ABSTRACT
Background/Aims@#The gastrointestinal symptom of diabetes mellitus, chronic constipation, seriously affects patients’ life. Whereas, the mechanism of chronic constipation is still ambiguous, resulting in a lack of effective therapies for this symptom. As a part of the smooth muscle cells, interstitial cells of Cajal, and platelet-derived growth factor receptor alpha-positive (PDGFRα+ ) cells syncytium (SIP syncytium), PDGFRα+ cells play an important role in regulating colonic motility. According to our previous study, in PDGFRα+cells in colons of diabetic mice, the function of the P2Y1 purinergic receptor/type 3 small-conductance calcium-activated potassium (SK3) channel signaling pathway is strengthened, which may lead to colonic dysmotility. The purpose of this study is to investigate the changes in SK3 channel properties of PDGFRα+ cells in diabetic mice. @*Methods@#Whole-cell patch clamp, Western blotting, superoxide dismutase activity measurement, and malondialdehyde measurement were main methods in the present study. @*Results@#The present study revealed that when dialysed with low calcium ion (Ca 2+ ) solution, the SK3 current density was significantly decreased in PDGFRα+ cells from diabetic mice. However, the SK3 current density in PDGFRα+ cells was enhanced from diabetic mice when dialysed with high Ca 2+ solution. Moreover, hydrogen peroxide-treatment mimicked this phenomenon in SK3 transgenic HEK293 cells. The subunit of SK3 channels, protein kinase CK2, was up-regulated in colonic muscle layers and hydrogen peroxidetreated HEK293 cells. Additionally, protein phosphatase 2A, the subunit of SK3 channels, was not changed in streptozotocin-treated mouse colons or hydrogen peroxide-treated HEK293 cells. @*Conclusion@#The diabetic oxidative stress-induced upregulation of CK2 contributed to modulating SK3 channel sensitivity to Ca 2+ in colonic PDGFRα+ cells, which may result in colonic dysmotility in diabetic mice.
ABSTRACT
Under physiological conditions, the motility of smooth muscle in digestive tract is mainly regulated by enteric nervous system (ENS). However, how neural signal is transmitted to smooth muscle is not fully understood. Autonomic nerve endings in the smooth muscle layer form large number of varicosities which contain neurotransmitters. It was considered that nerve pulses arriving at the varicosities may cause the release of neurotransmitters, which may diffuse to the smooth muscle cells to induce contractile or relaxant responses. Over the past decade, a new understanding of the neurotransmission between ENS and smooth muscle has emerged, which emphasizes the role of a functional syncytium consisting of the interstitial cells of Cajal (ICC), the platelet-derived growth factor receptor α positive (PDGFRα) cells and the smooth muscle cells. Within the syncytium, purine neurotransmitters bind to P2Y1 receptors on PDGFRα cells, activating small-conductance calcium activated potassium channel (SK3) to hyperpolarize PDGFRα cells, and thus hyperpolarize smooth muscle cells through gap junction, resulting in relaxation of smooth muscle. In this paper, we review the research progress in the field of inhibitory purinergic neurotransmission in the gastrointestinal tract.
Subject(s)
Interstitial Cells of Cajal , Muscle, Smooth , Myocytes, Smooth Muscle , Receptor, Platelet-Derived Growth Factor alpha , Synaptic TransmissionABSTRACT
<p><b>OBJECTIVE</b>To investigate the frequency of the mutations in Uyghur nonsyndromic deafness groups in Kashgar region of Xinjiang province by means of screening the common mutations of known deafness genes in China.</p><p><b>METHODS</b>One hundred and seventy-four Uyghur patients with hearing loss were involved in this study. Questionnaire survey was conducted and peripheral blood samples were collected for polymerase chain reaction. Screening was performed for 35delG, 176-191del16, 235delC, 299-300delAT, 1555A > G, 1494C > T, 2168A > G and IVS7-2A > G. DNA sequence analysis was performed for the samples with absent signals at some loci. SPSS 17.0 software was used to analyze the data.</p><p><b>RESULTS</b>Mutation of GJB2 was the most common among the three known deafness genes. 187delG was found for the first time in Uyghur groups with hearing loss and was a new pathological mutation of GJB2. The mutation rate of SLC26A4 was low in the experimental group with no significant difference when compared with the control group. The mtDNA 12S rRNA mutation rate in the deaf group was low but not detected in the control group. In addition, mutations were not detected in 17 cases among the 20 patients with positive family history.</p><p><b>CONCLUSION</b>The mutation rate and dominant mutation of Uyghur ethnic nonsyndromic deaf groups have their own characteristics, it is necessary to conduct a sequence analysis and a stemma studying for an aim of perfecting the mutation spectrum of Uyghur deafness gene.</p>