kidney biopsies. We recently challenged this view by demonstrating significant correlations of glomerular structural abnormalities with renal function in a histomorphometric study of biopsies from patients with various kidney diseases. We set out to confirm these findings in biopsies from patients with a single disease entity. IgA nephropathy was selected. An additional objective of the study was to determine the prognostic value of our histological predictors of renal function. Histomorphometric measurements were done in silver- and PAS-stained paraffin sections of biopsies from 83 patients with primary IgA nephropathy. The results were correlated with creatinine clearance at the time of biopsy. The prognostic value of the histomorphometric parameters and of several clinical characteristics were determined in a Cox proportional hazard model. All glomerular histomorphometric indices correlated with the severity of renal insufficiency, but quantitative estimates of the glomerular deposition of periodic acid-Schiff positive extracellular matrix (PAS-index) seemed to be the most important glomerular structural-functional correlate (r = 0.53, p<0.001). However, the correlation of quantitative estimates of the severity of interstitial extracellular matrix accumulation with renal function (quantitative interstitial index) was superior (r = 0.76, p<0.001). Creatinine clearance at biopsy and initial proteinuria were the strongest clinical predictors of renal survival. The severity of tubulointerstitial extracellular matrix accumulation was the strongest histological predictor of an adverse outcome. In conclusion, quantitative estimates of the severity of glomerular and tubulointerstitial extracellular matrix accumulation both correlate well with the severity of renal failure in biopsies from patients with IgA nephropathy. Creatinine clearance at biopsy, initial proteinuria and the severity of tubulointerstitial extracellular matrix accumulation are the best predictors of renal survival. On a more general note, the paradigm of the absence of correlation of glomerular pathology with renal function should be abandoned.

Adult↗

PubMed1997

Characterisation of the rat and mouse homologues of gC1qBP, a 33 kDa glycoprotein that binds to the globular 'heads' of C1q.

gC1qBP is a 33 kDa glycoprotein that binds to the globular 'heads' of C1q. We have cloned cDNAs encoding the rat and mouse homologues of gC1qBP. Comparison of the cDNA-derived amino acid sequences of gC1qBP reveals that either of the rodent sequences is 89.9% identical to the reported human sequence. Recombinant rat gC1qBP binds avidly to human C1q. gC1qBP mRNA is abundantly expressed in every rat and mouse tissue analysed. Rat mesangial cells synthesise gC1qBP, but do not express gC1qBP on the cell surface. In rat serum, gC1qBP is present at low levels.

Amino Acid Sequence↗

PubMed1997

Apoptosis of acinar cells in pancreas allograft rejection.

BACKGROUND: Recently it has been recognized that apoptosis of target cells may occur during liver and kidney allograft rejection and is probably induced by infiltrating cells. Pancreas rejection is also characterized by a cellular infiltrate, however, the occurrence of apoptosis has not been investigated. We assessed whether pancreas rejection was associated with apoptosis of target cells and an influx of granzyme B (GrB)-positive or CD68-positive cells. METHODS: Eighteen pancreas biopsies (10 of 18 with rejection) from 15 patients with a pancreas-kidney transplantation were stained with the in situ end-labeling method for apoptosis, and for CD3, GrB, and CD68. RESULTS: Significantly more apoptotic acinar cells were found in biopsies with rejection when compared with biopsies without rejection. No difference was observed between the groups for GrB+ or CD68+ cells. CONCLUSION: We conclude that pancreas rejection is associated with apoptosis of acinar cells, but not with an increased influx of GrB+ cells or macrophages.

Antigens, CD↗

PubMed1997

Tissue-specific characteristics of cytotoxic graft-infiltrating T cells during renal allograft rejection.

