Curcumin facilitates a transitory cellular stress response in Trembler-J mice

We have previously shown that oral administration of curcumin significantly decreases the percentage of apoptotic Schwann cells and partially mitigates the severe neuropathy phenotype of the Trembler-J (Tr-J) mouse model in a dose-dependent manner. Here we compared the gene expression in sciatic nerves of 2-week-old pups and adult Tr-J with the same age groups of wild-type mice and found a significant increase in gene expression for hypoxia, inflammatory response and heat-shock proteins, the latter specifically the Hsp70 family, in Tr-J mice. We also detected an activation of different branches of unfolded protein responses (UPRs) in Tr-J mice. Administering curcumin results in lower expression of UPR markers suggesting it relieves endoplasmic reticulum (ER) cell stress sensors in sciatic nerves of Tr-J mice while the level of heat-shock proteins stays comparable to untreated Tr-J mice. We further tested if Hsp70 levels could influence the severity of the Tr-J neuropathy. Notably, reduced dosage of the Hsp70 strongly potentiates the severity of the Tr-J neuropathy, though the absence of Hsp70 had little effect in wild-type mice. In aggregate, these data provide further insights into the pathological disease mechanisms caused by myelin gene mutations and further support the exploration of curcumin as a therapeutic approach for selected forms of inherited neuropathy and potentially for other genetic diseases due to ER-retained mutants.