NMR Spectroscopy Identifies Chemicals in Cigarette Smoke Condensate That Impair Skeletal Muscle Mitochondrial Function

Nontargeted Analysis in Tobacco Research: Challenges and Opportunities

Tobacco products are evolving at a pace that has outstripped tobacco control, leading to a high prevalence of tobacco use in the population. Researchers have been tirelessly developing suitable techniques to assess these products' emissions, toxicity, and public health impact. The nonclinical testing of tobacco products to assess the chemical profile of emissions is needed for evidence-based regulations. This testing has largely relied on targeted analytical methods that focus on constituent lists that may fall short in determining the toxicity of newly designed tobacco products. Nontargeted analysis (NTA), or the process of identifying and quantifying compounds within a complex matrix without prior knowledge of its chemical composition, is a promising technique for tobacco regulation, but it is not without challenges. The lack of standardized methods for sample generation, sample preparation, chromatographic separation, compound identification, and data analysis and reporting must be addressed so that the quality and reproducibility of the data generated by NTA can be benchmarked. This review discusses the challenges and highlights the opportunities of NTA in studying tobacco product constituents and emissions.

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.

Exercise Effects on Health-Related Quality of Life (HRQOL), Muscular Function, Cardiorespiratory Function, and Body Composition in Smokers: A Narrative Review

Smoking is amongst the leading global threats with high incidences of preventable premature mortality, morbidity, and various chronic diseases. The World Health Organization (WHO) proclaims a decrease in the prevalence of daily smoking in both males and females from 1980 to 2012, however, the number of regular smokers since then has exponentially increased. The low socio-income status individuals contribute greatly towards tobacco-attributable diseases due to limited access to healthcare systems, mostly in developing countries as compared to developed countries. Smoking affects the optimal functioning of the human body, which results in altered body system processes. Although a high intake of nicotine can lead to prolonged adherence and dependence on smoking, other factors, such as an individual's level of health-related quality of life (HRQOL), stress, depression, and anxiety, can produce similar effects. Smoking has a wide impact on lifestyle factors, which explains the increase in the number of sedentary smokers with decreased health fitness levels and poor lifestyle conditions. Therefore, this study seeks to investigate the exercise effects on health-related quality of life (HRQOL), muscular function, cardiorespiratory function, and body composition in smokers. Concurrently, exercise as an intervention has been sourced as a rehabilitation strategy during smoking cessation programmes to restore the diminishing health components, however, a high rate of relapse occurs due to intolerable withdrawal symptoms.

Effects of acute cigarette smoke concentrate exposure on mitochondrial energy transfer in fast- and slow-twitch skeletal muscle

The mechanisms underlying cigarette smoke-induced mitochondrial dysfunction in skeletal muscle are still poorly understood. Accordingly, this study aimed to examine the effects of cigarette smoke on mitochondrial energy transfer in permeabilized muscle fibers from skeletal muscles with differing metabolic characteristics. The electron transport chain (ETC) capacity, ADP transport, and respiratory control by ADP were assessed in fast- and slow-twitch muscle fibers from C57BL/6 mice (n = 11) acutely exposed to cigarette smoke concentrate (CSC) using high-resolution respirometry. CSC decreased complex I-driven respiration in the white gastrocnemius (CONTROL:45.4 ± 11.2 pmolO₂.s^-1.mg^-1 and CSC:27.5 ± 12.0 pmolO₂.s^-1.mg^-1; p = 0.01) and soleus (CONTROL:63.0 ± 23.8 pmolO₂.s^-1.mg^-1 and CSC:44.6 ± 11.1 pmolO₂.s^-1.mg^-1; p = 0.04). In contrast, the effect of CSC on Complex II-linked respiration increased its relative contribution to muscle respiratory capacity in the white gastrocnemius muscle. The maximal respiratory activity of the ETC was significantly inhibited by CSC in both muscles. Furthermore, the respiration rate dependent on the ADP/ATP transport across the mitochondrial membrane was significantly impaired by CSC in the white gastrocnemius (CONTROL:-70 ± 18 %; CSC:-28 ± 10 %; p < 0.001), but not the soleus (CONTROL:47 ± 16 %; CSC:31 ± 7 %; p = 0.08). CSC also significantly impaired mitochondrial thermodynamic coupling in both muscles. Our findings underscore that acute CSC exposure directly inhibits oxidative phosphorylation in permeabilized muscle fibers. This effect was mediated by significant perturbations of the electron transfer in the respiratory complexes, especially at complex I, in both fast and slow twitch muscles. In contrast, CSC-induced inhibition of the exchange of ADP/ATP across the mitochondrial membrane was fiber-type specific, with a large effect on fast-twitch muscles.

