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Pin-Lan Li, M.D., Ph.D. |
Education: M.D. Yichang Medical College, China, 1975, Ph.D. University of Heidelberg, Germany, 1992
Research interests:
Cardiovascular pharmacology
Research in my laboratory mainly deals with the cell and molecular regulation of coronary circulation and pathogenesis of renal glomerular injury associated with hyperhomocysteinemia and hypertension. Some specific projects and approaches are as follows:
Transmembrane Signaling Mechanisms in Coronary Endothelial Cells – Lipid Rafts and Molecular Trafficking: Beyond enzyme-mediated amplification in various cell-signaling cascades, we are now exploring another important mechanism that massively amplifies the signals when ligands bind to their receptors. This mechanism is characterized by clustering of membrane lipid microdomains (lipid rafts) and formation of different signaling platforms. In this process, many receptors and signaling molecules aggregate on stimulation, resulting in a very high density of the receptors and other signaling molecules in certain areas of cell membrane to form signaling platforms, which transmit and amplify the signals from receptor activation. A major focus of research is now on defining the mechanism mediating the formation of lipid rafts-associated redox signaling platforms in coronary endothelial cells and exploring the physiological and pathological significance of these redox signaling platforms. Many advanced cell and molecular approaches have been used such as confocal microscopy, fluorescence resonance energy transfer (FRET), electron spin resonance (ESR) spectrometry, high-speed fluorescence imaging, real time PCR, RNA interference, somatic gene manipulations and genetic engineered animal models.
Novel Intracellular Second Messengers, cADPR in Coronary Arterial Myocytes: Cyclic ADP-ribose (cADPR) serves as a second messenger to mediate intracellular Ca2+ mobilization independent of IP3 signaling pathway in different tissues or cells. Over the last 10 years, we have demonstrated that cADPR induces Ca2+ release from intracellular stores of coronary arterial smooth muscle cells and that inhibition of cADPR production results in the relaxation of coronary arteries. This cADPR-mediated Ca2+ signaling pathway is now considered as an important target in a redox feedforward regulation in vascular smooth muscle. When vascular smooth muscle cells are activated by different vasoconstrictor stimuli, an NADPH oxidase-associated redox signaling amplification is also initiated. In this process, NADH is used to produce superoxide and NAD+, which could result in cADPR increase since NAD+ is a substrate of ADP-ribosyl cyclase and superoxide can activate this cADPR producing enzyme. cADPR mobilizes intracellular Ca2+, enhancing vasoconstrictor response. Various approaches used in these projects include: high-speed fluorescence imaging of intracellular Ca2+, superoxide and other redox molecules, patch clamp, FRET, video microscopy of small artery functionality, RNA interference, ELISA, ESR, gene overexpression, and genetically engineered animal models.
Characteristics and Function of a Novel Lysosomal Ca2+ Release Channel - TRP-ML1 in Arterial Myocytes: Lysosomes are recently demonstrated as an intracellular Ca2+ store, where Ca2+ can be mobilized to produce cellular physiological responses. However, little is known how Ca2+ is released from this store in response to different agonists or stimuli. We have provided the first experimental evidence demonstrating that a Ca2+ release channel is present in lysosomes and that its identity may be mucolopin-1, a transient receptor potential (TRP) channel, namely, TRP mucolipin 1 (TRP-ML1). Given the action of nicotinic acid adenine dinucleotide phosphate (NAADP) stimulating lysosomal Ca2+ release, a hypothesis is that TRP-ML1 may be an NAADP-sensitive Ca2+ release channel in lysosomes of coronary arterial smooth muscle cells. This TRP-ML1 channel may mediate local Ca2+ bursts from lysosomes and leads to a two-phase Ca2+ release that participates in the vasomotor response of coronary arteries to agonists. We are now testing this hypothesis using different physiological, biochemical and molecular approaches including ion channel reconstitution, lipid bilayer channel recording, patch clamp, high-speed fluorescence imaging, HPLC, ELISA, confocal and electron microscopy, RNA interference, gene mutation and overexpression.
