Mesangial sclerotic change with persistent proteinuria in rats after two consecutive injections of monoclonal antibody 1-22-3

Renal Chemerin Expression is Induced in Models of Hypertensive Nephropathy and Glomerulonephritis and Correlates with Markers of Inflammation and Fibrosis

Chemerin and its receptor, chemokine-like receptor 1 (CmklR1), are associated with chemotaxis, inflammation, and endothelial function, especially in metabolic syndrome, coronary heart disease, and hypertension. In humans, circulating chemerin levels and renal function show an inverse relation. So far, little is known about the potential role of chemerin in hypertensive nephropathy and renal inflammation. Therefore, we determined systemic and renal chemerin levels in 2-kidney-1-clip (2k1c) hypertensive and Thy1.1 nephritic rats, respectively, to explore the correlation between chemerin and markers of renal inflammation and fibrosis. Immunohistochemistry revealed a model-specific induction of chemerin expression at the corresponding site of renal damage (tubular vs. glomerular). In both models, renal expression of chemerin (RT-PCR, Western blot) was increased and correlated positively with markers of inflammation and fibrosis. In contrast, circulating chemerin levels remained unchanged. Taken together, these findings demonstrate that renal chemerin expression is associated with processes of inflammation and fibrosis-related to renal damage. However, its use as circulating biomarker of renal inflammation seems to be limited in our rat models.

Synergistic therapeutic effects of Vitis vinifera extract and Silymarin on experimentally induced cardiorenal injury: The pertinent role of Nrf2

BACKGROUND

Cardiorenal crosstalk has gained growing scientific curiosity recently. Clinical observations have approved that heart and kidney performances are intimately interrelated; acute or chronic dysfunction of either is inevitably mirrored on the other. This coexistence usually has the poor prognosis and worsened outcome.

METHODS

We designed this study to explore therapeutic potentials of combined Vitis vinifera and Silymarin extracts on histopathological alterations of experimentally induced cardiorenal injury model. Moreover, to examine the pertinent role of Nrf2 in their bio-molecular actions. Sixty adult male Wistar albino rats were utilized, further subdivided into control, doxorubicin (DXR), DXR + Silymarin, DXR + Aqueous Vitis, DXR + Ethanolic Vitis, DXR + Ethanolic Vitis + Silymarin. Left ventricle and renal cortex sections from all groups were processed for histopathological examination, biochemical estimation of serum Urea, Creatinine, BUN, lipid profile and hs-CRP and real-time PCR of Nrf2 expression in cardiac and renal tissue homogenate were performed.

RESULTS

Our results proved that combined ethanolic extract of Vitis vinifera and Silymarin restored normal renal and cardiac histomorphology. Significant improvement of Creatinine, BUN, lipid profile and hs-CRP cardiac and renal biochemical indicators confirmed our results. Moreover, significant elevation of mRNA expression levels of Nrf2 proved that combined Vitis vinifera and Silymarin action was directly related to the redox-sensitive regulator pathway.

CONCLUSIONS

We concluded that synergistic therapeutic effect of Vitis vinifera extract and Silymarin on experimental cardiorenal injury model owes principally to promoting activation of the Keap1/Nrf2 signaling pathway.

Involvement of the intrarenal renin-angiotensin system in experimental models of glomerulonephritis

The intrarenal renin-angiotensin system (RAS) has several pathophysiologic functions not only in blood pressure regulation but also in the development of glomerulonephritis (GN). Angiotensin II (Ang II) is the biologically active product of the RAS. Locally produced Ang II induces inflammation, renal cell growth, mitogenesis, apoptosis, migration, and differentiation, regulates the gene expression of bioactive substances, and activates multiple intracellular signaling pathways, leading to tissue damage. Activation of the Ang II type 1 (AT1) receptor pathway results in the production of proinflammatory mediators, cell proliferation, and extracellular matrix synthesis, which facilitates glomerular injury. Previous studies have shown that angiotensin-converting enzyme inhibitors and/or AT1 receptor blockers have beneficial effects in experimental GN models and humans with various types of GN, and that these effects are more significant than their suppressive effects on blood pressure. In this paper, we focus on intrarenal RAS activation in the pathophysiology of experimental models of GN.

Control of NF-κB and inflammation by the unfolded protein response

Under inflammatory situations, endoplasmic reticulum (ER) stress occurs at local sites and modulates inflammatory processes. NF-κB is a key regulator for immune and inflammatory responses, and its activity is influenced by ER stress positively or negatively. Recent investigation suggested that ER stress induces activation of NF-κB in the early phase, whereas in the later phase, consequent unfolded protein response (UPR) inhibits NF-κB. This review summarizes current knowledge on potential mechanisms underlying the biphasic, bidirectional regulation of NF-κB by the UPR and possible roles for ER stress in the regulation of inflammation.

