Study On Cadmium Induced Apoptosis And Autophagy

Background: The intricate interconnection between cellular components can be influenced by factors such as diseases,stress and toxins.These factors can lead to the activation of signaling pathways which can induce a possible cell death or a build-up of resistance to promote cell survival.Autophagy is a lysosome-dependent intracellular degradative process which can lead to cell survival,but apoptosis on the other hand is a form of a highly regulated process of programmed cell death.This study sought to assess the interplay between cell apoptosis and autophagy using the heavy metal cadmium(Cd).Methodology: In this research,two different cell lines,mouse renal tubular epithelial cells(m RTECs)and human Ramos B cells(h RB)were used to study the mechanism by which Cd induces either autophagy or apoptosis in the kidney and immune cells respectively.Treatment used was Cd(different ?M concentrations)for both m RTEC and h RB cells.The survival rate and cytotoxicity levels of the cell cultures were determined.Next,real time quantitative polymerase chain reaction(RT-q PCR)and western blot analysis were conducted to determine the expression of the key markers of both autophagy(light chain 3-II(LC3),sequestosome-1(p62))and apoptosis(cleaved polyadenosine diphosphate ribose polymerase(c-PARP)and caspases).Immunofluorescence and fluorometric imaging were also conducted to observe the apoptotic and autophagic process whiles flow cytometry was used to measure the rate of apoptosis in h RB cell.Results: The results showed that in m RTEC,autophagy was blocked for apoptosis to occur whereas in h RB cells,Cd induced apoptosis through autophagy.This was shown by observing the expression levels of the various protein markers for both autophagy and apoptosis in the western blot analysis.In the h RB cells,Cd induced the accumulation of LC3-II and the degradation of p62,and Cd increased the expression of cleaved-PARP and cleaved-caspase 3.In h RB cell co-treatment with chloroquine(CQ)and methyladenine 3(3-MA)significantly reduced autophagy and also reduced apoptosis.However,the inhibition of autophagy resulted in the induction of apoptosis in Cd-exposed m RTEC cells.The increased accumulation of LC3-II and p62 in m RTEC cells was an indication of autophagy inhibition,whereas the increase in cleavedcaspase 3 expression was an indication of apoptosis.Summary: The result from this study indicates that Cd exposure can induce apoptosis by altering the basal autophagic level either by its inhibition as shown in m RTEC or promotion as shown in h RB cells.