sirolimus and Glomerulonephritis--Membranous

Amelioration of podocyte injury, which can lead to podocyte detachment, is the target of therapeutic intervention in glomerular diseases. Since podocytes are terminally differentiated cells with little or no proliferative ability, their loss results in permanent glomerular dysfunction. In immune-mediated glomerular diseases, a variety of immunomodulatory agents are used to maintain podocytes by systemic immunosuppression, which indirectly ameliorates podocyte injury by interrupting the input of immunological stress. However, in contrast to the indirect therapeutic strategy mediated by immunosuppression, recent data now suggest that immunomodulatory agents directly act on podocytes in an agent-dependent manner. Indeed, the therapeutic efficacy of immunomodulatory agents is, at least in part, derived by the direct action on podocytes. In this review, we discuss the molecular targets and mechanisms by which immunomodulatory agents alleviate podocyte injury and examine their clinical significance.

Topics: Abatacept; Adjuvants, Immunologic; Calcineurin Inhibitors; Everolimus; Glomerulonephritis; Glomerulonephritis, Membranous; Glomerulosclerosis, Focal Segmental; Glucocorticoids; Humans; Immunologic Factors; Immunosuppressive Agents; Levamisole; Mycophenolic Acid; Nephrosis, Lipoid; Nephrotic Syndrome; Podocytes; Ribonucleosides; Rituximab; Sirolimus; Tacrolimus; TOR Serine-Threonine Kinases

Chronic allograft nephropathy (CAN) represents the main cause of renal allograft loss after 1 yr of transplantation. Calcineurin inhibitor (CNI) use is associated with increased graft expression of profibrotic cytokines, whereas rapamycin inhibits fibroblast proliferation. The aim of this randomized, prospective, open-label, single-center study was to evaluate the histologic and clinical effect of rapamycin on biopsy-proven CAN. Eighty-four consecutive patients who had biopsy-proven CAN and received a transplant were randomized to receive either a 40% CNI reduction plus mycophenolate mofetil (group 1; 50 patients) or immediate CNI withdrawal and rapamycin introduction with a loading dose of 0.1 mg/kg per d and a maintaining dose aiming at through levels of 6 to 10 ng/ml (group 2; 34 patients). The follow-up period was 24 mo. At the end of follow-up, 25 patients (group 1, 10 patients; group 2, 15 patients) underwent a second biopsy. CAN lesions were graded according to Banff criteria. alpha-Smooth muscle actin (alpha-SMA) protein expression was evaluated in all biopsies as a marker of fibroblast activation. Graft function and Banff grading were superimposable at randomization. Graft survival was significantly better in group 2 (P = 0.0376, chi2 = 4.323). CAN grading worsened significantly in group 1, whereas it remained stable in group 2. After 24 mo, all group 1 biopsies showed an increase of alpha-SMA expression at the interstitial and vascular levels (P < 0.001); on the contrary, alpha-SMA expression was dramatically reduced in group 2 biopsies (P = 0.005). This study demonstrates that rapamycin introduction/CNI withdrawal improves graft survival and reduces interstitial and vascular alpha-SMA expression, slowing down the progression of allograft injury in patients with CAN.

Topics: Biopsy, Needle; Chronic Disease; Dose-Response Relationship, Drug; Drug Administration Schedule; Female; Glomerulonephritis, Membranous; Graft Rejection; Graft Survival; Humans; Immunohistochemistry; Immunosuppressive Agents; Kidney Failure, Chronic; Kidney Transplantation; Male; Probability; Prognosis; Proportional Hazards Models; Prospective Studies; Single-Blind Method; Sirolimus; Transplantation Immunology; Transplantation, Homologous

