Cigarette smoking differentially regulates inflammatory responses in a mouse model of nonalcoholic steatohepatitis depending on exposure time point

Maternal smoking and its short- or long-term impact on offspring liver pathologies: a review of experimental and clinical studies

This review investigates the correlation between prenatal tobacco exposure and the risk of liver diseases in offspring. By synthesizing data from clinical trials and animal studies, it provides a comprehensive overview of the potential mechanisms underlying this association. This review begins by analyzing the prevalence of maternal smoking and its impact on fetal development. It then discusses specific liver diseases observed in offspring exposed prenatally to tobacco, such as acute liver injuries and metabolic dysfunction-associated fatty liver disease, and discusses the underlying pathophysiological pathways. Current evidence indicates that altered fetal liver development, oxidative stress, and genetic modifications may predispose offspring to liver diseases. Furthermore, this review highlights the gaps in current research and the need for longitudinal studies to better understand the long-term effects of prenatal tobacco exposure on the liver. The review concludes with recommendations for public health policies aimed at enhancing our understanding of maternal smoking and mitigating its adverse effects on offspring, emphasizing the importance of smoking cessation during pregnancy.

Graphical abstract

Cigarette Smoke Contributes to the Progression of MASLD: From the Molecular Mechanisms to Therapy

Cigarette smoke (CS), an intricate blend comprising over 4000 compounds, induces abnormal cellular reactions that harm multiple tissues. Non-alcoholic fatty liver disease (NAFLD) is a prevalent chronic liver disease (CLD), encompassing non-alcoholic fatty liver (NAFL), non-alcoholic steatohepatitis (NASH), cirrhosis, and hepatocellular carcinoma (HCC). Recently, the term NAFLD has been changed to metabolic dysfunction-associated steatotic liver disease (MASLD), and NASH has been renamed metabolic dysfunction-associated steatohepatitis (MASH). A multitude of experiments have confirmed the association between CS and the incidence and progression of MASLD. However, the specific signaling pathways involved need to be updated with new scientific discoveries. CS exposure can disrupt lipid metabolism, induce inflammation and apoptosis, and stimulate liver fibrosis through multiple signaling pathways that promote the progression of MASLD. Currently, there is no officially approved efficacious pharmaceutical intervention in clinical practice. Therefore, lifestyle modifications have emerged as the primary therapeutic approach for managing MASLD. Smoking cessation and the application of a series of natural ingredients have been shown to ameliorate pathological changes in the liver induced by CS, potentially serving as an effective approach to decelerating MASLD development. This article aims to elucidate the specific signaling pathways through which smoking promotes MASLD, while summarizing the reversal factors identified in recent studies, thereby offering novel insights for future research on and the treatment of MASLD.

The causal relationship of cigarette smoking to metabolic disease risk and the possible mediating role of gut microbiota

BACKGROUND

Cigarette smoking is a leading cause of preventable death worldwide, with its associated diseases and conditions. Emerging evidence suggests that cigarette smoking contributes to a range of pathological metabolic injuries, including diabetes and nonalcoholic fatty liver disease (NAFLD). The impact of gut microbiota on metabolic health and diseases has been observed, but the causality remains uncertain.

OBJECTIVE

To confirm the causal relationship between cigarette smoking and metabolic diseases, and to investigate the possible mediating effect of gut microbiota on these connections.

METHODS

The relationships among cigarette smoking, metabolic diseases, and the gut microbiome were analyzed by Univariate Mendelian randomization (UVMR). Furthermore, to mitigate the impact of confounding factors, adjusted models were conducted via the multivariate Mendelian randomization (MVMR) method, aiming to improve the accuracy of prediction. Ultimately, the study evaluated the effect of the intermediary factor, gut microbiome, on the relationship between cigarette smoke and metabolic diseases.

RESULTS

The phenomenon that a causal relationship between cigarette smoke (249752 individuals) and gut microbiota (7738 individuals), diabetes (406831 individuals), NAFLD (377998 individuals), hypercholesterolaemia (463010 individuals), and obesity (463010 individuals) was observed using UVMR. In the MVMR model, the genetic connection between cigarette smoking, gut microbiota, and type 2 diabetes remained significant. Of note, paraprevotella_clara served an important mediating role in the type 2 diabetes associated with cigarette smoke.

