Ching-Yuan Su

Induction of heat-shock protein 72 in rat skeletal muscle does not increase tolerance to ischemia-reperfusion injury

Ischemia‐reperfusion injury is implicated in the failure of free flap and replant surgeries and is associated with the pathogenesis of a wide variety of clinical diseases including stroke, myocardial infarction, spinal injury, and compartment syndromes. We used a skeletal muscle flap model to test if the induction of heat‐shock protein 72 (HSP72) by mild hyperthermia provides tolerance against ischemia‐reperfusion injury. Immunocytochemistry and Western blot analysis verified increased production of HSP72 in the gracilis muscle of globally heated rats. Neutrophil accumulation in the microvasculature and postischemic muscle survival after ischemia‐reperfusion were unaltered by preischemic hyperthermia, indicating HSP72 induction is not sufficient to provide resistance against severe injury in skeletal muscle.

Gender difference in cytoprotection induced by estrogen on female and male bovine aortic endothelial cells

Before menopause, women have a lower risk of cardiovascular diseases than men. Studies attribute this gender difference to estrogenic protection in the female cardiovascular system. We have demonstrated that 17β-estradiol (E2) protects female bovine aortic endothelial cells against oxidative injury, probably through the induction of antioxidant enzyme activities. In this study, we examined whether E2 confers a differential protection on male and female cells. Bovine aortic endothelial cells from both genders were preconditioned for 24 h with E2 (1 nM to 10 µM), and their resistance to paraquat (1 mM, 3 h), a superoxide generator, was measured using an MTT assay. In contrast to the protection observed in female bovine aortic endothelial cells, there was no protective effect by E2 on male bovine aortic endothelial cells at physiologic concentrations. However, E2 at 1–10 µM attenuated paraquat’s toxicity in both male and female cells, probably through its direct antioxidant activity. E2 at 1 nM increased in female, but not in male, cells the activities of super-oxide dismutase, catalase, glutathione peroxidase, and glutathione reductase, which was associated with decreased levels of reactive oxygen species during subsequent paraquat exposure. This suggests that antioxidant enzyme induction plays some role in E2-augmented oxidative resistance in female endothelial cells.

Gene expression of the androgen repressed rat TR2 orphan receptor: a member of steroid receptor superfamily.

A full-length rat cDNA clone was obtained from the TR2 orphan receptor, a member of the steroid receptor superfamily, using cDNA library screening and 3′ RACE-PCR technology. Under these conditions, only the TR2-11 form of the TR2 orphan receptor, the major form found in prostate, was identified. The overall amino acid homology between human and rat TR2-11 orphan receptors was near 90% with one amino acid difference in the DNA-binding domain sequence. Northern blot analysis identified multiple forms of the TR2 orphan receptor mRNAs expressed in human and rat prostates. Androgens repressed TR2 orphan receptor mRNA levels in human prostate LNCaP cells and rat ventral prostate. Polyclonal anti-TR2 orphan receptor antibodies raised from a unique TR2 orphan receptor 20 amino acid peptide were used to localize the TR2 orphan receptor in the nuclei of prostate and epididymis epithelium cells. Together, these data demonstrate that the TR2 orphan receptor can be expressed at mRNA and protein levels in the human and rat prostrates and may have some potential function in mediating androgen action in these tissues.

Heme Oxygenase, Ginkgo Biloba Extract and its Terpenoids Protect Myocytes Against Oxidative Injury

A number of pharmacological approaches to protect against myocardial damage during ischemia reperfusion events (e.g. β-blockers, calcium antagonists, nitrates, and free radical scavengers) have met with limited success. For example, administration of exogenous antioxidants during and after myocardial ischemial-reperfusion were not sufficient to protect intracellular targets against reactive oxidant species, because exogenous antioxidants are membrane impermeable and cannot gain access to intracellular sites of free radical production and reaction. Development of other novel approaches to enhance endogenous cardioprotective mechanisms to minimize myocardial damage during ischemial-reperfusion is currently a major area of investigation. Since its first description by Murry et al. manipulation of myocardial protection via “ischemic preconditioning (I/P)” has been revealed to trigger endogenous protective mechanisms that increase cardiomyocytes resistance to oxidative stress (Murry et al., 1986; Parratt, 1994). Two classes of cellular protectants, heat shock proteins (HSPs) and endogenous anti-oxidant enzymes (Yellon and Baxter, 1995), have been postulated to participate in this I/P induced cardioprotection. Accumulation of HSP70 in myocytes was associated with an enhancement structural stabilization in cardiac tissue. It was shown that transfecting cells with HSP70 gene conferred cyto-protection against hydrogen peroxide, hypoxia/reoxygenation injury (Chong et al., 1998; Plumier et al., 1995). Overexpression of HSP70 dramatically reduced infarct size in hearts of transgenic HSP70 mouse model (Marber et al., 1995).