Eucalyptol reduces airway hyperresponsiveness in rats following cigarette smoke-exposed

The protective effects of medicinal plants against cigarette smoking: A comprehensive review

BACKGROUNDS

Cigarette smoking remains a pervasive and harmful habit, and it poses a significant public health concern globally. Tobacco smoke contains numerous toxicants and carcinogens that contribute to the incidence of various diseases, including respiratory ailments, cancer, and cardiovascular disorders. Over the past decade, there has been a growing interest in exploring natural remedies to mitigate the harmful effects of cigarette smoke (CS). Medicinal plants, with their rich phytochemical compositions, have emerged as potential sources of protective agents against CS-induced damage.

OBJECTIVES

The current review attempts to comprehensively review and provide a thorough analysis of the protective effects of medicinal plants, including ginseng, Aloe vera, Olea europaea, Zea mays, green tea, etc. against CS-related toxicities.

MATERIALS AND METHODS

A comprehensive research and compilation of existing literature were conducted. We conducted a literature search using the Web of Science, PubMed, Scopus, and Google Scholar. We selected articles published in English between 1987 and 2025. The search was performed using keywords including cigarette smoking, cigarette smokers, second-hand smokers, natural compounds, plant extracts, naturally derived products, natural resources, phytochemicals, and medicinal plants.

RESULTS

This review critically investigated recent literature focusing on the effects of medicinal plant extracts, essential oils, and isolated compounds on reducing the adverse consequences of CS exposure. These investigations encompassed several in vivo, in vitro, and clinical trials, clarifying the mechanisms underlying the protective effects of these plants. The notable antioxidant, anti-inflammatory, and detoxifying properties of these botanical interventions were also highlighted.

CONCLUSION

Collectively, this review emphasizes the potential of medicinal plants in alleviating the harmful effects of CS. The rich active constituents present in these plants offer various mechanisms that counteract oxidative stress, inflammation, and carcinogenesis induced by CS exposure. Further research is warranted to reveal the precise molecular mechanisms, derive dosing recommendations, and explore the efficacy of botanical interventions in large-scale clinical trials, ultimately improving public health outcomes and providing valuable insights for the smoking population worldwide.

Eucalyptol Ameliorates Retinal Microvascular Defects through Modulating ER Stress and Angiopoietin-Tie Signaling in Diabetic Eyes

Loss of the inner blood-retinal barrier (BRB) integrity is a main feature of ocular diseases such as diabetic macular edema. However, there is a lack of clarity on how inner BRB function is modulated within the diabetic retina. The current study examined whether eucalyptol inhibited inner BRB destruction and aberrant retinal angiogenesis in 33 mM glucose-exposed human retinal microvascular endothelial (RVE) cells and db/db mice. This study further examined the molecular mechanisms underlying endothelial dysfunction including retinal endoplasmic reticulum (ER) stress and angiopoietin (Ang)/Tie axis in conjunction with vascular endothelial growth factor (VEGF). Eucalyptol is a naturally occurring monoterpenoid and an achiral aromatic component of many plants including eucalyptus leaves. Nontoxic eucalyptol reduced the production of amyloid-β (Aβ) protein in glucose-loaded RVE cells and in diabetic mice. This natural compound blocked apoptosis of Aβ-exposed RVE cells in diabetic mouse eyes by targeting ER stress via the inhibition of PERK-eIF2α-ATF4-CHOP signaling. Eucalyptol promoted activation of the Ang-1/Tie-2 pathway and dual inhibition of Ang-2/VEGF in Aβ-exposed RVE cells and in diabetic eyes. Supply of eucalyptol reversed the induction of junction proteins in glucose/Aβ-exposed RVE cells within the retina and reduced permeability. In addition, oral administration of eucalyptol reduced vascular leaks in diabetic retinal vessels. Taken together, these findings clearly show that eucalyptol inhibits glucose-induced Aβ-mediated ER stress and manipulates Ang signaling in diabetic retinal vessels, which ultimately blocks abnormal angiogenesis and loss of inner BRB integrity. Therefore, eucalyptol provides new treatment strategies for diabetes-associated RVE defects through modulating diverse therapeutic targets including ER stress, Ang-1/Tie-2 signaling, and Ang-2/VEGF.

Cigarette smoke extract induces pyroptosis in human bronchial epithelial cells through the ROS/NLRP3/caspase-1 pathway

AIMS

Pyroptosis and inflammation are involved in the development of chronic obstructive pulmonary disease (COPD). However, the cigarette smoke-mediated mechanism of COPD remains unclear. In this study, we aimed to investigate the role of nucleotide-binding domain-like receptor protein-3 (NLRP3) inflammasome-mediated pyroptosis in the death of human bronchial epithelial (HBE) cells after cigarette smoke extract (CSE) exposure.

MAIN METHODS

The protein level of NLRP3 in lung tissue was measured after cigarette smoke exposure in vivo. In vitro, HBE cells were treated with CSE. Subsequently, the activity of caspase-1, lactate dehydrogenase (LDH) release, release of interleukin (IL)-1β and NLRP3 expression levels were measured. The involvement of reactive oxygen species (ROS) was also explored.

KEY FINDINGS

After exposure to CSE, increased release of LDH, the transcriptional and translational upregulation of NLRP3, the caspase-1 activity levels, and enhanced IL-1β and IL-18 release were observed in 16HBE cells. In addition, NLRP3 was required to activate the caspase-1. Our results suggested that pre-stimulated of 16HBE with a caspase-1 inhibitor, or using NLRP3 siRNA to silence NLRP3 expression, also caused the decrease of IL-1β release and pyroptosis.

SIGNIFICANCES

CSE induced inflammation and contributed to pyroptosis through the ROS/NLRP3/caspase-1 pathway in 16HBE cells. The NLRP3 inflammasome participates in CSE-induced HBE cell damage and pyroptosis, which could provide new insights into COPD.