Professor of Pharmacology
Ph.D., UT Health Science Center - Houston
| receptor mechanisms|| tyrosine hydroxylase|
| hypertension|| depression|
| Parkinson's disease|| aging|
| dopamine neurons|| Rapamycin|
My research has two major objectives: the first is directed toward understanding receptor mechanisms involved in regulating tyrosine hydroxylase (TH) gene expression, the rate limiting enzyme in the synthesis of catecholamines. The latter substances are crucially involved in various life-sustaining functions and are implicated in diseases such as hypertension, depression and Parkinsons disease. We are examining the signal transduction mechanisms that mediate the effects of selected neurotransmitter and neuromodulators on TH gene expression in a cultured adrenal chromaffin cell line. Most recently, we have focused on vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide (PACAP) receptors and glucocorticoid receptors. We have investigated both transcriptional and post-transcriptional responses to PACAP and VIP and found that the PAC1 receptor distinguishes between the two agonists by stabilizing TH mRNA in response to PACAP, but not VIP. We are investigating intracellular signaling pathways in this response. We also recently identified the glucocorticoid responsive element in the promoter region of the TH gene. We are examining how second messenger pathways that are stimulated by neuropeptide receptors modulate the transcriptional responses to glucocorticoids.
The second research objective is directed toward understanding the role of oxidative stress in the aging brain. One project is aimed at determining how reactive catecholamine metabolites contribute to neuropathology of aging and Parkinsons disease. We are particularly interested in the role that 3,4-dihydroxyphenylacetaldehyde (DOPAL) plays in degeneration of dopamine neurons. This highly reactive metabolite of dopamine becomes elevated in Parkinsons disease and is neurotoxic. Rotenone, a pesticide that reproduces the pathology of Parkinsons disease in rats, has been shown to elevate DOPAL in cultured cells. DOPAL is believed to be cleared by the mitochondrial aldehyde dehydrogenase (ALDH2). We have developed an ALDH2 knockout mouse to determine the role of this enzyme in DOPAL catabolism. We are also using this new mouse model to study the role of DOPAL in the pathology of Parkinsons disease.