Research Interests
We are interested in understanding the mechanisms by
which blood flow perfusion is regulated in the liver under the normal
and stress conditions. Hepatic
blood flow, particularly sinusoidal flow perfusion is essential for
normal functions and metabolism of hepatocytes and also plays a crucial
role in repair of injured cells in liver diseases.
Regulation of sinusoidal blood perfusion consists of a delicate
balance between the vasoconstrictor force and the vasodilator force
that involve close interactions among the sinusoidal cells (i.e.,
endothelial cells, Kupffer cells, hepatic stellate cells) and hepatocytes.
The primary interest of this laboratory is to delineate the
relationship between the sinusoidal cells and hepatocytes with respect
to their interaction contributing to the regulation of constrictor
and dilator forces in various stress conditions such as endotoxemic
shock, hemorrhagic shock, liver cirrhosis and liver transplant.
We recently discovered, for example, that endothelin, a locally
released vasoconstrictor by endothelial cells and perhaps more importantly
by hepatocytes under certain diseases, induces sinusoidal constriction
by contracting hepatic stellate cells thus reducing sinusoidal perfusion,
and this effect is opposed by vasodilators nitric oxide and carbon
monoxide. Our primary
goal is to elucidate the mechanisms that regulate the balance of local
constrictor and dilator forces in a variety of disease conditions
and ultimately find drug interventions that help maintain liver perfusion
under the stress conditions and rectify the injured tissue.
Ongoing Projects:
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Alterations in the regulatory mechanisms of hepatic microcirculatory
perfusion in cirrhosis.
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Mechanisms of predisposition of the cirrhotic liver to hemorrhage/resuscitation
and endotoxic shock.
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Mechanisms of hypercholesterolemia and hypertriglyceridemia induced
liver injury in Apo-CI transgenic mice.
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Effect of caloric restriction on steatohepatitis in hyperlipidemic
environment.
Areas of Interest:
Liver Microcirculation under Normal
and Pathological Conditions
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Physiologic Control and Regulation in Hepatic Blood Circulation
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Regulation and Dysregulation of Hepatic Microcirculation in Cirrhosis
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Regulation of Sinusoidal Perfusion in Shock and Postischemic Reperfusion
Liver Transplant
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Hypothermic Machine Perfusion Preservation
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Role of Kupffer Cells in Mediation of Microcirculatory Injury
during Acute Rejection
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Hyperacute Liver Rejection in Xenotransplant
Liver Regeneration
Courses Taught
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BIOL 3273
Animal Physiology
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BOIL 4600 Senior Seminar
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BIOL 6273 Advanced Human Physiology
(offered for graduate credit)
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BIOL 6050 Phathophysiology
(offered for graduate credit)
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BIOL 6000 Graduate Special Topics: Cell Membranes
(offered for graduate credit)
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BIOL 6104/8104 Integrated Systems Physiology (offered for
graduate credit)
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MEGR 6109/8109 Biotechnology and Bioengineering (offered
for graduate credit)
Professional Positions
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Associate Professor, Department of Biology, University of North
Carolina at Charlotte, Charlotte, North Carolina, 2003 - Present
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Assistant Professor, Department of Biology, University of North
Carolina at Charlotte, Charlotte, North Carolina, 1996 - 2003
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Postdoctoral Fellow, The Johns Hopkins University School of Medicine,
Baltimore, Maryland, 1992 - 1996
Education
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Postdoctoral Training, Johns Hopkins University School of Medicine
(1992-1996).
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Ph.D in Biomedical Science, Specialization in Physiology, 1992,
University of South Carolina, Columbia, South Carolina.
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M.A. in Sports Medicine, 1987, Springfield College, Springfield,
Massachusetts.
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B.S. in Sports Medicine, 1982, Chengdu College of Sports Medicine,
Chengdu, China .
Selected Publications
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Chun, K., J. Zhang, J. Biewer, D. Ferguson, and M. G. Clemens.
Microcirculatory failure correlates with lethal hepatocyte injury
in ischemic/reperfused rat livers. Shock. 1(1): 3-9, 1994.
