| Intracellular calcium signaling plays an important role in the smooth muscle contraction. The calcium concentration is a key factor in triggering the contraction of smooth muscle cells. Therefore, calcium channel has a crucial role in smooth muscle contraction function.In a variety of tissues and cells, store-operated calcium entry(SOCE) is an important way mediating calcium entry into the cells. SOCE refers that the emptying of intracellular calcium stores(usually means endoplasmic reticulum or sarcoplasmic reticulum) activates Orai1 channels on the cell membrane, thereby mediating extracellular calcium influx. The purpose of this reaction is mainly to supplement the loss of calcium in calcium store. The present study demonstrated that a single transmembrane protein STIM1 on endoplasmic reticulum membrane is a calcium sensor. When the calcium store is depleted, STIM1 will sense the depletion and thus be activated, causing STIM1 puncta formation and translocation into the endoplasmic reticulum-plasma membrane contact junction. After then, STIM1 interacts with Orai1 channels in the cell membrane. After Orai1 channels are opened, the channels mediate calcium influx response. Because this mechanism was well documented in recent years, the functional studies in various tissues has become a hot research filed. However, the changes of SCOE in smooth muscle tissue with aging has not been fully elucidated; thusin this study we used different muscle tissues to elucidate the function of SOCE in the contraction of smooth muscle cells.The study was divided into two parts to clarify the functional role of SOCE in smooth muscle contraction induced by agonists and the changes of SOCE with aging:(1) the change of agonist-induced store-operated Ca2+ entry and vasoconstriction patterns in mesenteric arteries and aortae with aging;(2) the change of store-operated Ca2+ entry in aged animals intestinal smooth muscle and its impact on the contractile function. Through this study, we can clarify the change of SOCE in aged animal muscle tissues. Furthermore, the study provides a new theoretical basis for the functional changing of various tissues with aging. In addition, the present study provides a new therapeutic target for clinical treatment for the diseases associated with aging as well.1. The change of agonist-induced store-operated Ca2+ entry and vasoconstriction patterns in mesenteric arteries and aortae with agingIn this study, the aged and young rats were the research objects, SOCE-induced vascular smooth muscle cell contraction evoked by agonists was investigated. At the same time, the changes of the contraction function in the vascular smooth muscle cells with aging were compared. Calcium imaging, vascular contraction measurement, western blot and immunofluorescence methods were used. SOCE-induced contractions evoked by agonists in young and aged rat thoracic aorta and mesenteric artery smooth muscle tissue were compared and the changes of Orai1 and STIM1 protein expression levels were investigated as well. Through the study, we found that(1) calcium imaging data showed that thapsigargin-induced vascular smooth muscle cell SOCE in aged rats mesenteric artery was ignificantly enhanced, but instead, SOCE in the thoracic aorta of aged rats was significantly reduced;(2) vessel contraction measurement results showed that SOCE-induced vessel contraction evoked by thapsigargin, α-receptor agonistphenylephrine or endothelin receptor agonist ET-1 was significantly increased in mesenteric artery smooth muscle tissue of aged rats, but reversely significantly reduced in the thoracic aorta smooth muscle tissue of aged rats;(3) western blot and immunofluorescence results showed that the expression levels of Orai1 were significantly increased in mesenteric artery smooth muscle in the aged rats, but reduced in the thoracic aorta smooth muscle in aged rats. Through the above study, we demonstrate that with aging SOCE will be significantly changed in vascular smooth muscle tissue. The contrasting patterns of Orai1 expression change in aged and young mesenteric artery and thoracic aorta smooth muscle tissue may be the cause of the changes of the contractile function. At the same time, because calcium signaling plays an important role in vascular smooth muscle contraction, our findings may provide a therapeutic target for the age-related diseases in clinical.2. The change of store-operated Ca2+ entry in aged animals intestinal smooth muscle and its impact on the contractile functionIn this study, with the use of aged and young mice, we further explored the changes of SOCE in intestinal smooth muscle tissue and its impact on the contractile function with aging. The tension measurement, western blotting and immunohistochemistry were used to detect and compare the changes of SOCE-induced contraction evoked by agonist in intestinal smooth muscle tissue of young and aged mice and the changes of protein expression levels of Orai1 and STIM1 as the main components of SOCE. We found that(1) there was no significant difference in the weight of the aged and young mice intestine tissues;(2) 80 mmol/L high potassium solution-induced contraction of the small intestine was significantly decreased in aged mice;(3) acetylcholine-induced small intestinal contractility was also significantly reduced in the aged mice;(4) small intestinal contractility induced by acetylcholine- and thapsigargin-evoked SOCE were significantly reduced in the aged mice;(5) western blotting and immunohistochemistryhave shown that the protein expression levels of Orai1 and STIM1 were significantly decreased in the aged intestinal smooth muscle tissue. The above results suggest that SOCE plays an important role in the mouse small intestinal smooth muscle contraction. In addition, with aging the decreased function of SOCE may be a reason to cause the impaired contractile function in small intestine. This study provides an evidence of the aged bowel dysfunction and disorders. Moreover, the present study also provide a new potential therapeutic target for clinical treatment. |
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