Membranous nephropathy (MN) is the most common cause of nephrotic syndrome in adults without diabetes. Primary MN has been associated with circulating antibodies against native podocyte antigens, including phospholipase A2 receptor (PLA2R); however, precision therapy targeting the signaling cascade of PLA2R activation is lacking. Both PLA2R and the mammalian target of rapamycin (mTOR) exist in podocytes, but the interplay between these two proteins and their roles in MN warrants further exploration. This study aimed to investigate the crosstalk between PLA2R activation and mTOR signaling in a human podocyte cell line. We demonstrated that podocyte apoptosis was induced by Group IB secretory phospholipase A2 (sPLA2IB) in a concentration- and time-dependent manner via upregulation of phosphoinositide 3-kinase (PI3K), protein kinase B (AKT), and mTOR, and inhibited by rapamycin or LY294002. Furthermore, aberrant activation of the PI3K/AKT/mTOR pathway triggers both extrinsic (caspase-8 and caspase-3) and intrinsic (Bcl-2-associated X protein [BAX], B-cell lymphoma 2 [BCL-2], cytochrome c, caspase-9, and caspase-3) apoptotic cascades in podocytes. The therapeutic implications of our findings are that strategies to reduce PLA2R activation and PI3K/AKT/mTOR pathway inhibition in PLA2R-activated podocytes help protect podocytes from apoptosis. The therapeutic potential of rapamycin shown in this study provides cellular evidence supporting the repurposing of rapamycin for MN treatment.

Topics: Apoptosis; Apoptosis Regulatory Proteins; Cell Line; Enzyme Activation; Glomerulonephritis, Membranous; Humans; MTOR Inhibitors; Phosphatidylinositol 3-Kinase; Podocytes; Proto-Oncogene Proteins c-akt; Receptors, Phospholipase A2; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases

Topics: Aged; Biopsy, Needle; Everolimus; Female; Follow-Up Studies; Glomerulonephritis, Membranous; Humans; Immunohistochemistry; Immunosuppressive Agents; Kidney Function Tests; Sarcoma, Kaposi; Severity of Illness Index; Sirolimus; Skin Neoplasms; Treatment Outcome

The podocyte functions as a glomerular filtration barrier. Autophagy of postmitotic cells is an important protective mechanism that is essential for maintaining the homeostasis of podocytes. Exploring an in vivo rat model of passive Heymann nephritis and an in vitro model of puromycin amino nucleotide (PAN)-cultured podocytes, we examined the specific mechanisms underlying changing autophagy levels and podocyte injury. In the passive Heymann nephritis model rats, the mammalian target-of-rapamycin (mTOR) levels were upregulated in injured podocytes while autophagy was inhibited. In PAN-treated podocytes, mTOR lowered the level of autophagy through the mTOR-ULK1 pathway resulting in damaged podocytes. Rapamycin treatment of these cells reduced podocyte injury by raising the levels of autophagy. These in vivo and in vitro experiments demonstrate that podocyte injury is associated with changes in autophagy levels, and that rapamycin can reduce podocyte injury by increasing autophagy levels via inhibition of the mTOR-ULK1 pathway. These results provide an important theoretical basis for future treatment of diseases involving podocyte injury.

Topics: Analysis of Variance; Animals; Autophagy; Autophagy-Related Protein 7; Blotting, Western; Fluorescent Antibody Technique; Glomerulonephritis, Membranous; Homeostasis; Male; Podocytes; Rats; Rats, Sprague-Dawley; RNA Interference; RNA, Small Interfering; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases; Ubiquitin-Activating Enzymes

Recent studies have shown a beneficial effect of rapamycin in passive and active Heymann Nephritis (HN). However, the mechanisms underlying this beneficial effect have not been elucidated.. Passive Heymann Nephritis (PHN) was induced by a single intravenous infusion of anti-Fx1 in 12 Sprague-Dawley male rats. One week later, six of these rats were commenced on daily treatment with subcutaneous rapamycin 0.5 mgr/kg (PHN-Rapa). The remaining six rats were used as the proteinuric control group (PHN) while six more rats without PHN were given the rapamycin solvent and served as the healthy control group (HC). All rats were sacrificed at the end of the 7th week.. Rapamycin significantly reduced proteinuria during the autologous phase of PHN. Histological lesions were markedly improved by rapamycin. Immunofluorescence revealed attenuated deposits of autologous alloantibodies in treated rats. Untreated rats showed decreased glomerular content of both nephrin and podocin whereas rapamycin restored their expression.. Rapamycin monotherapy significantly improves proteinuria and histological lesions in experimental membranous nephropathy. This beneficial effect may be mediated by inhibition of the alloimmune response during the autologous phase of PHN and by restoration of the normal expression of the podocyte proteins nephrin and podocin.

