Areas of Interest
Dr. Epstein's laboratory has been studying cyclic nucleotide
phosphodiesterases (PDE), a large family of isozymic enzymes
which control the cellular levels of two key signal transduction
molecules, cAMP and cGMP, and thereby play a role in controlling
a wide variety of critical cellular functions. Through cloning
and sequence analysis, he is identifying different forms of
phosphodiesterase and determining their expression and
subcellular localization during normal development and in
association with pathophysiological disease states. One disease
sate he is concentrating on in particular is leukemia. He has
found that a 63 kDa form of calmodulin-dependent PDE (PDE1B1) is
expressed in leukemia cells but not in normal quiescent human
lymphocytes. He cloned the cDNA for this gene and developed
antisense oligonucleotides (ASODNs) against it. When he disrupts
the expression of the gene for PDE1B1 with these AS ODNs, it
triggers apoptosis in leukemic cells without any effect on
normal resting lymphocytes. Hence these studies pioneer the
basis for a possible new therapy for leukemia. Similar studies
are now being undertaken with respect to breast cancer.
Lab Rotation Projects
Most of the emphasis of the lab at the moment is identifying
forms of PDE as targets for inducing apoptosis of cancer cells.
We are also collaborating with two colleagues in Pharmacology,
Drs. Joel Pachter and Stefan Brocke, to examine a potential role
for inhibitors of PDE to strengthen the blood brain barrier as a
means of treating Alzheimer’s Disease, and to examine a
potential role for PDEs in regulating lymphocyte chemotaxis and
transendothelial migration in relation to treating multiple
sclerosis. Students are free to design their own projects, but
possibilities are:
Project 1: We have found that stimulating the cAMP signaling
pathway can overcome the resistance to inducing apoptosis in
leukemic cells from patients that have developed glucocorticoid
resistance (see: Tiwari, S. et al. “Type 4 cAMP
Phosphodiesterase (PDE4) Inhibitors Augment Glucocorticoid-Mediated
Apoptosis in B Cell Chronic Lymphocytic Leukemia (B-CLL) in the
Absence of Exogenous Adenylyl Cyclase Stimulation.” Biochem.
Pharmacol. 69:473-483, 2005). The mechanism of this effect is,
however, still unknown. One hypothesis we have is that cAMP
signaling may enhance the expression and/or function of the
BH3-only proapoptotic proteins BAD and BIM, leading to apoptosis
of these resistant cells, and this could be examined as a
rotation project.
Project 2: Work from Dr. Pachter’s laboratory has pioneered a
method for culturing primary brain microvascular endothelial
cells (BMEC) in a manner in which the tight junctions of the
endothelial cells are preserved (see: Song, L. and Pachter, J.
S. Culture of murine brain microvascular endothelial cells that
maintain expression and cytoskeletal association of tight
junction-associated proteins. In Vitro Cell Dev Biol Anim, 39:
313-320, 2003). This therefore provides a model in vitro system
in which to examine the effects of agents on the blood brain
barrier. We hypothesize that PDE inhibitors will strengthen the
blood brain barrier by enhancing the expression of expression of
the tight junction-associated proteins, claudin-5, occludin, and
zona occludin-1 (ZO-1), and this could be examined as a rotation
project.
Project 3: PDE4 inhibitors have been shown to be effective in
ameliorating the pathogenesis associated with multiple sclerosis
(MS) in EAE animal models of this disease, though it is unclear
how they work in this regard. We hypothesize that PDE4
inhibitors block T lymphocyte chemotaxis and transendothelial
migration through their ability to induce phosphorylation and
inactivation of rhoA resulting in decreased phosphorylation of
myosin light chain, and, with the help of Dr. Brocke who is a
renowned expert in this area, this can be tested in a rotation
project.
Selected Publications
Dong, H, Osmanova, V, Epstein, P.M. and Brocke, S
Phosphodiesterase 8 (PDE8) Regulates Chemotaxis of Activated
Lymphocytes. Biochem. Biophys. Res. Commun. 345:7113-719, 2006.
Lerner, A. and Epstein, P.M. Cyclic Nucleotide
Phosphodiesterases as Targets for Treatment of Haematological
Malignancies. Biochem. J. 393:21-41, 2006.
Tiwari, S., Dong, H., Kim, E.J., Weintraub, L., Epstein, P.M.
and Lerner, A. Type 4 cAMP Phosphodiesterase (PDE4) Inhibitors
Augment Glucocorticoid-Mediated Apoptosis in B Cell Chronic
Lymphocytic Leukemia (B-CLL) in the Absence of Exogenous
Adenylyl Cyclase Stimulation. Biochem Pharmacol 69:473-483,
2005.
Lu Y., Li Y., Herin G.A., Aizenman E., Epstein P.M., and
Rosenberg, P.A. Elevation of Intracellular cAMP Evokes
Activity-Dependent Release of Adenosine in Cultured Rat
Forebrain Neurons. Eur. J. Neuroscience 19:2669-2681, 2004.
Le, M., Lu, Y., Li, Y., Greene, R.W., Epstein, Paul M., and
Rosenberg, P.A. Zaprinast Stimulates Extracellular Adenosine
Accumulation in Rat Pontine Slices. Neurosci Lett 371:12-17,
2004.
Andreeva, S.G., Dikkes, P., Epstein, P.M. and Rosenberg, P.A.
Expression of cGMP-Specific Phosphodiesterase 9A mRNA in the Rat
Brain. J. Neurosci 21:9068-9076, 2001.
Paskind, M., Johnston, C., Epstein, P.M., Timm, J.,
Wickramasinghe, D., Balenger, E., Rodman, L., Magada, D., and
Voss, J. 2000. Structure and Promoter Activity of the Mouse Cdc
25A Gene. Mammalian Genome 11:1063-1069. |