BACKGROUND: The alloresponse after renal transplantation was studied using alloreactive T cells generated in vivo (from renal biopsies) and in vitro (from mixed kidney lymphocyte cultures). METHODS: Tissue specificity of graft-infiltrating T cells (GIC) was investigated using donor-derived proximal tubular epithelial cells (PTEC) and splenocytes as targets in cytotoxicity assays. RESULTS: The outgrowth of cytotoxic T cells was associated with histologically proven interstitial rejection. GIC were categorized into four groups: (1) GIC cytotoxic for both PTEC and splenocytes (n=30), (2) noncytotoxic GIC (n=8), (3) GIC recognizing only splenocytes (n=1), and (4) GIC specifically recognizing PTEC (n=7). Similar tissue-specific T cells could be generated in vitro using mixed kidney lymphocyte cultures. Cytotoxicity of GIC from biopsies with moderate to severe rejection was CD8 independent, whereas cytotoxicity toward splenocytes was CD8 dependent. CONCLUSIONS: Our results show that polyclonal cytotoxic T-cell responses with tissue-specific characteristics are elicited during rejection episodes after renal transplantation.

CD3 Complex↗

PubMed1997

Pancreas and kidney allograft-infiltrating cells in simultaneous pancreas-kidney transplantation.

BACKGROUND: Rejection after pancreas-kidney transplantation may occur isolated or concurrently in both grafts. To get more insight into the cellular mechanisms underlying these rejection episodes, we compared the functional characteristics of pancreas and kidney graft-infiltrating T cells. METHODS: Graft-infiltrating T cell (GIC) lines were cultured from simultaneously taken pancreas and kidney biopsies from eight patients. CD4 to CD8 ratios were determined by fluorescence-activated cell sorter and cytotoxicity toward donor proximal tubular epithelial cells (PTEC) and donor spleen cells (DSC) using a standard cytotoxicity assay. Cytokine production was determined by enzyme-linked immunosorbent assay. RESULTS: CD4 to CD8 ratios were comparable between the pancreas and kidney lines for each patient, but differences were observed in cytotoxicity toward PTEC and DSC. For four of eight patients, the lysis of PTEC by pancreas GIC was less than the lysis induced by kidney GIC. This was also seen in three of five patients for lysis of DSC. The specificity of GIC lines toward mismatched donor antigens was studied for two patients and appeared to be comparable for pancreas and kidney. Most GIC lines produced interferon (IFN)-gamma (75.5+/-22.7 pg/ml), but no IL-10, indicating that the cell lines consisted primarily of Th1 and type 1 CD8+ cells. Mean production of IL-6 was 465.6+/-193.6 pg/ml. No major differences were observed between kidney and pancreas GIC for either cytokine. CONCLUSIONS: We conclude that pancreas and kidney GIC lines have the same phenotype, cytokine production, and allospecificity. Differences were, however, seen for lysis of PTEC and DSC, suggesting that tissue-specific antigens might play a role.

Biopsy↗

PubMed1997

Pancreatitis-associated protein: a putative marker for pancreas graft rejection.

BACKGROUND: Graft rejection is one of the major causes of graft loss after pancreas transplantation. Pancreatitis-associated protein (PAP) is synthesized by the pancreas due to pancreatic inflammation and has shown to be a good serum marker for injury of the pancreas. It may also be potentially useful in the early recognition of rejection and may thus improve pancreas survival. METHODS: We retrospectively evaluated PAP as an early serum marker of pancreas graft rejection in a cross-sectional study in which immunohistochemical analysis of pancreas biopsies was undertaken using antibodies against PAP. PAP concentrations were also measured in sera of blood donors and in patients with renal failure, renal replacement therapy, kidney transplantation alone, and simultaneous pancreas-kidney transplantation. RESULTS: All patients had elevated PAP serum levels compared with blood donors (median PAP: 22 ng/ml, range: 5-75 ng/ml; P<0.0001). Patients on renal replacement therapy had higher values than patients with renal failure (median: 420 ng/ml and 150 ng/ml, respectively). There was a strong inverse correlation between PAP levels and creatinine clearance (P<0.001). PAP values in simultaneous pancreas-kidney transplantation patients with histological rejection were significantly higher than values in those who were clinically stable (median: 925 ng/ml and 322 ng/ml, respectively; P=0.006). Rejection was significantly associated with PAP staining of acinar cell surface. There was also a significant correlation between surface positivity of staining and serum PAP levels (P=0.008). No positive PAP staining was observed in concurrently collected biopsies of renal allografts undergoing rejection. CONCLUSIONS: Serum PAP levels appear to strongly correlate with creatinine clearance measurements. In patients with a pancreas-kidney transplantation, PAP may prove to be a useful biological and histological marker of pancreatic graft rejection.