CONCLUSION

This work offered genetic evidence linking cigarette smoke to metabolic diseases, suggesting that the gut microbiota, particularly paraprevotella_clara, might be a crucial mediator in the development of type 2 diabetes caused by cigarette smoke. Our future studies should consider conducting other ethnic groups MR analyses, particularly with larger sample sizes. Still, more in vivo and in vitro work should be carried out to validate the precise effect and molecular mechanisms of the gut microbiome.

Impacts of smoking on alcoholic liver disease: a nationwide cohort study

Objectives

Smoking is a preventable risk factor for morbidity and mortality in patients with liver disease. This study aims to explore the additional risks of smoking in the development of alcoholic liver disease (ALD), cirrhosis, and hepatocellular carcinoma (HCC) in high-risk drinkers.

Methods

Data from the National Health Insurance Service, including claims and health check-up information spanning 2011 to 2017, were used. The overall alcohol consumption was calculated, and ALD was defined based on ICD-10 codes. High-risk drinking was defined as 7 or more drinks for men and 5 or more for women, twice weekly. Half of the high-risk drinkers were smokers, decreasing in men but stable at 20% for women.

Results

ALD prevalence was 0.97% in high-risk drinkers and 1.09% in high-risk drinkers who smoked, higher than 0.16% in social drinkers (p < 0.001). ALD incidence over 3-years was highest in high-risk drinkers who smoked (2.35%), followed by high-risk drinkers (2.03%) and social drinkers (0.35%) (p < 0.001). Cirrhosis and HCC followed similar patterns, with prevalence and incidence was highest in drinkers who smoked. 3-year mortality was 0.65% in high-risk drinkers who smoked, compared to 0.50% in high-risk drinkers and 0.24% in social drinkers (p < 0.001). Smoking increased the incidence of ALD, cirrhosis, and HCC by 1.32, 1.53, and 1.53 times, respectively (all p < 0.001). Gender-specific analysis revealed higher risk ratios (RR) for women in ALD, alcoholic cirrhosis, and HCC, particularly among high-risk drinkers who smoked. Women showed significantly increased RR in ALD (6.08 to 12.38) compared to men (4.18 to 4.40), and similar trends were observed for cirrhosis and HCC.

Conclusion

Smoking significantly heightens the risk of ALD, cirrhosis, and HCC, especially in women, among high-risk drinkers. This emphasizes the importance of smoking cessation, particularly for female patients with ALD.

Liver toxicity in rats after subchronic exposure to HTP aerosol and cigarette smoke

Background

Heated tobacco product (HTP) considered to be a novel tobacco product which was reported safer than traditional cigarettes evidenced by lower potential harmful components released. Liver is an important detoxification organ of the body, the chemical components in aerosols are metabolized in the liver after absorbed, so it is necessary to explore the effect of HTP on the liver.

Materials and Methods

The potential effect of HTP and cigarette smoke (CS) on SD rats was explored according to OECD 413 subchronic inhalation. The rats were randomly divided into Sham (air), different dosage of HTP groups (HTP_10, 23 and 50 μg nicotine/L aerosol) and Cig_23 (23 μg nicotine/L aerosol) group. After exposure, the clinical pathology, inflammation and oxidative stress were measured.

Results

The clinical pathology results showed that both HTP_50 and Cig_23 led to abnormality of ALT for male rats. CS and HTP exposure reduced the expression of IL-1β, IL-6 and TNF-α and mitochondrial medicated oxidative stress. In addition, the ATP production was reduced in Cig_23 group. Although inflammation and oxidative stress were displayed, no apoptosis were observed by TUNEL assay and these existed obvious pathological changes only in HTP_50 group, while in CS group with equivalent nicotine, hepatocytes swelling were observed in liver.

Conclusion

CS exposure induced liver damage through mitochondrial mediated oxidative stress and inflammation, which was also observed in high concentration of HTP exposure group. For the same equivalent nicotine, HTP may show lower toxic effect on liver than CS.

