The science behind bio forge

[THEHUGE]

Icariin stimulates angiogenesis by activating the MEK/ERK- and PI3K/Akt/eNOS-dependent signal pathways in human endothelial cells.Chung BH, Kim JD, Kim CK, Kim JH, Won MH, Lee HS, Dong MS, Ha KS, Kwon YG, Kim YM.
Vascular System Research Center and Department of Molecular and Cellular Biochemistry, School of Medicine, Kangwon National University, Chunchon, Kangwon-do 200-701, Republic of Korea.

We investigated the molecular effect and signal pathway of icariin, a major flavonoid of Epimedium koreanum Nakai, on angiogenesis. Icariin stimulated in vitro endothelial cell proliferation, migration, and tubulogenesis, which are typical phenomena of angiogenesis, as well as increased in vivo angiogenesis. Icariin activated the angiogenic signal modulators, ERK, phosphatidylinositol 3-kinase (PI3K), Akt, and endothelial nitric oxide synthase (eNOS), and increased NO production, without affecting VEGF expression, indicating that icariin may directly stimulate angiogenesis. Icariin-induced ERK activation and angiogenic events were significantly inhibited by the MEK inhibitor PD98059, without affecting Akt and eNOS phosphorylation. The PI3K inhibitor Wortmannin suppressed icariin-mediated angiogenesis and Akt and eNOS activation without affecting ERK phosphorylation. Moreover, the NOS inhibitor NMA partially reduced the angiogenic activity of icariin. These results suggest that icariin stimulated angiogenesis by activating the MEK/ERK- and PI3K/Akt/eNOS-dependent signal pathways and may be a useful drug for angiogenic therapy.

[THEHUGE]

Supplemental nitric oxide augments satellite cell activity on cultured myofibers from aged mice.Betters JL, Lira VA, Soltow QA, Drenning JA, Criswell DS.
Center for Exercise Science, Department of Applied Physiology & Kinesiology, University of Florida, P.O. Box 118206, Gainesville, FL 32611, USA.

Skeletal muscle regenerative potential is reduced with aging. We hypothesized that in vitro activation of muscle satellite cells would be compromised, and that nitric oxide (NO) supplementation would improve satellite cell activity in old muscle. Single intact myofibers were isolated from the gastrocnemius muscles of young (2mo), adult (10mo), and aged (22mo) mice. Fibers were centrifuged to stimulate satellite cells and incubated with a NO donor or control media for 48h. The number of activated satellite cells after centrifugation was reduced in aged fibers compared to young and adult. NO treatment increased satellite cell activation in all age groups. However, an age-dependent deficit in satellite cell activity persisted within treatment groups. In separate fibers, exogenous HGF was equally effective in activating satellite cells across age groups, indicating that events downstream of HGF release are intact in aged muscle. These data suggest that NO production limit muscle satellite cell activity in response to a submaximal mechanical stimulus, regardless of age. Further, the decline in satellite cell activity in early senescence can be partially abrogated by a NO donor.

[THEHUGE]

Follistatin induction by nitric oxide through cyclic GMP: a tightly regulated signaling pathway that controls myoblast fusion.Pisconti A, Brunelli S, Di Padova M, De Palma C, Deponti D, Baesso S, Sartorelli V, Cossu G, Clementi E.
Stem Cell Research Institute, Hospital San Raffaele, 20132 Milan, Italy.

The mechanism of skeletal myoblast fusion is not well understood. We show that endogenous nitric oxide (NO) generation is required for myoblast fusion both in embryonic myoblasts and in satellite cells. The effect of NO is concentration and time dependent, being evident only at the onset of differentiation, and direct on the fusion process itself. The action of NO is mediated through a tightly regulated activation of guanylate cyclase and generation of cyclic guanosine monophosphate (cGMP), so much so that deregulation of cGMP signaling leads to a fusion-induced hypertrophy of satellite-derived myotubes and embryonic muscles, and to the acquisition of fusion competence by myogenic precursors in the presomitic mesoderm. NO and cGMP induce expression of follistatin, and this secreted protein mediates their action in myogenesis. These results establish a hitherto unappreciated role of NO and cGMP in regulating myoblast fusion and elucidate their mechanism of action, providing a direct link with follistatin, which is a key player in myogenesis.

[THEHUGE]

Follistatin complexes Myostatin and antagonises Myostatin-mediated inhibition of myogenesis.Amthor H, Nicholas G, McKinnell I, Kemp CF, Sharma M, Kambadur R, Patel K.
Department of Veterinary Basic Sciences, Royal Veterinary College, London NW1 OTU, UK.