Acute-Phase Proteins↗

PubMed1997

Intracellular localization of the human receptor for the globular domains of C1q.

This study was performed to determine the localization of the recently described receptor for the globular domain of C1q, gC1qR. In contrast to previous reports, we were not able to detect significant surface expression of gC1qR on Raji cells, monocytes, neutrophils, human or rat mesangial cells, the endothelial cell line EA.hy 926, or HUVEC using FACS analysis. Only by using digoxigenin-conjugated Abs could some surface staining of gC1qR be observed on rat mesangial cells and neutrophils. However, after permeabilizing these cells with saponin, a strong positive intracellular staining for gC1qR was observed by FACS, fluorescence microscopy on coverslips, and confocal laser scanning microscopic analysis. By reflection contrast microscopy and electron microscopy on ultrathin sections of permeabilized Raji cells, it was shown that gC1qR is present in double membranous cytoplasmic vesicles located in the proximity of the plasma membrane. To determine whether certain conditions could induce surface expression of gC1qR, Raji cells were either stimulated with T cell growth factor, LPS, or driven to apoptosis by incubation with fenretinide or by serum depletion. None of the conditions resulted in significant surface expression of gC1qR. Our hypothesis that gC1qR is not a surface molecule but a soluble molecule that is secreted by cells is supported by the observation that gC1qR is found in significant concentrations in supernatants of several cultured cells and in normal human and rat sera. Our results suggest that the recently described gC1qR is not a cell surface receptor, but a soluble binding protein with affinity for the globular heads of C1q. Excreted gC1qR might act as a potential fluid phase regulator of complement activation.

Animals↗

PubMed1997

Increased expression of IL-15 in the synovium of patients with rheumatoid arthritis compared with patients with Yersinia-induced arthritis and osteoarthritis.

Recently, a new player in the cytokine network has been described that is produced by monocytes and can be detected in the rheumatoid synovium: interleukin-15 (IL-15). Since this cytokine may play a role in the accumulation and activation of T-cells, B-cells, and natural killer (NK) cells characteristic of synovial tissue (ST) from patients with rheumatoid arthritis (RA), the expression of IL-15 was studied in ST from RA patients in comparison with ST from patients with reactive arthritis (ReA) and osteoarthritis (OA) and the phenotype of IL-15-positive cells was determined. IL-15 expression was investigated by immunohistochemical analysis of ST from ten patients with RA, ten patients with Yersinia enterocolitica-induced ReA, and nine patients with OA. The immunohistological findings were quantified and the results obtained in the different patient groups were compared. To determine the phenotype of IL-15-expressing cells, double-labelling immunofluorescence was performed. The expression of IL-15 was significantly higher in ST from patients with RA than in ST from patients with ReA or OA. In double-label experiments, co-expression was observed with markers for macrophages, T-cells, and NK cells. The composition of the cellular infiltrate in the synovium of patients with RA might be partly explained by the specific increase in expression of IL-15 in rheumatoid ST. It can be speculated that IL-15 production by inflammatory cells other than macrophages may occur in the rheumatoid synovium.

Adult↗

PubMed1997

Analysis of the synovial cell infiltrate in early rheumatoid synovial tissue in relation to local disease activity.

OBJECTIVE: To define variations in the cellular infiltrate and in the expression of monokines in synovial tissue (ST) from rheumatoid arthritis (RA) patients with different durations of disease and different levels of disease activity. METHODS: The immunohistologic features of synovial biopsy specimens from 31 patients with early RA (< 1 year) and 35 patients with longstanding RA (> 5 years) were compared. The possible associations between these features and local disease activity, as measured by the score for pain in the biopsied knee joint were also evaluated. RESULTS: The immunohistologic features were not dependent on disease duration. We found a positive correlation between the scores for knee pain and the semiquantitative scores for the number of macrophages, as well as the expression of interleukin-6 and tumor necrosis factor alpha, whereas the correlation with the scores for CD4+ T cells was negative. Multivariate analysis showed that these correlations were highly statistically significant (P < 0.003). CONCLUSION: The results do not support the view that inflammatory mechanisms in the synovial tissues of RA patients differ between early and late stages of the disease. The findings presented here are consistent with the concept that early RA is the result of a synovitis process of longer duration and that macrophage-derived cytokines play an important role in maintaining the clinical signs of inflammation.

