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K L Gordon

Publications and source records attributed to K L Gordon.

At least 19 recordsLinked to original sources
PubMed2001

Hyperuricemia exacerbates chronic cyclosporine nephropathy.

BACKGROUND: Hyperuricemia frequently complicates cyclosporine (CSA) therapy. The observation that longstanding hyperuricemia is associated with chronic tubulointerstitial disease and intrarenal vasoconstriction raised the hypothesis that hyperuricemia might contribute to chronic CSA nephropathy. METHODS: CSA nephropathy was induced by the administration of CSA (15 mg/kg/day) for 5 and 7 weeks to rats on a low salt diet (CSA group). The effect of hyperuricemia on CSA nephropathy was determined by blocking the hepatic enzyme uricase with oxonic acid (CSA-OA). Control groups included rats treated with vehicle (VEH) and oxonic acid alone (OA). Histological and functional studies were determined at sacrifice. RESULTS: CSA treated rats developed mild hyperuricemia with arteriolar hyalinosis, tubular injury and striped interstitial fibrosis. CSA-OA treated rats had higher uric acid levels in association with more severe arteriolar hyalinosis and tubulointerstitial damage. Intrarenal urate crystal deposition was absent in all groups. Both CSA and CSA-OA treated rats had increased renin and decreased NOS1 and NOS3 in their kidneys, and these changes are more evident in CSA-OA treated rats. CONCLUSION: An increase in uric acid exacerbates CSA nephropathy in the rat. The mechanism does not involve intrarenal uric acid crystal deposition and appears to involve activation of the renin angiotensin system and inhibition of intrarenal nitric oxide production.

Animals↗
PubMed2001

Intravenous immunoglobulin protects against experimental thrombotic microangiopathy.

BACKGROUND: Intravenous immunoglobulin (IVIG) has been utilized in several forms of vasculitis and has many potential mechanisms of action, including the inhibition of C3 activation. We have previously demonstrated that IVIG can reduce glomerular injury in a model of membranous nephropathy mediated by C5b-9 [1]. C5b-9 has also been shown to mediate the thrombotic microangiopathy (TMA) induced by antibody to glomerular endothelial cells leading to a hemolytic uremic syndrome-type lesion [2]. METHODS: To test the hypothesis that IVIG might be effective in treating antibody-induced TMA, male uninephrectomized rats underwent right renal artery perfusion with goat anti-rat glomerular endothelial cell (GEN) antibody (20 mg/kg). Sheep IgG (200 mg/kg) was administered either 30 minutes before the renal artery perfusion (group I, N = 6) or 30 minutes postperfusion (group II, N = 9). A third control group received phosphate-buffered saline (PBS; group III, N = 12). A survival biopsy was performed at 15 minutes, and the animals were sacrificed on day 2. RESULTS: There were no significant differences in proteinuria or hematocrit between the groups. Animals pretreated with IVIG had significantly improved survival and renal function, which was associated with a decrease in glomerular C3 deposition. The protective effect of IVIG was abolished if the administration was delayed 30 minutes after perfusion. CONCLUSIONS: IVIG is effective in reducing injury in experimental TMA only if given prophylactically. The effect is mediated by inhibition of local intraglomerular complement activation.

Animals↗
PubMed2001

Impaired angiogenesis in the aging kidney: vascular endothelial growth factor and thrombospondin-1 in renal disease.