Inhibiting the C5-C5a receptor axis

Activation of the complement system is a major pathogenic event that drives various inflammatory responses in numerous diseases. All pathways of complement activation lead to cleavage of the C5 molecule generating the anaphylatoxin C5a and, C5b that subsequently forms the terminal complement complex (C5b-9). C5a exerts a predominant pro-inflammatory activity through interactions with the classical G-protein coupled receptor C5aR (CD88) as well as with the non-G protein coupled receptor C5L2 (GPR77), expressed on various immune and non-immune cells. C5b-9 causes cytolysis through the formation of the membrane attack complex (MAC), and sub-lytic MAC and soluble C5b-9 also possess a multitude of non-cytolytic immune functions. These two complement effectors, C5a and C5b-9, generated from C5 cleavage, are key components of the complement system responsible for propagating and/or initiating pathology in different diseases, including paroxysmal nocturnal hemoglobinuria, rheumatoid arthritis, ischemia-reperfusion injuries and neurodegenerative diseases. Thus, the C5-C5a receptor axis represents an attractive target for drug development. This review provides a comprehensive analysis of different methods of inhibiting the generation of C5a and C5b-9 as well as the signalling cascade of C5a via its receptors. These include the inhibition of C5 cleavage through targeting of C5 convertases or via the C5 molecule itself, as well as blocking the activity of C5a by neutralizing antibodies and pharmacological inhibitors, or by targeting C5a receptors per se. Examples of drugs and naturally occurring compounds used are discussed in relation to disease models and clinical trials. To date, only one such compound has thus far made it to clinical medicine: the anti-C5 antibody eculizumab, for treating paroxysmal nocturnal hemoglobinuria. However, a number of drug candidates are rapidly emerging that are currently in early-phase clinical trials. The C5-C5a axis as a target for drug development is highly promising for the treatment of currently intractable major human diseases.

Mechanisms of everolimus-induced glomerulosclerosis after glomerular injury in the rat

Despite the lack of nephrotoxicity, adverse effects of the new antiproliferative immunosuppressant everolimus have been reported. By varying time point and dose of everolimus treatment as well as the degree of glomerular injury, the specific conditions and potential mechanisms leading to adverse actions in the anti-Thy1 model have been determined. Only the combination of early and high-dose everolimus treatment (1-3 mg/kg bw) with a severe glomerular lesion ('full-dose' anti-Thy1 model) caused adverse effects with a high mortality rate, progressive apoptosis, crescent formation and glomerulosclerosis. In contrast, either later start or low-dose (0.3 mg/kg bw) therapy or treatment of a less severe lesion ('reduced dose' anti-Thy1 model) appeared to be relatively safe for the glomerular architecture. The adverse effects of everolimus were linked to its marked inhibition of endothelial cell, but not necessarily mesangial cell proliferation. In addition, everolimus markedly inhibited the angiogenic cytokine vascular endothelial growth factor in nephritic glomeruli in vivo. These experimental results suggest special caution regarding the use of everolimus in all situations of severe glomerular cell injury requiring extensive capillary repair, where at least adaption to a low dose needs to be considered.

Continuous, noninvasive monitoring of local microscopic inflammation using a genetically engineered cell-based biosensor

Using an inflammation-responsive regulatory element as a molecular sensor, we established a cell-based biosensor for continuous, noninvasive monitoring of local microscopic inflammation in vivo. Glomerular mesangial cells were stably transfected with a marker gene encoding secreted alkaline phosphatase (SEAP) under the control of the kappaB enhancer elements. The established cells secreted SEAP in vitro in response to proinflammatory cytokines as well as to soluble factors produced by inflamed glomeruli. To examine feasibility of using the established cells for in vivo monitoring of local microscopic inflammation, the sensor cells were transferred selectively into rat glomeruli via the renal circulation. After induction of acute glomerulonephritis, the serum level of SEAP was increased transiently in cell-transferred nephritic rats. The kinetics of serum SEAP was closely correlated with the natural course of the inflammation, and the increase in SEAP was attenuated by suppression of inflammation using an immunosuppressive drug, cyclophosphamide. Neither cell-transferred normal rats nor nephritic rats without cell transfer exhibited increase in the serum level of SEAP. When the sensor cells were transferred extrarenally, elevation of serum SEAP was not observed in nephritic rats, confirming that the locally settled sensor cells responded only to local inflammation. These results suggested that, without invasive procedures like tissue biopsies, continuous monitoring of microscopic inflammation is feasible in vivo via locally created, cell-based biosensors.