Investigating anti-inflammatory and apoptotic actions of fucoidan concentrating on computational and therapeutic applications

Fucoidan is linked to a variety of biological processes. Differences in algae species, extraction, seasons, and locations generate structural variability in fucoidan, affecting its bioactivities. Nothing is known about fucoidan from the brown alga Dictyota bartayresiana, its anti-inflammatory properties, or its inherent mechanism. This study aimed to investigate the anti-inflammatory properties of fucoidan isolated from D. bartayresiana against LPS-induced RAW 264.7 macrophages and to explore potential molecular pathways associated with this anti-inflammatory effects. Fucoidan was first isolated and purified from D. bartayresiana, and then, MTT assay was used to determine the effect of fucoidan on cell viability. Its effects on reactive oxygen species (ROS) formation and apoptosis were also studied using the ROS assay and acridine orange/ethidium bromide fluorescence labelling, respectively. Molecular docking and molecular dynamics simulation studies were performed on target proteins NF-κB and TNF-α to identify the route implicated in these inflammatory events. It was observed that fucoidan reduced LPS-induced inflammation in RAW 264.7 cells. Fucoidan also decreased the LPS-stimulated ROS surge and was found to induce apoptosis in the cells. Molecular docking and molecular dynamics simulation studies revealed that fucoidan's potent anti-inflammatory action was achieved by obstructing the NF-κB signalling pathway. These findings were particularly noteworthy and novel because fucoidan isolated from D. bartayresiana had not previously been shown to have anti-inflammatory properties in RAW 264.7 cells or to exert its activity by obstructing the NF-κB signalling pathway. Conclusively, these findings proposed fucoidan as a potential pharmaceutical drug for inflammation-related diseases.

Sappanone A Alleviates the Severity of Carbon Tetrachloride-Induced Liver Fibrosis in Mice

Liver fibrosis is a major challenge to global health because of its various complications, including cirrhosis and hepatocarcinoma, while no effective treatment is available for it. Sappanone A (SA) is a homoisoflavonoid extracted from the heartwood of Caesalpinia sappan Linn. with anti-inflammatory and antioxidant properties. However, the effects of SA on hepatic fibrosis remain unknown. This study aimed to investigate the protective effects of SA on carbon tetrachloride (CCl4)-induced liver fibrosis in mice. To establish a liver fibrosis model, mice were treated intraperitoneally (i.p.) with CCl4 for 4 weeks. SA (25, 50, and 100 mg/kg body weight) was i.p. injected every other day during the same period. Our data indicated that SA decreased liver injury, fibrotic responses, and inflammation due to CCl4 exposure. Consistently, SA reduced oxidative stress and its-mediated hepatocyte death in fibrotic livers. Of note, SA could not directly affect the activation of hepatic stellate cells. Mechanistically, SA treatment lessened oxidative stress-triggered cell death in hepatocytes after CCl4 exposure. SA down-regulated the expression of M1 macrophage polarization markers (CD86 and iNOS) and up-regulated the expression of M2 macrophage polarization markers (CD163, IL-10, and Arg1) in livers and macrophages. Meanwhile, SA induced the activation of peroxisome proliferator-activated receptor gamma (PPARγ). However, decreased inflammatory responses and the trend of M2 macrophage polarization provided by SA were substantially abolished by SR202 (a PPARγ inhibitor) treatment in macrophages. Additionally, SA treatment promoted fibrosis regression. Taken together, our findings revealed that treatment with SA alleviated CCl4-induced fibrotic liver in mice through suppression of oxidative stress-mediated hepatocyte death and promotion of M2 macrophage polarization via PPARγ. Thus, SA might pave the way for a new hepatoprotective agent to treat liver fibrosis.

CXCL5 Promotes Acetaminophen-Induced Hepatotoxicity by Activating Kupffer Cells

Kupffer cells (KCs) play a key part in the pathological process of acetaminophen (APAP)-induced acute liver injury (ALI), the leading cause of acute liver failure in the world. CXC motif chemokine ligand 5 (CXCL5) exerts proinflammatory effects in acute respiratory distress syndrome and arthritis. In the current study, we aim to reveal the effects of CXCL5 on the activation of KCs and the role of CXCL5 in the pathogenesis of APAP-induced hepatotoxicity. The in vivo study, conducted on mice intraperitoneally injected with APAP (300 mg/kg) to establish the ALI model and then treated with Anti-CXCL5 mAb at 30 min and 12 h after the APAP challenge, showed that CXCL5 expression significantly increased in injured livers, and Anti-CXCL5 mAb mitigated the degree of APAP-evoked ALI in mice which was proven through biochemicals and histological examination. Also, neutralization of CXCL5 had no significant effect on APAP metabolism in the liver but exhibited anti-inflammatory effects and ameliorated hepatocellular death in the injured liver. The in vitro data displayed that recombinant mouse CXCL5 treatment promoted APAP-induced cellular toxicity in primary hepatocytes co-cultured with KCs, compared with single-cultured hepatocytes. Consistent with the result, we found that the Anti-CXCL5 mAb gradient decreased LPS-induced expression of inflammatory cytokines in single-cultured KCs. Therefore, CXCL5 could stimulate KCs to produce inflammatory mediators, therefore damaging hepatocytes from APAP toxicity.