Adult↗

PubMed1997

Size-dependent effect of IgA on the IgA Fc receptor (CD89).

The IgA Fc receptor (FcR; CD89) is expressed on several types of cells of the myeloid cell lineage. We investigated whether different sizes of heat-aggregated IgA (aIgA) bind to CD89 and subsequently induce cellular activation. As a model we used the murine B cell line IIA1.6 transfected with CD89 or IIA1.6 cells transfected with CD89 as well as with the FcR gamma chain to study the binding of IgA to CD89. When these cells expressing CD89 were incubated with monomeric IgA, no significant binding of IgA to the cells was detectable by fluorescence-activated cell sorter analysis; however, incubation of the cells with aggregated IgA resulted in 93 +/- 2% positive cells. Incubation of the cells with different sizes of IgA-containing aggregates revealed optimal binding with aggregates containing five to six molecules of IgA per aggregate. No difference was observed between the binding to CD89 of both IgA1- or IgA2-containing aggregates. Furthermore, the binding of aIgA was found to be CD89-specific, since the binding of IgA was completely inhibited by the CD89-specific monoclonal antibody My43 and no detectable binding occurred to the IIA1.6 parent cell line. Activation studies using interleukin-2 (IL-2) production as a marker, showed that the FcR gamma chain is necessary to induce cellular activation. Only cells transfected with both CD89 and the FcR gamma chain (CD89+/gamma +) enhance the IL-2 production 10-12-fold upon stimulation with aggregates of IgA. Furthermore, triggering of CD89 only results in increase of intracellular calcium concentration ([Ca2+]i) in cells co-expressing FcR gamma chain. Mutation of the tyrosine residues in the FcR gamma chain immunoreceptor tyrosine-based activation motif of the FcR gamma chain abolishes this increase in [Ca2+]i, indicating association and involvement of the FcR gamma chain in CD89-mediated signaling.

Amino Acid Substitution↗

PubMed1997

Interferon-gamma induces biosynthesis of complement components C2, C4 and factor H by human proximal tubular epithelial cells.

In a previous study the authors demonstrated that the production of complement component C4 by human kidney proximal tubular epithelial cells (PTEC) is upregulated by interferon gamma (IFN-gamma). In the present study the authors describe that PTEC in culture express both mRNA and protein of the IFN-gamma receptor complex, and that culture of PTEC with 1000 U/ml IFN-gamma for 72 h results in enhanced production not only of C4 (36.1 ng/10(6) cells), but also of C2 (10.8 ng/10(6) cells) and Factor H (17.5 ng/10(6) cells). Unstimulated PTEC produced 0.5 ng/10(6) cells, 0.5 ng/10(6) cells and 0.4 ng/10(6) cells of C2, C4 and Factor H, respectively. The upregulation of the three complement components was dose- and time-dependent and specific for IFN-gamma because the effect of IFN-gamma was abolished by a monoclonal antibody directed against IFN-gamma. Furthermore no effect of other cytokines was observed. The regulation of synthesis of C2, C4 and Factor H occurred at the transcriptional level as shown by semi-quantitative RT-PCR and dot-blot analysis. Taken together with the observation that in normal kidney tissue the tubuli express IFN-gamma receptor alpha-chain and a signal transducing protein, the present study implies that enhanced production of complement by PTEC may occur during a local immune response by in situ generation of IFN-gamma by infiltrating T-cells in the interstitium of the kidney.

Complement C2↗

PubMed1997

A cyclic GMP- and G-kinase-dependent effect of azathioprine on migration by human neutrophils.

