Detrimental effects of transient cerebral ischemia on middle cerebral artery mitochondria in female rats

Mitochondria dysfunction, a potential cytoprotection target against ischemia-reperfusion injury in a mouse stroke model

More than 50 ​% of patients undergoing mechanical thrombectomy (MT) for ischemic stroke have a poor functional outcome despite timely and successful angiographic reperfusion, highlighting the need for adjunctive treatments to reperfusion therapy. Mitochondria are key regulators of cell fate, by controlling cell bioenergetics via oxidative phosphorylation (OXPHOS) and cell death through the mitochondrial permeability transition pore (mPTP). Whether these two main mitochondrial functions are altered by reperfusion and could represent a new cytoprotective approach remains to be elucidated in mice. Swiss male mice underwent either permanent or transient middle cerebral artery occlusion (pMCAO or tMCAO), with neuroscore evaluation and multimodal imaging. The area at risk of necrosis was evaluated by per-occlusion dynamic contrast-enhanced ultrasound. Final infarct size was assessed at day 1 by MRI. Cortical mitochondrial isolation was subsequently performed to assess mPTP sensitivity by calcium retention capacity (CRC) and OXPHOS. A cytoprotective treatment targeting mitochondria, ciclosporine A (CsA), was tested in tMCAO, to mimick the clinical situation of patients treated with MT. Reperfusion after 60 ​min of ischemia improves neuroscores but does not significantly reduce infarct size or mitochondrial dysfunction compared to permanent ischemia. CsA treatment at reperfusion mitigates stroke outcome, decreases final infarct size and improves mitochondrial CRC and OXPHOS. Mitochondrial dysfunctions, i.e. reduced mPTP sensitivity and decreased oxygen consumption rates, were observed in pMCAO and tMCAO regardless of the reperfusion status. CsA improved mitochondrial functions when injected at reperfusion. These suggest that both mPTP opening and OXPHOS alterations are thus early but reversible hallmarks of cerebral ischemia/reperfusion.

Three-dimensional object geometry of mitochondria-associated signal: 3-D analysis pipeline for two-photon image stacks of cerebrovascular endothelial mitochondria

Increasing evidence indicates the role of mitochondrial and vascular dysfunction in aging and aging-associated pathologies; however, the exact mechanisms and chronological processes remain enigmatic. High-energy demand organs, such as the brain, depend on the health of their mitochondria and vasculature for the maintenance of normal functions, therefore representing vulnerable targets for aging. This methodology article describes an analysis pipeline for three-dimensional (3-D) mitochondria-associated signal geometry of two-photon image stacks of brain vasculature. The analysis methods allow the quantification of mitochondria-associated signals obtained in real time in their physiological environment. In addition, signal geometry results will allow the extrapolation of fission and fusion events under normal conditions, during aging, or in the presence of different pathological conditions, therefore contributing to our understanding of the role mitochondria play in a variety of aging-associated diseases with vascular etiology.NEW & NOTEWORTHY Analysis pipeline for 3-D mitochondria-associated signal geometry of two-photon image stacks of brain vasculature.

Sex as a biological variable for cardiovascular physiology

There have been ongoing efforts by federal agencies and scientific communities since the early 1990s to incorporate sex and/or gender in all aspects of cardiovascular research. Scientific journals provide a critical function as change agents to influence transformation by encouraging submissions for topic areas, and by setting standards and expectations for articles submitted to the journal. As part of ongoing efforts to advance sex and gender in cardiovascular physiology research, the American Journal of Physiology-Heart and Circulatory Physiology recently launched a call for papers on Considering Sex as a Biological Variable. This call was an overwhelming success, resulting in 78 articles published in this collection. This review summarizes the major themes of the collection, including Sex as a Biological Variable Within: Endothelial Cell and Vascular Physiology, Cardiovascular Immunity and Inflammation, Metabolism and Mitochondrial Energy, Extracellular Matrix Turnover and Fibrosis, Neurohormonal Signaling, and Cardiovascular Clinical and Epidemiology Assessments. Several articles also focused on establishing rigor and reproducibility of key physiological measurements involved in cardiovascular health and disease, as well as recommendations and considerations for study design. Combined, these articles summarize our current understanding of sex and gender influences on cardiovascular physiology and pathophysiology and provide insight into future directions needed to further expand our knowledge.

Hemispheric analysis of mitochondrial Complex I and II activity in the mouse model of ischemia-reperfusion-induced injury

Brain ischemia/reperfusion injury results in a variable mixture of cellular damage, but little is known about possible patterns of mitochondrial dysfunction from the scope of hemispheric processes. The current study used high-resolution fluorespirometry to compare ipsi- and contralateral hemispheres' linked respiration and ROS emission after 60-minutes of filament induced middle cerebral artery occlusion (fMCAo) and 2, 24, 72, and 168 h after reperfusion in mice. Our findings highlight that experimental ischemic stroke resulted in higher mitochondrial respiration in the contralateral compared to the ipsilateral hemisphere and highest ROS emission in ipsilateral hemisphere. The largest difference between the ipsilateral and contralateral hemispheres was observed 2 h after reperfusion in Complex I and II ETS state. Oxygen flux returns to near baseline 72 h after reperfusion without any changes thereafter in Complex I and II respiration. Studying the effects of brain mitochondrial functionality after ischemic stroke in each cerebral hemisphere separately provides a better understanding about the molecular and compensatory processes of the contralateral hemisphere, a region of the brain often neglected in stroke research.