, 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.

Thus, this model may have limited value for the study of rectal transmission of HIV. Two other studies showed successful rectal infections BET bromodomain inhibitor of humanized mice (4, 37), with transmission rates of 6/7 and 11/14, respectively. Sun et al. (37) used NOD/SCID mice transplanted with fetal liver and thymus and later reconstituted with liver-derived CD34+ cells (BLT mice). Berges et al. (4) transplanted RAG2?/?��c?/? mice with CD34+ cells from fetal liver. Thus, a major difference is that we used cord blood-derived cells. So far, it is not clear which source of hematopoietic stem cells is optimal for the generation of humanized mice. In vitro, the colony-forming efficiency of CD34+ cells derived from fetal liver is higher than that of cord blood CD34+ cells (19).

However, in vivo cord blood-derived hematopoietic stem cells produced four times more mature human leukocytes than liver-derived cells, when the same number of stem cells was transplanted into adult NOD/SCID mice (18). When telomere length is used as a measure of replicative capacity of hematopoietic stem cells from fetal liver and cord blood, the differences are minimal (40), indicating that both are suitable for generating humanized mice. However, it is not known to what extent the origin of lymphoid cells may be critical for repopulation of the intestines with human cells. Different expression of cell adhesion molecules (30) could influence homing behavior and subsequent repopulation of lymphoid organs. That, in turn, may explain the lower infection rates we observed in our model using cord blood-derived cells for transplantation.

But when we reconstituted mice in parallel either with cord blood-derived or with fetal liver-derived cells, rectal transmission of HIV was not more efficient in the mice which had received liver-derived cells. Apart from the different origins of CD34+ cells, Berges et al. and we used similar models based on mice with the same genetic background. However, Berges et al. reported higher engraftment levels than the ones we detected. They found blood engraftment levels of almost 90%, whereas the mice used in our study had a mean engraftment of about 11%. But these values cannot be directly compared. Berges et al. measured the percentage of human cells in blood lymphocytes; we measured the percentage of human cells in all blood leukocytes, which include murine cells as well.

Since RAG2?/?��c?/? mice have no B, T, and NK cells of their own, obviously Batimastat all lymphocytes detected in humanized mice should be of human origin. In our cohort of mice transplanted with liver-derived cells, we saw no differences in engraftment levels compared to engraftment levels in littermates transplanted with cord blood-derived cells. This indicates that the origin of the stem cells probably has no major impact, at least in our hands, and that other factors are influencing HIV transmission rates in humanized mice.