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Zhang, J. X., W. Pegoli, Jr., and M. G. Clemens. Endothelin-1
induces direct constriction of hepatic sinusoids. American Journal
of Physiology. 266 (Gastrointest. Liver Physiol. 29): G624-G632,
1994.
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Bauer, M., J. X. Zhang, I. Bauer, and M. G. Clemens. Endothelin-1
induced alterations of hepatic microvasculation: sinusoidal and
extrasinusoidal sites of action. American Journal of Physiology.
267 (Gastrointest. Liver Physiol. 30): G143-G149, 1994.
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Zhang, J. X., D. V. Jones, and M. G. Clemens. Effect of activation
on neutrophil-induced hepatic microvascular injury in isolated rat
liver. Shock. 1(4): 273-278,1994.
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Zhang, J. X., M. Bauer, and M. G. Clemens. Vessel and target cell
specific actions of endothelin-1 and endothelin-3 in rat liver.
American Journal of Physiology. 269(Gastrointest. Liver Physiol.
32): G269-G277, 1995.
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Bauer, M., J. X. Zhang, I. Bauer, and M. G. Clemens. Endothelin-1
as a regulator of hepatic microcirculation: sublobular distribution
of effects and impact on hepatocellular secretory function. Shock.
1(6): 457-465, 1994.
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Clemens, M. G., M. Bauer, C. Gingalewski, E. Miescher, and J.
Zhang. Editorial review: hepatic intercellular communication in
shock and inflammation. Shock. 2(1): 1-9, 1994.
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Clemens, M. G., M. Bauer, C. Gingalewski, J. Zhang, and A. DeMaio.
Heterogeneity of hepatocellular response: role of intercellular
communication. In: Host defense dysfunction in trauma, shock and
sepsis, edited by E. Faist, F. Schildberg, and A. Baue. Berlin:
Springer Verlag, 1995.
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Bauer, M., N. C. Paquette, J. X. Zhang, I. Bauer, B. H. J. Pannen,
S. R. Kleeberger, and M. G. Clemens. Chronic ethanol consumption
increases hepatic sinusoidal contractile response to endothelin-1.
Hepatology. 22: 1565-1576,1995.
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Pannen, B. H. J., Bauer, M., J. X. Zhang, I. L. Robotham, M. G.
Clemens. Endotoxin pretreatment enhances the portal venous contractile
response to endothelin-1. American Journal of Physiology. 270: H7-15,
1996.
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Bauer, I., M. Bauer, B. H. J. Pannen, M. J. Leinwand, J. X. Zhang,
and M. G. Clemens. Chronic ethanol consumption exacerbates liver
injury following hemorrhagic shock: role of sinusoidal perfusion
failure. Shock. 4(5): 1-8, 1995.
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Pannen, B. H. J., M. Bauer, J. X. Zhang, I. L. Robotham, M. G.
Clemens. A time-dependent balance between endothelin and nitric
oxide regulates portal vascular resistance following endotoxin.
American Journal of Physiology. 271: H1953-H1961.
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Morita, Y., G. B. Bulkley, J. X. Zhang, and M. G. Clemens. Regulation
of prolonged endothelin-1-induced arterial constriction in the rat
mesenteric artery in vivo, American Journal of Physiology. In press.
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Rai, R., J.X. Zhang, M. G. Clemens, and A. M. Diel. Gadolinium
chloride alters acinar distribution of phagocytosis and balance
between pro-and anti-inflammatory cytokines. Shock. (6:4): 243-7,
1996.
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Bauer, M., B. H. J. Pannen, I. Bauer, C. Herzog, G. A. Wanner,
R. Hanselmann, J. X. Zhang, M. G. Clemens and R. Larson. Evidence
for a functional link between stress response and vascular control
in hepatic portal circulation. American Journal of Physiology. 271:
G929-G935, 1996.
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Pannen BHJ., Bauer M, Noldge-Schomburg GFE, Zhang JX, Robotham
JL, Clemens MG, Geiger KK. Regulation of hepatic blood flow during
resuscitation from hemorrhagic shock: role of NO and endothelins.
Am J Physiol. 272 (Heart Circ. Physiol. 41): H2736-H2745, 1997.