Post-inflammatory glomerular remodeling is influenced by transformed mesangial cells

To identify the role of transformed mesangial cells (MC) during glomerular remodeling, anti-thymocyte-1 (Thy1) nephritis; modified Thy1 nephritis (injections of anti-Thy1 antibody four times, weekly); and Thy1 nephritis treated with signal transduction inhibitor 571 (Thy1 + STI); were analyzed. At week 1 the index of MC proliferation in modified Thy1 nephritis and in mesangiolysis in Thy1 + STI nephritis was highest among the three models. From week 4, the index of alpha-smooth muscle actin (alpha-SMA) was significantly higher in modified Thy1 nephritis than the other two models. Production of the mesangial matrix including type IV collagen was increased in modified Thy1 but inhibited in Thy1 + STI nephritis. In contrast to modified Thy1 nephritis, the capillary numbers in glomeruli recovered to normal at week 4 in Thy1, and at week 8 in Thy1 + STI nephritis. At week 12, both the adhesive and sclerotic index was significantly higher in modified Thy1 than in the other two models. Data suggest that a moderate amount of mesangial matrix results in a complete repair of capillary loops. Overproduction of the mesangial matrix retards capillary remodeling and finally induces glomerulosclerosis. Insufficient mesangial matrix delays the repair of capillary loops. In conclusion, transformed MC may influence glomerular remodeling by changing the amount of mesangial matrix.

Uninephrectomy induces progressive glomerulosclerosis and apoptosis in anti-Thy1 glomerulonephritis

Administration of the anti-Thy1 antibody in rats induces reversible glomerulonephritis resembling human mesangiolytic and mesangioproliferative diseases. The purpose of the present study was to design a model of irreversible glomerulosclerosis, using the anti-Thy1 antibody injection after uninephrectomy, and examine it, focusing on apoptosis in the process of progressive sclerotic changes. Wistar rats were divided into three groups: one-kidney groups (group I and III) and a two-kidney group (group II). All groups were injected with the anti-Thy1 antibody (OX-7) at day 0, and group I and III were uninephrectomized at day -6. Only group III rats were given a half dose of OX-7 as compared with group I and II. Rats were killed for histological examinations at days 7, 14 and 30. In group I, progressive glomerular lesions, such as glomerular adhesion to Bowman's capsule, crescent formation, and collapse of capillary tufts were observed at days 14 and 30. No significant differences were observed in the pathological findings between group I and III. There was a significantly higher number of glomerular terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling-positive cells in group I as compared to group II at days 7 and 14. Moreover, the glomerular expression of transforming growth factor-beta, heparan sulfate proteoglycan and chondroitin sulfate proteoglycan significantly increased in group I as compared to group II at days 7 and 14. Progressive glomerulosclerosis can be induced in the rat by a single injection of the anti-Thy1 antibody after unilateral nephrectomy. It is suggested that apoptosis and extracellular matrix accumulation play an important role in the development of glomerulosclerosis.

The role of lymphocytes in the experimental progressive glomerulonephritis

BACKGROUND

Glomerular accumulation of leukocytes, including lymphocytes, is a common feature in most types of glomerulonephritis. However, the role of lymphocytes in progressive glomerulonephritis has not been elucidated. We examined the role of lymphocytes in the development of progressive mesangial proliferative glomerulonephritis induced by two injections of monoclonal antibody 1-22-3 in rats.

METHODS

To elucidate the role of lymphocytes, circulating lymphocytes were depleted using specific monoclonal antibodies to rat lymphocytes prior to the induction of progressive glomerulonephritis. The effects of lymphocyte depletion on proteinuria and glomerular alterations were assessed 7 and 56 days after the induction of progressive glomerulonephritis.

RESULTS

Significant glomerular accumulation of CD4+ T cells, CD8+ T cells, and ED3+-activated macrophage were observed after the induction of glomerulonephritis. Depletion studies showed that continuous treatment with anti-CD5, anti-CD4, or anti-CD8 treatment reduced proteinuria and ameliorated the glomerular lesions on day 56. Depletion of CD4+ T cells also reduced glomerular accumulation of CD8+ T cells and ED3+-activated macrophages, and reduced glomerular expression of mRNA for interferon-gamma (INF-gamma) (63.0% in anti-CD5 and 62.3% reduction in anti-CD4). Transit lymphocyte depletion limited in early stage of progressive glomerulonephritis demonstrated that CD4+ T-cell depletion, but not anti-CD8 treatment prevented glomerular injuries 56 days after the induction of progressive glomerulonephritis.

CONCLUSION

CD4+ T cells played a central role in the development of progressive glomerulonephritis, controlling recruitment and activation of CD8+ cytotoxic cells and/or macrophages.

Retinoic acid receptor alpha and retinoid X receptor specific agonists reduce renal injury in established chronic glomerulonephritis of the rat

