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Peptidoglycan recognition proteins (PGRPs) are pattern recognition molecules of the innate immune system via specific recognizing peptidoglycan, a unique component of bacterial cell wall. In the present study, a homologous gene encoding PGRP-S was identified and characterized from Apostichopus japonicus and designated as AjPGRP-S. The open reading frame of AjPGRP-S is 756 bp encoding a polypeptide of 251 amino acids (aa) with a signal peptide (1–24 aa) and a typical PGRP domain (37–178 aa). Phylogenetic analysis and sequence alignment revealed that AjPGRP-S is a member of the PGRP-S family. In healthy sea cucumbers, AjPGRP-S was expressed in all examined tissues with the highest distribution in body wall, muscle, and intestine. In Vibrio splendidus -infected sea cucumbers, AjPGRP-S was remarkably induced in coelomocytes. The recombinant AjPGRP-S (rAjPGRP-S) was shown to possess the highly amidase activity in the presence of Zn2+. Moreover, rAjPGRP-S exhibited agglutination abilities and strong bacteriostatic activities against V. splendidus , V. harveyi , V. parahaemolyticus , Staphylococcus aureus , and Micrococcus luteus. Furthermore, the agglutination ability can be enhanced in the presence of Zn2+. In conclusion, our results suggested that AjPGRP-S serves as a pattern recognition molecule involved in the immune response towards various pathogenic infections. • Complete cDNA sequence of S-type PGRP was identified in Apostichopus japonicus. • Vibrio splendidus challenge could significantly induce AjPGRP-S mRNA expression. • RAjPGRP-S was shown to possess the highly amidase activity in the presence of Zn2+. • RAjPGRP-S displayed both the agglutination abilities and bacteriostatic activities against examined bacteria. [ABSTRACT FROM AUTHOR]

Abstract: To examine the role of mitogen-activated protein kinase kinase 3 (MKK3) and p38 mitogen-activated protein kinase (p38-MAPK) in the cardioprotection afforded by antimycin A. Langendorff perfused murine hearts exposed to antimycin A or vehicle prior to global ischemia with p38-MAPK and HSP27 phosphorylation examined in the presence and absence of SB203580 or the presence (mkk3+/+) and absence (mkk3–/–) of MKK3. Infarct size was determined after 30 or 40 min of global ischemia and 2 h reperfusion. p38-MAPK dual phosphorylation in response to antimycin A was attenuated by co-administration of the antioxidant mercaptopropyonyl-glycine but unaffected by the absence of MKK3 or the presence of SB203580 at a concentration that inhibited the downstream phosphorylation of HSP27. Pre-ischemic exposure to antimycin A caused a significant reduction in subsequent infarction (I:R%) compared to vehicle on both the mkk3–/– and mkk3+/+ background (23.7±2.9 and 22.8±4.6 compared to 50.7±4.0 and 49.6±5.4 P =0.001, respectively). In C57Bl6 mice, antimycin A prior to ischemia reduced infarct size compared to vehicle (22.8 ± 6.1 vs. 48.3±5.2 P =0.01, respectively), an effect abolished by coincident SB203580. The cardiac protection initiated by antimycin A is dependent on the activation of p38-MAPK which occurs, at least in part, in response to oxygen-derived free radicals. The mechanism of this protective form of p38-MAPK activation is independent of the upstream kinase MKK3 and does not involve autophosphorylation. [Copyright &y& Elsevier]

Brief exposure to tumor necrosis factor (TNF) is known to trigger subsequent cardioprotection. TNF activates multiple downstream signaling cascades including p38-MAPK, a kinase known to initiate ischemic preconditioning. However, it is not known whether this kinase is similarly involved in TNF-induced cardioprotection. In isolated perfused murine hearts, subjected to 30-min global ischemia/2-h reperfusion, infarction/risk volume was significantly reduced by pretreatment with TNF for 15 min at 0.5 ng/ml, but not at 5 or 10 ng/ml, followed by 10-min washout vs. control (% I/R = 31 ± 3, 46 ± 5 or 54 ± 3 vs. 48 ± 5; P = 0.01, 0.80 and 0.25, respectively). This was in direct contrast to the concentration dependence of myocardial p38-MAPK phosphorylation, as measured by dual phosphorylated p38-MAPK, which was apparent at TNF concentrations of 5 and 10 ng/ml but not at 0.5 ng/ml vs. time-matched control (as % basal 315 ± 25, 422 ± 94 and 97 ± 25 vs. 95 ± 10; P < 0.01, 0.01 and =0.86, respectively). However, phosphorylation of p38-MAPK at 10 min of ischemia was similar among groups (as % basal 393 ± 98, 410 ± 67 and 369 ± 49 for time-matched control, 0.5 and 5 ng/ml, respectively). These patterns were also reflected in the phosphorylation of the downstream substrate HSP27. Furthermore, the effects of TNF on infarct size were not affected by SB203580 (1 μmol/l). These findings suggest that the pre-ischemic activation of p38-MAPK by TNF does not contribute to cardioprotection afforded by this agent. [Copyright &y& Elsevier]