Effects of Betulinic Acid Derivative on Lung Inflammation in a Mouse Model of Chronic Obstructive Pulmonary Disease Induced by Particulate Matter 2.5

Anti-Inflammatory Activities of Betulinic Acid: A Review

Inflammatory diseases have a high prevalence and has become of great interest due to the increase in life expectancy and the costs to the health care system worldwide. Chronic diseases require long-term treatment frequently using corticosteroids and non-steroidal anti-inflammatory drugs, which are associated with diverse side effects and risk of toxicity. Betulinic acid, a lupane-type pentacyclic triterpene, is a potential lead compound for the development of new anti-inflammatory treatments, and a large number of derivatives have been produced and tested. The potential of betulinic acid and its derivatives has been shown in a number of pre-clinical studies using different experimental models. Moreover, several molecular mechanisms of action have also been described. Here we reviewed the potential use of betulinic acid as a promissory lead compound with anti-inflammatory activity and the perspectives for its use in the treatment of inflammatory conditions.

Molecular mechanism of betulin palliative therapy for chronic obstructive pulmonary disease (COPD) based on P2X7 receptor target of gated ion channel

Background

The aim of this study was to discover the molecular mechanism of betulin palliative therapy for chronic obstructive pulmonary disease (COPD) based on the P2X7 receptor target of gated ion channel.

Methods

A COPD mouse model was developed. Changes in pulmonary ventilation function, pulmonary airway and vascular remodeling indicators, inflammatory cells, and inflammatory factors were determined after betulin intervention, and the pathological alterations of lung tissues were detected. An in vitro experimental model was constructed to observe the influence of betulin at varying concentrations on the proliferation of human bronchial epidermal cell line (16-HBE) cells and changes in inflammatory factors in cell supernatant. The expression levels of key proteins in 16-HBE cells transfected with overexpressed or silenced P2X7 genes were determined through quantitative reverse transcription polymerase chain reaction (RT-qPCR) and Western blot.

Results

After betulin intervention, pulmonary ventilation function in the 20 mg/kg betulin and 40 mg/kg betulin groups was improved. Levels of white blood cells (WBCs), neutrophils (Ns), tumor necrosis factor (TNF), TNF-ɑ, interleukin (IL)-1β, and IL-6 in the 2 groups also decreased significantly (all P<0.05). The pathological changes in COPD mice were detected. After betulin intervention, the pathological injury of the lung was reduced, the pathological score decreased significantly, and the remodeling indicators of pulmonary airway and pulmonary vessels diminished remarkably (all P<0.05). Betulin had no effect on the proliferation of 16-HBE cells in vitro. After cigarette smoke extract (CSE) stimulation, the rate of survival for 16-HBE cells decreased significantly. After betulin treatment, the survival rate of 16-HBE cells augmented remarkably, and the levels of TNF-ɑ, IL-6, and IL-1β in cell supernatant reduced substantially (all P<0.05). 16-HBE with overexpression and knockdown of P2X7 was constructed. After being treated with betulin, the relative expression levels of messenger RNA (mRNA) of ERK, JNK, rho-associated protein kinase (ROCK), nuclear factor-κB (NF-κB), and p38 in 16-HBE cells with P2X7 overexpression or knockdown were decreased significantly (all P<0.05), but the above indicators were largely unchanged (all P>0.05).

Conclusions

Betulin relieved lung pathological injury, ameliorated lung ventilation function, and diminished the level of inflammatory factors in COPD mice, playing a therapeutic role via the P2X7 signaling pathway.

Impaired AT2 to AT1 cell transition in PM2.5-induced mouse model of chronic obstructive pulmonary disease

Background

Particular matter 2.5 (PM2.5) is one of the most important air pollutant, and it is positively associated with the development of chronic obstructive pulmonary disease (COPD). However, the precise underlying mechanisms through which PM2.5 promotes the development of COPD remains largely unknown.

Methods

Mouse alveolar destruction were determined by histological analysis of lung tissues and lung function test. Alveolar type II cells (AT2) to alveolar type I cells (AT1) transition in PM2.5-induced COPD mouse model was confirmed via immunofluorescence staining and qPCR analysis. The differentially expressed genes in PM2.5-induced COPD mouse model were identified by RNA-sequencing of alveolar epithelial organoids and generated by bioinformatics analysis.

Results

In this study, we found that 6 months exposure of PM2.5 induced a significantly decreased pulmonary compliance and resulted in pulmonary emphysema in mice. We showed that PM2.5 exposure significantly reduced the AT2 to AT1 cell transition in vitro and in vivo. In addition, we found a reduced expression of the intermediate AT2-AT1 cell process marker claudin 4 (CLDN4) at day 4 of differentiation in mouse alveolar organoids treated with PM2.5, suggesting that PM2.5 exposure inhibited AT2 cells from entering the transdifferentiation process. RNA-sequencing of mouse alveolar organoids showed that several key signaling pathways that involved in the AT2 to AT1 cell transition were significantly altered including the Wnt signaling, MAPK signaling and signaling pathways regulating pluripotency of stem cells following PM2.5 exposure.

Conclusions

In summary, these data demonstrate a critical role of AT2 to AT1 cell transition in PM2.5-induced COPD mouse model and reveal the signaling pathways that potentially regulate AT2 to AT1 cell transition during this process. Our findings therefore advance the current knowledge of PM2.5-induced COPD and may lead to a novel therapeutic strategy to treat this disease.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-01996-w.