Topics: Animals; Disease Models, Animal; Gene Expression Regulation; Glomerulonephritis, Membranous; Intracellular Signaling Peptides and Proteins; Kidney Glomerulus; Male; Membrane Proteins; Proteinuria; Rats; Sirolimus

The effects of rapamycin (RAPA) were examined in active Heymann nephritis (HN), an experimental model of human membranous nephropathy (MN). Current opinion on the therapy of MN is controversial, and medications used for its treatment have not yielded the expected results.. In a two-part study, we examined the effects of RAPA (1.5 mg/kg/day) during the induction phase of HN and on the evolving disease. In both parts, control groups of immunized rats not treated with RAPA and control groups of unimmunized rats were observed and sacrificed concurrently with the treated groups.. During the induction phase no significant changes in proteinuria were observed in the group treated with RAPA, in comparison to those in the untreated group (p < 0.001). During the evolving disease RAPA significantly lowered proteinuria (p < 0.001). The characteristic pathohistologic changes and IgG depositions along the glomerular basement membrane were considerably diminished, and infiltration of CD8+ cells completely prevented.. RAPA demonstrated beneficial effects on disease progression, given either in the induction phase or during evolving HN. It would be desirable to investigate the effect of RAPA on patients with MN.

Topics: Animals; CD8-Positive T-Lymphocytes; Glomerular Basement Membrane; Glomerulonephritis, Membranous; Immunosuppressive Agents; Male; Proteinuria; Rats; Rats, Wistar; Sirolimus

Proteinuria is a risk factor for progression of chronic renal failure. A model of proteinuria-associated tubulointerstitial injury was developed and was used to examine the therapeutic effect of rapamycin. Two studies were performed. In study A, proteinuric rats were given sheep anti-Fx1A to induce experimental membranous nephropathy; control rats received normal sheep serum. Four weeks later, groups were subdivided and underwent laparotomy alone (two kidneys), nephrectomy alone (one kidney), or nephrectomy with polectomy (0.6 kidney). Renal function and morphology were evaluated 4 wk later. Whereas control rats never developed proteinuria, anti-Fx1A induced severe proteinuria. Proteinuria was unaffected by renal mass reduction. Proteinuric rats developed tubulointerstitial disease that was most severe in rats with 0.6 kidneys. Renal function (GFR) was reduced by loss of renal mass and was reduced further in proteinuric rats with 0.6 kidneys. In study B, the effect of rapamycin on the expression of candidate proinflammatory and profibrotic genes and the progression of proteinuria-associated renal disease were examined. All rats received an injection of anti-Fx1A and were nephrectomized and then divided into groups to receive rapamycin or vehicle. Gene expression, renal morphology, and GFR were evaluated after 4, 8, and 12 wk. Rapamycin reduced expression of the proinflammatory and profibrotic genes (monocyte chemotactic protein-1, vascular endothelial growth factor, PDGF, TGF-beta(1), and type 1 collagen). Tubulointerstitial inflammation and progression of interstitial fibrosis that were present in vehicle-treated rats were ameliorated by rapamycin. Rapamycin also completely inhibited compensatory renal hypertrophy. In summary, rapamycin ameliorates the tubulointerstitial disease associated with chronic proteinuria and loss of renal mass.

Topics: Animals; Cytokines; Disease Models, Animal; Fibrosis; Glomerulonephritis, Membranous; Immunosuppressive Agents; Kidney; Male; Proteinuria; Rats; Rats, Sprague-Dawley; Sirolimus