Biomedical subjects

L P Erwig

Publications and source records attributed to L P Erwig.

12 recordsLinked to original sources

PubMed2001

Combinatorial model of chemokine involvement in glomerular monocyte recruitment: role of CXC chemokine receptor 2 in infiltration during nephrotoxic nephritis.

A sequential model involving chemokines has been proposed for leukocyte extravasation into areas of inflammation; however, site-specific aspects remain to be elucidated. Hence, we studied the role of chemokines produced by mesangial (MC) or glomerular endothelial cells (GEC) and their receptors in glomerular recruitment of monocytes. Stimulation of MC with TNF-alpha up-regulated mRNA and protein of CC and CXC chemokines but not constitutive expression of the CX(3)C chemokine fractalkine. While growth-related activity (GRO)-alpha was immobilized to MC proteoglycans, monocyte chemotactic protein (MCP)-1 was secreted into the soluble phase. Firm adhesion and sequestration of monocytes on activated MC was supported by the GRO-alpha receptor CXCR2 and to a lesser extent by CX(3)CR, whereas the MCP-1 receptor CCR2 contributed to their transendothelial chemotaxis toward activated MC. In contrast, fractalkine mRNA and protein was induced by TNF-alpha in transformed rat GEC, and both CXCR2 and CX(3)CR mediated monocyte arrest on GEC in shear flow. The relevance of these mechanisms was confirmed in a rat nephrotoxic nephritis model where acute glomerular macrophage recruitment was profoundly inhibited by blocking CXCR2 or CCR2. In conclusion, our results epitomize a combinatorial model in which chemokines play specialized roles in driving glomerular monocyte recruitment and emphasize an important role for CXCR2 in macrophage infiltration during early phases of nephrotoxic nephritis.

Animals↗

PubMed2001

Macrophages in renal inflammation.

This review describes recent advances in macrophage biology in the context of renal inflammation. It highlights the importance of the activated macrophage for the progression and resolution of renal disease, and discusses recent and potential future approaches to modify macrophage function selectively within the kidney to activate them specifically to promote the healing of kidney disease.

Humans↗

PubMed2000

Activated macrophages direct apoptosis and suppress mitosis of mesangial cells.

During inflammation in the glomerulus, the complement of resident myofibroblast-like mesangial cells is regulated by mitosis and apoptosis, but the cellular mechanisms controlling the size of mesangial cell populations have remained obscure. Prompted by studies of development, we sought evidence that macrophages regulate mesangial cell number. Rat bone marrow-derived macrophages primed with IFN-gamma then further activated in coculture with LPS or TNF-alpha elicited a 10-fold induction of rat mesangial cell apoptosis and complete suppression of mitosis, effects inhibitable by the NO synthase inhibitors L-monomethyl arginine and L-N(6)-(1-iminoethyl) lysine dihydrochloride. Complete dependence upon macrophage-derived NO was observed in comparable experiments employing activated bone marrow macrophages from wild-type and NO synthase 2(-/-) mice. Nevertheless, when mesangial cells were primed with IFN-gamma plus TNF-alpha, increased induction by activated macrophages of mesangial apoptosis exhibited a NO-independent element. The use of gld/gld macrophages excluded a role for Fas ligand in this residual kill, despite increased expression of Fas and increased susceptibility to soluble Fas ligand exhibited by cytokine-primed mesangial cells. Finally, activated macrophages isolated from the glomeruli of rats with nephrotoxic nephritis also induced apoptosis and suppressed mitosis in mesangial cells by an L-monomethyl arginine-inhibitable mechanism. These data demonstrate that activated macrophages, via the release of NO and other mediators, regulate mesangial cell populations in vitro and may therefore control the mesangial cell complement at inflamed sites.

Animals↗

PubMed2000

Macrophages from inflamed but not normal glomeruli are unresponsive to anti-inflammatory cytokines.