Relatively high concentrations of azathioprine had an inhibitory effect on interleukin 8 (IL-8)- or formyl-methionyl-leucyl-phenylalanine-activated (fMLP)-chemotaxis by human neutrophils. However, application of low concentrations of azathioprine in a concentration gradient gave a chemotactic stimulation to random migration. Stimulation of migration was maximal at a concentration of 5 microM azathioprine; at higher concentrations stimulation decreased again. The activating effect of azathioprine is located in the mercaptopurine moiety of the molecule, since mercaptopurine also stimulated neutrophil migration. In contrast to some other chemotactic agents such as fMLP and IL-8, an activating concentration (5 microM) of azathioprine did not cause an upregulation of CD11b expression on neutrophils in suspension. High concentrations of azathioprine (1 mM) inhibited CD11b expression of fMLP- or IL-8- activated neutrophils; the latter could explain the inhibitory effect of azathioprine. Azathioprine caused a transient stimulation of cGMP level; inhibitors of guanylate cyclase inhibited azathioprine-stimulated migration, suggesting that cGMP was associated with the stimulating effect of azathioprine on migration. Antagonists of cGMP-dependent protein kinase (G-kinase) strongly inhibited azathioprine-activated migration, indicating that the effect of azathioprine proceeds via G-kinase. The antagonists had only a marginal effect on inhibition of IL-8-activated chemotaxis by high concentrations of azathioprine, thus the G-kinase seems not to be of great importance on the inhibitory effect of azathioprine.

Aminoquinolines↗

PubMed1997

Specificity of monoclonal antibodies against ABH and related structures tested by ELISA with synthetic glycoconjugates.

We have tested 88 monoclonal antibodies with proposed specificities against ABH- and related antigens in an ELISA with synthetic oligosaccharide conjugates as coating substances. All mabs were tested for binding towards A-, B-, and H type I trisaccharides, the B disaccharide, and the proposed anti-A and -AB were also tested on A tetrasaccharide type I. Of the 50 mabs with proposed A- and/or B-specificity, 28 showed a specific reaction in our ELISA. Cross-reactivity with other ABH-antigens was observed for 7 of these 50 anti-A/B mabs and 15 of them did not react in the ELISA. Only 2 of the 17 mabs submitted as anti-H bound to H trisaccharide type I, one of them showed a polyspecific reactivity pattern, and the remaining 14 did not react with our type I antigen. Of the mabs with other than ABH-specificities only one, supposedly anti-P1, showed cross-reactivity with one of our coating antigens, in this case the B trisaccharide.

ABO Blood-Group System↗

PubMed1997

The effect of sodium aurothiomalate on stimulated and non-stimulated migration by human neutrophils: the role of cyclic GMP.

Preincubation of human neutrophils with aurothiomalate had little effect on random migration or chemotactic migration towards the chemotactic peptide fMLP. However, a strong enhancement of migration was observed when aurothiomalate was present in a concentration gradient; the effect of the drug was chemotactic rather than chemokinetic. Thiomalate also caused a chemotactic enhancement of migration but here a tenfold higher concentration of the drug was required as compared with aurothiomalate. Aurothiomalate caused an increase of cellular cGMP level, and inhibitors of guanylate cyclase inhibited the activating effect of aurothiomalate. Three specific antagonists of cGMP-dependent kinase (G-kinase) strongly inhibited aurothiomalate-induced migration of electroporated neutrophils. The results suggest that stimulation of migration by aurothiomalate is mediated by cGMP and a G-kinase. Monoclonal anti-IL-8 inhibited aurothiomalate-induced stimulation of migration. Though no increased release of IL-8 could be established upon exposure of neutrophils to aurothiomalate, it seems conceivable that the stimulating effect of aurothiomalate is mediated by IL-8.

Cell Movement↗

PubMed1997

Possible role for CD40-CD40L in the regulation of interstitial infiltration in the kidney.

