Abstract
ObjectivesCombination therapy with mycophenolate mofetil, tacrolimus and steroids are effective in achieving complete remission in lupus nephritis (LN). Combination therapy uniquely downregulated caspase-1 compared with monotherapies, which can cleave gasdermin D (GSDMD) and was recently identified as the pyroptosis executioner. We therefore investigated whether combination therapy enabled the suppression of caspase-1/GSDMD-mediated pyroptosis in LN.MethodsExpression and activation of GSDMD were detected in kidney specimens of the human and mouse with LN using immunohistochemical staining and immunoblotting. Primary podocytes isolated from MRL/lpr mice were incubated with LPS+ATP, and pretreated with monotherapy or combination therapy. Inhibition of caspase-1/GSDMD-induced pyroptosis by combination therapy were assessed in MRL/lpr mice and human specimens. Pyroptosis was examined using a FAM caspase-1 kit and flow cytometry. The correlation between pyroptosis in peripheral blood and the systemic lupus erythematosus disease activity index (SLEDAI) was analyzed.ResultsKidney tissue specimens from LN patients and mice exhibited greatly increased expression levels and cleavage of GSDMD. In cultured podocytes, combination treatment significantly suppressed the activation of NLRP3 and caspase-1 and reduced GSDMD N-terminal levels. Combination therapy repressed disease progression through inhibition of caspase-1/GSDMD-mediated pyroptosis in both humans and MRL/lpr mice. Caspase-1/PI positive cell numbers in peripheral blood were positively correlated with SLE-DAI. LN patients with complete remission and partial remission had remarkably reduced caspase-1/PI positive cell numbers compared to baseline. Ac-FLTD-CMK, a GSDMD-derived inhibitor, prevented the development of LN.ConclusionCombination therapy suppressed caspase-1/GSDMD-mediated pyroptosis in vitro and in vivo and reduced disease progression.
Highlights
Lupus nephritis (LN) is kidney inflammation arising as a consequence of the autoimmune disease systemic lupus erythematous (SLE)
To investigate whether gasdermin D (GSDMD) contributed to the pathogenesis of LN, we first tested the protein expression level of GSDMD in kidney specimens taken from LN patients
Immunohistochemical analysis revealed remarkable increased expression levels of GSDMD in kidney biopsy specimens taken from LN patients with type IV, V, Combination Treatment Suppressed Caspase-1/GSDMD-Induced Pyroptosis in MRL/lpr Mice
Summary
Lupus nephritis (LN) is kidney inflammation arising as a consequence of the autoimmune disease systemic lupus erythematous (SLE). Combination therapy with mycophenolate mofetil (MMF), calcineurin inhibitors (CNI) and steroids produces complementary effects and minimizes toxicity [2]. This therapy is recommended as the initial treatment for LN and produces better efficacy and more complete remission compared with intravenous cyclophosphamide (IVCY) and steroids [3,4,5]. One of 45 downregulated genes that is uniquely modulated by combination therapy is caspase-1 [6] It is activated by inflammasomes, which are multiprotein oligomers comprised of NLRP3, pro-caspase-1 and apoptosis-associated speck like protein (ASC), with an integrated caspase affinity domain. The NLRP3 inflammasome drives autoinflammatory disorders by activating caspase-1, initiating the generation of proinflammatory cytokines e.g. IL-1b, which is known to trigger podocyte dysfunction in LN [7,8,9]
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