This study examined the properties and responsiveness to cytokines of macrophages purified from normal and nephritic glomeruli to ascertain whether macrophages activated in vivo develop programmed unresponsiveness to cytokines as do bone marrow-derived macrophages in vitro when activated by interferon-gamma (IFN-gamma), tumor necrosis factor (TNF), interleukin-4 (IL-4), or transforming growth factor-beta (TGF-beta). Macrophages from normal glomeruli did not generate nitric oxide (NO) spontaneously but only after treatment with IFN-gamma and TNF-alpha. NO generation by these macrophages was abrogated by administering IL-4, TGF-beta, or TNF-alpha before but not after IFN-gamma treatment. Glomerular macrophages also expressed beta-glucuronidase, which was increased by TGF-beta and decreased by IFN-gamma and TNF. By contrast, glomerular macrophages from rats with nephrotoxic nephritis did not express beta-glucuronidase even after exposure to TGF-beta. Furthermore, they generated NO spontaneously, and this spontaneous generation of NO was not suppressed by IL-4, TGF-beta, or TNF-alpha. Systemic treatment of nephritic rats with IL-4 reduced NO generation by 40% but did not prevent activation, which is similar to the effect of IL-4 on bone marrow-derived macrophages in vitro when given simultaneously with IFN-gamma. We conclude that macrophages infiltrating inflamed glomeruli have developed programmed unresponsiveness to activating cytokines. This may enable them to function appropriately in the complex conditions within an inflammatory focus.

Animals↗

PubMed2000

Gene transfer into inflamed glomeruli using macrophages transfected with adenovirus.

In vivo gene transfer to sites of inflammatory disease provides a novel method both for studying the effects of cytokines and growth factors, and for therapeutic intervention. Macrophages play a pivotal role in the development and control of inflammation and are therefore logical cells to use for genetic modification and in vivo gene delivery. In this study we show that macrophages (both cell lines and primary cultures) can be transfected by recombinant adenoviruses expressing beta-galactosidase, that the macrophages become activated by the transfection process as determined by generation of nitric oxide and can be easily manipulated to localise to inflamed glomeruli after direct injection into the renal artery of rats with an experimentally induced glomerular inflammation caused by nephrotoxic nephritis. The injection of transfected macrophages reduces the severity of injury in this model of glomerulonephritis as shown by a reduction in the degree of albuminuria. This approach provides a favourable system for gene delivery in inflammatory disease and shows that both the functional properties of the transfected macrophage as well the transgene it is engineered to produce are relevant for in vivo gene transfer. Gene Therapy (2000) 7, 263-270.

Adenoviridae↗

PubMed2000

Transforming growth factor-beta isoforms and glomerular injury in nephrotoxic nephritis.

BACKGROUND: Transforming growth factor-beta has three main isoforms (TGF-beta1, TGF-beta2, and TGF-beta3) that have distinct but overlapping functions in immunity, inflammation, and tissue repair. TGF-beta1 has been implicated in progressive renal scarring, but the roles of TGF-beta2 and TGF-beta3 are less clear. The purpose of this study was to characterize the expression of all three isoforms in nephrotoxic nephritis (NTN) in rats and to determine the effect of TGF-beta3 infusions on injury because of its reported combined anti-inflammatory and antifibrotic effects. METHODS: TGF-beta1, TGF-beta2, and TGF-beta3 expression was analyzed by immunohistochemistry and RNase protection assays. TGF-beta3 was administered by osmotic minipumps at 2 microg/day, a dose shown to alter glomerular macrophage function in vivo. Injury was assessed morphologically and functionally. RESULTS: The three TGF-beta isoforms showed a different distribution in normal rats and after the induction of nephritis. TGF-beta1 was only detected in glomeruli of the most severely nephritic rats. TGF-beta2 was found in glomerular neutrophils, whereas damaged podocytes expressed TGF-beta3. Infusions of TGF-beta3 did not reduce proteinuria over seven days after the induction of nephritis. They did, however, have a profound effect on glomerular macrophage number (7.76 +/- 4.1 in treated rats vs. 14.4 +/- 4.7 in controls, P < 0.02). The numbers of class II-positive macrophages were similar in the two groups, whereas class II-negative macrophages infiltrating glomeruli were significantly decreased (4.06 +/- 3.1 vs. 9.1 +/- 4.4, P < 0.02). TGF-beta did not influence the amount of glomerular matrix. CONCLUSIONS: TGF-beta isoforms have different expressions and presumptively different roles in NTN. The infusion of pharmacological doses of TGF-beta3 has profound effects on macrophages infiltrating nephritic glomeruli and reveals marked heterogeneity of infiltrating macrophages.