Retinoids, derivatives of vitamin A, inhibit mesangial cell proliferation, glomerular inflammation, and extracellular matrix deposition in acute anti-Thy1.1 glomerulonephritis (Thy-GN) of the rat. We examined a model, chronic mesangioproliferative Thy-GN (MoAb 1-22-3), which is more akin to human disease. Treatment started on day 23 when Thy-GN had already been established. Nonnephritic control and Thy-GN rats were treated orally for 67 days with vehicle or with two doses of either the retinoic acid receptor alpha-specific agonist AGN 195183 (RARalpha agonist) or the retinoid X receptor specific agonist AGN 194204 (RXR agonist). Doses of either the RARalpha or the RXR agonist significantly reduced albuminuria and normalized blood pressure during the course of treatment. The glomerulosclerosis index, glomerular cell and interstitial cell counts, and area of the interstitial space were significantly lower in nephritic rats treated with the RARalpha agonist or RXR agonist than with vehicle. The RARalpha and RXR agonist significantly reduced the infiltration of the glomerulus by macrophages. The increase in glomerular TGFbeta1 and prepro-ET(1) gene expression in vehicle-treated nephritic rats was significantly attenuated by RARalpha or RXR agonists. Glomerular expression of RXRalpha and RARalpha receptor mRNA was significantly greater in vehicle-treated nephritic rats than in nonnephritic controls. Treatment with RARalpha or RXR agonists tended to normalize retinoid-receptor gene expression. Our data indicate that both RARalpha agonists and RXR agonists reduce renal damage in rats with established chronic glomerulonephritis. Receptor-specific retinoids may provide a novel therapeutic approach for the treatment of chronic glomerulonephritis.

Blockade of TGF-beta action ameliorates renal dysfunction and histologic progression in anti-GBM nephritis

BACKGROUND

We tested whether the entire soluble extracellular domain of the human transforming growth factor-beta (TGF-beta) type II receptor, fused to the Fc portion of human immunoglobulin G (IgG1) (Tbeta-ExR) and expressed in skeletal muscles by adenovirus-mediated gene transfer (AdTbeta-ExR), can ameliorate renal dysfunction and histologic progression in a rat experimental anti-glomerular basement membrane (GBM) nephritis.

METHODS

Anti-GBM nephritis was induced in Wistar Kyoto rats by an intravenous injection of anti-rat glomerular basement membrane (GBM) sera. At day 1 (24 hours after induction), AdTbeta-ExR (1 x 109 pfu/mL) was injected into the femoral muscle in the treatment group, and an adenovirus vector-expressing bacterial beta-galactosidase (AdLacZ) was injected into the control group. Then, clinical and histologic changes were examined for 3 weeks after the induction of anti-GBM nephritis.

RESULTS

Tbeta-ExR was detected in the serum at day 7, but the serum concentration of Tbeta-ExR had decreased below the detectable level by day 14. Although blood pressure and the degree of proteinuria were similar in both groups, the deterioration of renal function was significantly blunted in the treatment group. Crescent formation and interstitial fibrosis were also ameliorated in the treatment group. These histologic improvements were accompanied by the decreased interstitial infiltration of macrophages and the decreased alpha-smooth muscle actin (alpha-SMA)-positive cells in the glomeruli and the interstitium.

CONCLUSION

This study demonstrated for the first time that the blockade of TGF-beta action by AdTbeta-ExR in the early stage of anti-GBM nephritis ameliorates the clinical and histologic progression. In addition, this study shed light on the development of a specific gene therapy for human crescentic glomerulonephritis.

Fractalkine expression and the recruitment of CX3CR1+ cells in the prolonged mesangial proliferative glomerulonephritis

BACKGROUND

We established the reversible and the prolonged models of mesangial proliferative glomerulonephritis (GN) with anti-Thy 1 antibody 1-22-3. However, the essential factors leading to the prolonged glomerular alterations have not been identified.

METHODS

The expressions of several chemokines and cytokines were compared in the reversible and the prolonged models. Expression of fractalkine and the number of the fractalkine receptor CX3CR1-positive cells in the glomeruli in the prolonged model were significantly higher than those in the reversible model. Then, the localization of fractalkine and the characteristics of CX3CR1+ cells were analyzed in glomeruli. To elucidate the significance of the fractalkine expression, we analyzed the expression in the model treated with angiotensin II receptor antagonist, candesartan.

RESULTS

Immunostaining of fractalkine was detected on endothelial cells on the fifth day, and fractalkine staining also was detected in the mesangial area on day 14. Major parts of the CX3CR1+ cells in the glomeruli were macrophages, especially ED3+ cells. Candesartan treatment ameliorated the glomerular morphological findings at six weeks after disease induction. Although the treatment did not ameliorate the morphological finding at two weeks, decreased expression of fractalkine and CX3CR1+ were already detected at two weeks in rats treated with candesartan.

CONCLUSIONS

Fractalkine expression and the recruitment of CX3CR1+ cells in glomeruli might play an important role in the development of the prolonged disease. These expressions could be predictors of the prolonged disease of the mesangial proliferative glomerulonephritis.

