Characterization of mitochondrial bioenergetics in neonatal anoxic model of rats

Chronic exposure to dim artificial light disrupts the daily rhythm in mitochondrial respiration in mouse suprachiasmatic nucleus

Circadian rhythms of physiology, behavior, and metabolism have an endogenous 24 h period that synchronizes with environmental cycles of light/dark and food availability. Alterations in light cycles are stressful and disrupt such diurnal oscillations. Recently, we witnessed a sudden rise in studies describing the mechanisms behind the interaction between the key characteristics of mitochondrial functions, peripheral clocks, and stress responses. To our knowledge, there is no study in the suprachiasmatic nuclei (SCN) describing the dysregulated mitochondrial bioenergetics under abnormal lighting conditions, which is common in today's modern world. Thus, we aimed to investigate the existence of daily changes in mitochondrial bioenergetics (respiratory control rate, RCR), mitochondrial abundance (mtDNA/nDNA), plasma corticosterone, and to test whether disturbances in the lighting conditions might influence such rhythms. To confirm this, mice were sacrificed, mitochondria were isolated from the suprachiasmatic nuclei in the brain and blood was collected, every 3 h at various time points zeitgeber time/circadian time, (0, 3, 6, 9, 12, 15, 18, 21, and 24 h) under 12:12 h light-dark (LD, 150 lux L: 0 lux D) cycle and chronic artificial dim lighting (LL, 5 lux: 5lux) conditions, of a 24 h period, respectively. Our results demonstrate the existence of robust daily rhythmicity in RCR, mtDNA/nDNA and plasma CORT under a normal LD cycle. However, these rhythms were significantly disrupted and clock genes expressions were dysregulated under chronic dim LL. Furthermore, mitochondrial abundance was significantly reduced during LL compared to their numbers under LD cycle. Our data demonstrate that the circadian clock regulates mitochondrial functions (RCR, number), essential for accomplishing daily energy demands and supply by the SCN neurons. Abnormal light exposure dysregulates mitochondrial functions in the SCN and may alter metabolism, resulting in obesity, diabetes, and other metabolic disorders. Therefore, properly designing lighting conditions in workplaces is essential to mitigate the adverse consequences of light on humans.

Indole-3-carbinol ameliorated the thioacetamide-induced hepatic encephalopathy in rats

Indole-3-carbinol (I3C) is reported to have hepatic and neuroprotective properties. However, the I3C role in the protection of the liver and brain in the pathological condition of hepatic encephalopathy has not been investigated. Therefore, in the present study, we have assessed the hepatic and neuroprotective roles of I3C against thioacetamide (TAA)- induced hepatic encephalopathy in Wistar rats. TAA (300mg/kg) was intraperitoneally administered to Wistar rats to induce hepatic encephalopathy. The elevated levels of ammonia in the blood, liver, and brain were substantially lowered by I3C treatment (25, 50, and 100mg/kg, oral, 7 days). I3C significantly ameliorated the TAA-induced liver dysfunction by decreasing the alanine transaminase, aspartate transaminase, and alkaline phosphatase enzymes and reduced the elevated cytochrome P4502E1 (CYP2E1) activity in the liver and brain. Further, I3C alleviated mitochondrial dysfunction and oxidative stress in the brain. I3C treatment improved the anti-inflammatory cytokine interleukin (IL)-10 while reducing inflammatory cytokines such as tumor necrosis factor-1 and IL-6 in hepatic encephalopathy rats. I3C reduced the levels of apoptotic indicators mediated by the mitochondria, including cytochrome c, caspase 9, and caspase 3. Concurrently, I3C mitigated the liver and brain histological abnormalities in hepatic encephalopathy rats. Therefore, the present study concluded that the I3C protected the liver and brain from TAA-induced hepatic encephalopathy injury by inhibiting CYP2E1 enzyme activity and decreasing ammonia, oxidative stress, inflammation, and apoptosis. The present study provides preclinical validation of I3C use as hepatic and neuroprotective for hepatic encephalopathy management.

Indole-3-carbinol ameliorated the neurodevelopmental deficits in neonatal anoxic injury in rats

Neonatal anoxia is linked to long-lasting neurodevelopmental deficits. Due to the lack of pharmacological intervention to treat neonatal anoxia, there is interest in finding new molecules for its treatment. Indole-3-carbinol (I3C) has shown neuroprotective effects in some disease conditions. However, the neuroprotective role of I3C in neonatal anoxia has not been explored. Consequently, we have investigated the effect of I3C on neonatal anoxia-induced brain injury and neurodevelopmental deficits. Rat pups after 30 h of birth were subjected to two episodes of anoxia (10 min in each) at a time interval of 24 h by flowing 100% nitrogen. I3C was administered within 30 min of the second episode of anoxia on a postnatal day (PND) 3 and continued for PND 9. Neurodevelopmental deficits, cortical mitochondrial membrane potential (MMP), opening of mitochondrial permeability transition pore (MPTP), electron transport chain (ETC) enzyme activities, oxidative stress, hypoxia-inducible factor-1α (HIF-1α) levels, histopathological changes, and apoptosis were measured. I3C treatment dose-dependently ameliorated the neurodevelopmental deficits and somatic growth in anoxic pups. I3C improved mitochondrial function by enhancing the MMP, mitochondrial ETC enzymes, and antioxidants. It blocked the MPTP opening and release of cytochrome C in anoxic pups. Further, I3C reduced the elevated cortical HIF-1α in neonatal anoxic pups. Furthermore, I3C ameliorated histopathological abnormalities and mitochondrial-mediated apoptotic indicators Cyt C, caspase-9, and caspase-3. Our study concludes that I3C improved neuronal development in anoxic pups by enhancing mitochondrial function, reducing HIF-1α, and mitigating apoptosis.

