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Biomedical subjects

Jeremy Hughes

Publications and source records attributed to Jeremy Hughes.

17 recordsLinked to original sources
PubMed2006

Apoptosis and glomerulonephritis.

Glomerulonephritis (GN) is a form of autoimmunity in which apoptosis may be a double-edged sword. Resolution of GN can be promoted by apoptosis of infiltrating leucocytes and excess resident glomerular cells, leading to efficient anti-inflammatory clearance by macrophages and mesangial cells. However, unscheduled apoptosis in glomerular cells, especially epithelial cells ('podocytes') may drive progression of GN to hypocellular, nonfunctional scar. Defects in clearance of apoptotic cells may also have deleterious local effects, in addition to promoting autoimmunity itself. Nevertheless, there is strong promise for novel therapies based on new knowledge of apoptosis in GN, especially in regulation of leucocyte clearance from the inflamed glomerulus.

Animals↗
PubMed2006

Nitric oxide is an important mediator of renal tubular epithelial cell death in vitro and in murine experimental hydronephrosis.

Macrophages play a pivotal role in tissue injury and fibrosis during renal inflammation. Although macrophages may induce apoptosis of renal tubular epithelial cells, the mechanisms involved are unclear. We used a microscopically quantifiable co-culture assay to dissect the cytotoxic interaction between murine bone marrow-derived macrophages and Madin-Darby canine kidney cells and primary murine renal tubular epithelial cells. The induction of tubular cell apoptosis by cytokine-activated macrophages was reduced by inhibitors of nitric oxide synthase whereas tubular cell proliferation was unaffected. Furthermore, cytokine-activated macrophages derived from mice targeted for the deletion of inducible nitric oxide synthase were noncytotoxic. We then examined the role of nitric oxide in vivo by inhibiting inducible nitric oxide synthase in the model of murine experimental hydronephrosis. l-N(6)-(1-iminoethyl)-lysine was administered in the drinking water between days 5 and 7 after ureteric obstruction. Macrophage infiltration was comparable between groups, but treatment significantly inhibited tubular cell apoptosis at day 7. Tubular cell proliferation was unaffected. Inducible nitric oxide synthase blockade also reduced interstitial cell apoptosis and increased collagen III deposition. These data indicate that nitric oxide is a key mediator of macrophage-directed tubular cell apoptosis in vitro and in vivo and also modulates tubulointerstitial fibrosis.

Animals↗
PubMed2005

Resident pleural macrophages are key orchestrators of neutrophil recruitment in pleural inflammation.

RATIONALE: The role played by resident pleural macrophages in the initiation of pleural inflammation is currently unclear. OBJECTIVE: To evaluate the role of resident pleural macrophages in the initiation of inflammation. METHODS: We have used a conditional macrophage ablation strategy to determine the role of resident pleural macrophages in the regulation of neutrophil recruitment in a murine model of experimental pleurisy induced by the administration of carrageenan and formalin- fixed Staphylococcus aureus. MEASUREMENTS AND MAIN RESULTS: Conditional macrophage ablation mice express the human diphtheria toxin receptor under the control of the CD11b promoter such that the administration of diphtheria toxin induces ablation of nearly 97% of resident macrophages. Ablation of resident pleural macrophages before the administration of carrageenan or S. aureus dramatically reduced neutrophil influx into the pleural cavity. In the carrageenan model, the reduction in neutrophil infiltration was associated with marked early reduction in the level of macrophage inflammatory protein 2 as well as reduced levels of various cytokines, including tumor necrosis factor alpha, interleukin 6, and interleukin 10. Adoptive transfer of nontransgenic macrophages partially restored neutrophil infiltration. We also stimulated macrophage-depleted and nondepleted pleural cell populations with carrageenan in vitro and determined the production of chemokines and cytokines. Chemokine and cytokine production was markedly reduced by macrophage depletion, reinforcing the role of resident pleural macrophages in the generation of mediators that initiate acute inflammation. CONCLUSION: These studies indicate a critical role for resident pleural macrophages in sensing perturbation to the local microenvironment and orchestrating subsequent neutrophil infiltration.