Animals↗

PubMed1999

Previous uptake of apoptotic neutrophils or ligation of integrin receptors downmodulates the ability of macrophages to ingest apoptotic neutrophils.

Clearance of apoptotic neutrophils (polymorphonuclear leukocyte [PMN]) by macrophages is thought to play a crucial role in resolution of acute inflammation. There is increasing evidence that ingestion of apoptotic cells modulates macrophage behavior. We therefore performed experiments to determine whether ingestion of apoptotic PMN modulated the uptake process itself. Rat bone marrow-derived macrophages (BMDM) ingested apoptotic PMN by a process that was enhanced by tumor necrosis factor (TNF) and attenuated by interferon (IFN)-gamma, interleukin (IL)-4, and IL-10. It was inhibitable by the tetrapeptide arg-gly-gln-ser (RGDS), therefore implicating the alphavbeta3/CD36/thrombospondin pathway. Interaction of apoptotic PMN with BMDM for 30 minutes, 48 hours before rechallenge reduced uptake of apoptotic PMN by 50% compared with previously unchallenged BMDM. Blocking initial uptake with RGDS abrogated the effect of preexposure. Comparable and sustained attenuation of uptake was obtained by ligating alphavbeta3 with the monoclonal antibody (MoAb), F11, after a delay of more than 90 minutes, whereas MoAbs to CD25 and CD45 had no effect. Ligation of alpha6beta1 and alpha1beta2, integrins not previously implicated in the engulfment of apoptotic cells also decreased uptake with similar kinetics to F11. Therefore, apoptotic PMN regulate their own uptake through an integrin-dependent process, which can be reproduced by ligation of other integrins expressed by macrophages.

Animals↗

PubMed1999

Macrophage activation and programming and its role for macrophage function in glomerular inflammation.

Macrophages have a central role in the control of inflammation because, depending on the local microenvironment, they can develop into cells that cause further injury or facilitate tissue repair. Understanding what signals determine whether macrophages develop into cells that promote injury or facilitate repair is one of the most important issues in inflammatory cell biology, not least because of the opportunities for developing novel therapies. This is highly relevant to glomerulonephritis because of the prominence of the macrophage infiltrate in all types of severe or progressive nephritis, and the present unsatisfactory nature of treatments for these diseases. This review will focuses on how macrophages are activated in vitro and in normal and inflamed glomeruli. The new concept of 'macrophage programming' is introduced and novel strategies to alter macrophage function within nephritic glomeruli that could be used for the treatment of glomerular inflammation are highlighted.

Animals↗

PubMed1998

Initial cytokine exposure determines function of macrophages and renders them unresponsive to other cytokines.

The functional properties of infiltrating macrophages (Mphi) must be tightly regulated to facilitate appropriate responses to complex conditions in an inflammatory focus. This study was designed to ascertain whether uncommitted Mphi that have been exposed to combinations of cytokines with opposing functions develop properties dictated by one cytokine or by cytokine mixtures. Uncommitted rat bone marrow-derived Mphi (BMDMs) were incubated with IFN-gamma, TNF-alpha, TGF-beta, IL-4, IL-6, and IL-10 alone or sequentially in combinations. After 48 h, function was assessed by nitric oxide (NO) generation, uptake of apoptotic neutrophils, and beta-glucuronidase expression. IFN-gamma followed 4 h later by TNF-induced NO generation. The pretreatment of BMDMs before IFN-gamma priming with TNF, TGF-beta, and IL-4 suppressed NO generation by 87%, 92%, and 85%, respectively; IL-10 had no effect. The same cytokines administered at 4 h after IFN priming had no effect on NO generation. The uptake of apoptotic polymorphonuclear leukocytes was augmented by TNF (40% vs 29% controls; p < 0.05) and decreased by IFN-gamma, IL-10, and IL-4. The TNF response was unaffected by subsequent treatment with IFN-gamma, IL-4, or IL-10. Similarly, the decreased polymorphonuclear leukocyte uptake induced by IFN-gamma, IL-4, or IL-10 was unaffected by the subsequent addition of TNF. Beta-glucuronidase expression was increased by TGF-beta and decreased by IFN-gamma. These responses were not modified by cytokines with the opposing function. Thus, the functional response of BMDMs to complex mixtures of cytokines was determined by the first cytokine to which they were exposed. Once activated, BMDMs become unresponsive to alternative activating signals, a finding which has obvious implications for Mphi function in vivo.

