Influence Of Atherosclerosis To The Molecular Expressions Of TRPC1-BK Signal Complex In Aortic Smooth Muscle Of Mice

[Backgrounds]Ischemic cardiovascular diseases like coronary atherosclerotic heart disease and ischemic cerebrovascular disease are popular but non-infectious diseases,and they have become a serious threat to human health.The initiation and progression of atherosclerotic plaque in aortas are the important pathophysiological basis of these diseases.Calcium ion inside smooth muscle cells not only acts as a main factor regulating cell contraction and relaxation processes.Morever,it also plays a key role in smooth muscle cell migration,proliferation,phenotype transformation,and the production of extracellular matrix,as a second messenger.Transient receptor potential channels are a kind of nonselective cation channels,including TRPC1-7,they are also receptors of cells.In these TRPC channels,TRPC1 was the first found by researchers.It is widely distributed in vascular smooth muscle cells to mediate transmission of Ca²⁺ across plasma membrane.It is different to classical voltage-gated Ca²⁺ channels that TRPC1 is a non-voltage dependent Ca²⁺ channel.When Ca²⁺ in sarcoplasmic reticulum is exhausted,TRPC1 channels open,and Ca²⁺ interflowing increases,in the end vasoconstriction happens.In conclusion,the main functions of TRPC1 in vascular smooth muscle cells are involving in cell constriction,dilation,proliferation,apoptosis and signal transduction between cells.TRPC1 affects physiological function of living organism by regulating calcium ion flow.Research has shown that a variety of pathophysiological mechanisms are associated with abnormal TRPC expression and activity.When TRPC expression is inhibited or TRPC channel blockers are used,intracellular calcium ion concentration is reduced and vasodilatation happens.At present,the TRPC family members are considered as molecular basisis calcium pool-operated calcium channel and receptor-operated calcium channel.As a kind of the calcium ion internal flow channel,TRPC channels are not only involved in many physiological functions,but also related to a variety of pathological process.Thus,researches on TRPC can provide new ideas for the prevention and treatment of related diseases.At present,although people understanding of TRPC1 channel is relatively simple,TRPC1 channels play an important role in vascular injury and disease.Expression of TRPC1 channel increases in vascular smooth muscle cells of atherosclerotic arteries,while following by inflowing of calcium ion to cell membrane through TRPC1 increased,and the intracellular calcium ion concentration increases,so in the end,arteries with atherosclerosis are more likely to occur vasoconstriction than normal arteries.The amount of TRPC1 increased in vascular smooth muscle cells of occlusive arteries,while intracellular calcium concentration decreases after inhibition of TRPC1 channels expression happens or using TRPC1 specific blockers.So the TRPC1 channel blocker is expected to become a new generation of calcium channel blockers targeting at vascular hyperplasia and vascular stenosis diseases.According to different sizes and pharmacological properties of conductivity,calcium activated potassium channels can be divided into three categories: large conductance Ca²⁺ activated potassium channel（BK）,middle conductance Ca²⁺ activated potassium channel and little conductance Ca²⁺ activated potassium channel.The BK channel has attracted much attention because of its function on regulating angiotasis of large vessels.BK is largely expressed in vascular smooth muscle cells.It is composed by 4 alpha subunits and 4 beta-1 subunits.When intracellular Ca²⁺ concentration is elevated,BK channel is activated,following by outflowing of K+,and cells appear hyperpolarization,which can inhibit calcium ion channel open process,reduce Ca²⁺ internal flow,and lead to vasodilatation.Arteries constricted significantly after using BK channel specific blocker iberiotoxin,which indicates that BK channel plays an important role in regulating arterial tension.Therefore,the BK channel agonist is also been expected to become a new generation of vasodilator agent for the treatment of vascular hyperplasia and vascular stenosis disease.There are a lot of cave structures constituted of structure protein caveolae on vascular smooth muscle cell membrane,in which channels,receptors and regulatory proteins gather together to form signal complexes.There are several reports on TRPC1 forms signal complexes with signaling molecule or membrane proteins to mediate signal transduction in caveolae,which demonstrates that TRPC1 is not work alone,but in the form of signal complexes.TRPC1 involves in depolarization of vascular smooth muscle cells on arteries,while BK involves in rteries a smooth muscle cells in addition to the pole,multipole BK channel to participate in repolarization of these cells.On one hand,when the TRPC channels open,Ca²⁺ internal flow increases and leads to vasoconstriction;on the other hand,due to activity of BK is regulated by intracellular calcium ion concentration,when TRPC channels open,intracellular Ca²⁺ concentration would be elevated,which can increase opening rate and frequency of BK channel,following by K+ outflow,cell repolarization and vasodilatation.In common artery smooth muscle cells,TRPC1 and BK connect with each other and form a signal complex,which raises efficiency of signal transmission between TRPC1 and BK significantly.Hyperpolarization generated by the TRPC1-BK signal complex could weaken cell membrane depolarization induced by stimulants,which can guard against artery smooth muscle cells excessive contraction.All in a word,TRPC channel and BK channel participate in the regulation of vasocontraction and vasodilatation through the calcium signal transduction pathway together in a coordinate manner.However,there are few study reports on TRPC1-BK signal complex or its role in vascular muscle up to now.To sum up,according to current understanding of TRPC1 and BK,TRPC1 and BK on the artery smooth muscle cells form a signal complex,and signal transduction pathway in the complex plays an important role in regulating in large artery tension.Furthermore,function of signal transduction is obviously injured when AS happens in arteries.[Methods]There were 10 mice both in atherosclerosis（AS）group and control group.After these mice been sacrificed,the aortas were isolated from mice thoracic cavity.Total mRNA and protein were extracted from vascular smooth muscle tissue.RT-PCR（reverse-transcription polymerase chain reaction）,Western blot and immunohistochemistry technologies were used to detect the expression quantity differences of mRNAs and proteins of TRPC1,BKα and BKβ1 subunit.[Results]The expression of TRPC1 mRNA was obviously higher than the control group（P<0.05）.However,the expressions of BKα and BKβ1 subunit mRNAs were apparently lower than the control group（both P<0.01）.Mice in ApoE^-/-group successfully developed AS.In the AS group,the expression of TRPC1 protein was significantly higher than the control group and appeared statistical difference（P<0.01）.The expressions of BKα and BKβ1 subunit proteins were lower than the control group（P<0.01 and P<0.05,respectively）.[Conclusion]The expressions of mRNAs and proteins of TRPC1-BK signal complex in aortic vascular smooth muscle tissue could all be influenced by AS in mice.All the above prompt speculation that TRPC1-BK signal complex may be a target of preventing as well as curing AS complications in the future.