We investigated the relationship of changes in the microvasculature to age-related structural and functional changes in the kidney to determine whether there was evidence of impaired angiogenesis and whether the loss of microvasculature could be accounted for by changes in the local production of angiogenic or antiangiogenic factors. Glomerular and peritubular capillary number, density, and endothelial cell proliferation were determined in aging (24 months; n = 9) and young (3 months; n = 8) rat kidneys and correlated with renal functional and structural changes and alterations in renal expression of vascular endothelial growth factor (VEGF) and thrombospondin-1 (TSP-1). Aging rats showed a focal decrease in both peritubular capillary (peritubular capillary staining, 5.4% +/- 1.8% versus 11.3% +/- 2.0% per 100 tubules; rarefaction index, 10.6% +/- 4.6% versus 0.6% +/- 0.1%, aging versus young rats; P < 0.05 and P: < 0.001, respectively) and glomerular capillary loops (27.3 +/- 6.9 versus 50.7 +/- 7.4/glomerulus, aging versus young rats; P < 0.001). The number of proliferating endothelial cells was decreased in aging rats compared with young rats (glomerular, 0.04 +/- 0.01 versus 0.15 +/- 0.03 positive cells/glomerular cross-section; peritubular, 0.7 +/- 0.2 versus 4.3 +/- 2.6 positive cells/mm(2); P < 0.05). In the aging kidney, VEGF expression was focally increased in the cortex compared with young rats, whereas a profound decrease was observed in the outer and inner medulla (total area of VEGF expression, 19.2% +/- 11.4% versus 39.3% +/- 7.6%; P < 0.05). Tubular VEGF expression correlated with peritubular capillary density (r(2) = 0.57; P < 0.01) and inversely correlated with tubular osteopontin (r(2) = -0.55; P < 0.05) and macrophage infiltration (r(2) = -0.64; P < 0.01). TSP-1 staining was increased in the glomeruli and tubulointerstitium of the aging rats. Glomerular TSP-1 score correlated inversely with glomerular capillary number (r(2) = -0.89; P < 0.001). Tubulointerstitial TSP-1 also correlated with percentage of positive staining of peritubular capillary (r(2) = -0.59; P < 0.001). Glomerular capillary number showed significant correlation with glomerulosclerosis score, as well as with 24-hour urinary protein excretion. Peritubular capillary density also inversely correlated with interstitial fibrosis score and urinary protein excretion. In conclusion, glomerular and peritubular capillary loss in the aging kidney correlate with alterations in VEGF and TSP-1 expression and also with the development of glomerulosclerosis and tubulointerstitial fibrosis. These findings suggest that impaired angiogenesis associated with progressive loss in renal microvasculature may have a pivotal role in age-related nephropathy.

Aging↗
PubMed2001

Post-cyclosporine-mediated hypertension and nephropathy: amelioration by vascular endothelial growth factor.

Recent studies have demonstrated a role for microvascular and tubulointerstitial injury in some models of salt-sensitive hypertension. We utilized a model of post-cyclosporin A (CsA) nephropathy and hypertension to test the hypothesis that treatment with an angiogenic factor aimed at ameliorating the microvascular and renal injury would prevent the development of hypertension. CsA was administered with a low-salt diet for 45 days, resulting in a renal lesion characterized by afferent arteriolopathy, focal peritubular capillary loss, and tubulointerstitial fibrosis. Rats were then placed on a high-salt diet and randomized to receive either vascular endothelial growth factor (VEGF(121)) or vehicle for 14 days. Placement of rats with established CsA nephropathy on a high-salt diet results in the rapid development of salt-sensitive hypertension. VEGF(121) treatment resulted in lower blood pressure, and this persisted on discontinuing the VEGF. VEGF(121) treatment was also associated with a decrease in osteopontin expression, macrophage infiltration, and collagen III deposition and markedly stimulated resolution of the arteriolopathy (20.9 +/- 7.8 vs. 36.9 +/- 6.1%, VEGF vs. vehicle, P < 0.05). In conclusion, CsA-associated renal microvascular and tubulointerstitial injury results in the development of salt-sensitive hypertension. Treatment of animals with established CsA nephropathy with VEGF reduces the hypertensive response and accelerates histological recovery. The vascular protective effect of VEGF may be due to the improvement of arteriolopathy. Angiogenic growth factors may represent a novel strategy for treating CsA-associated hypertension and renal disease.

Animals↗
PubMed2001

Mycophenolate mofetil prevents salt-sensitive hypertension resulting from nitric oxide synthesis inhibition.

