, 1998), it is tempting to speculate that nevertheless trypsinogen activation is a main target of the Rho-kinase inhibitor in AP. However, the relationship between trypsin activity on one hand and the inflammatory response on the other hand in SAP is not clearly delineated. It may be that both develop in parallel and potentiate each other or there may be a sequential relationship with one preceding the other. Nonetheless, we also observed that administration of Y-27632 after taurocholate challenge had no significant effect on inflammatory parameters or tissue damage in the pancreas, supporting the notion above that trypsinogen activation in acinar cells rather than secondary chemokine formation and neutrophil activation may be the main protective mechanism exerted by the Rho-kinase inhibitor.

In this context, it should be noted that targeting Rho-kinase activity may have a limited influence on the treatment of patients with on-going pancreatitis considering that Rho-kinase-regulated activation of trypsinogen is an early feature in AP and that delayed treatment with the Rho-kinase inhibitor did not ameliorate tissue damage in the inflamed pancreas. However, it is possible that high-risk patients undergoing endoscopic retrograde cholangiopancreatography may benefit from prophylactic administration of Rho-kinase inhibitors. Activation and extravascular accumulation of leucocytes are key components in the inflammatory response following injury and infection, but in certain instances, leucocytes may cause organ damage, including graft rejection and sepsis (Carlos and Harlan, 1994).

In fact, numerous studies have documented that leucocyte recruitment constitutes a rate-limiting step in pancreatitis by demonstrating markedly attenuated tissue destruction in neutrophil-depleted animals (Kyriakides et al., 2001). Herein, we observed that taurocholate challenge increased MPO activity and the number of extravascular neutrophils in the pancreas. Administration of Y-27632 greatly decreased both MPO levels (73%) and extravascular neutrophils (88%) in the pancreas, suggesting that Rho-kinase activity is a potent regulator of neutrophil trafficking in pancreatitis. Specific adhesion molecules regulate the recruitment process of leucocytes to extravascular sites of inflammation (Kelly et al., 2007).

Although the detailed role of specific adhesion molecules in supporting leucocyte recruitment in the pancreas is relatively unclear, numerous studies have shown that Mac-1 is a dominating molecule in mediating tissue infiltration of neutrophils (Asaduzzaman et al., 2008; Lee et al., 2009; Rahman et al., 2009). In the present GSK-3 study, we found that taurocholate challenge upregulated Mac-1 expression on neutrophils. Interestingly, administration of Y-27632 markedly reduced surface levels of Mac-1 on neutrophils, indicating that Rho-kinase signalling contributes to neutrophil expression of Mac-1 in pancreatitis.