Punicalagin, a pomegranate compound, induces apoptosis and autophagy in acute leukemia

Exploring the anticancer potential and mechanisms of action of natural coumarins and isocoumarins

Natural coumarins and isocoumarins show significant therapeutic potential against cancer in preclinical studies by targeting multiple pathways and processes. These compounds influence several critical cellular processes, such as apoptosis, autophagy, and cell cycle regulation, which are pivotal in cancer development and progression. Their capability to target multiple signalling pathways provides a strategic advantage over single-target therapies, which are often limited by drug resistance. Notably, coumarins have the potential to inhibit angiogenesis, the process through which tumours develop new blood vessels, thereby potentially restricting tumour growth and metastasis. Additionally, coumarins may enhance anticancer effects by modulating immune responses and reducing inflammation, thus offering a dual approach to combating cancer. They also show promise in addressing multidrug resistance, a significant challenge in cancer therapy, by targeting drug efflux proteins and potentially improving the efficacy of existing treatments. While preclinical studies are promising, further research is required to elucidate the pharmacokinetics, toxicity, and potential side effects of coumarins in humans. Continued clinical evaluation will be crucial to confirm their effectiveness in cancer patients. Nonetheless, their ability to target multiple pathways positions coumarin based molecules as potential candidates for future anti-cancer drug development.

Anticancer effects of pomegranate-derived peptide PG2 on CDK2 and miRNA-339-5p-mediated apoptosis via extracellular vesicles in acute leukemia

Acute leukemia has rapid onset and severe complications. Anticancer peptides from natural sources have demonstrated efficacy in eliminating various cancers through apoptosis signaling pathways. Additionally, extracellular vesicles containing microRNAs play pivotal roles in promoting tumorigenesis. Therefore, this study aimed to investigate the impact of PG2, a pomegranate peptide that regulates extracellular vesicles, on the induction of acute leukemia cell apoptosis. NB4 and MOLT-4 leukemia cell lines were treated with PG2 alone or in combination with daunorubicin to assess cell viability using the MTT assay. Extracellular vesicles were extracted from PG2-treated NB4 and MOLT-4 cells. Bioinformatic tools were utilized to predict target proteins and microRNAs, following which mRNA and protein expression were determined by using RT‒qPCR and western blotting, respectively. PG2 significantly reduced the viability of NB4 and MOLT-4 cells. Furthermore, the combination of PG2 with daunorubicin had a synergistic effect on NB4 and MOLT-4 cells. Subsequent treatment with PG2 or PG2-treated extracellular vesicles decreased CDK2 expression while increasing microRNA-339-5p and caspase-3 expression in NB4 and MOLT-4 cells. Our findings revealed that the anticancer activity of PG2 through the CDK2/miR-339-5p/caspase-3 pathway is mediated by extracellular vesicles, ultimately inducing apoptosis. PG2 holds promise as a potential antileukemic drug.

Expression of HOTAIR and PTGS2 as potential biomarkers in chronic myeloid leukemia patients in Brazil

Chronic myeloid leukemia (CML) is a clonal myeloproliferative neoplasm in which all the patients has the translocation (9;22) that generates de BCR::ABL1 tyrosine kinase. Despite this disease possessing a good biomarker (BCR::ABL1 transcripts level) for diagnosis and prognosis, many studies has been performed to investigate other molecules, such as the long noncoding RNAs (lncRNAs) and mRNAs, as potential biomarkers with the aim of predicting a change in BCR::ABL1 levels and as an associated biomarker. A RNAseq was performed comparing 6 CML patients with high BCR::ABL1 expression with 6 healthy control individuals, comprising the investigation cohort to investigate these molecules. To validate the results obtained by RNAseq, samples of 87 CML patients and 42 healthy controls were used in the validation cohort by RT-qPCR assays. The results showed lower expression of HOTAIR and PTGS2 in CML patients. The HOTAIR expression is inversely associated with BCR::ABL1 expression in imatinib-treated CML patients, and to PTGS2 showing that CML patients with high BCR::ABL1 expression showed reduced PTGS2 expression.

