Inhibitory effects of nicotine derived from cigarette smoke on thymic stromal lymphopoietin production in epidermal keratinocytes

Regulatory Mechanisms of Natural Active Ingredients and Compounds on Keratinocytes and Fibroblasts in Mitigating Skin Photoaging

Background

The mechanism underlying skin photoaging remains elusive because of the intricate cellular and molecular changes that contribute to this phenomenon, which have yet to be elucidated. In photoaging, the roles of keratinocytes and fibroblasts are vital for maintaining skin structure and elasticity. But these cells can get photo-induced damage during photoaging, causing skin morphological changes. Recently, the function of natural active ingredients in treating and preventing photoaging has drawn more attention, with researches often focusing on keratinocytes and fibroblasts.

Methods

We searched for studies published from 2007 to January 2024 in the Web of Science, PubMed, and ScienceDirect databases through the following keywords: natural plant, natural plant products or phytochemicals, traditional Chinese Medicine or Chinese herbal, plant extracts, solar skin aging, skin photoaging, and skin wrinkling. This review conducted the accordance of Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines.

Results

In total, 87 researches were included in this review (Figure 1). In keratinocytes, natural compounds may primarily regulate signal pathways such as the NF-κB, MAPK, PI3K/AKT, and Nrf2/ARE pathways, reducing inflammation and cellular damage, thus slowing skin photoaging. Additionally, in fibroblasts, natural active ingredients primarily promote the TGF-β pathway, inhibit MMPs activity, and enhance collagen synthesis while potentially modulating the mTOR pathway, thereby protecting the dermal collagen network and reducing wrinkle formation. Several trials showed that natural compounds that regulate keratinocytes and fibroblasts responses have significant and safe therapeutic effects.

Conclusion

The demand for natural product-based ingredients in sunscreen formulations is rising. Natural compounds show promising anti-photoaging effects by targeting cellular pathways in keratinocytes and fibroblasts, providing potential therapeutic strategies. However, comprehensive clinical studies are needed to verify their efficacy and safety in mitigating photoaging, which should use advanced pharmacological methods to uncover the complex anti-photoaging mechanisms of natural compounds.

Post-Translational Modifications in Atopic Dermatitis: Current Research and Clinical Relevance

Atopic dermatitis (AD) is a chronic and relapsing cutaneous disorder characterized by compromised immune system, excessive inflammation, and skin barrier disruption. Post-translational modifications (PTMs) are covalent and enzymatic modifications of proteins after their translation, which have been reported to play roles in inflammatory and allergic diseases. However, less attention has been paid to the effect of PTMs on AD. This review summarized the knowledge of six major classes (including phosphorylation, acetylation, ubiquitination, SUMOylation, glycosylation, o-glycosylation, and glycation) of PTMs in AD pathogenesis and discussed the opportunities for disease management.

Activation of α7 nicotinic acetylcholine receptor retards the development of endometriosis

BACKGROUND

Women with endometriosis have been shown to have a reduced vagal tone as compared with controls and vagotomy promoted while vagus nerve stimulation (VNS) decelerated the progression of endometriosis in mice. Extensive research also has shown that the activation of the cholinergic anti-inflammatory pathway by VNS activates α7 nicotinic acetylcholine receptor (α7nAChR), potently reducing inflammation. Yet whether α7nAChR plays any role in endometriosis is unknown. We evaluated its expression in normal endometrium, ovarian and deep endometriotic lesions, and evaluated its role in the development of endometriosis.

METHODS

Immunohistochemistry analyses of α7nAChR in endometriotic lesions as well as control endometrium, and quantification of tissue fibrosis by Masson trichrome staining were performed. Mouse experiments were conducted to evaluate the impact of α7nAChR activation or suppression on lesional progression and possible therapeutic effect. Finally, in vitro experiments were conducted to evaluate the effect of activation of α7nAChR on epithelial-mesenchymal transition (EMT), fibroblast-to-myofibroblast transdifferentiation (FMT), smooth muscle metaplasia (SMM) and fibrogenesis in an endometriotic epithelial cell line and primary endometriotic stromal cells derived from ovarian endometrioma tissue samples.

RESULTS

Immunostaining of α7nAChR was significantly reduced in human endometriotic epithelial cells as compared with their counterpart in normal endometrium. Lesional α7nAChR staining levels correlated negatively with lesional fibrosis and the severity of dysmenorrhea. The α7nAChR agonist significantly impeded the development of endometriotic lesions in mouse models possibly through hindrance of EMT and FMT. It also demonstrated therapeutic effects in mice with induced deep endometriosis. Treatment of endometriotic epithelial and stromal cells with an α7nAChR agonist significantly abrogated platelet-induced EMT, FMT and SMM, and suppressed cellular contractility and collagen production.