Animals↗
PubMed2005

Conditional macrophage ablation demonstrates that resident macrophages initiate acute peritoneal inflammation.

The role played by resident macrophages (Mphi) in the initiation of peritoneal inflammation is currently unclear. We have used a conditional Mphi ablation strategy to determine the role of resident peritoneal Mphi in the regulation of neutrophil (PMN) recruitment in experimental peritonitis. We developed a novel conditional Mphi ablation transgenic mouse (designated CD11bDTR) based upon CD11b promoter-mediated expression of the human diphtheria toxin (DT) receptor. The murine DT receptor binds DT poorly such that expression of the human receptor confers toxin sensitivity. Intraperitoneal injection of minute (nanogram) doses of DT results in rapid and marked ablation of F4/80-positive Mphi populations in the peritoneum as well as the kidney, and ovary. In experimental peritonitis, resident Mphi ablation resulted in a dramatic attenuation of PMN infiltration that was rescued by the adoptive transfer of resident nontransgenic Mphi. Attenuation of PMN infiltration was associated with diminished CXC chemokine production at 1 h. These studies indicate a key role for resident peritoneal Mphi in sensing perturbation to the peritoneal microenvironment and regulating PMN infiltration.

Acute Disease↗
PubMed2005

Desensitization of T lymphocyte function by CXCR3 ligands in human hepatocellular carcinoma.

AIM: Despite the presence of lymphocyte infiltration, human hepatocellular carcinoma (HCC) is typically a rapidly progressive disease. The mechanism of regulation of lymphocyte migration is poorly understood. In this study, we investigated various factors regulating T cell migration in HCC patients. We examined serum CXC chemokine levels in HCC patients and demonstrated the production of CXC chemokines by HCC cell lines. We determined the effect of both HCC patient serum and tumor cell conditioned supernatant upon lymphocyte expression of chemokine receptor CXCR3 as well as lymphocyte migration. Lastly, we examined the chemotactic responses of lymphocytes derived from HCC patients. METHODS: The serum chemokines IP-10 (CXCL10) and Mig (CXCL9) levels were measured by cytometric bead array (CBA) and the tumor tissue IP-10 concentration was measured by ELISA. The surface expression of CXCR3 on lymphocytes was determined by flow cytometry. The migratory function of lymphocytes to the corresponding chemokines was assessed using an in vitro chemotactic assay. Phosphorylation of extracellular signal-regulated kinase (ERK) was determined by Western blot analysis. RESULTS: Increased levels of IP-10 and Mig were detected in HCC patient serum and culture supernatants of HCC cell lines. The IP-10 concentration in the tumor was significantly higher than that in the non-involved adjacent liver tissues. HCC cell lines secreted functional chemokines that induced a CXCR3-specific chemotactic response of lymphocytes. Furthermore, tumor-cell-derived chemokines induced initial rapid phosphorylation of lymphocyte ERK followed by later inhibition of ERK phosphorylation. The culture of normal lymphocytes with HCC cell line supernatants or medium containing serum from HCC patients resulted in a significant reduction in the proportion of lymphocytes exhibiting surface expression of CXCR3. The reduction in T cell expression of CXCR3 resulted in reduced migration toward the ligand IP-10, and both CD4+ and CD8+ T cells from HCC patients exhibited diminished chemotactic responses to IP-10 in vitro compared to T cells from healthy control subjects. CONCLUSION: This study demonstrates functional desensitization of the chemokine receptor CXCR3 in lymphocytes from HCC patients by CXCR3 ligands secreted by tumor cells. This may cause lymphocyte dysfunction and subsequently impaired immune defense against the tumor.

Adult↗
PubMed2005

Chemokine receptors support infiltration of lymphocyte subpopulations in human hepatocellular carcinoma.

