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Protein phosphatase 2A activation promotes heart transplant acceptance in mice

ABSTRACT: Background: While heart transplantation is the standard treatment for heart failure, both acute and chronic transplant rejection frequently occur. Since the modulation of protein phosphatase PP2A activity is critical for tissue and organ homeostasis under physiological and pathophysiological conditions, PP2A may also affect the ability to tolerate transplanted organs. Here we demonstrate that administration of a novel class of small molecule activators of PP2A (SMAPs) prolonged cardiac allograft survival in a mouse heterotopic heart transplantation model. Mechanistically, SMAPs effectively suppressed the inflammatory immune response while increasing Treg population in the allografts, findings corroborated by functional analysis of RNAseq data derived from Tregs of treated splenic tissue. Importantly, SMAPs further prolonged CTLA4-Ig (an immunosuppressive agent utilized in organ transplantation)-induced cardiac rejection tolerance and extended allograft survival. SMAPs also strongly mitigated cardiac allograft vasculopathy as evidenced by a marked reduction of neointimal hyperplasia and smooth muscle cell proliferation. Mechanistic studies implicate SMAPs elicited suppression of MEK/ERK pathways as a unifying mechanism for the aforementioned effects in Tregs and SMCs. These findings highlight the potential of PP2A activation in improving alloengraftment in heart transplantation and add knowledge to the phosphatase driven regulation of the immune system in the context of organ transplantation.

ORGANISM(S): Mus musculus

PROVIDER: GSE236206 | GEO | 2023/07/20

REPOSITORIES: GEO

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Project description:BACKGROUND: Assessment of gene expression in peripheral blood may provide a noninvasive screening test for allograft rejection. We hypothesized that changes in peripheral blood expression profiles would correlate with biopsy-proven rejection and would resolve after treatment of rejection episodes. METHODS AND RESULTS: We performed a case-control study nested within a cohort of 189 cardiac transplant patients who had blood samples obtained during endomyocardial biopsy (EMB). Using Affymetrix HU133A microarrays, we analyzed whole-blood expression profiles from 3 groups: (1) control samples with negative EMB (n=7); (2) samples obtained during rejection (at least International Society for Heart and Lung Transplantation grade 3A; n=7); and (3) samples obtained after rejection, after treatment and normalization of the EMB (n=7). We identified 91 transcripts differentially expressed in rejection compared with control (false discovery rate <0.10). In postrejection samples, 98% of transcripts returned toward control levels, displaying an intermediate expression profile for patients with treated rejection (P<0.0001). Cluster analysis of the 40 transcripts with >25% change in expression levels during rejection demonstrated good discrimination between control and rejection samples and verified the intermediate expression profile of postrejection samples. Quantitative real-time polymerase chain reaction confirmed significant differential expression for the predictive markers CFLAR and SOD2 (UniGene ID No. 355724 and No. 384944). CONCLUSIONS: These data demonstrate that peripheral blood expression profiles correlate with biopsy-proven allograft rejection. Intermediate expression profiles of treated rejection suggest persistent immune activation despite normalization of the EMB. If validated in larger studies, expression profiling may prove to be a more sensitive screening test for allograft rejection than EMB. Experiment Overall Design: Case- control study with three groups. Patients with rejection (r1-r7), follow-up samples after treatment of rejection (post1-7), and controls with no rejection (con1-7)

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Protein phosphatase 2A activation promotes heart transplant acceptance in mice

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