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Clemens, M. G., B. H. J. Pannen, M. Bauer, J. X. Zhang. Remodeling
of hepatic microvascular responsiveness following ischemia/reperfusion.
Shock. (8:2): 80-5, 1997.
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Garcia-Pagán, J.C., J. X. Zhang, N. Sonin, K. Nakanishi, M. G.
Clemens. Ischemia/reperfusion induces an increase in the hepatic
portal vasoconstrictive response to endothelin-1. Shock.
11: 325-329, 1999.
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Sonin, N.V., J.C. Garcia-Pagán, K. Nakanishi, J. X. Zhang, M.
G. Clemens. Patterns of vasoregulatory gene expression in the liver
response to ischemia/reperfusion and endotoxemia. Shock.
11: 175-179, 1999.
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Clemens, MG and JX Zhang. Regulation of sinusoidal perfusion:
in vivo methodology and control by endothelins. Seminars in Liver
Disease. 19(4): 383-396, 1999.
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Baveja R, Zhang JX, and Clemens MG. In vivo assessment of endothelin-induced
heterogeneity of hepatic tissue perfusion. Shock. (In Press)
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Yokoyama,
Y., R. Baveja, N. Sonin, K. Nakanishi, J.X. Zhang, and M.G. Clemens.
Altered endothelin receptor subtype expression in hepatic
injury after ischemia/reperfusion.
Shock. 13(1): 72-8, 20
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Bauer,
M., I. Bauer, N. Sonin, N. Kresge, R. Baveja, D. Harding, Y. Yokoyama,
J.X. Zhang, M.G. Clemens. Functional significance of endothelin-B
receptor expression in endotoxemia.
Hepatology. 31(4):
937-47, 2000.
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Lee,
C.Y., J.X. Zhang, H. DeSilva, R.N. Coger, M.G. Clemens. Heterogeneous
flow patterns during hypothermic machine perfusion preservation
of livers. Transplantation.
70(12): 1797-1802, 2000.
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Yokoyama, Y., R. Baveja, N. Sonin,
M.G. Clemens, and J.X. Zhang. Hepatic neovascularization
following partial portal vein ligation: A novel mechanism of
chronic regulation in hepatic blood flow. American Journal of
Physiology. 280(1): G21-G31, 2001.
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Yokoyama, Y., A. Wawrzyniak, R.
Baveja, N. Sonin, M.G. Clemens, and J.X. Zhang. Altered
endothelin receptors in prehepatic portal hypertension in the rat:
predisposition of the hepatic microcirculatory dysfunction.
Journal of Hepatology. 35: 29-36, 2001.
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Baveja, R., J.X. Zhang, and M.G.
Clemens. In vivo assessment of endothelin-induced heterogeneity of
hepatic tissue perfusion. Shock. 15(3): 186-92, 2001.
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Baveja R, Zhang JX, and Clemens
MG. Endothelin-1 induces microheterogeneity of hepatic tissue PO2
in vivo. Shock. 15(3): 186-92, 2001.
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Baveja R, Keller S, Yokoyama Y,
Sonin N, Clemens MG, Zhang JX. LPS-induced imbalanced expression
of hepatic vascular stress genes in cirrhosis: possible mechanism
of increased susceptibility to endotoxemia. Shock. 17(4):
316-21, 2002.
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Yukihiro Yokoyama, Rajiv Baveja,
Nicole Kresge, Natalie Sonin, Kazuya Nakanishi Jian X. Zhang,
Christopher A. Gitzelmann and Mark G. Clemens Endothelin receptor
remodeling induces the portal venous hyper-response to
endothelin-1 following endotoxin pretreatment. Shock.
17(1): 36-40, 2002.
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Lee, C.Y., J.X. Zhang, Jon w.
Jones, James H. Southard, M.G. Clemens. Functional recovery of
preserved livers following warm ischemia: Improvement by machine
perfusion preservation. Transplantation. 74(7): 944-51,
2002.
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Yokoyama Y, Alterman DM, Sarmadi
AH, Baveja R, Zhang JX, Huynh T, Clemens MG. Hepatic vascular
response to elevated intraperitoneal pressure in the rat. J
Surg Res. 105(2): 86-94, 2002.
