Involvement of protein kinases in the potentiation of lipopolysaccharide-induced inflammatory mediator formation by thapsigargin in peritoneal macrophages

Abstract

We have explored the regulatory roles played by Ca2+-dependent signaling on lipopolysaccharide (LPS)-induced nitric oxide (NO), prostaglandin E2 (PGE2), tumor necrosis factor α (TNF-α), and interleukin-6 (IL-6) release in mouse peritoneal macrophages. To elevate intracellular Ca2+, we used thapsigargin (TG) and UTP. Although LPS alone cannot stimulate NO synthesis, co-addition with TG, which sustainably increased [Ca2+]i, resulted in NO release. UTP, via acting on P2Y6 receptors, can stimulate phosphoinositide (PI) turnover and transient [Ca2+]i increase, however, it did not possess the NO priming effect. LPS alone triggered the release of PGE2, TNF-α, and IL-6; all of which were potentiated by the presence of TG, but not of UTP. The stimulatory effect of LPS plus TG on NO release was inhibited by the presence of Ro 31-8220, Go6976, KN-93, PD 098059, or SB 203580, and abolished by BAPTA/AM and nuclear factor κB (NF-κB) inhibitor, PDTC. PGE2, TNF-α, and IL-6 release by LPS alone were attenuated by Ro 31-8220, Go6976, PD 098059, SB 203580, and PDTC. Using l-NAME, soluble TNF-α receptor, IL-6 antibody, NS-398, and indomethacin, we performed experiments to understand the cross-regulation by the four mediators. The results revealed that TNF-α up-regulated NO, PGE2, and IL-6 synthesis; PGE2 up-regulated NO, but down-regulated TNF-α synthesis; and PGE2 and IL-6 mutually up-regulated reciprocally. Taken together, murine peritoneal macrophages required a sustained [Ca2+]i increase, which proceeds after TG, but not UTP, stimulation, to enhance LPS-mediated release of inflammatory mediators, particularly for NO induction. Activation of PKC-, ERK-, and p38 MAPK-dependent signaling also are essential for LPS action. The positive regulatory interactions among these mediators might amplify the inflammatory response caused by endotoxin.

Lomerizine attenuates LPS-induced acute lung injury by inhibiting the macrophage activation through reducing Ca2+ influx

“…Consistently, the enzyme-linked immunosorbent assay (ELISA) results showed that LMZ dose-dependently reduced the protein levels of TNF-α, IL-1β and IL-6 induced by LPS ( Figures 2D–F ). Macrophages play a critical role in the pulmonary inflammation and are involved in tissue injury and inflammatory recovery processes ( Chen et al, 2001 ). To determine whether LMZ alleviates macrophage activation, we stained the cells from BALF with PE-CD11c, PerCP-Cy5.5-F4/80 and FITC-MHC class II antibodies.…”

“…Macrophages play a critical role in the pulmonary inflammation and are involved in tissue injury and inflammatory recovery processes (Chen et al, 2001). To determine whether LMZ alleviates macrophage activation, we stained the cells from BALF with PE-CD11c, PerCP-Cy5.5-F4/80 and FITC-MHC class II antibodies.…”

“…3.4 Lomerizine reduces the expression of pro-inflammatory cytokines via the Ca 2+ pathway in macrophages LPS has been reported to promote Ca 2+ influx in macrophages (Chen et al, 2001;Letari et al, 1991;Zhou et al, 2006). To determine the association between Ca 2+ influx and pro-inflammatory cytokines expression in macrophages, we detected Ca 2+ influx using a Fluo-4 AM green-fluorescent calcium indicator.…”