Follistatin is known to antagonise the function of several members of the TGF-beta family of secreted signalling factors, including Myostatin, the most powerful inhibitor of muscle growth characterised to date. In this study, we compare the expression of Myostatin and Follistatin during chick development and show that they are expressed in the vicinity or in overlapping domains to suggest possible interaction during muscle development. We performed yeast and mammalian two-hybrid studies and show that Myostatin and Follistatin interact directly. We further show that single modules of the Follistatin protein cannot associate with Myostatin suggesting that the entire protein is required for the interaction. We analysed the interaction kinetics of the two proteins and found that Follistatin binds Myostatin with a high affinity of 5.84 x 10(-10) M. We next tested whether Follistatin suppresses Myostatin activity during muscle development. We confirmed our previous observation that treatment of chick limb buds with Myostatin results in a severe decrease in the expression of two key myogenic regulatory genes Pax-3 and MyoD. However, in the presence of Follistatin, the Myostatin-mediated inhibition of Pax-3 and MyoD expression is blocked. We additionally show that Myostatin inhibits terminal differentiation of muscle cells in high-density cell cultures of limb mesenchyme (micromass) and that Follistatin rescues muscle differentiation in a concentration-dependent manner. In summary, our data suggest that Follistatin antagonises Myostatin by direct protein interaction, which prevents Myostatin from executing its inhibitory effect on muscle development

[THEHUGE]

The role of nitric oxide (NO) in control of LHRH release that mediates gonadotropin release and sexual behavior.McCann SM, Haens G, Mastronardi C, Walczewska A, Karanth S, Rettori V, Yu WH.
Pennington Biomedical Research Center, Louisiana State University, 6400 Perkins Road, Baton Rouge, Louisiana 70808-4124, USA. mccannsm@pbrc.edu

Nitric oxide (NO) plays a crucial role in reproduction at every level in the organism. In the brain, it activates the release of luteinizing hormone-releasing hormone (LHRH). The axons of the LHRH neurons project to the mating centers in the brain stem and by efferent pathways, evoke the lordosis reflex in female rats. In males, there is activation of NOergic terminals that release NO in the corpora cavernosa penis to induce erection by generation of cyclic guanosine monophosphate (cGMP). NO also activates the release of LHRH which reaches the pituitary and activates the release of gonadotropins by activating neural NO synthase (NOS) in the pituitary gland. Follicle stimulating hormone (FSH)RH selectively releases FSH also by activating NOS. Leptin releases LHRH by activating NOS to release FSH and LH with the same potency as LHRH. These actions are mediated by specific receptors on the gonadotropes for LHRH, FSHRH and leptin.

[THEHUGE]

Protein kinase G-mediated stimulation of basal Leydig cell steroidogenesis.Andric SA, Janjic MM, Stojkov NJ, Kostic TS.
Laboratory for Reproductive Endocrinology and Signaling, DBE, Faculty of Sciences, University of Novi Sad, Dositeja Obradovica Square 2, 21000, Novi Sad, Serbia.

The androgen-secreting Leydig cells produce cGMP, but the pathways responsible for generation and actions of this intracellular messenger have been incompletely characterized in these cells. Here, we show the presence of mRNA transcripts for the membrane-bound and soluble guanylyl cyclases (sGC), the cGMP-specific phosphodiesterase 5, and the cGMP-dependent protein kinase I (PKG I) and PKG II in purified rat Leydig cells from adult animals. Stimulation of both guanylyl cyclases and inhibition of phosphodiesterase 5 in vitro were accompanied by elevations in cGMP and androgen production, whereas inhibition of sGC and PKG led to a decrease in steroidogenesis. The stimulatory action of cGMP on steroidogenesis was preserved in cells with inhibited cAMP-dependent protein kinases. Experiments with exogenously added substrates revealed the dependence of cGMP-induced androgen synthesis on cholesterol but not on 22-OH cholesterol, pregnenolone, progesterone, and Delta(4)-androstenedione. These results suggest that cGMP contributes to the control of basal steroidogenesis in Leydig cells through the PKG-dependent modification of the StAR protein.

PMID: 17848628 [PubMed - indexed for MEDLINE]

--------------------------------------------------------------

Multiple roles of the messenger molecule cGMP in testicular function.Middendorff R, Davidoff MS, Behrends S, Mewe M, Miethens A, Müller D.
Institute of Anatomy, University of Hamburg, Germany. middendo@uke.uni-hamburg.de

The messenger molecule cyclic guanosine monophosphate (cGMP) is produced by different isoforms of the enzyme guanylate cyclase (GC). Natriuretic peptides (ANP and CNP) bind to and activate particulate GCs, whereas NO and CO activate a soluble form of GC. The specific relevance of the cGMP system for reproductive functions has been recently demonstrated by the successful use of sildenafil (Viagra), an inhibitor of cGMP-specific phosphodiesterase type 5, for the treatment of erectile dysfunction. In the testis, cGMP signal transduction pathways are involved in a variety of local functions, based on autocrine or paracrine effects. In particular, cGMP has been suggested to influence motility in spermatozoa, development of testicular germ cells, relaxation of peritubular lamina propria cells, testosterone synthesis in Leydig cells and dilatation of testicular blood vessels. The physiological significance of cGMP accumulation in Sertoli cells is not yet clear. Taken as a whole, the evidence suggests that cGMP-mediated processes might influence both the potentia coeundi within the penis and the potentia generandi at various levels within the testis.

PMID: 10702869 [PubMed - indexed for MEDLINE]