Tissue-specific mitochondrial toxicity of cigarette smoke concentrate: consequence to oxidative phosphorylation.

Cigarette smoke exposure is a well-known risk factor for developing numerous chronic health conditions, including pulmonary disease and cardiometabolic disorders. However, the cellular mechanisms mediating the toxicity of cigarette smoke in extrapulmonary tissues are still poorly understood. Therefore, the purpose of this study was to characterize the acute dose-dependent toxicity of cigarette smoke on mitochondrial metabolism by determining the susceptibility and sensitivity of mitochondrial respiration from murine skeletal (gastrocnemius and soleus) and cardiac muscles, as well as the aorta to cigarette smoke concentrate (CSC). In all tissues, exposure to CSC inhibited tissue-specific respiration capacity, measured by high-resolution respirometry, according to a biphasic pattern. With a break point of 451 ± 235 µg/mL, the aorta was the least susceptible to CSC-induced mitochondrial respiration inhibition compared with the gastrocnemius (151 ± 109 µg/mL; P = 0.008, d = 2.3), soleus (211 ± 107 µg/mL; P = 0.112; d = 1.7), and heart (94 ± 51 µg/mL; P < 0.001; d = 2.6) suggesting an intrinsic resistance of the vascular smooth muscle mitochondria to cigarette smoke toxicity. In contrast, the cardiac muscle was the most susceptible and sensitive to the effects of CSC, demonstrating the greatest decline in tissue-specific respiration with increasing CSC concentration (P < 0.001, except the soleus). However, when normalized to citrate synthase activity to account for differences in mitochondrial content, cardiac fibers' sensitivity to cigarette smoke inhibition was no longer significantly different from both fast-twitch gastrocnemius and slow-twitch soleus muscle fibers, thus suggesting similar mitochondrial phenotypes. Collectively, these findings established the acute dose-dependent toxicity of cigarette smoke on oxidative phosphorylation in permeabilized tissues involved in the development of smoke-related cardiometabolic diseases.NEW & NOTEWORTHY Despite numerous investigations into the mechanisms underlying cigarette smoke-induced mitochondrial dysfunction, no studies have investigated the tissue-specific mitochondrial toxicity to cigarette smoke. We demonstrate that, while aorta is least sensitive and susceptible to cigarette smoke-induced toxicity, the degree of cigarette smoke-induced toxicity in striated muscle depends on the tissue-specific mitochondrial content. We conclude that while the mitochondrial content influences cigarette smoke-induced toxicity in striated muscles, aorta is intrinsically protected against cigarette smoke-induced mitochondrial toxicity.

The amygdala modulates prepulse inhibition of the auditory startle reflex through excitatory inputs to the caudal pontine reticular nucleus.

BACKGROUND: Sensorimotor gating is a fundamental pre-attentive process that is defined as the inhibition of a motor response by a sensory event. Sensorimotor gating, commonly measured using the prepulse inhibition (PPI) of the auditory startle reflex task, is impaired in patients suffering from various neurological and psychiatric disorders. PPI deficits are a hallmark of schizophrenia, and they are often associated with attention and other cognitive impairments. Although the reversal of PPI deficits in animal models is widely used in pre-clinical research for antipsychotic drug screening, the neurotransmitter systems and synaptic mechanisms underlying PPI are still not resolved, even under physiological conditions. Recent evidence ruled out the longstanding hypothesis that PPI is mediated by midbrain cholinergic inputs to the caudal pontine reticular nucleus (PnC). Instead, glutamatergic, glycinergic, and GABAergic inhibitory mechanisms are now suggested to be crucial for PPI, at the PnC level. Since amygdalar dysfunctions alter PPI and are common to pathologies displaying sensorimotor gating deficits, the present study was designed to test that direct projections to the PnC originating from the amygdala contribute to PPI. RESULTS: Using wild type and transgenic mice expressing eGFP under the control of the glycine transporter type 2 promoter (GlyT2-eGFP mice), we first employed tract-tracing, morphological reconstructions, and immunohistochemical analyses to demonstrate that the central nucleus of the amygdala (CeA) sends glutamatergic inputs lateroventrally to PnC neurons, including GlyT2+ cells. Then, we showed the contribution of the CeA-PnC excitatory synapses to PPI in vivo by demonstrating that optogenetic inhibition of this connection decreases PPI, and optogenetic activation induces partial PPI. Finally, in GlyT2-Cre mice, whole-cell recordings of GlyT2+ PnC neurons in vitro paired with optogenetic stimulation of CeA fibers, as well as photo-inhibition of GlyT2+ PnC neurons in vivo, allowed us to implicate GlyT2+ neurons in the PPI pathway. CONCLUSIONS: Our results uncover a feedforward inhibitory mechanism within the brainstem startle circuit by which amygdalar glutamatergic inputs and GlyT2+ PnC neurons contribute to PPI. We are providing new insights to the clinically relevant theoretical construct of PPI, which is disrupted in various neuropsychiatric and neurological diseases.

Larrea tridentata Extract Mitigates Oxidative Stress-Induced Cytotoxicity in Human Neuroblastoma SH-SY5Y Cells.