Recent studies have suggested that subtle microvascular and tubulointerstitial injury in the kidney can cause salt-sensitive hypertension. To test this hypothesis, we determined whether the mild renal disease induced by transient blockade of nitric oxide (NO) synthesis would result in salt-sensitive hypertension and whether prevention of the renal injury by coadministration of the immunosuppressive agent mycophenolate mofetil (MMF) would block the development of salt sensitivity. N(omega)-nitro-L-arginine-methyl ester (L-NAME; 70 mg/100 ml in the drinking water) was administered for 3 wk to rats with or without MMF (30 mg x kg(-1) x day(-1) by gastric gavage), followed by a 1-wk "washout" period in which the MMF was continued, which was followed in turn by placement on a high-salt (4% NaCl) diet for an additional 4 wk. Renal histology was examined at 3 and 8 wk, and blood pressure was measured serially. L-NAME treatment resulted in acute hypertension and the development of mild renal injury. During the washout period, blood pressure returned to normal, only to return to the hypertensive range on exposure of the animals to a high-salt diet. MMF treatment prevented the development of hypertension in response to a high-salt diet. This correlated with the ability of MMF to inhibit specific aspects of the renal injury, including the development of segmental glomerulosclerosis, the infiltration of T cells and ANG II-positive cells, and the thickening of afferent arterioles.

Animals↗
PubMed2001

Hypokalemia induces renal injury and alterations in vasoactive mediators that favor salt sensitivity.

We investigated the hypothesis that hypokalemia might induce renal injury via a mechanism that involves subtle renal injury and alterations in local vasoactive mediators that would favor sodium retention. To test this hypothesis, we conducted studies in rats with diet-induced K+ deficiency. We also determined whether rats with hypokalemic nephropathy show salt sensitivity. Twelve weeks of hypokalemia resulted in a decrease in creatinine clearance, tubulointerstitial injury with macrophage infiltration, interstitial collagen type III deposition, and an increase in osteopontin expression (a tubular marker of injury). The renal injury was greatest in the outer medulla with radiation into the cortex, suggestive of an ischemic etiology. Consistent with this hypothesis, we found an increased uptake of a hypoxia marker, pimonidazole, in the cortex. The intrarenal injury was associated with increased cortical angiontensin-converting enzyme (ACE) expression and continued cortical angiotensin II generation despite systemic suppression of the renin-angiotensin system, an increase in renal endothelin-1, a decrease in renal kallikrein, and a decrease in urinary nitrite/nitrates and prostaglandin E(2) excretion. At 12 wk, hypokalemic rats were placed on a normal-K+ diet with either high (4%)- or low (0.01%)-NaCl content. Despite correction of hypokalemia and normalization of renal function, previously hypokalemic rats showed an elevated blood pressure in response to a high-salt diet compared with normokalemic controls. Hypokalemia is associated with alterations in vasoactive mediators that favor intrarenal vasoconstriction and an ischemic pattern of renal injury. These alterations may predispose the animals to salt-sensitive hypertension that manifests despite normalization of the serum K+.

Angiotensin II↗
PubMed2001

Elevated uric acid increases blood pressure in the rat by a novel crystal-independent mechanism.

An elevation in circulating serum uric acid is strongly associated with the development of hypertension and renal disease, but whether uric acid has a causal role or whether it simply indicates patients at risk for these complications remains controversial. We tested the hypothesis that uric acid may have a causal role in the development of hypertension and renal disease by examining the effects of mild hyperuricemia in rats. Mild hyperuricemia was induced in rats by providing a uricase inhibitor (oxonic acid) in the diet. Hyperuricemic rats developed elevated blood pressure after 3 weeks, whereas control rats remained normotensive. The development of hypertension was prevented by concurrent treatment with either a xanthine oxidase inhibitor (allopurinol) or a uricosuric agent (benziodarone), both of which lowered uric acid levels. Blood pressure could also be lowered by reducing uric acid levels with either allopurinol or oxonic acid withdrawal. A direct relationship was found between blood pressure and uric acid (r=0.75, n=69), with a 10-mm Hg blood pressure increase for each 0.03-mmol/L (0.5-mg/dL) incremental rise in serum uric acid. The kidneys were devoid of urate crystals and were normal by light microscopy. However, immunohistochemical stains documented an ischemic type of injury with collagen deposition, macrophage infiltration, and an increase in tubular expression of osteopontin. Hyperuricemic rats also exhibited an increase in juxtaglomerular renin and a decrease in macula densa neuronal NO synthase. Both the renal injury and hypertension were reduced by treatment with enalapril or L-arginine. In conclusion, mild hyperuricemia causes hypertension and renal injury in the rat via a crystal-independent mechanism, with stimulation of the renin-angiotensin system and inhibition of neuronal NO synthase.

