Domain V peptides inhibit beta2-glycoprotein I-mediated mesenteric ischemia/reperfusion-induced tissue damage and inflammation.

Reperfusion of ischemic tissue induces significant tissue damage in multiple conditions, including myocardial infarctions, stroke, and transplantation. Although not as common, the mortality rate of mesenteric ischemia/reperfusion (IR) remains >70%. Although complement and naturally occurring Abs are known to mediate significant damage during IR, the target Ags are intracellular molecules. We investigated the role of the serum protein, ß2-glycoprotein I as an initiating Ag for Ab recognition and ß2-glycoprotein I (ß2-GPI) peptides as a therapeutic for mesenteric IR. The time course of ß2-GPI binding to the tissue indicated binding and complement activation within 15 min postreperfusion. Treatment of wild-type mice with peptides corresponding to the lipid binding domain V of ß2-GPI blocked intestinal injury and inflammation, including cellular influx and cytokine and eicosanoid production. The optimal therapeutic peptide (peptide 296) contained the lysine-rich region of domain V. In addition, damage and most inflammation were also blocked by peptide 305, which overlaps with peptide 296 but does not contain the lysine-rich, phospholipid-binding region. Importantly, peptide 296 retained efficacy after replacement of cysteine residues with serine. In addition, infusion of wild-type serum containing reduced levels of anti-ß2-GPI Abs into Rag-1(-/-) mice prevented IR-induced intestinal damage and inflammation. Taken together, these data suggest that the serum protein ß2-GPI initiates the IR-induced intestinal damage and inflammatory response and as such is a critical therapeutic target for IR-induced damage and inflammation.

TLR4-mediated Cox-2 expression increases intestinal ischemia/reperfusion-induced damage.

Mesenteric IR induces significant inflammation and immune-mediated mucosal damage. TLR4 is a critical receptor in the induction of the inflammatory response and plays a role in intestinal homeostasis. To determine the role of TLR4 in IR-induced epithelial damage, we performed IR studies using TLR4(lps-def) and TLR4(lps-n) mice and analyzed mucosal damage and inflammation. We found that the absence of TLR4 or TLR4-induced signaling attenuated local mucosal damage with significantly decreased cytokine and eicosanoid secretion including PGE2 production. Similar results were seen in MyD88-/- mice. Wild-type mice treated with NS-398 (a Cox-2 inhibitor) not only decreased PGE2 production but also attenuated tissue damage. In contrast, PGE2 was not sufficient to induce damage in the TLR4(lps-def) mice. Together, these data indicate that TLR4 stimulation of Cox-2 activation of PGE2 production is necessary but not sufficient for intestinal IR-induced damage and inflammation.