Immunohistochemical analysis of sheep skin sections showed
Immunohistochemical analysis of sheep skin sections showed that sGC prtotein is expressed in the hair follicles with different location and abundance between white and black sheep skin (Fig. 6). In white sheep skin, Strong sGC positive signal was detected in the upper hair dermal papilla but no positive signals were found in the lower bulb and outer root sheath. While in black sheep skin, sGC immunostaining was detected in the lower bulb and weak positive signal was also found in the outer root sheath. It has been verified that melanocytes located in the matrix of hair follicle and outer root sheath contributed to color formation. But there are significantly fewer melanocytes in the outer root sheath than in the hair matrix (Slominski et al., 2004).
The further immunocytochemical analysis of melanocytes showed that sGC was expressed in melanocytes with positive signal (Fig. 7). Moreover, cGMP and cAMP was present with the sensitivity (Acetylated) of 3.8fmol/ml and 42fmol/ml, respectively, in the melanocytes in vitro by the ELASA method, which suggested that melanocytes of alpaca were capable of producing cGMP and cAMP. sGC catalyzes the conversion of GTP to cGMP in response to various extracellular stimuli. Regardless of species, all signal transduction through sGC takes place through an increased concentration of cGMP, which is capable of modulating cAMP levels through cGTP-regulated phosphodiesterases (PDEs) (Stangherlin et al., 2011). Phosphodiesterases allow crosstalk between cGMP and cAMP signaling pathways because they cause the concentration of one cyclic nucleotide to influence the degradation of the other (Denninger and Marletta. Denninger and Marletta. 1999). Here, the result suggested that cGMP would make melanins decreased by degradation of cAMP. The molecular mechanisms involved in the cAMP regulation of cellular functions in melanocytes have been well studied (Costin and Hearing 2007) and the important role of cAMP as a key messenger in the regulation of skin pigmentation has been well established (Buscà and Ballotti, 2000). cAMP activates protein kinase A (PKA), and PKA phosphorylates the CREB (cAMP responsive Ac-YVAD-CHO binding protein) family of transcription factors. Once phosphorylated, CREB proteins bind to the cAMP responsive element (CRE) domain present in the MITF promoter, thereby up-regulating its transcription (Buscà and Ballotti, 2000). As a transcription factor, MITF can specifically up-regulate the promoter activities of TYR, TYRP1 and TYRP2 genes (Park and Gilchrest 2002), which encode melanosomal glycoproteins known to be essential for melanin systhesis (Orlow et al., 1994). Given the role of sGC in the conversion of GTP to cGMP, which in turn can modulate cAMP levels, a potential function of sGC in the regulation of melanogenesis is speculated. As so, it is possible that sGC maybe a potential gene to transform the coat color of animals producing wool by the transgenic method.
Conclusions To conclude, our present study demonstrates that the expression of sGC is significantly higher in white vs. black sheep skin both at the mRNA and protein levels. Further, melanocytes of alpaca in vitro were capable of producing cGMP and cAMP. The results provided a new evidence to suggest an additional role for sGC participating in coat color formation in sheep.
Introduction Platelets are not only essential for both physiological and pathological hemostasis but also play significant roles in inflammation, atherosclerosis, and cancer [, , , , , ]. Platelets are the smallest circulating blood cells which have been also termed as sentinels of the vessel wall integrity. The fine-tuning between endogenous activating and inhibitory factors normally prevents spontaneous platelet adhesion to the vessel wall and subsequent platelet activation, thrombus formation and occlusion of blood vessels, the process of hemostasis. However, in the case of vascular injury, platelets adhere to injured endothelium and subendothelial matrix proteins such as collagen to form localized thrombi and prevent blood loss. Both decreased or increased function of human platelets may cause serious, even lethal complications such as bleeding or thrombotic diseases. In addition to their essential regulation of hemostasis and coagulation, activated platelets release and secrete, primarily from their α- and δ-granules, more than 300 biomolecules and proteins, which affect other platelets, blood and vascular cells and tissues [7,8]. These platelet factors regulate many complex physiological and pathophysiological processes such as microvascular integrity, wound healing, inflammation, tumor stability, and metastasis [7,8]. Among the very important vasoactive factors released are thromboxane A2 (TXA2) and adenosine 5′-diphosphate (ADP) which enhance the initial platelet response and recruit additional platelets to the growing thrombus. Targeting and blocking this enhanced platelet activation by TXA2 synthesis inhibitors (aspirin) and/or ADP-receptor antagonists (thienopyridines) has been well established as the most effective intervention to prevent and attenuate complications of various acute and chronic cardiovascular diseases [9,10]. Platelets also contain many components that contribute to innate and adaptive immunity. Fc and complement receptors are expressed on the platelet surface, and platelets can migrate to bacterial chemoattractants, generate free radicals and release antimicrobial peptides (reviewed in Refs. [5,6]).