Animals↗
PubMed2000

Vascular endothelial growth factor accelerates renal recovery in experimental thrombotic microangiopathy.

BACKGROUND: Renal microvascular injury characterizes thrombotic microangiopathy (TMA). The possibility that angiogenic growth factors may accelerate recovery in TMA has not been studied. METHODS: TMA was induced in rats by the selective right renal artery perfusion of antiglomerular endothelial cell IgG (30 mg/kg). Twenty-four hours later, rats received vascular endothelial growth factor (VEGF121, 100 microg/kg/day) or vehicle (control) daily until day 14. To evaluate renal function, the unperfused left kidney was removed at day 14, and rats were sacrificed at day 17. RESULTS: The induction of TMA was associated with loss of glomerular and peritubular capillary endothelial cells and decreased arteriolar density at day 1. Some spontaneous capillary recovery was present by day 17; however, repair was incomplete, and severe tubulointerstitial damage occurred. The lack of complete microvascular recovery was associated with reduced VEGF immunostaining in the outer medulla. VEGF-treated rats had more glomeruli with intact endothelium, less glomerular ischemia (collapsed glomeruli), and greater peritubular capillary density with less peritubular capillary loss. This was associated with less tubulointerstitial fibrosis, less cortical atrophy, and improved renal function. CONCLUSIONS: VEGF accelerates renal recovery in this experimental model of TMA. These studies suggest that angiogenic growth factors may provide a new therapeutic strategy for diseases associated with endothelial cell injury.

Animals↗
PubMed2000

Tubulointerstitial injury and loss of nitric oxide synthases parallel the development of hypertension in the Dahl-SS rat.

OBJECTIVE: Alterations in renal nitric oxide (NO) are involved in the hypertension of the Dahl salt-sensitive (Dahl-SS) rat We sought to identify the kinetics and sites of expression of the major NO synthase (NOS) isoforms. DESIGN: The renal expression of the major NOS were examined in Dahl-SS and salt-resistant rats (Dahl-SR) while on a low salt (0.1% NaCl) diet at 3 and 9 weeks of age. METHODS: Renal biopsies from Dahl-SS and Dahl-SR rats were compared for evidence of renal injury and for alterations in expression of the NOS enzymes by quantitative immunohistochemistry. RESULTS: At 3 weeks of age Dahl-SS and Dahl-SR rats have normal renal histology and similar immunohistochemical expression of NOS1, -2, and -3. At 9 weeks Dahl-SS rats had significantly higher blood pressure than Dahl-SR rats (P< 0.005 ), and lower macula densa NOS1 (P< 0.05) and cortical and medullary NOS3 (P< 0.05). NOS2 was reduced in cortical tubules in biopsies showing severe tubulointerstitial damage, but was not significantly different between Dahl-SS and Dahl-SR groups as a whole. Dahl-SS rats also manifested glomerular and tubulointerstitial injury. Tubular expression of osteopontin (OPN), which is an inhibitor of NOS2, correlated with the systolic BP in individual Dahl-SS rats (r2 = 0.80, P < 0.0001 ). CONCLUSION: Tubulointerstitial injury and the loss of NOS occur after birth and parallel the development of hypertension. We suggest that the structural and functional changes that occur with renal injury in the Dahl-SS rat may contribute to the development of hypertension.

Animals↗
PubMed1999

Salt-sensitive hypertension develops after short-term exposure to Angiotensin II.

