[Show abstract][Hide abstract] ABSTRACT: Traumatic brain injury (TBI) pathophysiology can be attributed to either the immediate, primary physical injury, or the delayed, secondary injury which begins minutes to hours after the initial injury and can persist for several months or longer. Because these secondary cascades are delayed and last for a significant time period post-TBI, they are primary research targets for new therapeutics. To investigate changes in mitochondrial function after a brain injury, both the cortical impact site and ipsilateral hippocampus of adult male rats 7 and 17 days after a controlled cortical impact (CCI) injury were examined. State 3, state 4, and uncoupler-stimulated rates of oxygen consumption, respiratory control ratios (RCRs) were measured and membrane potential quantified, and all were significantly decreased in 7 day post-TBI cortical mitochondria. By contrast, hippocampal mitochondria at 7 days showed only non-significant decreases in rates of oxygen consumption and membrane potential. NADH oxidase activities measured in disrupted mitochondria were normal in both injured cortex and hippocampus at 7 days post-CCI. Respiratory and phosphorylation capacities at 17 days post-CCI were comparable to naïve animals for both cortical and hippocampus mitochondria. However, unlike oxidative phosphorylation, membrane potential of mitochondria in the cortical lining of the impact site did not recover at 17 days, suggesting that while diminished cortical membrane potential at 17 days does not adversely affect mitochondrial capacity to synthesize ATP, it may negatively impact other membrane potential-sensitive mitochondrial functions. Memory status, as assessed by a passive avoidance paradigm, was not significantly impaired until 17 days after injury. These results indicate pronounced disturbances in cortical mitochondrial function 7 days after CCI which precede the behavioral impairment observed at 17 days.
Full-text · Article · Jan 2013 · Frontiers in Neuroenergetics
[Show abstract][Hide abstract] ABSTRACT: Cerebral inflammatory responses may initiate secondary cascades following traumatic brain injury. Changes in the expression of both cytokines and chemokines may activate, regulate, and recruit innate and adaptive immune cells associated with secondary degeneration, as well as alter a host of other cellular processes. In this study, we quantified the temporal expression of a large set of inflammatory mediators in rat cortical tissue after brain injury. Following a controlled cortical impact on young adult male rats, cortical and hippocampal tissue of the injured hemisphere and matching contralateral material was harvested at early (4, 12 and 24 hours) and extended (3, and 7 days) timepoints post-procedure. Naïve rats that received only anesthesia were used as controls. Processed brain homogenates were assayed for chemokine and cytokine levels utilizing an electrochemilumenscence-based multiplex ELISA platform. The temporal profile of cortical tissue samples revealed a multi-phasic injury response following brain injury. CXCL1, IFNγ, IL4, and IL5 reached peak concentrations 4 hours post-injury and immediately returned to levels not different from control tissue. The levels of IL1b, IL13, and TNFa were also highest at 4 hours post-injury although their expression remained significantly above levels in uninjured tissue at extended time points. Additionally, IL1b and IL13 levels displayed a biphasic temporal profile in response to injury, which may suggest their involvement in an anti-inflammatory process. Interestingly, CCL2 and CCL20 did not reach peak levels until 1 day post-injury. Peak CCL2 levels were significantly higher than peak levels of any other inflammatory mediator measured, thus suggesting a possible use as a biomarker. Fully elucidating chemokine and cytokine signaling properties after brain injury may provide increased insight into a number of secondary cascade events that are initiated or regulated by inflammatory responses.
Full-text · Article · Jan 2012 · Frontiers in Molecular Neuroscience
[Show abstract][Hide abstract] ABSTRACT: Thyroid-related hormones regulate the efficiency and expression of sarco-endoplasmic reticulum calcium ATPases in cardiac and skeletal muscle. However, little is known about the relationship between thyroid hormones and calcium (Ca2+) homeostasis in the brain. It is hypothesized that manipulating rat thyroid hormone levels would induce significant brain Ca2+ adaptations consistent with clinical findings. Adult male Sprague-Dawley rats were assigned to one of three treatment groups for 28 days: control, hypothyroid (6-n-propyl-2-thiouracil (PTU), an inhibitor of thyroxine (T4) synthesis), and hyperthyroid (T4). Throughout, rats were given weekly behavioral tests. Ca2+ accumulation decreased in the cerebellum in both hyper- and hypothyroid animals. This was specific to different ER pools of calcium with regional heterogeneity in the response to thyroid hormone manipulation. Behavioral tasks demonstrated sensitivity to thyroid manipulation, and corresponded to alterations in calcium homeostasis. Ca2+ accumulation heterogeneity in chronic hyper- and hypothyroid animals potentially explains clinical manifestations of altered thyroid status.
Full-text · Article · Jan 2012 · Indian journal of experimental biology