Renal mesangial cells have the capacity to synthesize and react to leukemia inhibitory factor.
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Animals↗
Biomedical subjects
R B Sterzel
Publications and source records attributed to R B Sterzel.
Vasoactive diadenosine polyphosphates promote growth of cultured renal mesangial cells.
Diadenosine polyphosphates (diadenosine triphosphate, Ap3A; diadenosine tetraphosphate, Ap4A; diadenosine pentaphosphate, Ap5A; diadenosine hexaphosphate, Ap6A) are potent vasoactive molecules stored and released by platelets. We examined whether these dinucleotides might contribute to the glomerular inflammatory response by stimulating the proliferation of mesangial cells. In cultured rat mesangial cells all four tested dinucleotides (10 to 100 mumol/L) significantly stimulated DNA synthesis as measured by [3H]thymidine uptake at 48 hours (x-fold increase compared with unstimulated control cells: Ap3A, 1.5; Ap4A, 1.8; Ap5A, 1.6; Ap6A, 1.6). In combination with the platelet products platelet-derived growth factor, epidermal growth factor, and serotonin, the dinucleotides synergistically increased DNA synthesis. Dinucleotides by themselves increased cell counts by 23% to 43% at day 2 and augmented mesangial cell growth induced by platelet-derived growth factor, epidermal growth factor, and serotonin. Furthermore, dinucleotides (100 mumol/L) rapidly induced a modest increase in expression of the early growth response gene Egr-1 at 30 minutes (x-fold increase over baseline control: Ap3A, 1.9; Ap4A, 2.8; Ap5A, 2.2; Ap6A, 2.1). We found that extracellular Ap4A was metabolized by mesangial cell ectoenzymes to mononucleotides and adenosine, which also have been shown to be mitogenic for mesangial cells. The combination of Ap4A with mononucleotides or adenosine failed to cause additive stimulation of DNA synthesis in mesangial cells. We conclude that diadenosine polyphosphates stimulate proliferation of cultured mesangial cells and augment mesangial cell growth induced by other mitogens released from platelets. Different molecular mechanisms may be involved in dinucleotide-induced mitogenesis of mesangial cells. Direct effects of dinucleotides on cultured mesangial cells. Direct effects of dinucleotides on cultured mesangial cells appear to play a role because dinucleotides rapidly caused activation of Egr-1.(ABSTRACT TRUNCATED AT 250 WORDS)
Analysis of Variance↗
[Molecular regulatory processes in glomerular cells of the kidney].
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Animals↗
Cytokine-induced expression of leukemia inhibitory factor in renal mesangial cells.
Leukemia inhibitory factor (LIF) is a pleiotropic cytokine, which shares many characteristics with interleukin-6 (IL-6). Recent observations indicate a role for LIF in inflammatory processes. To examine the potential involvement of LIF in the regulation of mesangial cell behavior, we studied LIF expression in early primary cultures of rat and human mesangial cells, as well as the response of mesangial cells to exogenous LIF. Growing or growth-arrested rat mesangial cells constitutively expressed very low levels of LIF mRNA, barely detectable by Northern blot analysis. Strong induction of LIF mRNA expression was caused by cytokines, such as interleukin-1 beta (5 ng/ml), tumor necrosis factor alpha (100 ng/ml) and PDGF (100 ng/ml), as well as LPS (200 ng/ml). The induction was transient with a peak after three to five hours. Dexamethasone (0.1 microM) almost completely inhibited the induction of LIF. Weak induction of LIF mRNA was observed after stimulation with basic fibroblast growth factor, endothelin and transforming growth factor beta. In combination with IL-1 beta, TGF beta showed synergistic effects on LIF induction. LIF itself or IL-6 had no effect on LIF mRNA expression. A similar induction pattern was observed for the expression of IL-6 mRNA. LIF protein was detected by specific ELISA in the supernatants of human mesangial cells stimulated by LPS or IL-1 beta. In addition, we found that mesangial cells not only express LIF but they are also target cells for LIF. Recombinant LIF effectively induced transient expression of the immediate early genes, c-fos, jun-B and Egr-1 in rat mesangial cells, with a maximum at 30 to 60 minutes. LIF was not mitogenic for mesangial cells. Our findings indicate that glomerular mesangial cells produce and react to LIF. As a cytokine with autocrine potential, LIF may play a physiological and/or pathophysiological role in the glomerulus, the exact nature and relevance of which remain to be explored.