CONCLUSIONS

α7nAChR is suppressed in endometriotic lesions, and its activation by pharmacological means can impede EMT, FMT, SMM, and fibrogenesis of endometriotic lesions. As such, α7nAChR can be rightfully viewed as a potential target for therapeutic invention.

TRIAL REGISTRATION

Not applicable.

Inflammasome involvement in CS-induced damage in HaCaT keratinocytes

Cigarette smoke (CS) alters cutaneous biological processes such as redox homeostasis and inflammation response that might be involved in promoting skin inflammatory conditions. Exposure to CS has also been linked to a destabilization of the NLRP3 inflammasome in pollution target tissues such as the lung epithelium, resulting in a more vulnerable immunological response to several exogenous and endogenous stimuli related to oxidative stress. Thus, CS has an adverse effect on host defense, increasing the susceptibility to develop lung infections and pathologies. In the skin, another direct target of pollution, inflammasome disorders have been linked to an increasing number of diseases such as melanoma, psoriasis, vitiligo, atopic dermatitis, and acne, all conditions that have been connected directly or indirectly to pollution exposure. The inflammasome machinery is an important innate immune sensor in human keratinocytes. However, the role of CS in the NLRP1 and NLRP3 inflammasome in the cutaneous barrier has still not been investigated. In the present study, we were able to determine in keratinocytes exposed to CS an increased oxidative damage evaluated by 4-HNE protein adduct and carbonyl formation. Of note is that, while CS inhibited NLRP3 activation, it was able to activate NLRP1, leading to an increased secretion of the proinflammatory cytokines IL-1β and IL-18. This study highlights the importance of the inflammasome machinery in CS that more in general, in pollution, affects cutaneous tissues and the important cross-talk between different members of the NLRP inflammasome family.

Protective Effects of Pinus halepensis Bark Extract and Nicotine on Cigarette Smoke-induced Oxidative Stress in Keratinocytes

BACKGROUND/AIM

Cigarette smoke (CS) is a major environmental health threat. The oxidative stress induced by CS on keratinocytes and the possible protective effect of nicotine, its receptor inhibitors, and Pinus halepensis bark extract in relation to known antioxidants were investigated.

MATERIALS AND METHODS

Primary mouse keratinocytes were exposed to cigarette smoke in the presence and absence of Pinus halepensis bark extract (1 μg/ml), rutin (50 μM) and ascorbic acid (250 μM), nicotine (1 μM) with or without mecamylamine (5 μM) and α-bungarotoxin (0.1 μM). Keratinocyte viability and oxidative stress were evaluated by MTT and fluorescence assays.

RESULTS

Pinus halepensis bark extract decreased the oxidative stress and increased the viability of keratinocytes, and moreover, these effects were more pronounced compared to the mixture of rutin and L-ascorbic acid. Nicotine significantly enhanced the viability potentiation of the beneficial effect induced by Pinus halepensis bark extract. Mecamylamine and α-bungarotoxin showed no specific effect.

CONCLUSION

Pinus halepensis bark extract in combination with nicotine may successfully reverse skin damage induced by cigarette smoke.

Nicotine attenuates concanavalin A-induced liver injury in mice by regulating the α7-nicotinic acetylcholine receptor in Kupffer cells

Nicotine, a potent parasympathomimetic alkaloid, manifests anti-inflammatory properties by activating nicotinic acetylcholine receptors (nAChRs). In this study, we evaluated the effects of nicotine on concanavalin A (ConA)-induced autoimmune hepatitis. Nicotine (0.5 and 1 mg/kg) was intraperitoneally administered to BALB/c mice and mice were intravenously injected with ConA (15 mg/kg) to induce hepatitis. The results showed that nicotine treatment ameliorated pathological lesions in livers and significantly suppressed the expression of pro-inflammatory cytokines in the livers. Such effects were mediated by inhibiting the nuclear factor-kappa B (NF-κB) signaling in livers. Interestingly, nicotine inhibited the ConA-induced inflammatory response in primary cultured Kupffer cells (KCs) but did not alter the proliferation of splenocytes. The protective effects of nicotine against ConA-induced hepatitis were abolished in KC-depleted mice, indicating the requirement of KCs in this process. Additionally, the expression of α7-nAChR on KCs was dramatically increased by nicotine treatment, and the protective effects of nicotine on ConA-induced liver injury were significantly suppressed by treatment with methyllycaconitine (MLA), a specific α7-nAChR antagonist. Consistently, in primary cultured KCs, the activation of NF-κB signaling was also regulated by nicotine treatment. This study suggests that nicotine increases α7-nAChR-mediated cholinergic activity in KCs resulting in decrease of ConA-induced autoimmune hepatitis through inhibiting NF-κB signaling.