Cigarette smoking and liver diseases

Cigarette smoking is a preventable risk factor for premature morbidity and mortality. A history of smoking is observed in approximately 40% of patients with liver disease, while a growing number of studies are investigating the potential impact of smoking in chronic liver diseases. This review discusses the effects of smoking on liver diseases, at multiple levels, with a focus on its potential causal role. Clinical evidence indicates that cigarette smoking negatively impacts the incidence and severity of fatty liver disease, fibrosis progression, hepatocellular carcinoma development, and the outcomes of patients with advanced liver disease. The underlying mechanisms are complex and involve different pathophysiological pathways including oxidative stress and oncogenic signals. Importantly, smoking promotes cardiovascular disease and extrahepatic cancers in patients with steatohepatitis and in transplant recipients. We discuss how promoting smoking cessation could improve the rates of treatment response (in clinical trials) and fibrosis regression, while reducing the risk of hepatocellular carcinoma and improving liver transplant outcomes. Finally, we discuss current challenges such as the referral of smokers to specialised units for smoking cessation.

Quercetin Improves Pulmonary Function and Prevents Emphysema Caused by Exposure to Cigarette Smoke in Male Mice

Chronic obstructive pulmonary disease (COPD) is the major cause of morbidity and mortality worldwide, and cigarette smoke is a key factor in the development of COPD. Thus, the development of effective therapies to prevent the advancement of COPD has become increasingly essential. We hypothesized that quercetin protects lungs in mice exposed to long-term cigarette smoke. Thirty-five C57BL/6 mice were exposed to cigarette smoke (12 cigarettes per day) for 60 days and pretreated with 10 mg/kg/day of quercetin via orogastric gavage. After the experimental protocol, the animals were euthanized and samples were collected for histopathological, antioxidant defense, oxidative stress and inflammatory analysis. The animals exposed to cigarette smoke showed an increase in respiratory rate and hematological parameters, cell influx into the airways, oxidative damage and inflammatory mediators, besides presenting with alterations in the pulmonary histoarchitecture. The animals receiving 10 mg/kg/day of quercetin that were exposed to cigarette smoke presented a reduction in cellular influx, less oxidative damage, reduction in cytokine levels, improvement in the histological pattern and improvement in pulmonary emphysema compared to the group that was only exposed to cigarette smoke. These results suggest that quercetin may be an agent in preventing pulmonary emphysema induced by cigarette smoke.

Lycopene Ameliorates Liver Inflammation and Redox Status in Mice Exposed to Long-Term Cigarette Smoke

Cigarette smoke (CS) is the major cause of preventable death worldwide, and it can also cause damage to extrapulmonary organs, such as the liver, mainly due the generation of reactive oxygen species (ROS). The liver is an essential organ for human survival since it is mainly responsible for the body metabolism and among other things and it is the place where many endogenous and exogenous substances undergo biological transformation. Lycopene is a nonprovitamin A carotenoid found in red fruits and vegetables, and its role as a potent antioxidant is well known. In this study, we hypothesized that lycopene could protect mouse liver against long-term CS exposure. Thirty C57BL/6 mice were exposed to twelve cigarette smoke (12 cigarettes per day) for 60 days and pretreated with 25 mg/kg/day or 50 mg/kg/day of lycopene via orogastric gavage. After euthanasia, the hepatic tissue was collected for histopathological, antioxidant defense, oxidative stress, inflammatory, and collagen deposition analysis. Our analysis demonstrated that lycopene results in a suitable outcome to ameliorate the pathological changes, inflammatory and antioxidant profile in a mouse model of long-term CS exposure, and collagen accumulation in the hepatic extracellular matrix. This study demonstrates for the first time that supplementation of lycopene can be a possible pharmacological tool for the treatment of hepatic damage caused by exposure to long-term CS.

