Deletion of macrophage migration inhibitory factor worsens stroke outcome in female mice

Abstract

Sex is an important factor in the response to ischemic insults in both the laboratory and the clinic. Inflammation and cell death are points where sex-specific pathways diverge in stroke, and serum estrogen levels status affect the response to inflammation. The cytokine macrophage migration inhibitory factor (MIF) is detrimental in experimental stroke models in male animals. However MIF is known to have sex-specific actions on inflammation and wound healing. The role of MIF in the ischemic female brain has not been evaluated. A transient middle cerebral artery occlusion (MCAO/90 minutes) model was used to induce stroke in male, intact female, and ovariectomized female wildtype (WT) and MIF knockout (KO) mice. Infarct size was quantified 72 hours after stroke. Protein and cytokine levels were assessed post stroke. Female MIF KO mice had significantly larger strokes compared to WT females (mean hemispheric infarct±SEM: 63%±2% versus 29%±3%; n=8; p<0.05). Ovariectomized female MIF KO mice also had larger infarcts than ovariectomized WT littermates (70%±3% versus 47%±4%; n=11; p<0.05). In males, however, infarct size was equivalent between MIF KO and WT mice (63%±2% versus 67%±3%; n=9; p=0.25). There were no significant differences in cytokine levels at 6 hours post-infarct between mice of either genotype in brain. MIF KO females displayed more microglial activation (ionized calcium binding adaptor molecule 1 (Iba1) immunofluoresence) after stroke than did WT mice or MIF KO males. The larger infarcts in MIF KO females were associated with an early increase in mitochondrial localization of Jun activation domain-binding protein 1 (JAB1). Loss of MIF exacerbated injury in the female brain after experimental stroke, which was independent of changes in pro-inflammatory cytokine levels. This response is sex-specific, and is in part independent of physiological serum levels of estrogen.

Partial MHC class II constructs as novel immunomodulatory therapy for stroke

“…In addition to cell surface receptors, MIF was shown to interact with intracellular Jun activation domain-binding protein (JAB1). It was postulated that after stroke, the absence of MIF leads to activation of JAB1, which in turn enters the mitochondria resulting in increased release of cytochrome c and cell apoptosis (Turtzo et al, 2013). …”

“…MIF has a deleterious role after 45 min of occlusion that results in milder infarcts in male MIF KO mice, but a protective role in females after 90 min of occlusion which results in more severe damage in MIF KO mice (Turtzo et al, 2013). This contrasting role of MIF was similarly observed in several EAE studies in which disease induction with reduced adjuvant concentration or reactivity resulted in milder disease severity and partial recovery compared to WT mice.…”

Inhibition of glycogen synthase kinase-3β enhances cognitive recovery after stroke: the role of TAK1

“…Whole-cell lysate (100 mg) from the right hemisphere of sham (Sh) and stroke (ss) mice was incubated for 1 h with 1 mg of the TAK1 antibody at room temperature to form the immune complex. Then, 100 mL of a 50% slurry of Protein A beads in PBS was added to the complex and incubated for 1 h at room temperature as described in Turtzo et al (2013). Beads were spun down, the unbound fraction removed and then the beads were extensively washed.…”

Sex Differences in the Cerebral Collateral Circulation

“…For example, 16-month-old female mice have larger infarctions compared to age-matched males despite equivalent circulating estrogen [19]. Also, deletion of macrophage migration inhibitory factor increases infarct volume in intact and ovariectomized females to that seen in males [20]. Female rat pups show better recovery of auditory and cognitive functions after hypoxic brain injury despite similar or greater anatomical damage than in males [10].…”