Interstitial infiltration by mononuclear cells is a hallmark of most inflammatory kidney diseases, and the degree of infiltration is associated with disease progression. It has been demonstrated that proximal tubular epithelial cells (PTEC) are an important source of different cytokines/chemokines and thereby play a central role in the regulation of the local inflammatory response. CD40 is a cell surface receptor involved in immune regulation for which the ligand is expressed on activated T cells. By different staining methods, CD40 was found expressed in cryosections on the basolateral side of tubuli, as well as on the surface of an SV40-transformed PTEC line (PTEC-TRL) and on primary PTEC cultures. Cross linking CD40 receptor on these cultured cells, using a CD40L-transfected mouse fibroblast, resulted in strong up-regulation of the production of the chemokines IL-8, MCP-1 and RANTES. For IL-8 and MCP-1 production, the stimulation index after CD40 activation ranged from two- to sevenfold. Much stronger effects were observed for RANTES production, where levels remained undetectable (< 0.1 ng/ml) in non-stimulated cultures, whereas CD40 activation resulted in a strong production reaching 5 ng/ml in a 72-hour culture period. These data suggest that CD40L-CD40 interactions between infiltrating activated T cells and PTEC might be an important factor in the regulation of interstitial infiltration within the kidney.

Animals↗

PubMed1997

Efficient induction of apoptosis in cultured rat glomerular mesangial cells by dimeric monoclonal IgA anti-Thy-1 antibodies.

Apoptosis of glomerular cells (GMC) has been observed in the early phase as well as the resolution phase of Thy-1 nephritis. Recently, we and others reported that IgG2a (ER4G) and IgG1 (OX7) monoclonal mouse anti-Thy-1 antibodies (anti-Thy-1 MoAb) are able to induce apoptosis of rat GMC in vivo. The purpose of this study was to investigate whether cross-linking of Thy-1 would influence the degree of apoptosis in cultured rat GMC using monomeric and dimeric IgA anti-Thy-1 MoAb. IgA anti-Thy-1 MoAb (ER4A) was generated by class switching of the IgG producing ER4 (ER4G) hybridoma. The ER4A clone spontaneously produces monomeric (m-ER4A) and dimeric IgA anti-Thy-1 MoAb *di-ER4A). Unaltered epitope specificity of ER4A was confirmed by blocking experiments of the binding of fluorescence labeled ER4G to cultured rat GMC with unlabeled ER4A on FACS. For the experiments of apoptosis, quiescent rat GMC were incubated for eight hours with medium alone or with medium in the presence of 10 micrograms/ml of m-ER4A, di-ER4A or control IgA MoAb of corresponding sizes. Apoptosis was assessed by morphological studies, agarose gel electrophoresis and quantitative FACS analyses using terminal deoxynucleotidyl transferase (TDT) method and the annexin V method. The TDT method detects specific-DNA nicking in apoptosis. The annexin V method detects early membrane changes during apoptosis. In morphological studies, cells incubated with m-ER4A and di-ER4A showed typical apoptotic features such as nuclear condensation and fragmentation. DNA isolated from the cells incubated with di-ER4A was cleaved into a distinctive ladder pattern compatible with apoptosis. In contrast, both medium alone and control IgA MoAb did not reveal detectable changes in morphological studies and agarose gel electrophoresis. In quantitative analyses by FACS using the TDT method and the annexin method, both m-ER4A and di-ER4A induced significantly higher percentages of apoptosis in rat GMC as compared to the controls. Furthermore, di-ER4A was considerably more efficient than m-ER4A in inducing apoptosis possibly through additional cross-linking of Thy-1 on the cell surface. This notion was confirmed by experiments, in which the addition of goat anti-mouse kappa antibodies enhanced apoptosis of rat GMC pre-sensitized with m-ER4A. Taken together, our results indicate that apoptosis of rat GMC by anti-Thy-1 antibodies is enhanced by cross-linking of Thy-1 on the cell surface. These studies are of importance for our understanding of mechanisms that may play a role in glomerular diseases.

Animals↗

PubMed1997

Extrahepatic C6 is as effective as hepatic C6 in the generation of renal C5b-9 complexes.

