Critical role of the calpain/calpastatin balance in acute allograft rejection

Abstract

Rejection of solid organ allograft involves alloreactive T-cell expansion. The importance of NF-jB and NFAT in this process is underscored by the therapeutic efficacy of immunosuppressive agents, which target the two transcription factors. Since calpains, calciumactivated proteases, are involved in the activation of NF-jB and NFAT, we investigated the role of calpains in allograft rejection. In human transplant kidneys undergoing acute or chronic rejection, we show an increased expression of CAPN 1 gene encoding l-calpain, associated with a marked expression of l-calpain, mainly in infiltrating T cells. To address the role of calpain in rejection, we used a skin transplant model in transgenic mice expressing high levels of calpastatin, a calpain-specific inhibitor. We show that calpain inhibition extended skin allograft survival, from 11 to 20 days. This delay was associated with a limitation in allograft infiltration by T cells. In vitro, calpain inhibition by calpastatin transgene expression limited dramatically T-cell migration but, unexpectedly, increased slightly T-cell proliferation. Amplification of IL-2 signaling via the stabilization of IL-2R common c-chain provided an explanation for the proliferation response. This is the first study establishing that calpain inhibition delays allograft rejection by slowing down T-cell migration rather than proliferation.Key words: Allograft . Calpain . Calpastatin . T cells IntroductionSolid organ transplantation represents an important means of treating end stage organ failure. However, this strategy is limited by the immune response mounted by the recipient against donor tissue. Acute allograft rejection involves T cells of the adaptive immune system in addition to cells of the innate immune system [1]. T-cell receptor (TCR) engagement in naïve T cells initiates changes in gene expression that are essential for the generation of effector T cells. They require the activation of transcription factors, primarily NF-kB and NFAT [2,3]. TCR/CD28-induced NF-kB activation characteristically elicits the expression of both IL-2 and IL-2 receptor a chain together with the antiapoptotic molecule Bcl-x L [2]. NFAT, which is activated by the calmodulin-dependent phosphatase calcineurin, is also required for the expression of the IL-2 gene through its interaction with proteins of the AP1 family of transcription factors [3]. Given the importance of these two pathways in the generation à These authors contributed equally to this work. Eur. J. Immunol. 2011. 41: 473-484 DOI 10.1002 Leukocyte signaling 473 of effector T cells, a number of different pharmacological inhibitors of NF-kB and/or calcineurin/NFAT are currently used as immunosuppressive agents in transplantation, including steroids, cyclosporin A and tacrolimus (FK-506) [4]. Calpains are calcium-activated neutral cysteine proteases [5]. Two major isoforms, calpain m (or I) and calpain m (or II), which require micromolar and millimolar Ca 21 concentrations for activity, respectively, are ubiquitously expressed, whereas the ...

Icaritin inhibits T cell activation and prolongs skin allograft survival in mice

“…Also, there are possibilities for it to suppress T cell activation by suspending ERK and Jak-STAT pathway or inducing apoptosis based on its pharmacological effects independent on estrogen [8][9][10][11]. Recently, calpastatin, even slightly increasing T cell proliferation, was shown to extend skin graft survival by slowing down T cell migration, which provides another idea to explore its mechanism on transplantation protection [41].…”

RNA sequencing of chorionic villi from recurrent pregnancy loss patients reveals impaired function of basic nuclear and cellular machinery

“…Among these, C3 and PLTP have also literature evidence for the involvement of RPL and/or function at the feto-maternal interface185859. For CAPNS1 a role in acute allograft rejection has been reported60.…”

Calpains Released by T Lymphocytes Cleave TLR2 To Control IL-17 Expression

“…Intracellular calpain activity was determined in spleen lymphocytes or PBMCs (3 3 10 6 ), as previously described (9). For measuring calpain activity in the extracellular milieu, isolated spleen lymphocytes or PBMCs were cultured in 24-well tissue culture dishes in RPMI 1640 medium (3 3 10 6 cells in 500 ml).…”

“…T lymphocyte activation after TCR/CD3 complex engagement increases calpain expression (5). In turn, calpain activity is involved in T lymphocyte migration (6), secretion of IL-2 and cell surface expression of IL-2R subunit a (CD25) (7), secretion of IFN-g and Th1 commitment (8), and secretion of IL-17 and Th17 commitment (9).…”