Dr. Alexander K. Murashov, M.D., Ph.D.
| ||Associate Professor |
Phone: (252) 744-3111
Brody School of Medicine, 6N-74
600 Moye Blvd.
Greenville, NC 27834
1. Epigenetic effect of exercise and high fat diet on offspring susceptibility to obesity and diabetes.
2. Micro RNAs in molecular mechanisms of peripheral nerve regeneration and axon growth.
3. Treating spinal cord injury with stem cells.
Epigenetic effect of paternal high fat diet on offspring susceptibility to obesity and diabetes. Obesity is an important global public health problem (Seidell, 2000), and is a risk factor formorbidity and mortality (Pemberton et al., 2010). National statistics demonstrate continued increases in overweight and obesity among young adults and children over the past three decades (Loomba et al., 2008). Additionally, the obesity epidemic is linked to a startling rise in the incidence of type II diabetes among children. Both obesity and type II diabetes are heritable traits with estimates of >0.70 (Walley et al., 2006), and diabetes heritability estimates ranging from 0.21 to 0.72 (Mathias et al., 2009). Although observations suggest that both genetic and environmental components may play equally important roles in the etiology of type II diabetes, changes in the gene pool of the population over this time frame are not sufficient to explain the recent increase of type II diabetes in adolescents. Rather, such rapid increases in heritable traits are likely due to epigenetic modification of the genome (Permutt et al., 2005) by environment factors (e.g., high fat intake, physical inactivity, etc.). Of particular interest is whether modifications to the genome induced by the environment (i.e., epigenetic effects) may be passed to offspring. Recent studies demonstrating the perpetuation of type II diabetes into second generation offspring in response to maternal diet, support the heritability of these long-term programming effects (Dunn and Bale, 2009). While most studies of epigenetic effects are focused on maternal influences on susceptibility to diabetes, several new lines of evidence indicate that obese (Loomba et al., 2008) and/or diabetic fathers (Harjutsalo et al., 2006) are also likely to have obese offspring predisposed to diabetes. The molecular basis for these epigenetic transgenerational effects is not known, but is likely to involve epigenetic modifications in the methylation state of the DNA, histones and microRNAs (Handel et al., 2010). In the current proposal we propose to test the hypothesis that exposure of male mice to a high fat diet will increase susceptibility to obesity and glucose intolerance in offspring. We further presume that these phenotypic changes will be linked to alterations in DNA methylation, gene and miRNA expression. Aims: 1.To determine effects of paternal high fat diet on offspring postnatal development, post-weaning metabolic profile, and glucose tolerance in comparison to age-matched control offspring of male mice on standard chow. 2.To investigate susceptibility of the offspring from high fat fed fathers to develop obesity and glucose intolerance when fed a high fat diet. 3.To investigate the molecular basis of the epigenetic transgenerational effect of paternal high fat diet by comparing patterns of DNA methylation, gene and miRNA expression of offspring from fathers fed a high fat diet to control offspring from fathers on standard diet.
Molecular mechanisms of peripheral nerve regeneration and axon growth. The peripheral nerve axons are unique in their robust regeneration capacity. A potential role for intra-axonal translation in axon regeneration is of particular interest, considering the fact that selected mRNAs are delivered to sites, that are long distances away from the neuronal cell body. Although axonally translated mRNAs are being identified with increasing frequency, the mechanisms regulating the localized protein synthesis remain largely unknown. We recently asked if axons in severed peripheral nerve have the potential to regulate local protein synthesis through the RNA interference (RNAi); highlighted in the FASEB Journal press release “Getting on your nerves ... and repairing them” 02/15/2007. Our work has shown that PNS axons in vivo and in vitro contain pivotal miRNA machinery proteins, including Dicer, Ago2, and FMRP. While a recent study uncovered a critical role for the miRNA pathway in regulation of actin filament dynamic and spine development in synapto-dendritic compartment, very little is known at present regarding the role of miRNA biogenesis within the axons. In our laboratory, we investigate the function of the miRNA machinery proteins and micro RNAs in PNS axons with particular focus on individual roles of miRNAs and key biosynthetic enzymes in regulation of intra-axonal translation and axonal regeneration. We employ a murine model of sciatic nerve crush to investigate axon remodeling. We examine the nerve from the level of axon function using electrophysiology to the mRNA and protein level using immunohistochemistry and genomic and proteomic analyses. We also perform cell culture and biochemical assays to help resolve mechanistic questions. Interested people may inquire about possible openings in the laboratory.