Creosote bush (Larrea tridentata; LT) leaves extracts were tested for their potential efficacy to mitigate cellular oxidative stress on human SH-SY5Y cells. Here, the differential nuclear staining assay, a bioimager system, and flow cytometric protocols, concurrently with several specific chemicals, were used to measure the percentage of cell viability and several facets implicated in the cytoprotective mechanism of LT extracts. Initially, three LT extracts, prepared with different solvents, ethanol, ethanol:water (e/w), and water, were tested for their capacity to rescue the viability of cells undergoing aggressive H2O2-induced oxidative stress. Results indicate that the LT extract prepared with a mixture of ethanol:water (LT-e/w; 60:40% v/v) displayed the most effective cytoprotection rescue activity. Interestingly, by investigating the LT-e/w mechanism of action, it was found that LT-e/w extract decreases the levels of H2O2-provoked reactive oxidative species (ROS) accumulation, mitochondrial depolarization, phosphatidylserine externalization, caspase-3/7 activation, and poly (ADP-ribose) polymerase (PARP) cleavage significantly, which are hallmarks of apoptosis. Thus, out of the three LT extracts tested, our findings highlight that the LT-e/w extract was the most effective protective reagent on SH-SY5Y cells undergoing oxidative stress in vitro, functioning as a natural anti-apoptotic extract. These findings warrant further LT-e/w extract examination in a holistic context.

Assessing the Antioxidant Properties of Larrea tridentata Extract as a Potential Molecular Therapy against Oxidative Stress.

Oxidative stress has been linked to neurodegenerative diseases such as Huntington's, Parkinson's, Alzheimer's and amyotrophic lateral sclerosis diseases. Larrea tridentata (LT) also known as Creosote Bush is an evergreen shrub found in the Chihuahuan desert which has been used medicinally by Native American tribes in southwestern North America and the Amerindians of South America. However, studies of the antioxidant capacity of the crude extract of LT towards the discovery of novel molecular therapies bearing antioxidants and drug-like properties are lacking. In this study, we assessed the antioxidant properties of Larrea tridentata, collected specifically from the Chihuahuan desert in the region of El Paso del Norte, TX, USA. LT phytochemicals were obtained from three different extracts (ethanol; ethanol: water (60:40) and water). Then the extracts were evaluated in eight different assays (DPPH, ABTS, superoxide; FRAP activity, nitric oxide, phenolic content, UV visible absorption and cytotoxicity in non-cancerous HS27 cells). The three extracts were not affecting the HS27 cells at concentrations up to 120 µg/mL. Among the three extracts, we found that the mixture of ethanol: water (60:40) LT extract has the most efficient antioxidant properties (IC50 (DPPH at 30 min) = 111.7 ± 3.8 µg/mL; IC50 (ABTS) = 8.49 ± 2.28 µg/mL; IC50 (superoxide) = 0.43 ± 0.17 µg/mL; IC50 (NO) = 230.4 ± 130.4 µg/mL; and the highest phenolic content was estimated to 212.46 ± 7.05 mg GAE/L). In addition, there was a strong correlation between phenolic content and the free-radical scavenging activity assays. HPLC-MS study identified nine compounds from the LT-ethanol: water extract including Justicidin B and Beta peltain have been previously reported as secondary metabolites of Larrea tridentata.

The neuroprotective role of ferrostatin-1 under rotenone-induced oxidative stress in dopaminergic neuroblastoma cells.

Endoplasmic reticulum (ER) proteins including protein disulfide isomerase (PDI) are playing crucial roles in maintaining appropriate protein folding. Under nitrosative stress, an excess of nitric oxide (NO) radical species induced the S-nitrosylation of PDI cysteines which eliminate its isomerase and oxidoreductase capabilities. In addition, the S-nitrosylation-PDI complex is the cause of aggregation especially of the α-synuclein (α-syn) protein (accumulation of Lewy-body aggregates). We recently identified a potent antioxidant small molecule, Ferrostatin-1 (Fer-1), that was able to inhibit a non-apoptotic cell death named ferroptosis. Ferroptosis cell death involved the generation of oxidative stress particularly lipid peroxide. In this work, we reported the neuroprotective role of ferrostatin-1 under rotenone-induced oxidative stress in dopaminergic neuroblastoma cells (SH-SY5Y). We first synthesized the Fer-1 and confirmed that it is not toxic toward the SH-SY5Y cells at concentrations up to 12.5 µM. Second, we showed that Fer-1 compound quenched the commercially available stable radical, the 2,2-diphenyl-1-picrylhydrazyl (DPPH), in non-cellular assay at 82 %. Third, Fer-1 inhibited the ROS/RNS generated under rotenone insult in SH-SY5Y cells. Fourth, we revealed the effective role of Fer-1 in ER stress mediated activation of apoptotic pathway. Finally, we reported that Fer-1 mitigated rotenone-induced α-syn aggregation.

Evidence for altered hippocampal function in a mouse model of the human 22q11.2 microdeletion.

22q11.2 chromosomal deletions are recurrent copy number mutations that increase the risk of schizophrenia around thirty-fold. Deletion of the orthologous chromosomal region in mice offers an opportunity to characterize changes to neuronal structure and function that may account for the development of this disease. The hippocampus has been implicated in schizophrenia pathogenesis, is reduced in volume in 22q11.2 deletion carriers and displays altered neuronal structure in a mouse model of the mutation (Df(16)A(+/-) mice). Here we investigate hippocampal CA1 physiology, hippocampal-dependent spatial memory and novelty-induced hippocampal activation in Df(16)A(+/-) mice. We found normal spatial reference memory (as assayed by the Morris water maze test) as well as modest but potentially important deficits in physiology. In particular, a reduction in the level of inhibition of CA1 pyramidal neurons was observed, implying a decrease in interneuron activity. Additionally, deficits in LTP were observed using certain induction protocols. Induction of c-Fos expression by exploration of a novel environment suggested a relative sparing of CA1 and dentate gyrus function but showed a robust decrease in the number of activated CA3 pyramidal neurons in Df(16)A(+/-) mice. Overall, experiments performed in this 22q11.2 deletion model demonstrated deficits of various degrees across different regions of the hippocampus, which together may contribute to the increased risk of developing schizophrenia.