BRAIN BACTERIAL PEPTIDOGLYCAN IS REGION-SPECIFIC AND CHANGES AFTER ISCHEMIC STROKE

Abstract Introduction Sleep disorders and ischemic stroke (IS) are large health burdens. Almost half the USA population reports disturbed sleep and 795,000 Americans suffer a stroke annually. Despite dysregulated sleep being a stroke risk factor that can exacerbate injury and prolong recovery, sleep deprivation immediately preceding experimental stroke is neuroprotective. Bacteria and microbial products associate with (patho-)physiologies, including sleep phenotypes and IS. Peptidoglycans (PGs) are bacterial cell wall components found in diseased and healthy adults, and in developing and sleep-deprived brains. Although they influence atherosclerosis, an IS risk factor, PGs have not been characterized in post-stroke brain. Methods Aged (63 weeks) male wildtype mice (n=5) underwent permanent left middle cerebral artery occlusion, a model that mimics atherosclerotic IS, the most common type in humans. Surgeries began at Zeitgeber time (ZT) 12, lasted 30-40 minutes, and were followed by a 2-2.5-hour recovery period before sacrifice at ZT15. Brain stem (BS), somatosensory and prefrontal cortices (Sctx, PFC) were dissected, homogenized in phosphate buffered saline, and centrifuged. A standardized murine peptidoglycan ELISA (MyBioSource) was used for PG/MP quantification in resultant supernates. Brain areas in the left (L) IS, and right (R) control, hemispheres were compared by two-way ANOVA and Tukey’s HSD tests. Results Mean PG values are expressed as ng/mg tissue wet weight ± SEM. Post-IS PG in the injured L Sctx (4.28±0.48) was lower (F(2,21)=49.29, p<0.05) than the uninjured R Sctx (5.66±0.29; p=0.048). There were no hemispheric PG differences in either BS or PFC. L hemispheric PG was greater in BS (7.59±0.40) versus Sctx (p=0.0008) and PFC (3.82±0.21, p=0.0002). R hemispheric PG was also greater in BS (8.26±0.53) versus Sctx (p=0.005) and PFC (3.56±0.56, p=0.0006) and in Sctx versus PFC (p=0.02). Conclusion This study confirms our parallel study, presented in a separate abstract herein (English et al), that PG regulation is unique within brain areas. Additionally, PG values in uninjured Sctx and in BS were similar between studies. Finally, current results suggest that reduced cerebral blood flow induced by IS reduces PG in the affected brain area. Further, PG may have a role in sleep deprivation-related IS injury and recovery. Support (If Any) W.M. Keck Foundation and NIH (NS025378)