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Renal matrix and adhesion in injury and inflammation.
Over the past year, there have been major advances in the descriptive analysis of the extracellular matrix in the kidney. Several aspects of the interaction of matrix molecules with renal and, in particular with glomerular cells via specific integrin receptors, have also been studied. Most results on cell-matrix interactions have been obtained by in vitro investigations of glomerular mesangial cells in two-dimensional culture. The regulation of matrix formation and degradation has been shown to involve the concerted action of several soluble factors, notably transforming growth factor-beta, as well as the effects of nonsoluble matrix components themselves, such as collagens and proteoglycans. The mediation of such complex interactions between cells, matrix, and cytokines is facilitated by the tightly regulated expression of cell surface receptors, eg, cytokine receptors and integrins of the beta 1 series, which bind specific matrix molecules. New results have yielded more insight into the regulation not only of matrix formation but also of the specific interactions between cells and matrix and of the modulation of cytokine activity by matrix molecules. Using experimental rat models and transgenic mouse models of kidney disease, the first in vivo findings using immunohistochemistry and mRNA analysis have confirmed that major changes occur in the expression of matrix molecules, integrins, and cytokines in the process of glomerular inflammation. With the advent of specific modulators of the bioactivity of ligands and receptors, it is hoped that more information will be forthcoming on the functional relevance of various components of the cell-matrix-cytokine crosstalk in the normal and injured kidney.
Animals↗
The pathobiology of the mesangium.
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Animals↗
Extracellular ATP stimulates proliferation of cultured mesangial cells via P2-purinergic receptors.
We examined the role of the platelet product ATP in regulating replication and secretory activity of cultured rat mesangial cells (MCs). Extracellular ATP (25-100 microM) significantly increased [3H]thymidine uptake of growth-arrested MCs 2.1-fold; cell counts increased by 35.1%. Addition of ATP to MCs in combination with other platelet products, such as platelet-derived growth factor, isoform BB (100 ng/ml), and serotonin (1 microM), resulted in strong synergistic mitogenicity (up to 45.6-fold over control). As immediate signaling events following stimulation with ATP, we found increased production of inositol phosphates (3.2-fold increase for inositol bisphosphate and 1.6-fold increase for inositol trisphosphate by 30 s) and release of prostaglandin E2 (PGE2, 9.2-fold increase by 5 min). When we studied the rank order of potency of various ATP analogues for the production of inositol phosphates and PGE2, ATP, UTP, and adenosine 5'-O-(3-thio)triphosphate (ATP gamma S) were the most potent agonists. Although ATP and ATP gamma S were also strong mitogens, UTP was not. Additional inhibitor studies indicated that protein kinase C or cyclooxygenase products were not involved in the mitogenic effects of ATP. In summary, the major platelet product ATP is a potent comitogen for cultured MCs and strongly synergizes with other growth factors. The experiments with ATP analogues point to different receptors mediating mitogenesis, generation of inositol phosphates, and PGE2 production. The precise mechanism of the mitogenic action of ATP on MCs remains to be characterized.
Adenosine Triphosphate↗
Effect of vasoactive agents on induction of Egr-1 in rat mesangial cells: correlation with mitogenicity.
The early growth response gene 1 (Egr-1) is a member of the family of immediate early response genes. Egr-1 encodes a nuclear phosphoprotein that binds a specific nonameric DNA sequence through three zinc-finger domains and functions as a transcriptional activator. We tested whether the vasoactive agents platelet-derived growth factor (PDGF), arginine vasopressin (AVP), serotonin (5-HT), and angiotensin II (ANG II) induced Egr-1 mRNA in cultured rat mesangial cells (MCs) and investigated the role of protein kinase C (PKC) in mediating the induction process. PDGF, AVP, and 5-HT induced Egr-1 mRNA within 15 min, reaching peak levels at 45-60 min. After PDGF and 5-HT stimulation, Egr-1 mRNA levels returned to baseline within 4 h, whereas AVP induced a sustained increase for up to 8 h. There was a very close correlation between doses required for Egr-1 induction and induction of MC proliferation. ANG II was a very weak MC mitogen and induced only a small increase in Egr-1 mRNA. Comparison of control cells with cells depleted of PKC by 48 h of PMA treatment revealed that induction of Egr-1 by PDGF and 5-HT is independent of PKC. In contrast, however, the Egr-1 response to AVP was diminished in PKC-depleted cells. AVP induced Egr-1 mRNA 10.9-fold in control cells, compared with 7.8-fold in PKC-depleted cells. Egr-1 mRNA after AVP stimulation remained elevated in control cells for up to 8 h but returned to baseline after 120 min in PKC-depleted cells. Similar results were obtained using the PKC-inhibitor H-7. Using immunocytochemistry, PDGF and AVP were found to induce Egr-1 protein within 30 min localized to the nucleus. We conclude that there is a strong correlation between induction of Egr-1 after stimulation with PDGF, AVP, 5-HT, and ANG II and the proliferative response elicited by these agents in MCs. AVP induces Egr-1 by both PKC-dependent and PKC-independent pathways, whereas the effects of PDGF and 5-HT are independent of PKC.