Standardization and validation of novel ex-vivo method for mitochondrial bioenergetics using mitochondrial modulators

Mitochondria is an essential organelle; it produces 95% of the adenine triphosphate (ATP) of cells, their dysfunction is related to the pathogenesis of multiple diseases, such as diabetes mellitus, cardiovascular and neurological disorders. Various pharmacologic agents are known to target mitochondrial function. Moreover, the toxic side effects of multiple drugs used to treat diseases are related to the impairment of mitochondrial function. Thus, there is a need to develop a method to evaluate the effect of pharmacologic agents for their potential and side effects to identify effective mitochondrial-modulating agents. Therefore, the objective of this study was to develop and validate an ex-vivo method for studying the effect of pharmacologic agents on mitochondrial function and rescue of dysfunction. Dimethyl sulfoxide (DMSO) concentrations that drugs were soluble in and maintained mitochondrial function were determined. Metformin (MET) is a known mitochondrial complex-1 inhibitor tested for its ability to compromise mitochondrion function. Coenzyme Q10 (Q10) and Resveratrol (RSV), which are known to enhance mitochondrial function, were added alone and dose-dependent, tested for the ability to rescue metformin-induced mitochondrial dysfunction. Ex-vivo liver and brain mitochondrial function was assessed using an oxytherm Clark-type oxygen electrode. DMSO was found to be toxic above 10% and drugs insoluble below 5%. The addition of 0.5 mg/ml MET decreased liver and brain mitochondrial respiratory control rate (RCR). At the same time, Q10 improved RCR in normal mitochondria and a concentration-dependent manner in MET-induced dysfunctional mitochondria. RSV was added in the last step of the experiment to confirm that compromised function is due to MET. Hence this method can be used to screen pharmacological agents for their potential therapeutics or toxic effect on mitochondria.

Mitochondrial dysfunction in perinatal asphyxia: role in pathogenesis and potential therapeutic interventions

Perinatal asphyxia (PA)-induced brain injury may present as hypoxic-ischemic encephalopathy in the neonatal period, and long-term sequelae such as spastic motor deficits, intellectual disability, seizure disorders and learning disabilities. The brain injury is secondary to both the hypoxic-ischemic event and oxygenation-reperfusion following resuscitation. Following PA, a time-dependent progression of neuronal insult takes place in terms of transition of cell death from necrosis to apoptosis. This transition is the result of time-dependent progression of pathomechanisms which involve excitotoxicity, oxidative stress, and ultimately mitochondrial dysfunction in developing brain. More precisely mitochondrial respiration is suppressed and calcium signalling is dysregulated. Consequently, Bax-dependent mitochondrial permeabilization occurs leading to release of cytochrome c and activation of caspases leading to transition of cell death in developing brain. The therapeutic window lies within this transition process. At present, therapeutic hypothermia (TH) is the only clinical treatment available for treating moderate as well as severe asphyxia in new-born as it attenuates secondary loss of high-energy phosphates (ATP) (Solevåg et al. in Free Radic Biol Med 142:113-122, 2019; Gunn et al. in Pediatr Res 81:202-209, 2017), improving both short- and long-term outcomes. Mitoprotective therapies can offer a new avenue of intervention alone or in combination with therapeutic hypothermia for babies with birth asphyxia. This review will explore these mitochondrial pathways, and finally will summarize past and current efforts in targeting these pathways after PA, as a means of identifying new avenues of therapeutic intervention.

Trpv4 regulates Nlrp3 inflammasome via SIRT1/PGC-1α pathway in a cuprizone-induced mouse model of demyelination

Increasing evidence has demonstrated that the Nod-like receptor pyrin domain containing 3 (Nlrp3) inflammasome overactivated during demyelinating disorders. It has been implicated that transient receptor potential type 4 (Trpv4) is regarded as a polymodal ionotropic receptor that plays an important role in a multitude of pathological conditions, including inflammation. The aim of this study was to investigate whether the Trpv4 channel regulates Nlrp3 inflammasome in the corpus callosum of mice with demyelination. Our results showed that CPZ treatment significantly increased the expression of Trpv4, activated Nlrp3 inflammasome, reduced peroxisome proliferator-activated receptor gamma coactivator 1α (PGC-1α) and decreased mitochondrial function. siRNA-mediated Nlrp3 knockdown inhibited glial activation and alleviated demyelination. Whereas knockdown of Trpv4 by siRNA markedly ameliorated Nlrp3 inflammasome activation and restored mitochondrial function as well as reducing the level of reactive oxygen species (ROS). Meanwhile, glial activation, demyelination and behavioral impairment induced by CPZ were also alleviated by siRNA-mediated Trpv4 knockdown. Furthermore, immunoprecipitation and use of a lysine acetylation assay showed that Sirtuin1 (SIRT1) mediated the PGC-1α deacetylation, which is involved in Nlrp3 inflammasome activation. These findings suggest that Trpv4 regulates mitochondrial function through the SIRT1/PGC-1α pathway, which further trigger Nlrp3 inflammasome activation in the CPZ-induced demyelination in mice.