Retinoid receptor-specific agonists alleviate experimental glomerulonephritis

Retinoids are potent antiproliferative and anti-inflammatory compounds. We previously demonstrated that the natural pan-agonists all-trans retinoic acid (RA) and 13-cis RA efficiently preserve renal structure and function in rat mesangioproliferative glomerulonephritis. We examine effects of synthetic retinoid receptor-specific agonists 1) to identify common and receptor subtype-specific pathways in this model and 2) to characterize effects of retinoids on the renal endothelin (ET) system. Vehicle-injected control rats were compared with rats treated with daily subcutaneous injections of agonists specific for retinoid A (Ro-137410) and retinoid X (Ro-257386) receptors and the complex anti-activator protein-1 active retinoid BMS-453 7 days after induction of anti-Thy1.1 nephritis (n = 7-9/group). The different retinoids lowered glomerular ET-1 and ET type A and B receptor gene expression in control and nephritic rats with comparable efficacy. Reduction of glomerular c-Fos and GATA-2 mRNA expression levels suggests downregulation of transcription factors required for ET expression. The different retinoids were similar in their action on the glomerular capillary occlusion score, number of total glomerular cells, and glomerular infiltrating macrophage count. They differed in their ability to normalize blood pressure (Ro-257386 > BMS-453 > arotinoid), albuminuria (BMS-453 > Ro-257386 > arotinoid), and creatinine clearance (arotinoid > BMS-453 > Ro-257386). No signs of toxicity were observed. We conclude that all retinoid agonists with different subtype specificity are highly efficient in reducing renal damage and proliferation of mesangial cells. Retinoid X and A receptor-specific pathways are apparently involved in the antiproliferative, anti-inflammatory, and anti-ET action. Further studies are indicated to define the potential use of retinoid agonists in inflammatory renal disease.

Podocyte injuries exacerbate mesangial proliferative glomerulonephritis

BACKGROUND

From the observations of morphology seen in early phases of the experimental models of the irreversible mesangial proliferative glomerulonephritis, we hypothesized that podocyte injury is one of the important factors in bringing upon irreversible glomerular alterations. To verify this hypothesis, we investigated whether podocyte injury induced by puromycin aminonucleoside (PAN) injection affects the mesangial alterations of anti-Thy 1.1 glomerulonephritis.

METHODS

Female Wistar rats were injected with 0.5 mg monoclonal antibody (mAb) 1-22-3 five days after the injection of 10 mg or 5 mg/100 g body weight (BW) of puromycin aminonucleoside (PAN), and sacrificed at 7 days or 8 weeks after the mAb 1-22-3 injection.

RESULTS

Consecutive injections of 10 mg/100 g BW of PAN and mAb 1-22-3 caused the irreversible mesangial alteration with persistent proteinuria (at week 8, proteinuria 100.3 +/- 57.8 mg/24 h, matrix score 1.13 +/- 0.52, collagen type I score 2.04 +/- 0.53, mRNA for collagen type I 227 +/- 79% to the group with a single injection of 1-22-3). Although single injection of 5 mg/100 g BW of PAN was not capable of inducing abnormal proteinuria, consecutive injections of 5 mg/100 g BW of PAN and mAb 1-22-3 also caused irreversible mesangial alteration and persistent proteinuria.

CONCLUSIONS

Podocyte injury might be an important factor that exacerbates mesangial proliferation and mesangial matrix expansion. The irreversible mesangial alterations caused by consecutive injections of PAN and mAb 1-22-3 may be a novel model that could be used to analyze the mechanism of progressive mesangial alteration.

Isotretinoin alleviates renal damage in rat chronic glomerulonephritis

BACKGROUND

Retinoids, derivatives of vitamin A, have strong anti-inflammatory and antiproliferative properties. We previously demonstrated that the pan-agonists all-transretinoic acid (RA) and isotretinoin (13-cis RA) alleviate renal damage in rat acute glomerulonephritis (GN) induced by anti-Thy-1.1 mAb OX-7.

METHODS

The present study examined the effects of low dose and high dose treatment with isotretinoin in the chronic glomerulonephritis model, Thy-GN. Thy-GN was induced by a single intravenous injection of monoclonal antibody (mAb) 1-22-3 in uninephrectomized Wistar rats (N = 7 to 10 per group). Control and nephritic groups were treated with vehicle (veh), low dose isotretinoin (2 mg/kg body wt), or high dose isotretinoin (10 mg/kg body wt). The experiment was terminated 60 days after induction of Thy-GN.

RESULTS

In animals with Thy-GN, isotretinoin abrogated the increase in blood pressure and significantly reduced albuminuria. Glomerulosclerosis index, glomerular and interstitial cell counts, as well as the area of the interstitial space were significantly lower in nephritic rats treated with low and high dose isotretinoin compared to vehicle-treated nephritic controls. Treatment with isotretinoin also significantly reduced the number of glomerular and interstitial macrophages. The increase of transforming growth factor (TGF)-beta1, TGF receptor II and prepro-endothelin-1 gene expression in vehicle-treated nephritic rats was significantly attenuated by isotretinoin.

CONCLUSIONS

Treatment with isotretinoin significantly reduces glomerular and interstitial damage in rats with chronic glomerulonephritis as indicated by different functional and histological markers. Retinoids may provide a novel therapeutic option for the treatment of glomerulonephritis.