We hypothesized that short-term exposure to angiotensin II (Ang II) could result in structural and functional changes in the kidney that would favor sodium retention and the development of sustained hypertension. To test this hypothesis, rats were exposed to pressor doses (435 ng. kg-1. min-1) of Ang II for 2 weeks. The infusion of Ang II was associated with acute hypertension, renal dysfunction, proteinuria, and focal tubulointerstitial and vascular damage. At sites of the tubulointerstitial damage, there was a reduction in peritubular capillary endothelial cell staining. By use of immunostaining, we found focal loss of endothelial nitric oxide synthase (eNOS) in the peritubular capillaries at sites of injury and a generalized reduction in eNOS in collecting ducts, thin loops of Henle, and vascular bundles in the medulla. When the Ang II infusion ended, the rats became normotensive and renal function returned toward normal. However, exposure of the rats to high salt diet (4% NaCl) resulted in the redevelopment of hypertension after 3 to 4 weeks. Rats maintained on a high salt diet with no prior exposure to Ang II and rats placed on low salt diet (0.1% NaCl) after exposure to Ang II remained normotensive. Thus, we report a new model of salt-sensitive hypertension induced by transient exposure to pressor doses of Ang II. The mechanism may relate to microvascular injury with peritubular capillary loss coupled with functional changes, such as a loss in intrarenal nitric oxide formation, that could alter the ability of the kidney to excrete a salt load.

Angiotensin II↗
PubMed1999

Renal injury and salt-sensitive hypertension after exposure to catecholamines.

We investigated whether chronic infusion of phenylephrine could induce structural and functional changes in the kidney of rats with the subsequent development of salt-sensitive hypertension. Rats were infused with phenylephrine (0.15 mmol/kg per day) by minipump, resulting in a moderate increase in systolic blood pressure (BP) (17 to 25 mm Hg) and a marked increase in BP variability as measured by an internal telemetry device. After 8 weeks, the phenylephrine infusion was stopped with the return of BP to normal, and a nephrectomy was performed for histological studies. Glomeruli were largely spared, but focal tubulointerstitial fibrosis was present, with the de novo expression of osteopontin by injured tubules, macrophage and "myofibroblast" accumulation, and focal increases in mRNA for transforming growth factor beta by in situ hybridization. Peritubular capillaries at sites of injury had distorted morphology with shrinkage, rounding, and focal rarefaction, and endothelial cell proliferation was also identified. Rats were randomized to a high (8% NaCl or 1.36 mol/kg) or low (0.1% NaCl or 17 mmol/kg) salt diet. After 4 to 8 weeks, phenylephrine-treated rats on a high salt diet developed marked hypertension, which was in contrast with phenylephrine-treated rats placed on a low salt diet or vehicle-treated rats given a high salt diet. Hypertension after phenylephrine exposure correlated with the initial mean systolic BP (r(2)=0.99) and the degree of BP lability (r(2)=0.99) during the phenylephrine infusion, the amount of osteopontin expressed in the initial biopsy/nephrectomy (r(2)=0.74), and the final glomerular filtration rate (r(2)=0.58). These studies provide a mechanism by which a markedly elevated sympathetic nervous system can induce salt-dependent hypertension even when the hyperactive sympathetic state is no longer engaged.

Adrenergic alpha-Agonists↗
PubMed1998

Role of intrinsic renal cells versus infiltrating cells in glomerular crescent formation.

BACKGROUND: Studies were undertaken to characterize the cellular composition that occurs in glomeruli and the tubulointerstitium of a passive model of complement-independent crescentic nephritis in mice. METHODS: Glomerulonephritis was induced by the injection of antibody to whole rabbit glomeruli, and tissue was examined histologically at 7, 14 and 28 days. RESULTS: Mice developed proteinuria, glomerular crescents, and progressive glomerulosclerosis and tubulointerstitial fibrosis. The majority of the cells within the crescents appeared to be intrinsic ezrin-positive epithelial cells of visceral or parietal origin. Many of the ezrin positive cells were proliferating and expressing the PDGF receptor. Despite expression of the macrophage adhesive protein, osteopontin, the early crescents were devoid of infiltrating macrophages, T cells or myofibroblasts, which could be explained by the finding that the Bowman's capsule remained intact. Tubulointerstitial damage also occurred, and included tubular dilation and atrophy, periglomerular and patchy interstitial infiltration and interstitial fibrosis with increased interstitial deposition of type IV collagen and laminin. Interstitial infiltrating cells included macrophages, CD4+ T lymphocytes, CD8+ T lymphocytes, and activated myofibroblasts. Tubular osteopontin expression was increased in the areas of tubulointerstitial damage and was associated with interstitial macrophage infiltration. CONCLUSIONS: We describe an experimental model of complement-independent murine crescentic nephritis associated with tubulointerstitial injury. Proliferating glomerular epithelial cells are the main cellular components of the crescents in this model.