Mimicking cigarette smoke exposure to assess cutaneous toxicity

Cigarette smoke stands among the most toxic environmental pollutants and is composed of thousands of chemicals including polycyclic aromatic hydrocarbons (PAHs). Despite restrict cigarette smoking ban in indoor or some outdoor locations, the risk of non-smokers to be exposed to environmental cigarette smoke is not yet eliminated. Beside the well-known effects of cigarette smoke to the respiratory and cardiovascular systems, a growing literature has shown during the last 3 decades its noxious effects also on cutaneous tissues. Being the largest organ as well as the interface between the outer environment and the body, human skin acts as a natural shield which is continuously exposed to harmful exogenous agents. Thus, a prolonged and/or repetitive exposure to significant levels of toxic smoke pollutants may have detrimental effects on the cutaneous tissue by disrupting the epidermal barrier function and by exacerbating inflammatory skin disorders (i.e. psoriasis, atopic dermatitis). With the development of very complex skin tissue models and sophisticated cigarette smoke exposure systems it has become important to better understand the toxicity pathways induced by smoke pollutants in more realistic laboratory conditions to find solutions for counteracting their effects. This review provides an update on the skin models currently available to study cigarette smoke exposure and the known pathways involved in cutaneous toxicity. In addition, the article will briefly cover the inflammatory skin pathologies potentially induced and/or exacerbated by cigarette smoke exposure.

Cholinergic Modulation of Type 2 Immune Responses

In recent years, the bidirectional relationship between the nervous and immune system has become increasingly clear, and its role in both homeostasis and inflammation has been well documented over the years. Since the introduction of the cholinergic anti-inflammatory pathway, there has been an increased interest in parasympathetic regulation of both innate and adaptive immune responses, including T helper 2 responses. Increasing evidence has been emerging suggesting a role for the parasympathetic nervous system in the pathophysiology of allergic diseases, including allergic rhinitis, asthma, food allergy, and atopic dermatitis. In this review, we will highlight the role of cholinergic modulation by both nicotinic and muscarinic receptors in several key aspects of the allergic inflammatory response, including barrier function, innate and adaptive immune responses, and effector cells responses. A better understanding of these cholinergic processes mediating key aspects of type 2 immune disorders might lead to novel therapeutic approaches to treat allergic diseases.

Induction of thymic stromal lymphopoietin by a steroid alkaloid derivative in mouse keratinocytes

Thymic stromal lymphopoietin (TSLP) plays critical roles in inducing and exacerbating allergic diseases. Chemical compounds that induce TSLP production can enhance sensitization to antigens and exacerbate allergic inflammation. Hence, identifying such chemicals will be important to prevent an increase in allergic diseases. In the present study, we found, for the first time, that a steroid alkaloid derivative, code no. 02F04, concentration and time dependently induced mRNA expression and production of TSLP in a mouse keratinocyte cell line, PAM212. In particular, the activity of 02F04 was selective to TSLP. As an analogue of the liver X receptor (LXR) endogenous ligand, 02F04 rapidly increased ATP-binding cassette transporter A1 (ABCA1) expression by regulating the nuclear receptor of LXR. However, instead of being inhibited by the LXR antagonist, 02F04-induced TSLP production was delayed and markedly suppressed by inhibitors of phospholipase C (PLC), pan-protein kinase C (PKC), PKCδ, Rho-associated protein kinase (ROCK), extracellular signal-regulated kinase (ERK) 1/2, and IκΒ kinase 2 (IKK2). Treatment with 02F04 caused the formation of F-actin filaments surrounding the nucleus of PAM212 cells, which then disappeared following addition of ROCK inhibitor. 02F04 also induced phosphorylation of ERK1/2 from 2h after treatment, with a maximum at 24h, and increased nuclear factor-κB (NF-κB) promoter activity by 1.3-fold. Taken together, these results indicate that 02F04-induced TSLP production is regulated via distinct signal transduction pathways, including PLC, PKC, ROCK, ERK1/2, and NF-κB but not nuclear receptors. 02F04, with a unique skeletal structure in inducing TSLP production, can represent a potential new tool for investigating the role of TSLP in allergic diseases.