An anti-CD5 monoclonal antibody ameliorates proteinuria and glomerular lesions in rat mesangioproliferative glomerulonephritis

BACKGROUND

Increased numbers of lymphocytes have been identified in biopsy specimens of human mesangial proliferative glomerulonephritis (GN). However, the causal relationship between infiltrating T lymphocytes and mesangial changes in mesangial proliferative GN has not been previously evaluated. In this study, we elucidated the role of lymphocytes in the development of mesangial proliferative GN.

METHOD

Immunohistological and flow cytometric analyses as well as a reverse transcription-polymerase chain reaction (RT-PCR) studies were performed in monoclonal antibody (mAb) 1-22-3-induced Thy 1.1 GN. To elucidate the role of these lymphocytes, depletion studies were carried out using anti-CD8 mAb (OX-8), which depletes both CD8+ T lymphocytes and natural killer (NK) cells and anti-CD5 mAb (OX-19), which depletes both CD4+ and CD8+ T lymphocytes.

RESULTS

Immunofluorescence (IF) studies revealed that NK cells and CD4+ T lymphocytes were recruited into glomeruli. Glomerular mRNA expression for interferon-gamma, interleukin-2 (IL-2), IL-10, and perforin increased after induction of GN. Increased expressions of several chemokines, which have the potential to attract lymphocytes, were also detected. Anti-CD8 mAb treatment completely prevented the recruitment of NK cells; however, it had no protective effect on proteinuria and mesangial injury. By contrast, anti-CD5 mAb treatment suppressed the recruitment of CD4+ T lymphocytes into glomeruli and reduced proteinuria (60.4 +/- 25.7 vs. 120.0 +/- 32.3 mg/day, P < 0.05) and mesangial changes evaluated by total number of cells in glomeruli (63.2 +/- 6.0 vs. 81.4 +/- 5.9, P < 0.01) and alpha-smooth muscle actin staining score (1.4 +/- 0.2 vs. 2.2 +/- 0. 4, cf2eth P < 0.01) on day 14 after induction of GN. mRNA expression for IL-2 was significantly reduced by OX-19 treatment.

CONCLUSION

T lymphocytes participate in the development of mesangial proliferative GN.

Extracellular matrix deposition and cell proliferation in a model of chronic glomerulonephritis in the rat

BACKGROUND

Resident glomerular cell proliferation, matrix deposition and secretion of matrix metalloproteinases play a major role in the progression of chronic glomerular disease. These features were studied in a novel approach in a rat model of chronic glomerulonephritis induced by four injections of an anti-Thy 1.1 antiserum at weekly intervals.

METHODS

Chronic immune mediated mesangial injury was induced in male Sprague-Dawley rats by repeated intravenous injection of an anti-Thy 1.1 antiserum. One week after the first and fourth injection of the antiserum proteinuria was evaluated and the kidneys were removed. Immunohistology was performed for proliferating cells, monocytes and collagen type IV. Furthermore, mRNA expression of collagen type IV, TGF-beta and the matrix degrading enzyme MMP-2 as well as MMP-2 protein expression were studied.

RESULTS

Urinary protein excretion was dramatically increased after one antiserum injection and stayed elevated at a lower level after the fourth antiserum injection. After the initial induction of nephritis, 7 days following antiserum, resident glomerular cell proliferation was increased whereas with repeated injections of the antiserum cell numbers were not different from controls, as measured 1 week after the fourth injection. In contrast, extracellular matrix accumulation (collagen type IV) increased after the first antiserum injection and further increased after the fourth antiserum injection. The mRNA expression for collagen type IV increased after the first antiserum injection and showed further increase after the fourth antiserum injection. Induction of nephritis also stimulated glomerular mRNA expression of MMP-2 and TGF-beta, both of which remained at a high level after the fourth antiserum injection. Glomerular protein levels of MMP-2 also increased after the first antiserum injection and showed a further slight increase after the fourth injection.

CONCLUSION

Increased cellular proliferation is involved in an early stage of this disease, while enhanced expression of glomerular matrix and augmented mRNA and protein expression of the matrix degrading enzyme MMP-2 continue into the chronic phase, and contribute to the extensive structural remodeling process that accompanies this form of glomerular injury.

The concept of glomerular self-defense

The balance between local offense factors and defense machinery determines the fate of tissue injury: progression or resolution. In glomerular research, the most interest has been on the offensive side, for example, the roles of leukocytes, platelets, complement, cytokines, eicosanoids, and oxygen radical intermediates. There has been little focus on the defensive side, which is responsible for the attenuation and resolution of disease. The aim of this review is to address possible mechanisms of local defense that may be exerted during glomerular injury. Cytokine inhibitors, proteinase inhibitors, complement regulatory proteins, anti-inflammatory cytokines, anti-inflammatory eicosanoids, antithrombotic molecules, and extracellular matrix proteins can participate in the extracellular and/or cell surface defense. Heat shock proteins, antioxidants, protein phosphatases, and cyclin kinase inhibitors may contribute to the intracellular defense. This article outlines how the glomerulus, when faced with injurious cells or exposed to pathogenic mediators, defends itself via the intrinsic machinery that is brought into play in resident glomerular cells.

