Francisco Javier Rodríguez

To examine the role of neutrophils, their presence and the degree of infiltration, as important determinants of ischemia and reperfusion injury of the liver, male Sprague-Dawley rats were subjected to 60 and 90 min of total-liver ischemia. The presence of neutrophils, assessed by the measurement of liver tissue myeloperoxidase (MPO), and the degree of neutrophil liver infiltration, determined by the naphthol AS-D chloroacetate esterase technique, correlated well with animal survival and response to FK506 and cyclosporine administration. Lipid peroxidation, measured by the malondialdehyde (MDA) test in liver tissue, was another factor closely linked with liver function and survival. Pretreatment with FK506 (0.3 mg/kg) and CsA (5 mg/kg) was given at 4 hr and 1 hr before ischemia and at the time of reperfusion. Control ischemic animals showed increased neutrophil liver infiltration, high MPO and MDA liver levels, and diminished overall survival. FK506 and CsA-treated animals had better survival and diminished neutrophil liver infiltration, as well as MPO and MDA levels. The mechanism by which FK506 and CsA protected the animals from severe liver ischemic injury is unknown. Our data indicated that the presence and the degree of infiltration of neutrophils were important components of liver ischemia/reperfusion injury in the rat. So it is possible that one of the fundamental effects of the FK506 and CsA might be through the inhibition of the presence and infiltration of neutrophils in liver tissue.

The Wnts are a family of glycoproteins that regulate cell proliferation, fate decisions, and differentiation. In our study, we examined the contribution of Wnts to the development of ventral midbrain (VM) dopaminergic (DA) neurons. Our results show that beta-catenin is expressed in DA precursor cells and that beta-catenin signaling takes place in these cells, as assessed in TOPGAL [Tcf optimal-promoter beta-galactosidase] reporter mice. We also found that Wnt-1, -3a, and -5a expression is differentially regulated during development and that partially purified Wnts distinctively regulate VM development. Wnt-3a promoted the proliferation of precursor cells expressing the orphan nuclear receptor-related factor 1 (Nurr1) but did not increase the number of tyrosine hydroxylase-positive neurons. Instead, Wnt-1 and -5a increased the number of rat midbrain DA neurons in rat embryonic day 14.5 precursor cultures by two distinct mechanisms. Wnt-1 predominantly increased the proliferation of Nurr1+ precursors, up-regulated cyclins D1 and D3, and down-regulated p27 and p57 mRNAs. In contrast, Wnt-5a primarily increased the proportion of Nurr1+ precursors that acquired a neuronal DA phenotype and up-regulated the expression of Ptx3 and c-ret mRNA. Moreover, the soluble cysteine-rich domain of Frizzled-8 (a Wnt inhibitor) blocked endogenous Wnts and the effects of Wnt-1 and -5a on proliferation and the acquisition of a DA phenotype in precursor cultures. These findings indicate that Wnts are key regulators of proliferation and differentiation of DA precursors during VM neurogenesis and that different Wnts have specific and unique activity profiles.