Sepsis-Induced Alteration in T-Cell Ca2+ Signaling in Neonatal Rats

Abstract

Sepsis-induced suppression in T-cell proliferation follows deranged Ca²⁺ signaling in adult rats. In preliminary studies, we observed suppression in T-cell proliferation in septic neonatal rats as well. In this study, we assessed splenic T-cell cytosolic Ca²⁺ concentration, [Ca²⁺]_i, as its elevation plays an important role in T-cell proliferation. Also, we investigated the role of PGE₂ in sepsis-related changes in T-cell [Ca²⁺]_i in animals pretreated with cyclooxygenase-1 (COX-1) inhibitor (resveratrol) and cyclooxygenase-2 (COX-2) inhibitor (NS-398). Sepsis was induced in 15-day-old rat pups by intraperitoneal implantation of fecal pellets containing Escherichia coli and Bacteroides fragilis. The sham group consisted of pups implanted with sterile fecal pellets. Septic and sham pups were sacrificed 24 h after implantation and their spleens were removed. The spleens from sham and septic pups, along with spleens from unoperated control pups, were processed for single cell suspensions, and T cells were isolated using nylon wool columns. Fura-2 fluorophotometry was employed for the measurement of [Ca²⁺]_i (in nM units) in T cells stimulated with concanavalin A (ConA). Our results show that ConA-mediated T-cell [Ca²⁺]_i response is significantly suppressed in septic neonatal rats. Pretreatment of pups with COX-2, but not COX-1 inhibitor, prevented the decrease in the [Ca²⁺]_i response. These findings suggest that PGE₂ might induce the attenuation in T-cell Ca²⁺ signaling during sepsis in neonatal rats.