Long-term observation of glomerulonephritis induced by multiple injections with anti-Thy-1 antibody in rats

Multiple injections with a mouse monoclonal anti-rat Thy-1 antibody (five times, at weekly intervals) induced marked glomerular sclerotic lesions which are characterized by adhesion of glomerular capillaries to Bowman's capsule and persistent proteinuria in rats. Abnormal production of type I collagen and increased accumulation of type IV collagen and fibronectin were observed in these glomeruli. The glomerular expression of mRNA for these matrix components and transforming growth factor-beta1 (TGF-beta1) were markedly increased at 4 days after the last injections with anti-Thy-1 antibody, but decreased to below the levels of control rats at 5 weeks. This may be down-regulation of mRNA in mesangial cells. The glomerular sclerotic lesions were not progressive but the process of glomerular healing seemed to be retarded. The proteinuria and the glomerular adhesion were irreversible.

Suppressive effects of sairei-to on monoclonal antibody 1-22-3-induced glomerulonephritis: analysis of effective components

The effects of traditional Chinese medicine (Sairei-to) on experimental glomerulonephritis induced in rats by monoclonal antibody (mAb) 1-22-3 injection was examined. The level of proteinuria in the Sairei-to-treated group was significantly lower than that in the PBS treated group. This suppressive effect was caused by the major component of Sairei-to, Syo-saiko-to but not by another component, Gorel-san. The suppressive effect of Syo-saiko-to was identified in its components (Bupleuri radix, Pinelliae tuber and Zingiberis rhizoma), but not in the other combined components (Ginseng radix and Zizyphi fructus). Further study revealed that the suppressive effects of the combined components were mainly derived from Bupleuri radix. It was demonstrated that the actual active ingredient is probably Saikosaponin-d. Light microscopy revealed that Sairei-to and its effective components suppressed the proliferation of mesangial cells and mesangial matrix expansion. Semiquantitative morphological studies of glomerular lesions on the eighth day showed that Syo-saiko-to and its combined components (Bupleuri radix, Zingiberis rhizoma and Pinelliae tuber) suppressed mesangial matrix expansion significantly compared with phosphate-buffered saline control groups (matrix score: 28.0 +/- 19.1 vs 102.3 +/- 14.1; 30.9 +/- 30.1 vs 102.3 +/- 14.1, P < 0.005, respectively). It was concluded that Saikosaponin-d, as well as Bupleuri radix, Syo-saiko-to and Sairei-to can suppress proteinuria and morphological changes in the rat glomerulonephritis model induced by mAb 1-22-3.

Thy-1-mediated phosphatidylinositol turnover in cultured rat glomerular mesangial cell

Thy-1 glycoprotein is expressed in rat glomerular mesangial cells, and anti-Thy-1 nephritis induced by anti-Thy-1 antibodies is a model of human renal diseases. In this study, we examined Thy-1-mediated biological reactions in cultured rat glomerular mesangial cells utilizing two anti-Thy-1 monoclonal antibodies (mAbs), 1-22-3 and OX-7. Incubation of the cells with these mAbs resulted in increased inositol trisphosphate (IP3) levels. The rise in IP3 produced by mAb 1-22-3 was greater than that produced by mAb OX-7 at the same dose. Incubation of mesangial cells with these mAbs resulted in an increase in the intracellular free calcium concentration ([Ca2+]i). mAb 1-22-3 induced a sustained increase in [Ca2+]i, while that induced by mAb OX-7 lasted 1-2 min, then decreased to the basal level. An transient increase in [Ca2+]i was also observed in Ca(2+)-free medium, indicating that these [Ca2+]i increases are due to release of Ca2+ from internal stores by IP3 without calcium flux across cell membrane. When cells were pretreated with protein tyrosine kinase (PTK) inhibitors (herbimycin A or genistein), Thy-1-mediated increases in [Ca2+]i were inhibited. These data suggest that Thy-1 induces the production of IP3 (including inositol 1,4,5-triphosphate, an intracellular Ca(2+)-releasing factor) and that PTKs may contribute to the Thy-1-mediated elevation of [Ca2+]i which presumably results from phospholipase C activation following Thy-1-mediated signaling in rat mesangial cells.

