BMAL1/FOXA2-induced rhythmic fluctuations in IL-6 contribute to nocturnal asthma attacks

Therapeutic Evaluation of Wumei Pill (WP) for Nocturnal Asthma in Bmal1 Gene Knockout Mice

OBJECTIVE

Previous clinical studies have demonstrated that Wumei Pill (WP), a traditional Chinese medicine formula, can effectively alleviate nocturnal asthma-related anxiety and improve nighttime symptoms. The therapeutic mechanism of WP may involve regulation of inflammatory chemokines in peripheral blood. This mechanism is potentially linked to modulation of the circadian clock gene ARNT-like protein-1 (Bmal1), but precise pathways underlying this interaction remain unclear, requiring further investigation.

METHODS

Bmal1 knockout and wild-type mice were utilized to establish asthma models. Techniques such as flow cytometry, RT-PCR, and ELISA were employed to measure the levels of serum inflammatory mediators, specifically IFN-γ, CXCL16, I-TAC, and PARC. Furthermore, the pathological alterations in airway thickness were assessed. Additionally, we investigated the regulation of the Bmal1 gene and its influence on the circadian rhythm-related recruitment of leukocytes, as well as the expression patterns of downstream mediators.

RESULTS

Compared to the wild-type (WT) group, the model group showed significantly higher levels of CXCL16, I-TAC, and PARC (p < 0.05), as well as a notable decrease in IFN-γ expression. WP treatment effectively normalized the levels of these inflammatory factors in the model group, indicating a regulatory effect of WP on inflammatory chemokines.

CONCLUSION

The knockout of the Bmal1 gene, a crucial regulator of circadian rhythms, disrupts the circadian expression of inflammatory chemokines. Treatment with WP modulated Bmal1 expression, influencing the release of these mediators, offering a promising strategy for managing nocturnal asthma. Notably, wild-type nocturnal asthma mice exhibited significantly better control of airway inflammation compared to their Bmal1-deficient counterparts, highlighting the importance of circadian regulation in the pathophysiology of asthma.

State of the art: Alternative overlap syndrome-asthma and obstructive sleep apnea

In the general population, Bronchial Asthma (BA) and Obstructive Sleep Apnea (OSA) are among the most prevalent chronic respiratory disorders. Significant epidemiologic connections and complex pathogenetic pathways link these disorders via complex interactions at genetic, epigenetic, and environmental levels. The coexistence of BA and OSA in an individual likely represents a distinct syndrome, that is, a collection of clinical manifestations attributable to several mechanisms and pathobiological signatures. To avoid terminological confusion, this association has been named alternative overlap syndrome (vs overlap syndrome represented by the chronic obstructive pulmonary disease-OSA association). This comprehensive review summarizes the complex, often bidirectional links between the constituents of the alternative overlap syndrome. Cross-sectional, population, or clinic-based studies are unlikely to elucidate causality or directionality in these relationships. Even longitudinal epidemiological evaluations in BA cohorts developing over time OSA, or OSA cohorts developing BA during follow-up cannot exclude time factors or causal influence of other known or unknown mediators. As such, a lot of pathophysiological interactions described here have suggestive evidence, biological plausibility, potential or actual directionality. By showcasing existing evidence and current knowledge gaps, the hope is that deliberate, focused, and collaborative efforts in the near-future will be geared toward opportunities to shine light on the unknowns and accelerate discovery in this field of health, clinical care, education, research, and scholarly endeavors.

Mediation of FOXA2/IL-6/IL-6R/STAT3 signaling pathway mediates benzo[a]pyrene-induced airway epithelial mesenchymal transformation in asthma

Benzo [a]pyrene (BaP), a toxic pollutant, increases the incidence and severity of asthma. However, the molecular mechanisms underlying the effects of BaP in asthma remain unclear. In terms of research methods, we used BaP to intervene in the animal model of asthma and the human bronchial epithelial (16HBE) cells, and the involved mechanisms were found from the injury, inflammation, and airway epithelial to mesenchymal transition (EMT) in asthma. We also constructed small interfering RNAs and overexpression plasmids to knockdown/overexpress IL-6R and FOXA2 in 16HBE cells and a serotype 9 adeno-associated viral vector for lung tissue overexpression of FOXA2 in mice to determine the mechanism of action of BaP-exacerbated asthma airway EMT. We observed that BaP aggravated inflammatory cell infiltration into the lungs, reduced the Penh value, increased collagen fibres in the lung tissue, and increased serum IgE levels in asthmatic mice. After BaP intervention, the expression of FOXA2 in the lung tissue of asthmatic mice decreased, the production and secretion of IL-6 were stimulated, and STAT3 phosphorylation and nuclear translocation increased, leading to changes in EMT markers. However, EMT decreased after increasing FOXA2 expression and decreasing that of IL-6R and was further enhanced after low FOXA2 expression. Our results revealed that BaP exacerbated airway epithelial cell injury and interfered with FOXA2, activating the IL-6/IL-6R/STAT3 signaling pathway to promote airway EMT in asthma. These findings provide toxicological evidence for the mechanism underlying the contribution of BaP to the increased incidence of asthma and its exacerbations.

Hypoxia Induces Alterations in the Circadian Rhythm in Patients with Chronic Respiratory Diseases

The function of the circadian cycle is to determine the natural 24 h biological rhythm, which includes physiological, metabolic, and hormonal changes that occur daily in the body. This cycle is controlled by an internal biological clock that is present in the body's tissues and helps regulate various processes such as sleeping, eating, and others. Interestingly, animal models have provided enough evidence to assume that the alteration in the circadian system leads to the appearance of numerous diseases. Alterations in breathing patterns in lung diseases can modify oxygenation and the circadian cycles; however, the response mechanisms to hypoxia and their relationship with the clock genes are not fully understood. Hypoxia is a condition in which the lack of adequate oxygenation promotes adaptation mechanisms and is related to several genes that regulate the circadian cycles, the latter because hypoxia alters the production of melatonin and brain physiology. Additionally, the lack of oxygen alters the expression of clock genes, leading to an alteration in the regularity and precision of the circadian cycle. In this sense, hypoxia is a hallmark of a wide variety of lung diseases. In the present work, we intended to review the functional repercussions of hypoxia in the presence of asthma, chronic obstructive sleep apnea, lung cancer, idiopathic pulmonary fibrosis, obstructive sleep apnea, influenza, and COVID-19 and its repercussions on the circadian cycles.