Angiotensin II↗
Interactions between glomerular mesangial cells, cytokines, and extracellular matrix.
This brief overview summarizes recent information on the interactions of glomerular mesangial cells (MC) with soluble cytokines and nonsoluble extracellular matrix (ECM). The presently available knowledge stems largely from glomerular cell culture studies and from experimental work with laboratory animals. ECM production by MC appears to be regulated primarily by the paracrine or autocrine effects of cytokines, such as interleukin 1, platelet-derived growth factor, and transforming growth factor beta. However, ECM itself also affects the behavior of cultured MC, e.g., with regard to cell replication and the production of ECM components and other proteins. At present, little is known about the recognition of ECM and cytokines by MC that allows these interactions to take place. First results indicate that MC, like other cell types, possess surface proteins belonging to the beta 1 integrin family, which serve as specific receptors for ECM molecules. Receptors for the cytokines platelet-derived growth factor, insulin-like growth factor 1, epidermal growth factor, and transforming growth factor beta have also been demonstrated on MC. The expression of various receptors on MC appears to be affected by the ECM substratum. Thus, it is becoming apparent that mesangial ECM is not only important as a mechanical scaffold of the glomerular capillary tuft but that it also contains and conveys information relevant for the regulation of the MC phenotype, e.g., by modulating the MC response to cytokines. The available evidence suggests that alterations of ECM composition in glomerular disease can directly or indirectly affect MC behavior, e.g., by promoting cell replication and further accumulation of ECM, eventually resulting in progressive mesangial and glomerular sclerosis.
Animals↗
Extracellular matrix protein: gene expression and synthesis in cultured rat mesangial cells.
Production of extracellular matrix (ECM) by mesangial cells (MCs) contributes to progressive glomerulosclerosis. Our previous immunocytochemical studies on ECM production by MCs [1] were extended by examining the gene expression and protein synthesis using Northern blotting and ELISA. ELISA demonstrated that fetal calf serum (FCS) stimulated the synthesis of collagen I (CI), III (CIII) and IV (CIV), and laminin (LM). At and after confluence, the amounts of CIII, CIV and LM per DNA amount began to decrease, whereas that of CI did not. Northern blotting indicated that the mRNA expressions for CIV and LM were transiently increased by FCS. The mRNA expressions for CI and CIII decreased until confluence and then returned to the initial levels. These results suggest that FCS and cellular confluence affected the synthesis of ECM at both the level of gene expression and protein synthesis. The mRNA expressions for CIV and LM paralleled the protein synthesis and appeared tightly regulated. CI and CIII synthesis and mRNA expression were not coordinate and were not regulated in the same manner as the basement membrane matrix components.
Animals↗
Atrial natriuretic peptide in the locus coeruleus and its possible role in the regulation of arterial blood pressure, fluid and electrolyte homeostasis.
Atrial natriuretic factor (ANP) is present in neuronal cells of the locus coeruleus and its vicinity in the pontine tegmentum and moderate amount of ANP is detectable in this area by radioimmunoassay. The ANP (both peripheral and brain-born) is known as a neuropeptide which may influence the body salt and water homeostasis and blood pressure by targeting both central and peripheral regulatory mechanisms. Whether this pontine ANP cell group is involved in any of these regulatory mechanisms, the effect of various types of hypertension and experimental alterations in the salt and water balance on ANP levels was measured by radioimmunoassay in the locus coeruleus of rats. Adrenalectomy, as well as aldosterone and dexamethasone treatments failed to alter ANP levels in the locus coeruleus. Reduced ANP levels were measured in spontaneously hypertensive (both young and adult) rats, and in diabetes insipidus (Brattleboro) rats with vasopressin replacement. In contrast to these situations, elevated ANP levels were found in rats with DOCA-salt or 1-kidney-1-clip hypertension. These data suggest a link between ANP levels in the locus coeruleus and fluid volume homeostasis. Whether this link is causal and connected with the major activity of locus coeruleus neurons (noradrenergic influence on brain regulatory activities) needs further informations.