Anti-inflammatory activity of 3-cinnamoyltribuloside and its metabolomic analysis in LPS-activated RAW 264.7 cells

BACKGROUND

Inflammation is a response to tissue injuries, which is indispensable and important for human health, but excessive inflammation can potentially cause damage to the host organisms. Camellia nitidissima Chi, one traditional medicinal and edible plant in China, was reported to exhibit anti-inflammation capability. Hence, this study was conducted to isolate the bioactive compounds from the flowers of C. nitidissima Chi and evaluate their anti-inflammatory activity.

METHODS

The phytochemicals from the flowers of C. nitidissima Chi were isolated and purified by silica gel, Sephadex LH-20 gel, C18 reversed silica gel, semi-preparative HPLC, and identified by the spectrum technologies. The anti-inflammatory activity of isolated compounds was evaluated using cultured macrophage RAW 264.7 cells. Whereafter the potential metabolic mechanism of the anti-inflammatory activity of the bioactive compound was investigated by a 1H-NMR based metabolomics approach. The metabolites in 1H-NMR spectra were identified by querying the Human Metabolome Database and Madison Metabolomics Consortium Database online. And the multivariate statistical analysis was performed to evaluate the variability of metabolites among samples and between sample classes.

RESULTS

The compound isolated from the flowers of C. nitidissima Chi was identified as 3-cinnamoyltribuloside (3-CT). 3-CT could inhibit the NO production and the mRNA expression of iNOS involved in lipopolysaccharide (LPS)-activated RAW 264.7 cells. Moreover, 3-CT could inhibit the expression of a series of inflammatory cytokines, including TNF-α, IL-1β, and IL-6, both at the mRNA level and protein level. The 1H-NMR based metabolomics approach was applied to investigate the potential metabolic mechanism of the anti-inflammatory activity of 3-CT. Thirty-five metabolites were identified and assigned. Orthogonal signal correction partial least-squares discriminant analysis (OSC-PLS-DA) of the 1H-NMR data showed 3-CT could balance the significant changes in many endogenous metabolites (e.g., choline, glucose, phenylalanine) induced by LPS in RAW 264.7 cells, which related to cholinergic anti-inflammatory pathway, oxidative stress, energy metabolism, and amino acids metabolism.

CONCLUSION

3-CT, isolated from the flowers of C. nitidissima Chi, had potent anti-inflammatory activity in LPS-activated RAW 264.7 cells. Furthermore, our results indicated that 3-CT had effects on the cholinergic anti-inflammatory pathway, oxidative stress, energy metabolism, and amino acids metabolism in LPS-activated RAW 264.7 cells.

AK-1, a Sirt2 inhibitor, alleviates carbon tetrachloride-induced hepatotoxicity in vivo and in vitro

Background/Aim: Acute liver injury (ALI) is a life-threatening clinical syndrome that is usually caused by toxic chemicals, drugs, or pathogen infections. Sirtuin2 (Sirt2), an NAD⁺-dependent deacetylase, appears to play detrimental roles in liver injury. Here, we evaluated the therapeutic application targeting Sirt2 in carbon tetrachloride (CCl₄)-induced ALI, by using AK-1 (a Sirt2 inhibitor).Methods: For in vivo experiments, a single injection of CCl₄ was used to induce ALI. One hour later, mice were intraperitoneally injected with AK-1 and were sacrificed 24 h after CCl₄ administration. For in vitro experiments, primary mouse hepatocytes were used to determine the effects of AK-1 on oxidative stress and hepatocellular death induced by CCl₄.Results: AK-1 alleviated CCl₄-induced ALI as confirmed by histopathologic analysis, and decreased levels of serum biochemicals and inflammatory cytokines. Although it barely affected the expression of hepatic cytochrome P450 enzymes, AK-1 attenuated CCl₄-induced oxidative stress and its related cell death. Mechanistically, Sirt2 inhibition significantly increased the nuclear protein level of nuclear factor erythroid 2-related factor 2 (Nrf2), and meanwhile decreased phosphorylation of c-Jun N-terminal kinases (JNK), in normal and injured livers. Similar results were observed in vitro. AK-1 significantly attenuated CCl₄-induced cytotoxicity and oxidative stress by up-regulating the activity of Nrf2, and down-regulating JNK signaling in hepatocytes.Conclusions: Our results suggest that AK-1 treatment attenuated oxidative stress and cell death in the ALI model, at least partially, via activating Nrf2 and inhibiting JNK signaling, and that Sirt2 inhibition might be a potential approach to cure ALI.