Heme Oxygenase-1 is an Essential Cytoprotective Component in Oxidative Tissue Injury Induced by Hemorrhagic Shock

Hemorrhagic shock causes oxidative stress that leads to tissue injuries in various organs including the lung, liver, kidney and intestine. Excess amounts of free heme released from destabilized hemoproteins under oxidative conditions might constitute a major threat because it can catalyze the formation of reactive oxygen species. Cells counteract this by rapidly inducing the rate-limiting enzyme in heme breakdown, heme oxygenase-1 (HO-1), which is a low-molecular-weight stress protein. The enzymatic HO-1 reaction removes heme. As such, endogenous HO-1 induction by hemorrhagic shock protects tissues from further degeneration by oxidant stimuli. In addition, prior pharmacological induction of HO-1 ameliorates oxidative tissue injuries induced by hemorrhagic shock. In contrast, the deletion of HO-1 expression, or the chemical inhibition of increased HO activity ablated the beneficial effect of HO-1 induction, and exacerbates tissue damage. Thus, HO-1 constitutes an essential cytoprotective component in hemorrhagic shock-induced oxidative tissue injures. This article reviews recent advances in understanding of the essential role of HO-1 in experimental models of hemorrhagic shock-induced oxidative tissue injuries with emphasis on the role of its induction in tissue defense

Development of a novel analgesic for cancer pain targeting brain-derived neurotrophic factor

Brain-derived neurotrophic factor (BDNF) is necessary for nerve growth. BDNF is expressed in the dorsal root ganglion (DRG) and modulates pain transduction from peripheral nociceptors. TrkB, which is a BDNF receptor with a tyrosine kinase domain, acts as a pain modulator on the cell membrane of second neuron. If an exogenous truncated TrkB lacking a tyrosine kinase domain can competitively block the binding of BDNF to endogenous TrkB, inhibitory effects on pain are expected. We constructed two expression vectors coding truncated TrkB-GFP fusion proteins, lacking intracellular tyrosine kinase domain, with and without the transmembrane domain. By transfection of the vectors to HEK293 cells, the expression and localization of the modified receptor proteins were confirmed. The truncated TrkB with the transmembrane domain, TM (+), was localized on cell membrane surface of the transfected cells, and capable of BDNF binding on cell surface. TM (-) without the transmembrane domain was secreted from the transfected cells, and the secreted TrkB protein was confirmed the capability for binding with BDNF by pull-down assay. Furthermore, we developed a rat model of cancerous osteocopic pain for evaluating an analgesic effect of the modified TrkB vectors on cancer pain. Pain-related behavior, as assessed by von Frey tests, indicated hyperalgesia after cancer cell administration. BDNF expression was higher on the affected side of the DRG at the third lumbar vertebra L3 than on the unaffected side. When the modified TrkB vectors were administrated to the cancer pain model rats, both the TM (+) and TM (-) vector administration groups exhibited an analgesic effect. These results suggest that the modified TrkB receptors and their vectors are applicable as molecular targeted drugs for pain control in cancer patients