Animals↗
PubMed1998

Tubulointerstitial disease in aging: evidence for underlying peritubular capillary damage, a potential role for renal ischemia.

Aging is associated with a progressive decline in renal function and the development of glomerulosclerosis and interstitial fibrosis. Although many studies have addressed the cellular mechanisms of age-related glomerulosclerosis, less is known about the tubulointerstitial fibrosis. In this study, aging (24 mo) rats develop tubulointerstitial fibrosis characterized by tubular injury and focal tubular cell proliferation, myofibroblast activation, macrophage infiltration with increased immunostaining for the adhesive proteins osteopontin and intercellular adhesion molecule-1, and collagen IV deposition. Aging rats demonstrated immunostaining for endothelial nitric oxide synthase (eNOSIII) in renal tubular epithelial cells and infiltrating mononuclear cells in areas of tubulointerstitial injury, with a relative loss of staining of the peritubular capillaries compared with young rats. The aging rats also displayed focal loss of peritubular capillaries (as noted by focally decreased RECA-1 and OX-2 staining) in areas of tubulointerstitial injury. The areas of fibrosis and hypocellularity were associated with increased apoptosis of tubular and interstitial cells compared with young (3 mo) rats (25.4 +/- 5.3 versus 3.5 +/- 2.5 TUNEL-positive cells/0.25 mm2 in old versus young rats, P = 0.0001). It is concluded that tubulointerstitial fibrosis in aging is an active process associated with interstitial inflammation and fibroblast activation. The progressive loss of cells in areas of fibrosis may be due to accelerated apoptosis. Furthermore, the tubulointerstitial injury may be the consequence of ischemia secondary to peritubular capillary injury and altered eNOS expression.

Actins↗
PubMed1998

Endogenous fibroblast growth factor-2 mediates cytotoxicity in experimental mesangioproliferative glomerulonephritis.

Fibroblast growth factor-2 (FGF-2) is released from mesangial cells in experimental mesangioproliferative glomerulonephritis induced with anti-Thy 1.1 antibody. To investigate the functional role of released FGF-2, rats received either neutralizing anti-FGF-2 IgG or a functional peptide antagonist of FGF-2 (FGF119-126) before or shortly after induction of anti-Thy 1.1 nephritis. In additional experiments, rats were treated with bolus injections of FGF-2 from 2 to 6 h after disease induction. The data showed that anti-FGF-2 therapy led to significant reductions of early mesangial cell injury (mesangiolysis, microaneurysm formation) and the subsequent mesangioproliferative changes (glomerular de novo expression of alpha-smooth muscle actin, mesangial cell proliferation, matrix accumulation, and platelet influx). Conversely, injections of FGF-2 augmented both mesangial injury and the subsequent mesangioproliferative changes. Studies on the mechanisms underlying the amplification of mesangial cell injury by FGF-2 showed that anti-FGF-2 therapy reduced cell death at 2 and 8 h after disease induction by 58 and 54%, respectively. This was associated with significant reductions in the number of glomerular H2O2- and OH -producing cells, as well as reduced glomerular production of nitric oxide. These data suggest that release of constitutively expressed FGF-2 after immune-mediated cell injury contributes to glomerular cell damage and thus identify FGF-2 as a novel mediator of cytotoxicity.

Animals↗
PubMed1997

Mesangial cell proliferation mediated by PDGF and bFGF is determined by levels of the cyclin kinase inhibitor p27Kip1.