Adrenalectomy↗
Role of ornithine decarboxylase for proliferation of mesangial cells in culture.
To elucidate the role of polyamine metabolism in the regulation of mesangial cell growth, we examined the involvement of ornithine decarboxylase (ODC), the rate limiting enzyme for polyamine synthesis, in the mitogenesis of cultured rat mesangial cells (MCs). Resting MCs, stimulated with fetal calf serum (FCS 10%), showed an induction of ODC activity from undetectable values in resting cells to mean = 5035 nmol CO2/10(10) cells.hr (range 3157 to 7154, N = 5), which is 25-fold above the detection limit. We found a single peak of ODC activity eight to ten hours after stimulation, declining to 22 to 34% of peak levels after 24 hours. 3H-thymidine (TdR) uptake, an S-phase marker of MC replication, peaked at 24 hours, reaching 10.7-fold values of resting MCs. ODC mRNA levels were low in resting cells. After serum stimulation there was a two- to 10-fold increase in ODC mRNA with a maximum after six hours. ODC activity with similar kinetics but lower peak levels was also induced by incubating MCs with mitogens, such as platelet-derived growth factor (PDGF-AB 20 ng/ml), arginine vasopressin (AVP 10(-7) M), phorbol myristate acetate (PMA 10(-7) M), interleukin 1 alpha and beta (IL-1 alpha 10 U/ml, IL-1 beta 10 U/ml). In the presence of alpha-difluoromethylornithine (DFMO), an enzyme-activated irreversible inhibitor of ODC, the growth rate of MCs, assessed by cell counts and by 3H-TdR uptake, was markedly reduced by 62 to 100%. This antiproliferative effect of DFMO could be reversed by addition of putrescine, the reaction product of ODC.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Interleukin 6 is an autocrine growth factor for mesangial cells.
Interleukin 6 (IL-6) induces the acute phase response, differentiation of B cells, proliferation of T cells, thymocytes, hematopoietic progenitors, hybridoma and plasmacytoma cells. Monocytes, T cells, fibroblasts, epithelial and endothelial cells secrete IL-6. Since IL-6 responsive cell-types may participate in the pathogenesis of glomerular inflammation, we studied the secretion of IL-6 by rat MCs, using the IL-6 dependent hybridoma cell line B9. The results of our studies indicate that MCs secrete IL-6 with a molecular weight of 17-42 kDa and isoelectric point of 4.0 to 5.3 MC-IL-6 activity could be blocked by a polyclonal antimurine-IL-6 antibody. MC express IL-6 mRNA as determined by Northern blot. Furthermore, our data demonstrate that IL-6 acts as an autocrine growth factor for MC. Incubation of subconfluent MC with recombinant IL-6 results in a dose-dependent increase of 3H-thymidine incorporation and number of MCs. Moreover, reverse phase HPLC fractions of MC-CM containing IL-6 activity increase 3H-thymidine incorporation by MC. In addition to its possible paracrine role in mediating the immune response in the glomerulus, MC-IL-6 may also be one of the autocrine signals leading to mesangial cell proliferation in vivo.
Animals↗
Brain-gut peptides, renal function and cell growth.
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Animals↗
Arginine vasopressin enhances pHi regulation in the presence of HCO3- by stimulating three acid-base transport systems.
Growth factors raise intracellular pH (pHi) by stimulating Na+/H+ exchange in the absence of HCO3-. In mutant cells that lack the Na+/H+ exchange activity, this alkalinization does not occur, and the cells do not proliferate without artificial elevation of pHi. It has therefore been widely suggested that an early pHi increase is a necessary signal for mitogenesis. In the presence of HCO3- however, growth factors fail to raise pHi in A431 cells, renal mesangial cells and 3T3 fibroblasts. In mesangial cells, arginine vasopressin (AVP) raises pHi in the absence of HCO3-, but lowers it when HCO3- is present; growth is stimulated under both conditions. We report here that, in the presence of HCO3-, AVP stimulates two potent HCO3- transporters, as well as the Na+/H+ exchanger. These are the Na+-dependent and Na+-independent Cl-/HCO3- exchangers. Our results indicate that AVP causes acidification in the presence of HCO3- because, at the resting pHi, it stimulates Na+-independent Cl-/HCO3- exchange (which lowers pHi) more than it stimulates the sum of Na+/H+ exchange and Na+-dependent Cl-/HCO3- exchange (both of which raise pHi). The stimulation of three acid-base transporters by the growth factor AVP greatly enhances the ability of the cell to regulate pHi.
