Postoperative ileus (POI) is a well-known complication of abdominal surgery. Patients with POI usually experience nausea, bloating, and an inability to tolerate transoral feeding [1]. POI progression is divided into early neurogenic and late inflammation phases. Surgical trauma-induced adrenergic nerve activation dominates the neurogenic phase of inhibition of motility. Stimulation of nociceptors and mechanoreceptors ceases at abdominal closure. Inflammation dominates the progression of POI for 2–4 days postoperatively.

Numerous studies have elucidated the role of myeloid cells in POI [2], [3], [4]. A recent study observed focal T-cell aggregation in the duodenum of patients with functional dyspepsia [5]. Moreover, memory Th1 cells are vital for the progression of POI [6]. However, the mechanism underlying lymphocyte activation after mechanical stimulation in POI remains enigmatic.

Surgery may lead to unavoidable tissue damage and release of damage-associated molecular patterns (DAMPs), such as dsDNA, nicotinamide adenine dinucleotide (NAD), and adenosine triphosphate (ATP) [7]. DAMPs are recognized by pattern recognition receptors (PRRs), which trigger inflammatory cascades. Myeloid cells activated by DAMPs facilitate the upregulation of inflammation-related genes, including interleukin-6 (IL-6), cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS) [8]. Previous studies have reported the effects of DAMPs on lymphocytes. Extracellular ATP can facilitate calcium influx and enhance IL-2 production in activated T cells [9]. High mobility group box 1 (HMGB1) is crucial in controlling the CXCL11-induced accumulation of CD8+ T cells in the tumor microenvironment [10].

NAD is mainly located in the mitochondria and cytoplasm and performs its biological activity under physiological conditions [11]. During hypoxia, stress, and acute inflammation, NAD is released into the extracellular matrix [12] and recognized as one of the components of DAMPs. A high concentration of extracellular NAD agitates the purinergic receptor P2X7R. As a calcium channel, P2X7R activated by NAD triggers calcium influx and activation of related in-cell calcium signals. P2X7R signaling has also been reported to mediate the activation of the NLRP3 inflammasome, resulting in cytokine release (including IL-1β, TNFα, and IL-6) [13]. A P2X7R inhibitor was reported to improve gastrointestinal (GI) motility and ameliorate local inflammation in mice with POI; however, the detailed mechanism remains unelucidated [14].

In present study, we confirmed the release of DAMPs after surgery by measuring the concentration of NAD in abdomen and tissue. Furthermore, NAD caused impaired gastrointestinal (GI) transit independently of surgery. P2X7R was highly expressed in intestinal T lymphocytes compared with lymph nodes. Exogenous NAD promoted the expression of IFN-γ and TNF-α in intestinal T lymphocytes via the P2X7R signal. Our study unveiled the proinflammatory mechanism of NAD to intestinal residential T cells via the P2X7R pathway, which may provide a clue for the treatment of POI.