In order to study the contribution of extrahepatic C6 to anti-Thy1.1 nephritis, C6 deficient PVG/c- livers were grafted in C6 sufficient PVG/c+ rats (Tx-L). Infusion of anti-Thy1.1 antibodies in Tx-L and PVG/c+ rats resulted in generation of C5b-9 complexes and subsequent glomerular injury, while infusion of anti-Thy1.1 antibodies in PVG/c- rats revealed no detectable C6 deposition. Because C6 mRNA was expressed in both liver and kidney tissue of PVG/c+ rats, we assessed whether production of C6 in the kidney alone was sufficient for glomerular injury. One kidney of a PVG/c- rat was replaced with a PVG/c+ kidney (Tx + K) followed by administration of anti-Thy1.1 antibodies. C6 deposits were detectable neither in PVG/c+ kidneys nor in PVG/c- kidneys of Tx + K rats, indicating that C6 production in PVG/c+ kidneys alone is not sufficient to contribute to renal injury. That C6 production had occurred was suggested by the presence of equal amounts C6 mRNA in control PVG/c+ kidneys and in grafted PVG/c+ kidneys of Tx + K rats. C6 mRNA expression in kidney tissue of PVG/c+ rats is presumably derived from peritubular sites. In conclusion, we have demonstrated that extrahepatic, but not renal synthesis of, C6 is sufficient to contribute to glomerular injury during anti-Thy1.1 nephritis.

Animals↗

PubMed1997

Induction of mesangial interleukin-6 synthesis by apoptotic U937 cells and monocytes.

Infiltration of the glomerular mesangium by monocytes and macrophages is a central pathologic feature in various forms of glomerulonephritis. Dependent on the presence and activity of local survival factors, monocytes may undergo apoptosis. Therefore, we looked for the interaction between cultured human mesangial cells (HMC) and intact, necrotic or apoptotic monocytic cells with different stages of programmed cell death (U937 cells and blood-derived human monocytes) and the possible evoked secretory responses of HMC. Interleukin-6 (IL-6) synthesis of HMC after a two hour co-culture with late apoptotic U937 cells was significantly increased (505 +/- 55 pg/ml) as compared to intact U937 cells (349 +/- 27 pg/ml; HMC alone, 319 +/- 62 pg/ml), and was further elevated after 20 hours (815 +/- 108 pg/ml). U937 cells alone, after incubation in HMC-conditioned medium or after coincubation with HMC, did not produce any detectable IL-6. A high mesangial IL-6 synthesis in response to apoptotic U937 cells was dependent on the cellular contact between HMC and U937 and could not be mimicked by apoptotic U937 culture supernatants. Radiolabeling studies indicated that HMC bound (16.6 +/- 2.4%) and ingested (12.5 +/- 1.9%) apoptotic U937 cells to a much higher amount as compared to intact U937 (5.3 +/- 2.0% binding; 5.0 +/- 1.1% phagocytosis). Binding and ingestion of monocytic cells undergoing apoptosis was confirmed by morphologic studies using electron microscopy. Incubation of HMC with a blocker of the CD36/ vitronectin receptor (VnR) dependent recognition mechanism of phagocytes for apoptotic leukocytes (RGDS peptide) did not alter binding, phagocytosis or IL-6 synthesis of HMC in response to apoptotic U937. Phospho-L-serine as an antagonist of the phosphatidylserine (PS) mediated recognition pathway for apoptotic cell disposal was able to reduce binding and IL-6 production by HMC but not phagocytosis. Thus, binding of apoptotic monocytic cells by HMC rather than ingestion may be the prerequisite for a stimulated secretory response. To elucidate whether binding and phagocytosis of particles in general might stimulate HMC to produce IL-6, we looked for mesangial IL-6 production after binding and ingestion of opsonized zymosan particles. In this case, IL-6 synthesis was markedly down-regulated. Furthermore, HMC proliferated after zymosan treatment, whereas after apoptotic cell uptake the mesangial cell number remained constant. In conclusion, apoptotic monocytic cells provoked an enhanced mesangial IL-6 synthesis by a PS-dependent recognition mechanism. This secretory response may have secondary implications for humoral or cellular processes within the mesangium.

Apoptosis↗