Mesangial cell proliferation in vitro is regulated by many cytokines. Platelet-derived growth factor (PDGF) and basic fibroblast growth factor (bFGF) are potent mesangial cell mitogens, whereas transforming growth factor-beta1 (TGF-beta1) reduces their effects. We examined how these cytokines regulate rat mesangial cell proliferation at the level of the cell-cycle. Quiescent mesangial cells in vitro express the cyclin kinase inhibitor, p27Kip1 (p27), and PDGF- and bFGF-induced mesangial cell proliferation is associated with a substantial decrease in p27 levels. Consequently there is a marked increase in expression (Western blot analysis, immunostaining) of cyclin A and CDK2. The decline in p27 levels was prevented by TGF-beta1 during inhibition of PDGF- and bFGF-induced mesangial cell proliferation. To determine the functional role of p27 during cytokine-mediated mesangial cell proliferation, the expression of p27 was reduced with specific p27Kip1 antisense oligodeoxynucleotides. Reducing the levels of p27 resulted in an increased magnitude of mesangial cell proliferation (BrdU and 3H-thymidine incorporation) induced by PDGF and bFGF compared to non-transfected mesangial cells and mesangial cells transfected with control mismatch oligodeoxynucleotides. Furthermore, the onset of maximal proliferation occurred earlier in mesangial cells transfected with antisense compared to control. The reduction in proliferation by TGF-beta1 were not altered by decreased p27 expression. Reducing p27 expression in the absence of mitogens was not associated with entry into the cell-cycle. These results suggest cytokine mediated mesangial cell proliferation is associated with specific cell-cycle proteins, and that the levels of p27 may be important in determining the mesangial cell's proliferative response to PDGF and bFGF in vitro.

Animals↗
PubMed1996

Differential expression of transforming growth factor-beta isoforms and receptors in experimental membranous nephropathy.

In membranous nephropathy (MN) overproduction of matrix by glomerular epithelial cells (GEC) is believed to be responsible for glomerular basement membrane thickening and spikes. We studied experimental MN in rats (passive Heymann nephritis, PHN) at 5, 10 and 30 days. PHN rats exhibited a marked increase in GEC immunostaining for TGF-beta 2 at all time points. TGF-beta 3 staining was increased at day 10 only, and TGF-beta 1 was unchanged. Glomerular mRNA for TGF-beta 2 and -beta 3 was increased by day 5 when urine protein increased, whereas TGF-beta 1 was not. TGF-beta 2 bioactivity was increased at day 5. There was also a marked increase in GEC immunostaining for TGF-beta receptor type I (T beta IR) and TGF-beta receptor type II (T beta IIR) at all time points in PHN. mRNA levels for both receptors increased at day 5. Increases in protein expression and mRNA levels for the TGF-beta 2 and -beta 3 isoforms, and T beta IR and T beta RII were prevented by complement depletion. We conclude that complement-mediated injury to the GEC in vivo is associated with the up-regulation of TGF-beta 2 and -beta 3 isoforms, an increase in TGF-beta 2 bioactivity, and an increase in T beta RI and T beta RII expression. This contrasts with changes in TGF-beta 1 reported in mesangial disease, suggesting that TGF-beta 2 and -beta 3 may be important in diseases of the GEC. The differential expression of TGF-beta isoforms and receptors may be important determinants of the GEC response to injury.

Animals↗
PubMed1996

Transfected CD59 protects mesangial cells from injury induced by antibody and complement.

CD59 is a complement regulatory protein on the glomerular cells that inhibits C5b-9 assembly and insertion. We employed an overexpression strategy to determine the functional significance of CD59 in mesangial cells. We made a CD59 expression vector tagged with FLAG utilizing site-directed mutagenesis and PCR, which allows transfected CD59 to be distinguished from the constitutively expressed protein. In stable clones, overexpressed CD59 was clearly detected immunocytochemically both by anti-FLAG and anti-CD59 antibody in a granular pattern. The overexpression of CD59 was also confirmed by Western blotting. To determine if overexpression of CD59 by mesangial cells protected these cells from C5b-9 attack, we performed complement-mediated cell lysis assays. CD59-transfected mesangial cells demonstrated marked resistance to complement-mediated cell lysis which was reversed in the presence of antibody to CD59. We also investigated the role of CD59 in protecting cells from the effects of membrane insertion of sublytic quantities of C5b-9. Overexpressed CD59 suppressed production of superoxide, one of the inflammatory mediators induced by sublytic C5b-9 attack. These results demonstrate directly that transfected CD59 functions as a potent protector of mesangial cells against both lytic and sublytic attack by C5b-9. CD59 may be an important regulator of complement-mediated disease in the glomerular mesangium.

Animals↗