The presence of lymphocyte infiltration in human hepatocellular carcinoma (HCC) is evident. However, immune regulation of lymphocytes in HCC is poorly characterized. In this study, we investigated the chemokine receptor and memory, activation and adhesion markers of major leukocyte subsets present in tumor, nontumor liver, and peripheral blood. T cells from both tumor and peritumor liver displayed high levels of activation and homing markers. CCR5 and CXCR3 were expressed in a large proportion of CD45RO+, CD69+, CD27+, and CD11a+ T cells from tumor compared with T cells from circulation. The proportion of CCR6- and CXCR3-expressing natural killer cells (NK) and natural killer T cells (NKT) was significantly increased in the tumor and nontumor liver compared with peripheral blood. This study demonstrates the role of chemokine receptors in the recruitment of specific lymphocyte subsets to the liver in HCC and suggests the importance of these receptors in regulation of immune defense against HCC.

Adult↗
PubMed2005

Conditional ablation of macrophages halts progression of crescentic glomerulonephritis.

The presence of macrophages in inflamed glomeruli of rat kidney correlates with proliferation and apoptosis of resident glomerular mesangial cells. We assessed the contribution of inflammatory macrophages to progressive renal injury in murine crescentic glomerulonephritis (GN). Using a novel transgenic mouse (CD11b-DTR) in which tissue macrophages can be specifically and selectively ablated by minute injections of diphtheria toxin, we depleted renal inflammatory macrophages through days 15 and 20 of progressive crescentic GN. Macrophage depletion reduced the number of glomerular crescents, improved renal function, and reduced proteinuria. Morphometric analysis of renal tubules and interstitium revealed a marked attenuation of tubular injury that was associated with reduced proliferation and apoptosis of tubular cells. The population of interstitial myofibroblasts decreased after macrophage depletion and interstitial fibrosis also decreased. In the presence of macrophages, interstitial myofibroblasts exhibited increased levels of both proliferation and apoptosis, suggesting that macrophages act to support a population of renal myofibroblasts in a high turnover state and in matrix deposition. Finally, deletion of macrophages reduced CD4 T cells in the diseased kidney. This study demonstrates that macrophages are key effectors of disease progression in crescentic GN, acting to regulate parenchymal cell populations by modulating both cell proliferation and apoptosis.

Animals↗
PubMed2005

Apoptosis in glomerulonephritis.

PURPOSE OF REVIEW: Although glomerular cell apoptosis may be detrimental in acute and chronic inflammation, it is also a key component of the reparative glomerular remodelling that can follow injury. All glomerular cells are vulnerable to apoptosis although there are often differences in the nature of the initiating stimulus and the factors that are protective. The purpose of this review is to outline how modulation of this process may inhibit glomerular injury and promote tissue repair. RECENT FINDINGS: In-vitro studies are providing more information on the factors that regulate apoptosis in individual glomerular cell types. It has now become apparent that growth factors such as vascular endothelial growth factor may have protective actions on several cell types and this may facilitate future treatments that promote the survival of multiple cell types within injured glomeruli. Work in this field has also emphasized that many current treatment strategies may exert a beneficial impact upon renal cell death. SUMMARY: Although the advent of various antiapoptotic agents such as caspase inhibitors and recombinant growth factors does provide future opportunities to modulate apoptosis for therapeutic gain in patients with glomerulonephritis, there is still some way to go before such reagents are used to treat human disease. However, there is scope for optimism that such treatments will reach the clinic in due course.

Animals↗
PubMed2004

Apoptosis in glomerulonephritis.

Apoptosis is of fundamental importance and plays a key role in determining the outcome of glomerulonephritis. Under ideal circumstances,apoptosis deletes infiltrating leukocytes and excess numbers of resident cells that are surplus to requirements, thereby facilitating tissue remodeling and the restoration of normal tissue architecture. Apoptosis also has a darker side, however, and may be responsible for the deletion of critically important resident glomerular cells, resulting in hypocellular scarring and loss of renal function. Recent data indicate that glomerular cell apoptosis may be manipulated to improve outcome in experimental models of renal inflammation. It is hoped that further research will provide novel therapeutic strategies for patients with inflammatory glomerulonephritis.

Apoptosis↗
PubMed2004

Osteopontin and calcium stone formation.