Alpha5 Nicotinic Acetylcholine Receptor Contributes to Nicotine-Induced Lung Cancer Development and Progression

Nicotine and nicotinic acetylcholine receptors (nAChRs) are considered to be involved in lung cancer risk, onset and progression, but their precise physiological roles in these contexts remain unclear. Our previous studies suggested that α5-nAChR mediates nicotine-induced lung cancer cell proliferation, migration, and invasion in vitro. In this study, we aimed to determine the role of α5-nAChR in the development and progression of non-small cell lung cancer (NSCLC). Our microarray results reveal that knockdown of the CHRNA5 gene encoding α5-nAChR significantly modulates key pathways including the cell cycle, DNA replication, pathway in cancer. α5-nAChR knockdown in cultured A549 cells affected cell cycle distribution, apoptosis, and cyclin expression. In vivo, α5-nAChR silencing inhibited the growth of lung tumors, especially in the context of nicotine exposure. Importantly, α5-nAChR expression in patient tumors correlated with the primary T stage, N stage, and reduced survival time. These results reveal that α5-nAChR silencing inhibits the progression of nicotine-related NSCLC, making this receptor a potential pharmacological target for the treatment of nicotine-related lung carcinogenesis.

Nicotine induces TIPE2 upregulation and Stat3 phosphorylation contributes to cholinergic anti-inflammatory effect

Cholinergic anti-inflammatory pathway has therapeutic effect on inflammation-associated diseases. However, the exact mechanism of nicotine-mediated anti-inflammatory effect is still unclear. TIPE2, a new member of tumor necrosis factor-α-induced protein-8 family, is a negative regulator of immune homeostasis. However, the roles of TIPE2 in cholinergic anti-inflammatory effect are still uncertain. Here, we demonstrated that nicotine exerts its anti-inflammatory effect by TIPE2 upregulation and phosphorylated stat3 mediated the inhibition of NF-κB activation, which was supported by the following evidence: firstly, both nicotine and TIPE2 inhibit pro-inflammatory cytokine release via NF-κB inactivation. Secondly, nicotine upregulates TIPE2 expression via α7 nicotinic acetylcholine receptor. Moreover, the enhancement of stat3 phosphorylation and decrease of LPS-induced p65 translocation were achieved by nicotine treatment. Importantly, nicotine treatment augments the interaction of phosphorylated stat3 and p65, indicating that the inhibitory effect of nicotine on NF-κB activation was mediated with protein-protein interactions. Hence, this study revealed that TIPE2 upregulation and stat3 phosphorylation contribute to nicotine-mediated anti-inflammation effect, indicating that TIPE2 and stat3 might be potential molecules for dealing with inflammation-associated diseases.

The potential protective role of taurine against experimental allergic inflammation

AIMS

Taurine has been widely evaluated as a potential therapeutic agent in chronic inflammatory disorders and various infections. However, the potential role of taurine in regulating allergic inflammatory responses is currently unknown.

MATERIALS AND METHODS

The present study was designed to evaluate the in vitro effects of taurine on the levels of thymic stromal lymphopoietin (TSLP) and other pro-inflammatory cytokines and activation of caspase-1 and nuclear factor (NF)-κB as well as the phosphorylations of c-Jun N-terminal kinase (JNK) and p38 in phorbol 12-myristate 13-acetate and calcium ionophore A23187 (PMACI)-triggered human mast cell line, HMC-1 cells. Furthermore, we assessed the therapeutic effects of taurine on ovalbumin (OVA)-induced allergic rhinitis (AR) animal models.

KEY FINDINGS AND SIGNIFICANCE

Here, the obtained results showed that taurine dose-dependently inhibited the production and mRNA expression of TSLP and pro-inflammatory cytokines in HMC-1 cells exposed to PMACI. Taurine attenuated the phosphorylation of JNK and p38 in activated HMC-1 cells. Moreover, taurine brought a significant inhibition of the activities of NF-κB and caspase-1. In an OVA-induced AR animal model, the increased levels of nose rubbing, histamine, immunoglobulin E, TSLP, and interleukin IL-1β were dramatically reduced by the administration of taurine. In summary, taurine could serve as potential novel remedy of allergic inflammatory disorders.