Mesangial cell-derived transforming growth factor-beta 1 reduces macrophage adhesiveness with consequent deactivation

Adhesion of macrophages is a crucial event that determines the number and function of macrophages at inflammatory sites. The aim of this study was to elucidate the role of mesangial cells in the regulation of macrophage adhesiveness. J774.2 macrophages were suspended in serial dilutions of mesangial cell conditioned medium (MC medium) and seeded on plastic tissue culture plates. MC medium did not affect the initial adhesion of macrophages but induced subsequent detachment in a concentration-dependent manner. A similar effect was observed when macrophages were plated on plastic coated with laminin, collagen type IV or Matrigel. The reduced adhesiveness was reversible, and cell viability was unaffected by MC medium, indicating that the effect is not due to cytotoxicity. Conditioned media from fibroblastic, epithelial and endothelial cell lines did not induce macrophage detachment. To identify the active component in MC medium, we examined the involvement of transforming growth factor-beta 1 (TGF-beta 1) in the process. Mesangial cells constitutively expressed TGF-beta 1 mRNA, and MC medium contained the active form of TGF-beta 1. Exogenously added TGF-beta 1 induced macrophage detachment in a dose-dependent manner, and an anti-TGF-beta 1 neutralizing antibody partially abolished the activity of MC medium, indicating the involvement of TGF-beta 1 as an active component. Compared to adherent cells, detached macrophages showed reduced mitogenic activity and blunted induction of IL-1 beta and IL-6 in response to lipopolysaccharide. These data demonstrate that TGF-beta 1 is a mesangial cell-derived factor that impairs adhesiveness of macrophages and confers blunted responses to a specific stimulus. These findings suggest one potential mechanism for macrophage clearance from inflamed glomeruli.

Progressive renal lesions induced by administration of monoclonal antibody 1-22-3 to unilaterally nephrectomized rats

A new animal model of progressive glomerulosclerosis was developed by administering a single i.v., injection of MoAb 1-22-3 to unilaterally nephrectomized rats. Renal morphological analysis revealed that glomerular lesions characterized by mesangial cell proliferation and mesangial matrix expansion were induced in about 95% of the glomeruli. Approximately 20% of the glomeruli of the unilaterally nephrectomized rats showed sclerosis or segmental sclerosis by week 6 after MoAb injection and crescent formation was observed in some glomeruli (ca 4%). Cellular infiltration was also noted in some parts of the interstitium. Increased expression of transforming growth factor-beta (TGF-beta) was observed in the unilaterally nephrectomized rats treated with MoAb 1-22-3, but we could not demonstrate pathological involvement of platelet-derived growth factor (PDGF), even though early-stage mesangial cell proliferation was observed. The mechanism of mesangial cell proliferation in this model remains to be elucidated. The relatively short period of time needed to induce the sclerotic changes in considered to be a great advantage of this model for clarifying the mechanisms involved in the chronic progression of mesangial proliferative glomerulonephritis.

Gene transfer into the rat renal glomerulus via a mesangial cell vector: site-specific delivery, in situ amplification, and sustained expression of an exogenous gene in vivo

To evaluate the pathophysiological function of specific molecules in the renal glomerulus, selective, sustained, and modifiable expression of such molecules will be required. Towards achieving this end, we devised a gene transfer system using the glomerular mesangial cell as a vector for gene delivery. A reporter gene which encodes bacterial beta-galactosidase was introduced into cultured rat mesangial cells, and the stable transfectants were transferred into the rat kidney via the renal artery, leading to selective entrapment within the glomeruli. In the normal kidney, the reporter cells populated into 57 +/- 13% of glomeruli site specifically, and the expression of beta-galactosidase was sustained for 4 wk and declined thereafter. Within the glomerulus, some of the reporter cells remained in the glomerular capillaries, while others repopulated the mesangial area and, in part, extended their cytoplasmic processes toward the surrounding capillaries. When the cells were transferred into glomeruli subjected to transient mesangiolysis induced by monoclonal antibody 1-22-3, in situ expression of beta-galactosidase was amplified 7-12-fold, and the enhanced level of expression continued for up to 8 wk. The mesangial cell vector system thus achieves site-specific delivery of an exogenous gene into the glomerulus and is amenable to in situ amplification and sustained expression by preconditioning of the target site.

Sustained expression of TGF-beta 1 underlies development of progressive kidney fibrosis

We found that TGF-beta 1 expression and increased matrix production is transient and self-limited in nephritic glomeruli from rats with acute, reversible glomerulonephritis induced by a single injection of an antibody reactive with glomerular mesangial cells. In contrast, in rats given a second antibody injection, one week later, the glomerular expression of TGF-beta 1 mRNA and TGF-beta 1 protein remained elevated through 18 weeks and was associated with a large infiltration of mononuclear cells, with staining features of fibroblastic/myofibroblastic cells, strongly expressing TGF-beta 1 in the tubulointerstitium of the kidney. By 18 weeks kidneys from animals receiving two antibody injections showed glomerulosclerosis and tubulointerstitial fibrosis with striking deposition of collagens type I and III, whereas kidney tissue from animals given one antibody injection was indistinguishable from normal control. The histological changes were accompanied by persistent proteinuria and elevated levels of blood urea nitrogen. Extracellular matrix markers of TGF-beta 1 activity, a special isoform of fibronectin, tenascin, biglycan and plasminogen activator inhibitor-1, were significantly elevated in kidneys undergoing fibrosis. These data suggest that sustained TGF-beta 1 expression contributes to the development of progressive kidney fibrosis.