Neuroprotective effects of punicalagin and/or micronized zeolite clinoptilolite on manganese-induced Parkinson's disease in a rat model: Involvement of multiple pathways

BACKGROUND

Manganism, a central nervous system dysfunction correlated with neurological deficits such as Parkinsonism, is caused by the substantial collection of manganese chloride (MnCl2) in the brain.

OBJECTIVES

To explore the neuroprotective effects of natural compounds, namely, micronized zeolite clinoptilolite (ZC) and punicalagin (PUN), either individually or in combination, against MnCl2-induced Parkinson's disease (PD).

METHODS

Fifty male albino rats were divided into 5 groups (Gps). Gp I was used as the control group, and the remaining animals received MnCl2 (Gp II-Gp V). Rats in Gps III and IV were treated with ZC and PUN, respectively. Gp V received both ZC and PUN as previously reported for the solo-treated plants.

RESULTS

ZC and/or PUN reversed the depletion of monoamines in the brain and decreased acetyl choline esterase activity, which primarily adjusted the animals' behavior and motor coordination. ZC and PUN restored the balance between glutamate/γ-amino butyric acid content and markedly improved the brain levels of brain-derived neurotrophic factor and nuclear factor erythroid 2-related factor 2/heme oxygenase-1 and decreased glycogen synthase kinase-3 beta activity. ZC and PUN also inhibited inflammatory and oxidative markers, including nuclear factor kappa-light-chain-enhancer of activated B cells, Toll-like receptor 4, nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 and caspase-1. Bcl-2-associated X-protein and B-cell leukemia/lymphoma 2 protein (Bcl-2) can significantly modify caspase-3 expression. ZC and/or PUN ameliorated PD in rats by decreasing the levels of endoplasmic reticulum (ER) stress markers (p-protein kinase-like ER kinase (PERK), glucose-regulated protein 78, and C/EBP homologous protein (CHOP)) and enhancing the levels of an autophagy marker (Beclin-1).

DISCUSSION AND CONCLUSION

ZC and/or PUN mitigated the progression of PD through their potential neurotrophic, neurogenic, anti-inflammatory, antioxidant, and anti-apoptotic activities and by controlling ER stress through modulation of the PERK/CHOP/Bcl-2 pathway.

Review of Pharmacological and Medicinal Uses of Punica granatum

Pomegranates (Punica granatum) are a fruit renowned for their rich history, diverse uses, and substantial health benefits. Current research on the botanical features, nutritional profile, and medicinal properties of pomegranates is summarized in this study. Botanically, the pomegranate is classified as a deciduous shrub with a unique fruit structure comprising numerous seeds, or arils, embedded in a leathery skin. Nutritionally, pomegranates are a significant source of antioxidants, particularly punicalagin, and anthocyanins, which contribute to their purported health benefits. Emerging evidence suggests that pomegranate consumption may have favorable effects on cardiovascular health, anti-inflammatory responses, and cancer prevention. Clinical studies highlight their potential to enhance blood flow, prevent arterial plaque formation, and reduce the risk of heart disease, heart attacks, and strokes. This review also examines traditional and contemporary uses of pomegranates in medicine and cuisine, highlighting their cultural significance and potential therapeutic applications. Despite promising findings, limitations in current research methodologies and the need for more robust clinical trials are discussed. This review aims to synthesize current research on the botanical characteristics, nutritional profile, and medicinal properties of pomegranates (Punica granatum), with a focus on their health benefits and applications in traditional and contemporary contexts. Future research directions are proposed to better understand the mechanisms underlying the health benefits of pomegranates and to optimize their use in preventive and therapeutic contexts.

Effect of punicalagin on the autophagic cell death in triple-negative breast cancer cells