Animals↗

PubMed1997

Role of beta-adrenergic and cholinergic systems in acclimatization to hypoxia in the rat.

To role of beta-adrenergic and muscarinic cholinergic systems on maximal treadmill exercise performance and systemic O2 transport during hypoxic exercise (PIO2 approximately 70 Torr) was studied in rats acclimatized to hypobaric hypoxia (PIO2 approximately 70 Torr for 3 weeks, A rats) and in non-acclimatized littermates (NA rats). Untreated A rats had lower resting (fH) and maximal heart rate (fHmax) and cardiac output (Q), and higher maximal O2 uptake (VO2max) than NA. The only effect of cholinergic receptor blockade with atropine (Atp) was an increase in pre-exercise fH to comparable levels in A and in NA. beta 1-adrenergic receptor blockade with atenolol (Aten) lowered pre-exercise fH and (fHmax) to comparable values in A and in NA rats. However, since both pre-exercise fH and fHmax were lower in untreated A, the effect of Aten was relatively smaller in A. Aten reduced maximal exercise cardiac output (Qmax) in NA; however, tissue O2 extraction increased such that VO2max was not affected. Aten did not influence Qmax or any other parameter of systemic O2 transport in A. In conclusion the increased cholinergic tone may be responsible for the lower resting fH but not the lower fHmax of A; the integrity of the beta-adrenergic system is not necessary to attain VO2max in hypoxia either in A or in NA; the decreased response to beta-adrenergic stimulation in A limits the efficacy of this system on the mechanisms of systemic O2 transport and reduces the effect of its blockade on these mechanisms.

Acclimatization↗

PubMed1994

Effect of hematocrit on systemic O2 transport in hypoxic and normoxic exercise in rats.

The effect of hematocrit (Hct) on O2 transport in hypoxic [inspired PO2 (PIO2) approximately 70 Torr] and normoxic (PIO2 approximately 145 Torr) exercise was studied in rats acclimatized to 3 wk of PIO2 at approximately 70 Torr (A rats) and in nonacclimatized littermates (NA rats). Isovolumic exchange transfusion of plasma or red blood cells was used to lower Hct in A rats from approximately 60 to 45% and to raise Hct of NA rats from 45 to 60%: Controls were A and NA rats exchange transfused with whole blood at constant Hct. Lowering Hct of A rats lowered the arterial O2 concentration (CaO2) and the arterial-mixed venous O2 difference and increased the maximal cardiac output (Qmax) without changes in maximal O2 uptake (VO2 max) or in the product of Qmax x CaO2, circulatory O2 convection at maximal exercise (TO2 max). Raising Hct in NA rats produced the opposite changes in CaO2, arterial-mixed venous O2 difference, and Qmax, but VO2 max and TO2 max increased significantly, both in hypoxia and normoxia, because of relatively small changes in Qmax. In NA rats, a steeper slope of the line relating VO2 max to calculated mean capillary PO2 at high Hct suggested a higher tissue O2 diffusing capacity with high Hct. For a given Hct and Qmax, systemic arterial pressure was higher in A rats. The data suggest that 1) the effect of Hct on systemic hemodynamics is different in A and NA rats, resulting in different effects on VO2 max; 2) factors in addition to Hct contribute to the high systemic vascular resistance of A rats; and 3) increased diffusive conductance for O2, as well as increased TO2 max, could be responsible for the effect of Hct on VO2 max of NA rats.

Acclimatization↗

PubMedDate not supplied

Rapidly progressive glomerulonephritis.

The management of rapidly progressive glomerulonephritis has been transformed over the past thirty years. It has become one of the few forms of glomerulonephritis that can be effectively treated, and today overall renal survival is as high as 70%. Effective management of patients with RPGN requires prompt and accurate diagnosis so that patients are appropriately treated, and long term follow up to minimise the risk of relapse in patients with some types of those disease.

Animals↗