Pimecrolimus protects neuron‐like SH‐SY5Y cells against anti‐inflammatory and anti‐oxidant effects of both microglial secretome and hydrogen peroxide

Abstract Calcineurin inhibitors have been found to exhibit a preventive role against neuroinflammation, which represents a crucial underlying mechanism in neurodegenerative diseases (ND). Additionally, they possess suppressive effects on the activation of apoptotic pathways, which constitute another mechanism underlying such diseases. Given that pimecrolimus, a calcineurin inhibitor, impedes the synthesis of pro‐inflammatory cytokines, such as interleukin (IL)‐2, IL‐4, and IL‐10, and influences apoptotic processes, it is noteworthy to test its potential neuroprotective properties. Thus, the objective of this investigation was to assess the potential protective effects of pimecrolimus against the degenerative consequences of both microglial secretomes and hydrogen peroxide (H 2 O 2 ), an oxidant agent. The survival rates of HMC3 microglia cells, neuron‐like differentiated SH‐SY5Y (d‐SH‐SY5Y) cells, and their co‐culture were determined using the 3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐Diphenyltetrazolium Bromide (MTT) method. Furthermore, the levels of pro‐inflammatory cytokines IL‐1β and IL‐6, and anti‐inflammatory cytokine IL‐10 were measured using ELISA kits, besides total antioxidant and oxidant capacities in conditioned media of cells. Additionally, the effect of pimecrolimus on neurite length in these cell groups was evaluated through morphological observations. This study revealed, for the first time, that pimecrolimus exerts preventive effects on neurodegenerative processes by virtue of its anti‐inflammatory and ‐antioxidant activities. It holds promise as a potential treatment option for ND.