Asthma is the most prevalent chronic respiratory disorder observed in children, characterized by recurring wheezing, shortness of breath, chest tightness, or cough in clinical practice. At present, the pathogenesis of asthma remains partially understood; nevertheless, airway inflammation, airway hyperresponsiveness (AHR), and airway remodeling are crucial causes behind the onset of asthma (Naja et al., 2018). The prevalence of asthma among 0-14-year-old urban children in China has increased significantly, the prevalence rate rose from 1.09% in 1990 to 3.02% in 2010, an increase of over 50% every decade (Lin et al., 2018). Asthma not only incurs significant medical and health costs, but also has a detrimental impact on children's well-being, education, and daily functioning.

With the improvement of living standards, obesity has become a chronic metabolic disease that seriously threatens life and health globally (Pereira and Oliveira, 2021). In 2016, roughly 124 million children across the globe were recorded as obese, yielding an approximated obesity rate of 6.7% (Hales et al., 2017). According to the International Consensus on Childhood Asthma (ICON), obesity and asthma together form a distinct phenotype of asthma known as obese asthma. Obese asthma presents graver clinical manifestations than uncomplicated asthma and, furthermore, poses more significant obstacles to clinical intervention. In fact, the pursuit of a more comprehensive understanding of the molecular mechanisms that cause obese asthma is ongoing. Recently published evidence suggests that enhanced bronchial inflammation, triggered by systemic or local inflammatory effects of obesity itself, may explain the higher rates of respiratory disease in obese young people, independently of asthma (Gutmann et al., 2024). As noted in our previous study, proinflammatory M1 adipose tissue macrophages (ATMs) are predominant in obese individuals and may contribute to the initiation and exacerbation of asthma by enhancing systemic inflammation (Lin et al., 2024). In addition, the expression of interferon (IFN)-stimulated genes associated with IFN-related signaling pathways has been reported to be specifically affected in obese asthmatics (Alhamdan et al., 2021). Recently, the identified extracellular vesicle microRNA miRNA signatures seemed to be capable to disentangle underlying molecular mechanisms of obese asthma, which may serve as a basis for the development of stratified treatments (Alhamdan et al., 2023; Vázquez-Mera et al., 2023). Either way, the study of obesity and asthma deserves considerable attention, and investigating the common mechanisms between them may lead to novel therapeutic approaches for these conditions.

Pulmonary alveolar macrophages (AMs) are essential innate immune components with various functions including phagocytosis, release of inflammatory and chemokines, and activation of helper T lymphocyte (Th) 1/Th2 response (Neupane et al., 2020). They are vital in maintaining the stability of the lung environment, eliminating pathogens, and restoring lung function. Due to their high heterogeneity and plasticity, they can differentiate into distinct functional subtypes upon stabilization or infection, which mainly classified as M1 and M2 (Wang et al., 2022b; Zhang et al., 2021). M1 macrophages, induced by IFN-γ and LPS, exhibit anti-inflammatory properties. In contrast, M2 macrophages, induced by interleukin (IL)-4 and IL-13, are involved in anti-inflammatory responses. Recent studies have confirmed that the onset of asthma is related to Th2/M2 differentiation (Lee et al., 2021). Moreover, the relationship between obesity and low-grade inflammation (characterized by an increase in M1 macrophages) has been proposed to explain the pathogenesis of obese asthma (Lee et al., 2023). Obesity and asthma are risk factors for each other, but both depend on different macrophage phenotypes. We need to continuously deepen our understanding of how M1 and M2 macrophages simultaneously affect the pathological processes of obese asthma.

Celastrol is a potent bioactive compound naturally derived from Tripterygium wilfordii roots. According to Umut Ozcan's research team, celastrol possesses potential as a novel weight loss medication due to its ability to enhance leptin sensitivity, reduce food consumption and successfully decrease the weight of obese mice (Liu et al., 2015). Furthermore, celastrol has demonstrated significant potential in reducing inflammation, combatting cancer, and addressing autoimmune disorders (Luo et al., 2022; Shirai et al., 2023). The previous investigation carried out by our laboratory demonstrated that celastrol decreased AHR by suppressing Th17 responses in obese asthmatic mice (Zeng et al., 2018). Other studies have suggested that celastrol regulates the polarization of peritoneal macrophages, resulting in a reduction of the inflammatory state and insulin resistance in lightweight mice (Zhou et al., 2018). To date, no studies have reported the effect of celastrol on AMs polarization, especially for obese asthma.

PI3K/Akt signaling pathway was reported to control macrophage survival, proliferation, and migration, and correlates with macrophage polarization (Vergadi et al., 2017; Yu et al., 2019). Akt activation is required for M2 macrophages activation, as Akt inhibition abolishes the upregulation of M2 genes (Liu et al., 2019). PI3K, the upstream regulator of Akt, has been shown to mediate the phenotype of M2 macrophages (Zhao et al., 2021). Upregulation of miR-24 in macrophages, a negative regulator of M1 activation that promotes M2 polarization, leads to reduced expression of the class IA PI3K subunit p110 d (Fordham et al., 2015). It was found that celastrol alleviates autoimmune hepatitis through the PI3K/AKT signaling (Wang et al., 2022a). In addition, celastrol has shown potential in protecting the kidneys from ischemia-reperfusion injury by suppressing oxidative stress and enhancing cell survival through the PI3K/AKT signaling pathways (Younis and Ghanim, 2022). Here, we speculated that celastrol may regulate macrophage polarization through the PI3K/AKT signaling pathway.

To address this, we used celastrol to investigate its role in AMs polarization in obese asthmatic mice. In vitro, RAW264.7 macrophage cells were cultured and the effects of celastrol on LPS-induced macrophage polarization were investigated. We also sought to determine whether the PI3K/AKT pathway contributes to AMs polarization in obese asthma. Our research provides a unique insight into the pathogenesis of obese asthma and offers potential for a new therapeutic approach to this type of asthma.