Intermittent ethanol vapor exposure enhances ferroptosis following repeated mild traumatic brain injury in the frontal lobe of adolescent rats; potential role of mitochondrial dysregulation

Abstract

Adolescents involved in sports have increased risk of traumatic brain injuries (TBI), and frequently participate in binge alcohol consumption in comparison to non-athletic peers. Recovery from a TBI requires substantial energy, and effcient metabolic activity, which depend on intact mitochondria structure and function. Alcohol impairs mitochondrial function, including mitochondrial dynamics and metabolism); that may ultimately lead to cell death. Among cell death pathways, the iron-dependent programmed cell death known as ferroptosis; which has been shown to be predominant in TBI is especially sensitive to changes in mitochondrial energy production. Whether alcohol affects TBI-associated alterations in mitochondrial function and promotes ferroptosis is not known. The aim of this study was to determine how alcohol contributes to repeated-mild TBI (rmTBI)-induced alterations in mitochondrial function (dynamics & metabolism) and ferroptosis signaling in the prefrontal cortex of adolescent male rats. Adolescent male Wistar rats were randomly assigned to i) Sham + Air (control), ii) Sham + ethanol (EtOH), iii) rmTBI + Air, or iv) rmTBI + EtOH. Starting on postnatal day 45, the animals received 3 days of intermittent EtOH vapor exposure (14 hrs on/10 hrs off). Twenty-four hours after the final EtOH exposure, animals were given an mTBI or sham procedure. This sequence was repeated for four cycles. Seven days after the final rmTBI, animals were euthanized, and brains excised for analysis, specifically the frontal lobe. Our preliminary results demonstrate that mitochondrial fusion protein, OPA1, expression was not altered in the PFC by either rmTBI or by EtOH exposure alone. However, rmTBI+EtOH resulted in a significant increase in OPA1 expression. EtOH exposure produced a significant increase in COX-IV (a subunit of ETC complex IV) expression. However, COX-IV expression was not significantly different between rmTBI or rmTBI + EtOH and controls. Mitochondrial complex I activity was not altered by rmTBI, EtOH, or rmTBI + EtOH. Expression of transferrin receptor (TfR1), a specific marker of ferroptosis was significantly increased by rmTBI and EtOH this effect was further exacerbated in the rmTBI + EtOH group. Overall, our study shows that the combination of rmTBI with EtOH exposure affects OPA1-mediated mitochondrial fusion. Additionally, exposure to EtOH increases complex IV expression. Moreover, both rmTBI and EtOH exposure independently triggered signaling pathways associated with ferroptosis, and this effect was synergistically increased when with rmTBI+ EtOH. These findings underscore the intricate interplay between EtOH exposure and rmTBI, influencing crucial mitochondrial proteins and markers of ferroptosis in the frontal lobe of the adolescent rat brain. Further research is needed to fully comprehend the underlying mechanisms and implications of these observations. This research was supported by NIH/NIAAA R01 AA025792 (PEM, NWG) & T32 AA007577 (PEM). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.