Osteopontin (OPN) is a phosphorylated protein of wide tissue distribution that is found in association with dystrophic calcification including in the organic matrix of kidney stones. It is a strong inhibitor of crystal formation and growth in vitro, but there is still debate regarding its effects upon crystal adhesion to tubular epithelial cells. In this brief review, we will outline the evidence implicating OPN in stone disease with the primary emphasis being on the interaction of OPN with calcium oxalate (CaOx), the major constituent of calcium containing stones. Finally, preliminary data is presented regarding the amounts and features of OPN present in the urine of stone formers and normal individuals.

Animals↗
PubMed2003

The wt1-heterozygous mouse; a model to study the development of glomerular sclerosis.

In the present study, it is shown that mice heterozygous for wt1 develop glomerular sclerosis and the nature and time course of events leading to the glomerular scarring are determined. Wt1-heterozygous (wt1het) mice and their wild-type littermates were closely monitored from birth and plasma levels of urea, creatinine, and albumin were compared with histological data and clinical features. One of the first indications of nephropathy in the wt1het mouse was the development of proteinuria, accompanied by progressive elevation of the plasma levels of urea and creatinine. Subsequently, the mice developed albuminuria, which correlated with thickening of the glomerular basement membrane and fusion of the podocyte foot processes. Glomerulosclerosis was a relatively late event, accompanied by severe albuminuria and loss of WT1, nephrin, CD2AP, and alpha-actinin-4.

Albuminuria↗
PubMed2003

Osteopontin is a critical inhibitor of calcium oxalate crystal formation and retention in renal tubules.

Calcium nephrolithiasis is the most common form of renal stone disease, with calcium oxalate (CaOx) being the predominant constituent of renal stones. Current in vitro evidence implicates osteopontin (OPN) as one of several macromolecular inhibitors of urinary crystallization with potentially important actions at several stages of CaOx crystal formation and retention. To determine the importance of OPN in vivo, hyperoxaluria was induced in mice targeted for the deletion of the OPN gene together with wild-type control mice. Both groups were given 1% ethylene glycol, an oxalate precursor, in their drinking water for up to 4 wk. At 4 wk, OPN-deficient mice demonstrated significant intratubular deposits of CaOx crystals, whereas wild-type mice were completely unaffected. Retained crystals in tissue sections were positively identified as CaOx monohydrate by both polarized optical microscopy and x-ray powder diffraction analysis. Furthermore, hyperoxaluria in the OPN wild-type mice was associated with a significant 2- to 4-fold upregulation of renal OPN expression by immunocytochemistry, lending further support to a renoprotective role for OPN. These data indicate that OPN plays a critical renoprotective role in vivo as an inhibitor of CaOx crystal formation and retention in renal tubules.

Animals↗
PubMed2002

Effects of cyclosporine in osteopontin null mice.

BACKGROUND: Osteopontin (OPN) is a macrophage adhesive and cell survival factor that is up-regulated in tubules in tubulointerstitial disease. We have previously reported that rats with cyclosporine (CsA) nephropathy have increased tubular osteopontin that correlates with the infiltration of macrophages and interstitial fibrosis. This study tested the hypothesis that the absence of OPN would ameliorate CsA nephropathy. METHODS: OPN knockout (-/-) and wild type (+/+) mice were fed a low salt diet (Na+ 0.01%) for one week and then received daily CsA injections (30 mg/kg, SC) until sacrifice at two weeks. Afferent arteriolopathy, tubulointerstitial injury, macrophage infiltration, collagen III deposition, transforming growth factor-beta (TGF-beta) expression, and tubular and interstitial cell proliferation and apoptosis were evaluated. RESULTS: Wild type mice developed early features of CsA nephropathy, with arteriolar hyalinosis and cortical and tubulointerstitial fibrosis. Despite comparable CsA levels, OPN-/- mice had less arteriolopathy (15 vs. 24%, P < 0.05), a 20% reduction in cortical macrophage infiltration (P < 0.05), and 20% reduction in interstitial collagen deposition (P < 0.05). OPN-/- mice also showed less cortical interstitial cell proliferation but no differences in tubular cell proliferation or apoptosis. OPN+/+ mice also developed some neurotoxicity, consisting of ataxia, and this was associated with increased mortality at two weeks. CONCLUSION: OPN partially mediates arteriolopathy, early macrophage recruitment and fibrosis in murine CsA nephropathy. OPN also may be involved in CsA associated neurotoxicity.

