PDGFR?~+ Cell/SK3 Channel And Its Mechanism In Diabetes-induced Colonic Slow Transit

Reflecting the aging global population and the improvement of living standards,the increasing prevalence of diabetes mellitus?DM?has attracted extensive attention from the whole society.DM is a kind of metabolic disease,which affects all the systems in the patients,including nervous system,respiratory system,gastrointestinal system,circulatory system and so on.Patients with DM suffer from a variety of gastrointestinal?GI?complications,such as diarrhoea,gastroparesis,chronic constipation and faecal incontinence.Among these complications,chronic constipation is the most common GI symptom of DM that significantly affects patient quality of life.Unfortunately,the mechanisms of chronic constipation in DM patients remain ambiguous,leading to no effective therapeutic trials available concerning this complaint.Thus,it is of great significance to explore the mechanism of diabetes-induced slow transit constipation.Platelet-derived growth factor receptor alpha-positive cells?PDGFR?⁺cells?are one kind of GI interstitial cells.PDGFR?⁺cells and ICCs are electrically coupled to smooth muscle cells?SMCs?by gap junctions,forming a syncytium called the SIP syncytium.Small-conductance Ca²⁺-activated K⁺channels?SK3?and purinergic P2Y1 receptors,which are highly expressed in PDGFR?⁺cells,are fundamental to regulating the motility of GI tract.In GI tract,PDGFR?⁺cells transduce purine rgic signals from enteric motor neurons and exert inhibitory effect on colonic motility.In the recent study of our laboratory,we have recently found that PDGFR?⁺cells were proliferative and exhibited increased density,which was mediated by the forkhead box O3?FOXO3?up-regulation via the inhibition of the phosphatidylinositol-4,5-bisphosphate 3-kinase/protein kinase B?PI3K/Akt?signaling pathway in STZ-induced diabetic mice.However,the consequences of PDGFR?⁺cell over-expression on colonic motility in diabetic mice have not been studied previously.Based on the previous study of our laboratory,the present study was designed to investigate the role of over-expressed PDGFR?⁺cell in diabetes-induced colonic dysmotility and reveal the mechanism of diabetes-induced slow transit constipation.Our study may provide a potential target for the treatment of diabetes-induced slow transit constipation.In our study,we investigate the role of PDGFR?⁺cells,SK3 channels and P2Y1 receptors in the diabetic-induced slow transit constipation by the combination of the electrophysiological methods and the molecular biological methods in the STZ-induced type 1 mouse model.Firstly,we confirmed the occurrence of the slow transit constipation in diabetic mice,with the recording of the colonic migrating motor complex.Next,we found that the expressions of PDGFR?⁺cells,SK3 channels and P2Y1 receptors were up-regulated using the molecular biological methods.The isometric contractile experiments and intracellular recordings revealed that the colonic smooth muscles are more sensitive to the SK3 and P2Y1 agonists and antagonists in diabetic mice and the up-regulated SK3 channels and P2Y1 receptors mediated the hyperpolarization of diabetic smooth muscle cells.Additionally,in intracellular recording,the amplitude of fIJP was increased in diabetic mice,which was mediated by the purinergic neurotransmitters-P2Y1 receptors-SK3 channels signaling pathway.Besides,the whole-cell patch technique showed that the sensitivity of SK3channels to Ca²⁺in PDGFR?⁺cells in diabetic mice were decreased.Next,the calcium imaging showed that the ATP-induced Ca²⁺increase was elevated in PDGFR?⁺cells in diabetic mice.These results suggested that:The diabetes mellitus results in the slow transit constipation in STZ-induced type 1 mouse model.The up-regulated purinergic neurotransmitters-P2Y1 receptors-SK3 channels signaling pathway in PDGFR?⁺cells mediated the RMP hyperpolarization of smooth muscle cells,resulting in the colonic dysmotility,which eventually led to the slow transit constipation in diabetic mice.The sensitivity of SK3 channels to Ca²⁺in PDGFR?⁺cells in diabetic mice were decreased and the functionally up-regulated P2Y1 receptors promoted the activation of SK3channels,which indicated the alteration of dynamic characteristics of SK3channels in diabetic mice.