Treating spinal cord injury with stem cells. Spinal cord injury (SCI) is often followed by chronic pain, which is persistent, intense and refractory to the currently available therapies. While the experiments over the last decade have demonstrated the involvement of a variety of endogenous factors limited success has been achieved in chronic pain treatment. Recent reports revealed a considerable therapeutic potential of embryonic stem (ES) cells. ES cells may be used to generate a variety of cells of adult organism and subsequently applied for treatment of human diseases including injuries of the nervous system. In spite of the recent progress in using ES cell to treat experimental SCI the mechanism of stem cell therapeutic action remains largely unknown. That is why, our long-range goal is to investigate molecular mechanisms of ES cell therapeutic action in the traumatically injured spinal cord. We have recently reported that transplantation of neuronal and glial precursors dramatically improves sensorimotor function after contusion injury. Moreover, our preliminary observations showed that ES cells predifferentiated into dorsal interneurons could restore sensory function and prevent development of chronic pain after SCI. Research from our laboratory indicates that transplantation of ES cells has neurotrophic effects, which can be observed as early as two days after transplantation. This neurotrophic action also persists for a long period, up to 60 days (last examined time point). The initial analyses revealed a decrease in levels of inflammatory cytokines, and increase in neurotrophic factors, and cyclic adenosine monophosphate (cAMP) two days after transplantation. These preliminary data let us to hypothesize that (a) ES cells, predifferentiated into dorsal interneurons, may provide upon transplantation anatomical, neurochemical and physiological recovery and prevent development of chronic pain; and (b) that the mechanism of therapeutic action of ES cells involves secretion of neurotrophins with subsequent activation of cAMP in the host tissue, promoting regeneration of axonal fibers. To verify our hypothesis, we are examining some of the signaling pathways activated in the host cells and stem cells after transplantation. Specifically, we are using the variations of co-culture experiments and molecular biological approaches to determine if there are correlative changes in cell survival and regeneration and the associated signaling pathways.
EMPLOYMENT / EDUCATION
Associate Professor (2006-present)
Assistant Professor (1999-2006)
Department of Physiology
Brody School of Medicine at East Carolina University
Associate Research Scientist (1995-1999)
Postdoctoral Scientist (1992-1995)
New York, NY, USA
NHMRC Research Officer (1990-1992)
Visiting Scientist (1990)
Howard Florey Institute of Experimental Physiology and Medicine
University of Melbourne
Group Leader, Stress Physiology (1988-90)
P.K. Anokhin Institute of Normal Physiology
Academy of Medical Sciences
Assistant Professor (1987-1988)
Department of Normal Physiology,
Sechenov 1st Medical Institute,
Ministry of Health,
Doctor of Philosophy in Physiology (1987)
P.K. Anokhin Institute of Normal Physiology
Academy of Medical Sciences
Doctor of Medicine in Pediatrics (1983)
N.I. Pirogov 2nd Moscow Medical Institute
Ministry of Health
1: Wu D, Raafat A, Pak E, Clemens S, Murashov AK. Dicer-microRNA pathway is
critical for peripheral nerve regeneration and functional recovery in vivo and
regenerative axonogenesis in vitro. Exp Neurol. 2012 Jan;233(1):555-65. Epub 2011
Dec 8. PubMed PMID: 22178326; PubMed Central PMCID: PMC3268911.
2: Wu D, Pak ES, Wingard CJ, Murashov AK. Multi-walled carbon nanotubes inhibit
regenerative axon growth of dorsal root ganglia neurons of mice. Neurosci Lett.
2012 Jan 17;507(1):72-7. Epub 2011 Dec 6. PubMed PMID: 22172934; PubMed Central
3: Wu D, Raafat M, Pak E, Hammond S, Murashov AK. MicroRNA machinery responds to
peripheral nerve lesion in an injury-regulated pattern. Neuroscience. 2011 Sep
8;190:386-97. Epub 2011 Jun 12. PubMed PMID: 21689732; PubMed Central PMCID:
4: Glazova M, Hollis S, Pak ES, Murashov AK. Embryonic stem cells inhibit
expression of erythropoietin in the injured spinal cord. Neurosci Lett. 2011 Jan
13;488(1):55-9. Epub 2010 Nov 5. PubMed PMID: 21056627.