Effects of cigarette smoke on in situ mitochondrial substrate oxidation of slow- and fast-twitch skeletal muscles

Epidemiological and clinical evidence suggests that cigarette smoke exposure alters glucose and fatty acid metabolism, leading to greater susceptibility to metabolic disorders. However, the effects of cigarette smoke exposure on mitochondrial substrate oxidation in the skeletal muscle are still poorly understood. Accordingly, this study aimed to examine the acute effects of cigarette smoke on mitochondrial respiratory capacity, sensitivity, and concurrent utilization of palmitoylcarnitine (PC), a long-chain fatty acid, and pyruvate, a product of glycolysis, in permeabilized gastrocnemius and soleus muscle fibers exposed to an acute (1 h) dose (4 %) of cigarette smoke concentrate. Cigarette smoke decreased both mitochondrial respiratory capacity (CONTROL: 50.4 ± 11.8 pmol_O2/s/mg_wt and SMOKE: 22.3 ± 4.4 pmol_O2/s/mg_wt, p < 0.01) and sensitivity for pyruvate (CONTROL: 0.10 ± 0.04 mM and SMOKE: 0.11 ± 0.04 mM, p < 0.01) in the gastrocnemius muscle. In the soleus, only the sensitivity for pyruvate-stimulated mitochondrial respiration trended toward a decrease (CONTROL: 0.11 ± 0.04 mM and SMOKE: 0.23 ± 0.15 mM, p = 0.08). In contrast, cigarette smoke did not significantly alter palmitoylcarnitine-stimulated mitochondrial respiration in either muscle. In the control condition, pyruvate-supported respiration was inhibited by the concurrent addition of palmitoylcarnitine in the fast-twitch gastrocnemius muscle (-27.1 ± 19.7 %, p < 0.05), but not in the slow-twitch soleus (-9.2 ± 17.0 %). With cigarette smoke, the addition of palmitoylcarnitine augmented the maximal respiration rate stimulated by the concurrent addition of pyruvate in the gastrocnemius (+18.5 ± 39.3 %, p < 0.05). However, cigarette smoke still significantly impaired mitochondrial respiratory capacity with combined substrates compared to control (p < 0.05). Our findings underscore that cigarette smoke directly impairs mitochondrial respiration of carbohydrate-derived substrates and is a primary mechanism underlying cigarette smoke-induced muscle dysfunction, which leads to a vicious cycle involving excess glucose conversion into fatty acids and lipotoxicity.

Skeletal Muscle Mitochondrial Dysfunction in Chronic Obstructive Pulmonary Disease: Underlying Mechanisms and Physical Therapy Perspectives

Skeletal muscle dysfunction (SMD) is a prevalent extrapulmonary complication and a significant independent prognostic factor in patients with chronic obstructive pulmonary disease (COPD). Mitochondrial dysfunction is one of the core factors that damage structure and function in COPD skeletal muscle and is closely related to smoke exposure, hypoxia, and insufficient physical activity. The currently known phenotypes of mitochondrial dysfunction are reduced mitochondrial content and biogenesis, impaired activity of mitochondrial respiratory chain complexes, and increased mitochondrial reactive oxygen species production. Significant progress has been made in research on physical therapy (PT), which has broad prospects for treating the abovementioned potential mitochondrial-function changes in COPD skeletal muscle. In terms of specific types of PT, exercise therapy can directly act on mitochondria and improve COPD SMD by increasing mitochondrial density, regulating mitochondrial biogenesis, upregulating mitochondrial respiratory function, and reducing oxidative stress. However, improvements in mitochondrial-dysfunction phenotype in COPD skeletal muscle due to different exercise strategies are not entirely consistent. Therefore, based on the elucidation of this phenotype, in this study, we analyzed the effect of exercise on mitochondrial dysfunction in COPD skeletal muscle and the regulatory mechanism thereof. We also provided a theoretical basis for exercise programs to rehabilitate this condition.