Activation of CXCR2 by Extracellular Matrix Degradation Product Acetylated Pro-Gly-Pro Has Therapeutic Effects against Sepsis

Abstract

Rationale: Acetylated Pro-Gly-Pro (Ac-PGP) is an endogenous degradation product of extracellular collagen that binds to leukocyteexpressed chemoattractant receptor CXCR2. Although certain agents that block CXCR2-mediated signaling protect against experimental sepsis, the roles of Ac-PGP and CXCR2 in sepsis are unclear. Objectives: To investigate the role of Ac-PGP and its receptor, CXCR2, in murine models of cecal ligation and puncture (CLP)-induced polymicrobial sepsis and organ injury. Methods: The impact of in vivo Ac-PGP treatment on animal survival after induction of experimental sepsis was assessed. Vital organ inflammation and immune cell apoptosis were evaluated by histology, and the modulation of proinflammatory cytokine production and bactericidal activity by Ac-PGP in mouse and human blood leukocytes was measured. Measurements and Main Results: The activation of CXCR2 by tripeptide agonist Ac-PGP dramatically improved survival in three experimental sepsis models. Ac-PGP elicited bactericidal activity via the generation of hydrogen peroxide, inhibited lung inflammation, and reduced immune cell apoptosis. Fluorescein isothiocyanate-labeled PGP bound directly to CXCR2, and the protective effect of Ac-PGP in sepsis was abolished in CXCR2-deficient mice. Ac-PGP treatment enhanced the production of type 1 cytokines (IFN-g and IL-12) but inhibited the production of proinflammatory cytokines (tumor necrosis factor [TNF]-a, IL-1b, and IL-6) in vivo. In vitro, Ac-PGP directly increased IFN-g production and decreased the LPS-stimulated production of TNF-a by mouse splenocytes and human leukocytes. Furthermore, direct treatment of LPS-stimulated splenocytes with IFN-g resulted in diminished secretion of TNF-a and IL-6. Conclusions: CXCR2 and Ac-PGP are thus novel target and starting molecules, respectively, for the development of therapeutic agents against sepsis.Keywords: Sepsis; Acetylated-Pro-Gly-Pro; CXCR2Sepsis is a complex clinical syndrome common in major intensive care units that results from a harmful or damaging host response to infection (1). It is estimated that more than 200,000 deaths have been caused by sepsis in the United States (2). Moreover, the incidence of severe sepsis and septic shock has dramatically increased during the past two decades (3). Because the mortality of severe sepsis and septic shock is so high, the development of new and efficient therapeutic agents against sepsis is critical (1, 3).Sepsis-induced mortality is closely associated with failed regulation of the inflammatory response, which is caused by substantial impairment of the innate immune system (4-6). It has also been shown that excessive apoptosis of lymphocytes occurs during sepsis, which results in multiorgan failure (7,8). During the early stage of sepsis, several proinflammatory cytokines including tumor necrosis factor (TNF)-a and IL-1b are dramatically increased, which causes systemic dysfunction of the host immune system (9-11). In addition, the crucial role that invasive bacteria play in the progression and pat...

A novel natural compound from garlic (Allium sativum L.) with therapeutic effects against experimental polymicrobial sepsis

“…NMR spectra ( 1 H, 13 C, COSY, HMQC, and HMBC) were recorded in CD 3 OD on a NMR (Varian Inova 500, Santa Clara, CA, USA) spectrometer operating at 500 MHz for 1 H and 125 MHz for 13 C, running gradients and using residual solvent peaks as internal references. High-resolution mass spectra were recorded on a Q-TOF (Agilent, Q-TOF 6530/AB Sciex, Q-TOF 4600, Santa Clara, CA, USA) mass spectrometer.…”

“…To test whether SMFM had any therapeutic effect against sepsis, we conducted experiments using a cecal ligation and puncture (CLP) model using six week old male wild type ICR mice, as described previously (12,13). After ligating the cecum below the ileocecal valve, we punctured through both surfaces twice using a 22-gauge needle, and the abdomen was closed.…”

“…at 37 o C. We then counted colony forming units (CFUs) from the samples, as described previously (13).…”

“…The percentage of apoptotic (TUNEL-positive) cells was measured by counting 500 cells under a light microscope, as described previously (13).…”

“…The levels of cytokines present in the peritoneal fluid were determined using an enzyme-linked immunosorbent assay (ELISA; BD Biosciences Pharmingen, San Jose, CA, USA), as described previously (13).…”