Impaired mitochondrial respiration and protein nitration in the rat hippocampus after acute inhalation of combustion smoke

Abstract

Survivors of massive inhalation of combustion smoke endure critical injuries, including lasting neurological complications. We have previously reported that acute inhalation of combustion smoke disrupts the nitric oxide homeostasis in the rat brain. In this study, we extend our findings and report that exposure to smoke induces protein nitration in the rat hippocampus and that mitochondrial proteins are a sensitive nitration target in this setting. Mitochondria have central roles in energy metabolism and cellular signaling and are critical to proper cell function. Here, analyses of the mitochondrial proteome showed elevated protein nitration in the course of a 24-h recovery following exposure to smoke. Mass spectrometry identification of several significantly nitrated mitochondrial proteins revealed diverse functions and involvement in central aspects of mitochondrial physiology. The nitrated proteins include the ubiquitous mitochondrial creatine kinase, F1-ATP synthase α subunit, dihydrolipoamide dehydrogenase (E3), succinate dehydrogenase Fp subunit, and voltage-dependent anion channel (VDAC1) protein. Furthermore, acute exposure to combustion smoke significantly compromised the respiratory capacity of hippocampal mitochondria. Interestingly, elevated protein nitration and reduced mitochondrial respiration in the hippocampus persisted beyond the time required for restoration of normal oxygen and carboxyhemoglobin blood levels after the cessation of exposure to smoke. Thus, the data indicate that timing of the different smoke inhalation-induced effects varies among tissues. Taken together, our findings suggest that nitration of essential mitochondrial proteins may contribute to the reduction in mitochondrial respiratory capacity and underlie, in part, the brain pathophysiology after acute inhalation of combustion smoke.

Neuroglobin mitigates mitochondrial impairments induced by acute inhalation of combustion smoke in the mouse brain

“…Accordingly, brain manifestations of acute exposure to combustion smoke span a broad range of adversely affected targets (Lee et al, 2005; Lee et al, 2009; Zou et al, 2009; Lee et al, 2010; Lee et al, 2011; Zou et al, 2013) and we sought to identify those targets, which are protected by neuroglobin in this setting. To this end, we first produced a transgenic mouse with neuron-specific overexpression of Ngb and demonstrated that Ngb protects primary neurons by raising the threshold of nitric oxide mediated neuronal injury (Singh et al, 2013) and that in vivo, elevated Ngb attenuates the formation of smoke-induced oxidative DNA damage in the mouse brain (Lee et al, 2011).…”

“…We have previously developed combustion smoke-inhalation model for the awake rodent (Lee et al, 2005; Chen et al, 2007; Lee et al, 2009; Lee et al, 2010; Lee et al, 2011). Male CB57BL/6 mice (25–30 gram) wild type and transgenic (Ngb-tg), with neuron specific overexpression of neuroglobin under the control of rat synapsin 1 promoter were used (Lee et al, 2011).…”

“…Because previously Ngb was found neuroprotective in several settings of brain injury, we sought to elucidate potential roles of elevated Ngb in a setting of acute inhalation of combustion smoke. We had developed the awake rodent model of smoke inhalation (Lee et al, 2005; Lee et al, 2009; Lee et al, 2010) to facilitate investigation of mechanisms, which underlie neurological deficits that tend to develop in survivors of acute inhalation of combustion smoke (Hartzell, 1996; Rossi et al, 1996; Stefanidou et al, 2008). We investigated the effects of elevated neuronal Ngb, in vitro, in a setting of nitric oxide challenge (Singh et al, 2013) and in vivo, in a model of acute inhalation of smoke (Lee et al, 2011).…”

Progressive neuropsychiatric and brain abnormalities after smoke inhalation

“…Previous animal studies have shown that oxidative DNA damage caused by inhibition of mitochondrial respiratory complexes may contribute to neuronal dysfunction and progressive brain injury 1 3. The patient's course of illness between 3 and 14 years after inhalation injury may have resulted, in part, from impaired mitochondrial respiration and oxidative DNA damage.…”

Reactive oxygen species in disease: Rebuttal of a conventional concept

“…There was no scientific or mechanistic explanation that confirmed this suggestion nor was it associated with a systemic overproduction of free radicals. The basis of the discussion was reverted to animal studies, which had established a nonphysiological environment that was causal for increased ROS production, inhibition of mitochondrial respiration and oxidative DNA damage (12)(13)(14). Such investigations reinforce and reiterate that oxidative damage does not occur under normal physiological conditions.…”