Perinatal Brain Injury and Inflammation: Lessons from Experimental Murine Models

Perinatal brain injury or neonatal encephalopathy (NE) is a state of disturbed neurological function in neonates, caused by a number of different aetiologies. The most prominent cause of NE is hypoxic ischaemic encephalopathy, which can often induce seizures. NE and neonatal seizures are both associated with poor neurological outcomes, resulting in conditions such as cerebral palsy, epilepsy, autism, schizophrenia and intellectual disability. The current treatment strategies for NE and neonatal seizures have suboptimal success in effectively treating neonates. Therapeutic hypothermia is currently used to treat NE and has been shown to reduce morbidity and has neuroprotective effects. However, its success varies between developed and developing countries, most likely as a result of lack of sufficient resources. The first-line pharmacological treatment for NE is phenobarbital, followed by phenytoin, fosphenytoin and lidocaine as second-line treatments. While these drugs are mostly effective at halting seizure activity, they are associated with long-lasting adverse neurological effects on development. Over the last years, inflammation has been recognized as a trigger of NE and seizures, and evidence has indicated that this inflammation plays a role in the long-term neuronal damage experienced by survivors. Researchers are therefore investigating the possible neuroprotective effects that could be achieved by using anti-inflammatory drugs in the treatment of NE. In this review we will highlight the current knowledge of the inflammatory response after perinatal brain injury and what we can learn from animal models.

2,4 Dinitrophenol Attenuates Mitochondrial Dysfunction and Improves Neurobehavioral Outcomes Postanoxia in Neonatal Rats

Following anoxia, a rapid and marked mitochondrial-linked cell death occurs in the cerebral cortex of newborn rats which leads to insult advancement within a couple of days and causes lifelong neurobehavioral abnormalities. The present study investigated the role of 2,4 dinitrophenol (2,4 DNP) in three doses, i.e.,1, 2.5, and 5 mg/kg on anoxia-induced time-dependent mitochondrial dysfunction and associated neurobehavioral outcome using a well-established global model of anoxia. Briefly, rat pups of 30-h age (P2) were subjected to two episodes of anoxia (10 min each) at 24 h of the time interval in an enclosed chamber supplied with 100% N₂ and immersed in a water bath (35-37 °C) to avoid hypothermia. Results demonstrated that the uncoupler 2,4 DNP, in the dose 2.5 and 5 mg/kg injected i.p. within 5 min after second anoxic episode significantly (P < 0.05) preserved mitochondrial function on day 7 preferentially by maintaining mitochondrial membrane potential (MMP) and inhibiting mitochondrial permeability transition (MPT) pore. Further, 2,4 DNP preserved mitochondrial function by improving different states of mitochondrial respiration (s2, s3, s4, s5), respiratory control ratio (RCR), antioxidant enzyme system like superoxide dismutase (SOD) and catalase (CAT), and mitochondrial complex enzymes (I, II, IV, V) after anoxia. Furthermore, a marked decrease in the levels of expression of cytochrome C (cyt C) and pro-apoptotic (Bcl-2 family) and apoptotic (caspase-9/3) proteins was observed on day 7 indicating that the treatment with 2,4 DNP prevented mitochondrial dysfunction and further insult progression (day 1 to day 7). Moreover, 2,4 DNP decreased the apoptotic cell death on day 7 and overall improved the neurobehavioral outcomes like reflex latency and hanging latency which suggests its role in treating neonatal anoxia.

Neonatal Hypoxia Ischaemia: Mechanisms, Models, and Therapeutic Challenges

Neonatal hypoxia-ischaemia (HI) is the most common cause of death and disability in human neonates, and is often associated with persistent motor, sensory, and cognitive impairment. Improved intensive care technology has increased survival without preventing neurological disorder, increasing morbidity throughout the adult population. Early preventative or neuroprotective interventions have the potential to rescue brain development in neonates, yet only one therapeutic intervention is currently licensed for use in developed countries. Recent investigations of the transient cortical layer known as subplate, especially regarding subplate's secretory role, opens up a novel set of potential molecular modulators of neonatal HI injury. This review examines the biological mechanisms of human neonatal HI, discusses evidence for the relevance of subplate-secreted molecules to this condition, and evaluates available animal models. Neuroserpin, a neuronally released neuroprotective factor, is discussed as a case study for developing new potential pharmacological interventions for use post-ischaemic injury.