| Toxoplasma gondii(T.gondii)is a parasitic protozoon causing worldwide zoonotic toxoplasmosis.In recent years,the reason of public attention arousing is the infection of the T.gondii damages the hosts’ central nervous system(CNS),which causes toxoplasmic encephalitis(TE).Because of differences of virulence,the T.gondii has been divided into 3 genotypes including I,II,and III.And the type II T.gondii(Prugniaud,Pru)are the commonest in human.Moreover,different hosts have different susceptibility such as during the parasite infection,rats normally have no clinical symptoms but mice suffer from vital TE.Unfortunately,there is no report focus on the reason of these differences.The key of TE is T.gondii destructs the blood-brain barrier(BBB)to invade the hosts’ CNS.Some studies have shown two main mechanisms of T.gondii’s CNS invasion,which are the transcellular crossing mechanism and the immune cells carrying mechanism.But,there is a lot of potential that’s unrealized for two questions,which are whether there is a more efficient way for T.gondii to break through the BBB? or there are hosts’ molecules that can assist the T.gondii invasion? Furthermore,epidemiological studies have found that the infection rate of T.gondii in cancer patients is significantly higher than normal people,and there is no data to support a mechanism that cancer promotes the invasion of T.gondii.Therefore,this study aimed to seek the specific homologous differentially expressed proteins(HDEPs)in differently susceptible hosts of T.gondii to find the key evidence for the new pathway of T.gondii invasion of CNS,and try to explain the reason for the high positive rate of T.gondii in cancer patients.In this study,an i TRAQ-based strategy has established to identify 269 HDEPs in infected Kun Ming(KM)mice’s and 381 in Sprague Dawley(SD)rats’ brains.Then,KEGG pathways database was used to analyze the DEPs patterns.Interestingly,the complement and coagulation cascades pathway and the tight junction(TJ)pathway were specifically identified in mice brain,related to the host immune system and the T.gondii invasion of CNS,respectively.Among the pathways the expression of the complement component 3(C3)was increased 11 times.Therefore,in this study,we focused on exploring the role of C3 during the T.gondii infection.In vivo,establishing experimental mice models treated with C3 a and CVF,suing methods of ELISA,microscopic examination,transmission electron microscope(TME),and Evan’s blue(EB)we discovered three main findings.1)The amounts of C3 a in peripheral blood were increased when mice were acutely infected with T.gondii.2)C3a could increase the number and the size of brain cysts,but the CVF had the opposite results.3)T.gondii broken TJ of BBB around day 8 post infection,which could be advanced by the C3 a and delayed by CVF.Moreover,in vitro,we found the infection of T.gondii stimulated the C3 /C3 a expressions of several mice’s cells,and the C3 a was able to broke the TJ between endothelial cells.Moreover,we established mice’s Lewis lung cancer(LLC)models with T.gondii infection.We found that the LLC+Pru group had the most and the biggest brain cysts.More importantly,the LLC cells could express C3/C3 a which increased the C3/C3 a amount of peripheral blood,but T.gondii infection inhibited this phenomenon and decreased the growth of the LLC tumor.In short,this study first proved that T.gondii breaks the TJ of BBB to invade hosts’ CNS,through increasing the C3/C3 a expression of hosts.And the LLC also expresses C3/C3 a to promote the invasion.In contrast,so the T.gondii infecting suppresses the C3/C3 a expression of LLC that cancer development is slowed down.In conclusion,the differential expression proteomics study provided a reference for us to find new biomarkers and mechanisms of the hosts’ CNS injuries caused by T.gondii infection.And,it was proved that C3 a destroys TJ to promote T.gondii invasion of CNS,so that this research added new theoretical bases for the studies of T.gondii invasion and exploration of control measures.Moreover,the role of C3/C3 a between LLC cells and T.gondii explained the reason why cancer patients have higher T.gondii infection rate and also provided a new perspective for the application of T.gondii in cancer treatment. |