Animals↗
PubMed2001

Impaired angiogenesis in the remnant kidney model: I. Potential role of vascular endothelial growth factor and thrombospondin-1.

Few studies have examined the role of the microvasculature in progressive renal disease. It was hypothesized that impaired angiogenesis might occur in the diseased kidney and could contribute to renal scarring. Progressive renal disease was induced in rats by 5/6 renal ablation and those rats were compared with sham-operated control animals at multiple time points, for examination of changes in the microvasculature and the expression of angiogenic factors. An early angiogenic response was documented in remnant kidneys, with increases in the proliferation of peritubular (1 wk) and glomerular (2 wk) endothelial cells. Subsequently, however, there was a decrease in endothelial cell proliferation, which was reduced to levels below those of sham-treated animals, in conjunction with interstitial expression of the antiangiogenic factor thrombospondin-1 (TSP-1) and decreased tubular expression of the proangiogenic factor vascular endothelial growth factor (VEGF). Both the increase in TSP-1 expression and the loss of VEGF expression were correlated with capillary loss and the development of glomerulosclerosis and interstitial fibrosis. Progressive macrophage infiltration was correlated both spatially and quantitatively with the sites of absent or diminished VEGF expression. In addition, macrophage-associated cytokines (interleukin-1beta, interleukin-6, and tumor necrosis factor-alpha) inhibited VEGF mRNA expression and protein secretion by cultured tubular epithelial cells of the medullary thick ascending limb, under both normoxic and hypoxic conditions. Impaired angiogenesis characterizes the remnant kidney model and is correlated with progression. The impaired angiogenesis may be mediated by alterations in the renal expression of TSP-1 and VEGF, with the latter being regulated by macrophage-associated cytokines.

Animals↗
PubMed2001

Impaired angiogenesis in the remnant kidney model: II. Vascular endothelial growth factor administration reduces renal fibrosis and stabilizes renal function.

Impaired angiogenesis and decreased vascular endothelial growth factor (VEGF) expression were recently documented in the remnant kidney (RK) model of progressive renal failure. VEGF (50 microg/kg, twice daily) was administered to RK rats between weeks 4 and 8 after surgery, and rats were euthanized at week 8 for histologic study. During the administration of VEGF (n = 7) or vehicle (n = 6), systemic BP was comparable in the two groups. VEGF treatment resulted in improved renal function and lower mortality rates, compared with the vehicle-treated group. Renal histologic analyses confirmed a 3.5-fold increase in glomerular endothelial cell proliferation (0.14 +/- 0.03 versus 0.04 +/- 0.02 proliferating endothelial cells/glomerulus, VEGF versus vehicle, P < 0.05), a twofold increase in peritubular capillary endothelial cell proliferation (1.60 +/- 0.30 versus 0.78 +/- 0.17 cells/mm(2), VEGF versus vehicle, P < 0.01), a threefold decrease in peritubular capillary rarefaction (P < 0.01), and a twofold increase in endothelial nitrix oxide synthase expression (P < 0.05) in the VEGF-treated group; an eightfold increase in urinary nitrate/nitrite levels (P < 0.05) was also noted. Although the difference in glomerulosclerosis scores did not reach statistical significance (0.67 +/- 0.42 versus 1.22 +/- 0.63, VEGF versus vehicle; range, 0 to 4; P = NS), VEGF-treated rats exhibited less interstitial collagen type III deposition (9.32 +/- 3.26 versus 17.45 +/- 7.50%, VEGF versus vehicle, P < 0.01) and reduced tubular epithelial cell injury, as manifested by osteopontin expression (5.57 +/- 1.60 versus 9.58 +/- 3.45%, VEGF versus vehicle, P < 0.01). In conclusion, VEGF treatment reduces fibrosis and stabilizes renal function in the RK model. The use of angiogenic factors may represent a new approach to the treatment of kidney disease.

Animals↗