Activated protein C prevents LPS-induced pulmonary vascular injury by inhibiting cytokine production

Abstract

We investigated the effect of activated protein C (APC) on pulmonary vascular injury and the increase in tumor necrosis factor (TNF) levels in lipopolysaccharide (LPS)-treated rats to determine whether APC reduces LPS-induced endothelial damage by inhibiting cytokine production. Intravenously administered LPS (5 mg/kg) induced pulmonary vascular injury, as indicated by an increase in the lung wet-to-dry weight ratio. LPS-induced pulmonary vascular injury was prevented by APC but not by active site-blocked factor Xa [dansyl glutamyl-glycyl-arginyl chloromethyl detone-treated activated factor X (DEGR-Xa)], a selective inhibitor of thrombin generation, or inactivated APC [diisopropyl fluorophosphate-treated APC (DIP-APC)]. APC, but not DEGR-Xa or DIP-APC, significantly inhibited the LPS-induced increase in the plasma level of TNF. APC significantly inhibited the production of TNF by LPS-stimulated monocytes in a dose-dependent fashion in vitro, but DIP-APC did not. APC did not inhibit the functions of activated neutrophils in vitro. These findings suggest that APC prevented LPS-induced pulmonary vascular injury by inhibiting TNF production by monocytes and not via its anticoagulant activity. The serine protease activity of APC appears to be essential for inhibition of TNF production.

Immune Regulation by Microvascular Endothelial Cells: Directing Innate and Adaptive Immunity, Coagulation, and Inflammation

“…EPCR precludes leukocyte influx by blocking the integrin CD11b/ CD18, as its deficiency induces neutrophilic infiltration and enhanced chemokine production in LPS-challenged mice compared with wild-type animals (71). In experimental endotoxininduced inflammation, activated PC inhibits pulmonary vascular injury by inhibiting TNF-␣ release (72) and limits accumulation of activated leukocytes (73). In human EC-based in vitro systems, activated PC modulates expression of genes related to anti-inflammatory and cell survival pathways, including inhibition of NF-B binding to target sites and multiple NF-B-regulated genes, such as cytokines, chemokines, and adhesion molecules (74,75).…”

Activated Protein C Up-Regulates IL-10 and Inhibits Tissue Factor in Blood Monocytes

“…For example, in the THP-1 monocytic cell line and in peripheral blood monocytes, activated protein C down-regulates TNF (9 -11), IL-1␤, IL-6, and IL-8 (12), presumably by inhibiting NF-B nuclear translocation (10) and/or down-regulating the transcription of NF-B subunits (13). In vivo studies of animals challenged with endotoxin have shown that activated protein C prevents the production of proinflammatory cytokines (14,15) and inhibits leukocyte accumulation in injured tissues (16).…”

Modulation of Monocyte Function by Activated Protein C, a Natural Anticoagulant

“…More recently, activated protein C has been shown to inhibit inflammation (13)(14)(15)(16)(17)(18), apoptosis (19 -22), and to prevent increases in vascular permeability (23,24). With respect to its antiinflammatory properties, activated protein C has been shown to down-regulate the production of TNF by monocytes (13)(14)(15) and to suppress expression of leukocyte adhesion molecules in endothelial cells (16), presumably by inhibiting NF-B nuclear translocation (14) and/or down-regulating the transcription of NF-B subunits (16).…”

“…With respect to its antiinflammatory properties, activated protein C has been shown to down-regulate the production of TNF by monocytes (13)(14)(15) and to suppress expression of leukocyte adhesion molecules in endothelial cells (16), presumably by inhibiting NF-B nuclear translocation (14) and/or down-regulating the transcription of NF-B subunits (16). In animals challenged with endotoxin, activated protein C inhibited the production of proinflammatory cytokines (17,18) and inhibited leukocyte accumulation in injured tissue (25). Likewise, the PROWESS trial revealed that recombinant activated protein C infusion reduced levels of IL-6, a proinflammatory cytokine (4).…”