4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
Portal hypertension ameliorates arterial hypertension in spontaneously hypertensive rats.
Systemic hemodynamic effects of portal hypertension in arterial hypertension and their relationship to serum bile acid levels were investigated using spontaneously hypertensive rats 2 and 15 weeks after partial portal vein ligation (SHR-PVL) or sham operation (SHR-SH) and normotensive controls. Mean arterial pressure in SHR-PVL at 2 weeks was decreased to normal due to a decrease in peripheral resistance. Mean arterial pressure and peripheral resistance in SHR-PVL at 15 weeks did not differ from SHR-SH. Resolution of this arterial hypotensive effect and systemic hyperdynamic circulation was associated with decreased portal-systemic shunting. Bile acid levels were increased in both SHR-PVL groups. These results suggest that an endogenous circulating vasodilator(s) associated with portal hypertension ameliorates the systemic vasoconstriction in SHR. Bile acids, while not direct mediators of these hemodynamic events, may be prototypic of this vasodilator. This arterial hypertensive model may aid further investigation of the mechanisms contributing to the hyperdynamic state in portal hypertension.
Animals↗
Studies of the mitogenic effect of serotonin in rat renal mesangial cells.
A vasoactive inflammatory amine, serotonin, stimulates DNA synthesis in rat glomerular mesangial cells in a dose-dependent manner and acts synergistically with either insulin or epidermal growth factor (EGF). The combined effects of 10(-6) M serotonin and these peptide hormones are nearly equal to those induced by 10% fetal bovine serum. Serotonin stimulates the turnover of polyphosphoinositols resulting in a transient rise in intracellular free Ca2+ concentration, as measured either with the photoprotein aequorin, or with fura-2. This is accompanied by a transient increase in 45Ca2+ efflux from prelabeled cells. Serotonin also induces a prompt and sustained threefold increase in Ca2+ influx rate across the plasma membrane and a rapid and sustained twofold increase in cellular 1,2-diacylglycerol content. In addition, there is an increase in the extent of phosphorylation of an acidic 80-kDa protein, a putative substrate for protein kinase C. Activators of protein kinase C (including phorbol 12-myristate 13-acetate or 1,2-dioctanoylglycerol) mimic the mitogenic effect of serotonin. The effect of serotonin on cell proliferation is partially inhibited in a reversible manner by LiCl. Treatment of mesangial cells with insulin plus EGF for 60 min leads to a small but consistent increase in the content of inositol phosphates and 1,2-diacylglycerol. Their effects are additive to those of serotonin. Moreover, insulin and EGF significantly stimulate the phosphorylation of the 80-kDa protein, and potentiate the serotonin-induced phosphorylation of this protein.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Rat mesangial cells produce granulocyte-macrophage colony-stimulating factor.
Because inflammatory processes in renal glomeruli may involve monocyte-macrophages (MPs) and T-lymphocytes, we have investigated whether products of glomerular mesangial cells (MCs) can stimulate the proliferative activity of these effector cells. We found that cultured rat MCs (subcultures 2-15), maintained under serum-free conditions, secrete a soluble factor into the supernate [MC-conditioned medium (CM)], which supports growth of the T-helper cell-derived line HT-2. Moreover, MC-CM increased [3H]thymidine incorporation by thioglycollate-elicited peritoneal MPs but did not induce growth of the interleukin 2 (IL-2)- or interleukin 4 (IL-4)-dependent cell line CTLL-2. Further functional, serological, and biochemical analysis of MC-CM revealed that rat MCs secrete a cytokine that, by all of the techniques used, is indistinguishable from granulocyte-macrophage colony-stimulating factor (GM-CSF). Both northern blot and in situ hybridization with a specific cDNA probe for murine GM-CSF showed that MCs express GM-CSF mRNA transcripts. The present findings indicate that cultured rat MCs produce GM-CSF. Release of GM-CSF by MCs in vivo may play a role in the interaction of MCs with MPs, T-cells, and neutrophils in glomerular disease.
Animals↗