Inflammasome Activation Involved in the Early Inflammation Following Intestinal Transplantation: Implications in Acute Rejection

Introduction: Dysfunction of intestinal mucosal barrier plays an important role in alloreactive complications such as rejection, infection, and inflammation following intestinal transplantation (ITx). Inflammasome studies are of newly emerging interest due to their crucial regulatory capacity in intestinal homeostasis. We hypothesized that inflammasome-associated genes were differentially expressed between the rejecting and non-rejecting allografts prior to the onset of rejection. Methods: Serial ITx biopsy samples from 5 healthy and 9 rejecting patients were analyzed. Specifically, we studied the transcript abundance in rejecting allografts at baseline vs. healthy allografts at baseline (Test A) and rejecting allografts vs. healthy > 6 months’ allografts (Test B). The baseline time points are defined as samples obtained intraoperatively during transplantation ranging through five weeks postoperatively. We utilized RNA sequencing (RNA-seq) to evaluate the gene expression differences within allografts that subsequently experienced rejection. The false discovery rate (FDR) was employed to determine significance thresholds and quantify the overall error rate when the group comparison was analyzed. Results: We found 1,541 DEGs (FDR <0.01 and a fold change (FC) expression greater than 2.0) in Test A and 725 DEGs in Test B, respectively. Critically, we found a significantly higher transcript abundance of host inflammasome-related genes, including NLRP3 (NOD-like receptor (NLR) family pyrin domain containing 3), NLRC4 (NLR Family CARD Domain Containing 4), SOCS3 (Suppressor of Cytokine Signaling 3) and NOD2 both at baseline and during rejection. Interestingly, we identified NLRP12 was highly elevated in rejecting allografts but not at baseline. NLRP12 is known to play a negative regulator of inflammation by suppressing key components of the canonical and noncanonical NF-κB signaling. We also observed that the expression of AIM2 (Absent in Melanoma 2) was significantly altered in only rejecting allografts at baseline. Using a gene-list of significant differentially expressed gene (DEG), we observed enrichment of transcription factor NOD2-associated gene set during rejection. Conclusions: We performed a transcriptomics analysis using RNA-seq and identified dynamic transcriptomic differences over time. Our results demonstrated a shared continuous upregulation of pro-inflammatory gene signatures related to NOD2-dependent NLRP3 inflammasome activation pathways. This finding warrants further investigations for novel therapeutic approaches for ITx patients.