5: Pan X, Murashov AK, Stellwag EJ, Zhang B. Monitoring microRNA expression
during embryonic stem-cell differentiation using quantitative real-time PCR
(qRT-PCR). Methods Mol Biol. 2010;650:213-24. PubMed PMID: 20686954.
6: Murashov AK. A brief introduction to RNAi and microRNAs in stem cells. Methods
Mol Biol. 2010;650:15-25. Review. PubMed PMID: 20686940.
7: Lever TE, Simon E, Cox KT, Capra NF, O'Brien KF, Hough MS, Murashov AK. A
mouse model of pharyngeal dysphagia in amyotrophic lateral sclerosis. Dysphagia.
2010 Jun;25(2):112-26. Epub 2009 Jun 3. PubMed PMID: 19495873.
8: Verrier JD, Lau P, Hudson L, Murashov AK, Renne R, Notterpek L. Peripheral
myelin protein 22 is regulated post-transcriptionally by miRNA-29a. Glia. 2009
Sep;57(12):1265-79. PubMed PMID: 19170179; PubMed Central PMCID: PMC2713384.
9: Glazova M, Pak ES, Moretto J, Hollis S, Brewer KL, Murashov AK.
Pre-differentiated embryonic stem cells promote neuronal regeneration by
cross-coupling of BDNF and IL-6 signaling pathways in the host tissue. J
Neurotrauma. 2009 Jul;26(7):1029-42. PubMed PMID: 19138107.
10: Lever TE, Gorsek A, Cox KT, O'Brien KF, Capra NF, Hough MS, Murashov AK. An
animal model of oral dysphagia in amyotrophic lateral sclerosis. Dysphagia. 2009
Jun;24(2):180-95. Epub 2008 Dec 24. PubMed PMID: 19107538.
11: Becerra GD, Tatko LM, Pak ES, Murashov AK, Hoane MR. Transplantation of
GABAergic neurons but not astrocytes induces recovery of sensorimotor function in
the traumatically injured brain. Behav Brain Res. 2007 Apr 16;179(1):118-25. Epub
2007 Feb 1. PubMed PMID: 17324477; PubMed Central PMCID: PMC1880895.
12: Murashov AK, Chintalgattu V, Islamov RR, Lever TE, Pak ES, Sierpinski PL,
Katwa LC, Van Scott MR. RNAi pathway is functional in peripheral nerve axons.
FASEB J. 2007 Mar;21(3):656-70. Epub 2007 Jan 5. PubMed PMID: 17209129.
13: Hendricks WA, Pak ES, Owensby JP, Menta KJ, Glazova M, Moretto J, Hollis S,
Brewer KL, Murashov AK. Predifferentiated embryonic stem cells prevent chronic
pain behaviors and restore sensory function following spinal cord injury in mice.
Mol Med. 2006 Jan-Mar;12(1-3):34-46. PubMed PMID: 16838066; PubMed Central PMCID:
14: Kokiko ON, Murashov AK, Hoane MR. Administration of raloxifene reduces
sensorimotor and working memory deficits following traumatic brain injury. Behav
Brain Res. 2006 Jun 30;170(2):233-40. Epub 2006 Apr 3. PubMed PMID: 16580743.
15: Murashov AK, Pak ES, Katwa LC. Parallel development of cardiomyocytes and
neurons in embryonic stem cell culture. Biochem Biophys Res Commun. 2005 Jul
8;332(3):653-6. PubMed PMID: 15894285.
16: Murashov AK, Pak ES, Hendricks WA, Owensby JP, Sierpinski PL, Tatko LM,
Fletcher PL. Directed differentiation of embryonic stem cells into dorsal
interneurons. FASEB J. 2005 Feb;19(2):252-4. Epub 2004 Nov 15. PubMed PMID:
17: Islamov RR, Chintalgattu V, Pak ES, Katwa LC, Murashov AK. Induction of VEGF
and its Flt-1 receptor after sciatic nerve crush injury. Neuroreport. 2004 Sep
15;15(13):2117-21. PubMed PMID: 15486493.