Emerging roles of thioredoxin cycle enzymes in the central nervous system.

The thioredoxins (Trxs) constitute a family of enzymes which catalyze the reduction of protein disulfide bonds. Recent animal studies have revealed the importance of the Trx superfamily in various experimental systems. For example, the homozygous disruption of the genes encoding cytoplasmic (TRX1) or mitochondrial Trx (TRX2) in mice generates lethal embryonic phenotypes. In contrast, transgenic mice overexpressing TRX1 show an extended life span and are relatively resistant to ischemia- mediated brain damage. In addition to their capacity to detoxify peroxides in concert with peroxiredoxins and Trx reductases, Trx isozymes perform multiple redox signaling functions mediated by their specific interaction with various proteins, including redox-regulated kinases and transcription factors. Recent studies indicate that specific isoforms of Trx cycle enzymes, targeted to different cell compartments, are key regulators of fundamental processes, such as gene expression, cell growth and apoptosis. The present review is primarily focused on the emerging neuroprotective role of these proteins in the central nervous system.

Lipoprotein lipase and endothelial lipase expression in mouse brain: regional distribution and selective induction following kainic acid-induced lesion and focal cerebral ischemia.

Lipoprotein and endothelial lipases are members of the triglyceride lipase gene family. These genes are expressed in the brain, where the encoded proteins are fulfilling functions that have yet to be elucidated. In this study, we examined the distribution of their respective mRNAs in the C57BL/6 mouse brain by in situ hybridization. In control mice, we observed widespread expression of lipoprotein lipase (LPL) mRNA mainly in pyramidal cells of the hippocampus (CA1, CA2 and CA3 areas), in the striatum and in several cortical areas. Endothelial lipase (EL) mRNA expression was restricted to CA3 pyramidal cells of the hippocampus, to ependymal cells in the ventral part of the third ventricle and to some cortical cell layers. To gain insight into the role played by lipases in the brain, neurodegeneration was induced by intraperitoneal injection of kainic acid (KA) or by occlusion of the middle cerebral artery (MCA). Upon injection of KA, a rapid increase in EL mRNA expression was observed in the piriform cortex, hippocampus, thalamus and neocortex. However, the levels of LPL mRNA were unaffected by KA injection. Remarkably, after focal cerebral ischemia, the expression of EL was unaffected whereas a dramatic increase in LPL expression was observed in neocortical areas of the lesioned side of the brain. These results show that LPL and EL transcripts are selectively upregulated in function of the type of brain injury. LPL and EL could thus fulfill a function in the pathophysiological response of the brain to injury.