Treatment with Leukemia Inhibitory Factor Alters Mitochondrial Function and Pro‐Inflammatory Cytokine Expression in the Spleens of Aged Rats

Abstract

BackgroundThe goal of this study was to determine whether LIF differentially affects pro‐inflammatory signaling in aged male and female animals and determine whether changes in inflammatory signaling after LIF treatment were linked to the mitochondrial function in splenocytes.Methods18‐month‐old male/female Sprague‐Dawley rats underwent middle cerebral artery occlusion (MCAO). Animals were treated with PBS or LIF at 6, 24, and 48 h after MCAO (125 μg/kg). Protein levels of the LlF receptor (LIFR), TNFα, IL‐1β, IL‐3, IFNγ, CXCL8, CXCL9, and CXCL10 were measured in splenic tissue using immunoblotting and ELISA. A Griess Assay kit was used to measure nitrite in spleen tissue. The oxygen consumption rate in electron transport chain States III‐V was measured to assess mitochondrial function. Statistical analyses were performed using one or two‐way ANOVA followed by Fisher's LSD post hoc test.ResultsAged male rats (*p<0.05) and aged female rats (***p<0.001) showed significant decreases in spleen size after MCAO + PBS treatment. LIF treatment significantly increased the spleen weight in aged males (**p<0.01). Among female rats, LIF significantly increased spleen weight compared to PBS‐treated (****p<0.001) and sham‐operated groups (**p<0.01) among aged females. LIF treatment resulted in a significant increase in splenic LIFR and CXCL9 expression regardless of sex (**p<0.01). Aged male rats showed significantly higher levels of IL‐1β in the spleen compared to their female counterparts (**p<0.01). MCAO + LIF treatment significantly altered levels of IFNγ compared to sham animals (*p<0.05) in a sex‐dependent manner (*p<0.05). IL‐3 levels were significantly increased in the spleens of female rats after MCAO + LIF treatment compared to sham females (****p<0.0001), MCAO + PBS females (**p<0.01), and MCAO + LIF males (***p<0.001). However, drug treatment did not significantly alter splenic IL‐3 levels among aged male rats. Levels of nitrite significantly increased in the spleens of aged female rats after MCAO + PBS treatment (*p<0.05), but returned to sham levels after LIF treatment (**p<0.01). Aged males showed significantly higher levels of nitrite after MCAO + LIF treatment (**p<0.01). There was no significant change in TNFα, CXCL8, or CXCL10 levels between treatment groups among aged male and female animals. The OCR was significantly increased in State III and State V (Complex II) after MCAO+ LIF treatment compared to MCAO + PBS treatment (***p<0.01), but not State IV or State V (Complex I).ConclusionsLIF treatment promotes alterations in mitochondrial activity and cytokine expression in the spleen at 72 h after MCAO, with some cytokines exhibiting sex‐specific differences in their expression. These data demonstrate that rats show sex differences in the post‐stroke inflammatory response after stroke and differential responses to LIF.Support or Funding InformationExperiments were supported by the following awards: VA Award # 5I01BX003405‐02 (Sullivan) and NINDS Award # 5R01NS091146‐04 (Pennypacker)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.