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Baveja R, Kresge N, Ashburn JH,
Keller S, Yokoyama Y, Sonin N, Zhang JX, Huynh T, Clemens MG.
Potentiated hepatic microcirculatory response to endothelin-1
during polymicrobial sepsis. Shock. 18(5): 415-22, 2002.
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Baveja R, Yokoyama Y, Korneszczuk
K, Zhang JX, Clemens MG. Endothelin 1 impairs oxygen delivery in
livers from LPS-primed animals. Shock. 17(5): 383-8,
2002.
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Rensing H, Bauer I, Zhang JX,
Paxian M, Pannen BH, Yokoyama Y, Clemens MG, Bauer M.
Endothelin-1 and heme oxygenase-1 as modulators of sinusoidal tone
in the stress-exposed rat liver. Hepatology. 36(6):
1453-65, 2002.
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Yokoyama Y, Xu H, Kresge N, Keller
S, Sarmadi AH, Baveja R, Clemens MG, Zhang JX. Role of
thromboxane A2 in early BDL-induced portal hypertension.
American Journal of Physiology. 284(3): G453-60, 2003.
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Lee CY,
Jain S, Duncan HM, Zhang JX, Jones JW Jr, Southard JH, Clemens MG.
Survival transplantation of preserved non-heart-beating donor rat
livers: preservation by hypothermic machine perfusion.
Transplantation. 76(10): 1432-6, 2003.
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Xu, H, Lee CY,
Clemens MG, Zhang JX. Prolonged hypothermic machine perfusion
preserves hepatocellular function but potentiates endothelial
cell dysfunction in rat livers. Transplantation. 77(11):1676-82.
2004.
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Jain S, Xu H,
Duncan H, Jones JW Jr, Zhang JX, Clemens MG, Lee CY. Ex-vivo study
of flow dynamics and endothelial cell structure during extended
hypothermic machine perfusion preservation of livers. Cryobiology.
48(3):322-32. 2004.
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Ashburn JH,
Baveja R, Kresge N, Korneszczuk K, Keller S, Karaa A, Yokoyama Y,
Zhang JX, Huynh T, Clemens MG. Remote trauma sensitizes hepatic
microcirculation to endothelin via caveolin inhibition of eNOS
activity. Shock. 22(2):120-30. 2004.
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Xu
H, Korneszczuk K, Karaa A, Lin T, Clemens MG, Zhang JX. Thromboxane
A2 from Kupffer cells contributes to the hyperresponsiveness of
hepatic portal circulation to endothelin-1 in endotoxemic rats. Am J
Physiol Gastrointest Liver Physiol. 288(2):G277-83. 2005.
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Xu H, Zhang JX,
Jones JW, Southard JH, Clemens MG, Lee CY. Hypothermic machine
perfusion of rat livers preserves endothelial cell function.
Transplant Proc. Jan-Feb;37(1):335-7. 2005.
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Keller
S, Karaa A, Paxian M, Clemens MG, Zhang JX. Inhibition of
endothelin-1-mediated up-regulation of iNOS by bosentan ameliorates
endotoxin-induced liver injury in cirrhosis. Shock.
Mar;25(3):306-13. 2006.
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Yokoyama Y, Wawrzyniak A, Sarmadi AM,
Baveja R, Gruber HE, Clemens MG, Zhang JX. Hepatic Arterial Flow
Becomes the Primary Supply of Sinusoids Following Partial Portal
Vein Ligation in Rats. J Gastroenterol Hepatol. Oct;21(10):1567-74,
2006.
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Karaa
A, Kamoun WS, Xu H, Zhang J, Clemens MG. Differential effects of
oxidative stress on hepatic endothelial and Kupffer cell eicosanoid
release in response to endothelin-1. Microcirculation.
Sep;13(6):457-66, 2006.
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Miller AM, Masrorpour M, Klaus C, and Zhang JX. LPS Exacerbates
Endothelin-1 Induced Activation of Cytosolic Phosoholipase A2 and
Thromboxane A2 Production from Kupffer Cells of the Prefibrotic Rat
Liver. Journal of Hepatology. Feb;46(2):276-85. 2007.
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