Dear all, I have been observing the activation of phosphorylated ERK1/2 in my healthy human retinal pigmented epithelium cells (ARPE-19) now and then during experiment. The healthy control group was treated similarly with the other treatment groups just that it was without oxidative stress induction. I have tried different harvesting methods (scrapping & trypsin) and also used a new vial of cell line but it didn't solve the problem. Could you please enlighten me about the possible reasons and how do I troubleshoot it?

Thank you very much!