| Extraintestinal pathogenic Escherichia coli(ExPEC)is a zoonotic pathogen,and it has been reported that its infection range is far greater than other known E.coli.Clinical data show that Ex PEC is a most important cause of central nervous system(CNS)infection pathogens.The central nervous system(CNS)is a sealed organ in the body.The pathogenic microbial infection CNS is mainly caused by two ways.The first way is microbe through the infection adjacent tissue and then to the intracranial proliferation.And the second way is microbe through blood infection and penetrate the blood-brain barrier so as to causing CNS infection.Among two ways,pathogenic microorganisms causing CNS infection by blood is the most common form.Meningitis is one of the common form of CNS infection.Pathogenic microorganisms adhere blood vessels and promotes neutrophils into the CNS,which leads to an inflammatory process.Caveolae is specific membrance microdomains which is enriched in caveolins and cholesterol.It can play huge role in signal transduction and endocytosis.The epidermal cell surface is enriched in caveolae.Cholesterol is the most abundant component of the caveolae.And caveolin-1 is the principal functional protein of caveolse.These two components are necessary to the structure and function of caveolae.Through a series of in vitro experiments,caveolin-1 was found to have a high affinity for unsaturated long chain fatty acids,which indicate that caveolin-1 may be involved in the transport of cholesterol in the cave.However,the role of cholesterol and caveolin-1 in ExPEC break through into the host’s blood-brain barrier is unclear.In this rearch,we use PCN033,a kind of extraintestinal pathogenic Escherichia coli,as the representative CNS-infecting strain.By detecting the level of transcription and translation of caveolin-1 before and after infection as well as the correlation of signaling pathways.The results show that,caveolae plays an important role in PCN033 invasion.It also provides emerging antimicrobial resistant pathogensa of anti-Ex PEC infections.Mainly research results are as follows:1.Caveolae is present on the surface of brain micro vascular endothelial cells(BMECs)Caveolin-1 is a marker protein of caveolae.Caveolin-1 and caveolin-2 and caveolin-3genes were detected by PCR using cDNA from HBMEC.The results showed that,caveolin-1 and caveolin-2 were found in HBMEC.At the same time,the caveolin-1and caveolin-2 protein was detected on the total protein of HBMEC.The results showed that caveolin-1 and caveolin-2 in caveolin were present in HBMEC and functionally through the phosphorylation of caveolin-1 after infection.2.Caveolae’s function in endothelial cells The epidermal cell surface is enriched in caveolae.In this research,we investigated whether the use of caveolae pathway inhibitors will affect the ability of ExPEC invasion of brain tissue changes.And interference or over expression of caveolin-1 in HBMEC can casuse the ability of Ex PEC invasion change.The results showed that,using caveolae pathway inhibitor depletes the ability of Ex PEC invasion.At the same time,the invasion ability of ExPEC was significantly decreased after shRNA interference of caveolin-1,and the invasion ability of ExPEC was significantly increased after over expression of caveolin-1.This suggests that,Ex PEC can pass through vascular endothelial cells via caveolae-mediated endocytosis,which leading to meningitis.3.Caveolin regulates signal transduction molecular mechanismsSREBP is a cholesterol sensor that undergoes negative feedback regulation when intracellular cholesterol levels change.It binds to the SRE element after cleavage to negatively regulate the transcription level of the gene.But the form of SREBP in this experiment is still unknown.In this reaearch,RT-PCR was used to detect the changes of SREBP form in HBMEC.The results showed that,SREBP-1a and SREBP-1c play functions.And the transcription level of CAV-1 was also significantly improved after Inhibition of SREBP by a small molecule. |
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