Molecular Mechanisms of Hyperhomocysteinemia-induced Arteriosclerosis and Glomerular Sclerosis: Hyperhomocysteinemia (hHcys) is a novel risk factor or pathogenic factor for atherosclerosis and glomerular sclerosis associated with hypertension. We are now investigating the molecular mechanisms mediating the pathogenic action of homocysteine (Hcys) in the development of glomerular sclerosis with a major focus on the contribution of guanine nucleotide exchange factors (GEF). The hypothesis to be tested is that the GEF-Vav as a target signaling molecule of Hcys activates Rac-NADPH oxidase and thereby triggers the cascade of glomerular injury and sclerosis including local oxidative stress, podocytes dysfunction, extracellular matrix deposition and fibrosis. A series of cellular, molecular and whole animal experimental approaches are used to test this hypothesis, such as pull-down assay of Rac GTPase, ESR, Western blot analysis, real time PCR, RNA interference, gene overexpression, dominant active or negative gene mutants, in vivo molecular imaging, isolated glomeruli approaches, HPLC, immunocytochemistry, and whole animal monitoring of arterial pressure and renal functions.
Li X, Hong S, Li PL, and Zhang Y. (2011) Docosahexanoic acid-Induced coronary
arterial dilation: Actions of 17S-hydroxy
docosahexanoic acid on K+ channel activity.
J Pharmacol Exp Ther. 336(3):891-9.
Wang Z, Tang L, Zhu Q,
Yi F, Zhang F, Li PL, Li N. (2011) Hypoxia-inducible factor-1α contributes
to the profibrotic action of angiotensin II in renal medullary
interstitial cells. Kidney
Int. 79(3):300-10.
Boini KM, Zhang C, Xia M, Han WQ, Brimson
C, Poklis JL, and Li PL. (2010) Visfatin-induced lipid raft redox
signaling platforms and dysfunction in glomerular endothelial cells.
Biochim Biophys Acta. 2010 Dec;1801(12):1294-304.
Xia M,
Zhang C, Boini KM, Thacker AM, and Li PL. (2011) Membrane raft-lysosome
redox signalling platforms in coronary endothelial dysfunction induced by
adipokine visfatin.
Cardiovasc Res. 89(2):401-9.
Hull LC, Rabender C, Gabra BH,
Zhang F, Li PL, and Dewey WL. (2010) Role of CD38, a cyclic
ADP-ribosylcyclase, in morphine antinociception and tolerance.
J Pharmacol Exp Ther. 334(3):1042-50.
Boini KM, Zhang C,
Xia M, Poklis JL, and Li PL. (2010) Role of sphingolipid mediator ceramide
in obesity and renal injury in mice fed a high-fat diet.
J Pharmacol Exp Ther. 334(3):839-46.
Zhang C, and Li PL.
(2010) Membrane raft redox signalosomes in endothelial cells.
Free Radic Res. 44(8):831-42.
Zhang C, Yi F, Xia M, Boini
KM, Zhu Q, Laperle LA, Abais JM, Brimson CA, and Li PL. (2010) NMDA
receptor-mediated activation of NADPH oxidase and glomerulosclerosis in
hyperhomocysteinemic rats.
Antioxid Redox Signal. 13(7):975-86.
Wang Z, Zhu Q, Xia M,
Li PL, Hinton SJ, and Li N. (2010) Hypoxia-inducible factor
prolyl-hydroxylase 2 senses high-salt intake to increase hypoxia inducible
factor 1alpha levels in the renal medulla.
Hypertension. 55(5):1129-36.
Zhang F, Xia M, and Li PL.
(2010) Lysosome-dependent Ca(2+) release response to Fas activation in
coronary arterial myocytes through NAADP: evidence from CD38 gene
knockouts.
Am J Physiol Cell Physiol. 298(5):C1209-16.
Zhang C, Hu JJ,
Xia M, Boini KM, Brimson CA, Laperle LA, and Li PL. (2010) Protection of
podocytes from hyperhomocysteinemia-induced injury by deletion of the
gp91phox gene.
Free Radic Biol Med. 48(8):1109-17.
Bao JX, Xia M, Poklis
JL, Han WQ, Brimson C, and Li PL. (2010) Triggering role of acid
sphingomyelinase in endothelial lysosome-membrane fusion and dysfunction
in coronary arteries.
Am J Physiol Heart Circ Physiol. 298(3):H992-H1002.
Zhang C,
Hu JJ, Xia M, Boini KM, Brimson C, and Li PL. (2010) Redox signaling via
lipid raft clustering in homocysteine-induced injury of podocytes.
Biochim Biophys Acta. 2010 Apr;1803(4):482-91.
Bao JX, Jin
S, Zhang F, Wang ZC, Li N, and Li PL. (2010) Activation of membrane NADPH
oxidase associated with lysosome-targeted acid sphingomyelinase in
coronary endothelial cells.
Antioxid Redox Signal. 2(6):703-12.