Triple-negative breast cancer (TNBC) is a highly heterogeneous disease defined by the absence of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER-2), resulting in poor clinical outcomes and high mortality. The present study was aimed to evaluate the efficacy of Punicalagin (PCG), a polyphenol obtained from the Punica granatum, against TNBC. We evaluated the therapeutic potential of PCG in TNBC (MDA-MB-231, BT-20) and ER + (MCF-7) breast cancer cells. A dose-dependent inhibition of MDA-MB-231 cell proliferation was observed with PCG (12.5-100 μM). However, only 50 and 100 μM doses of PCG inhibited the growth of BT-20 and MCF-7 cells. PCG significantly increased mitochondrial ROS in TNBC cells and induced autophagy across all cell lines, as evidenced by an increase in autophagic vacuoles and a decrease in the ratio of LC3-II/LC3-I. PCG suppressed PI3K/Akt and activated phosphorylated c-Jun N-terminal kinase (p-JNK) signaling. Based on these findings, it can be concluded that PCG is capable of significantly inhibiting the proliferation of TNBC cells through the suppression of the PI3K/Akt pathway as well as the initiation of the JNK pathway. PCG could thus be potentially useful as a therapeutic agent for the treatment of TNBC.

Graphical abstract

Therapeutic potential of dietary bioactive compounds against anti-apoptotic Bcl-2 proteins in breast cancer

Breast cancer remains a leading cause of cancer-related mortality among women worldwide. One of its defining features is resistance to apoptosis, driven by aberrant expression of apoptosis-related proteins, notably the overexpression of anti-apoptotic Bcl-2 proteins. These proteins enable breast cancer cells to evade apoptosis and develop resistance to chemotherapy, underscoring their critical role as therapeutic targets. Diet plays a significant role in breast cancer risk, potentially escalating or inhibiting cancer development. Recognizing the limitations of current treatments, extensive research is focused on exploring bioactive compounds derived from natural sources such as plants, fruits, vegetables, and spices. These compounds are valued for their ability to exert potent anticancer effects with minimal toxicity and side effects. While literature extensively covers the effects of various dietary compounds in inducing apoptosis in cancer cells, comprehensive information specifically on how dietary bioactive compounds modulate anti-apoptotic Bcl-2 protein expression in breast cancer is limited. This review aims to provide a comprehensive understanding of the interaction between Bcl-2 proteins and caspases in the regulation of apoptosis, as well as the impact of dietary bioactive compounds on the modulation of anti-apoptotic Bcl-2 in breast cancer. It further explores how these interactions influence breast cancer progression and treatment outcomes.

Pomegranate (Punica granatum L.) phytochemicals target the components of metabolic syndrome

Pomegranate (Punica granatum L.) is a multipurpose dietary and medicinal plant known for its ability to promote various health benefits. Metabolic syndrome (MetS) is a complex metabolic disorder driving health and socioeconomic challenges worldwide. It may be characterized by insulin resistance, abdominal obesity, hypertension, and dyslipidemia. This study aims to conduct a review of pomegranate's effects on MetS parameters using a mechanistic approach relying on pre-clinical studies. The peel, juice, roots, bark, seeds, flowers, and leaves of the fruit present several bioactive compounds that are related mainly to anti-inflammatory and antioxidant activities as well as cardioprotective, antidiabetic, and antiobesity effects. The use of the juice extract can work as a potent inhibitor of angiotensin-converting enzyme activities, consequently regulating blood pressure. The major bioactive compounds found within the fruit are phenolic compounds (hydrolysable tannins and flavonoids) and fatty acids. Alkaloids, punicalagin, ellagitannins, ellagic acid, anthocyanins, tannins, flavonoids, luteolin, and punicic acid are also present. The antihyperglycemia, antihyperlipidemia, and weight loss promoting effects are likely related to the anti-inflammatory and antioxidant effects. When considering clinical application, pomegranate extracts are found to be frequently well-tolerated, further supporting its efficacy as a treatment modality. We suggest that pomegranate fruit, extract, or processed products can be used to counteract MetS-related risk factors. This review represents an important step towards exploring potential avenues for further research in this area.

Progress in the study of autophagy-related proteins affecting resistance to chemotherapeutic drugs in leukemia

Leukemia is a life-threatening malignant tumor of the hematopoietic system. Currently, the main treatment modalities are chemotherapy and hematopoietic stem cell transplantation. However, increased drug resistance due to decreased sensitivity of leukemia cells to chemotherapeutic drugs presents a major challenge in current treatments. Autophagy-associated proteins involved in autophagy initiation have now been shown to be involved in the development of various types of leukemia cells and are associated with drug resistance. Therefore, this review will explore the roles of autophagy-related proteins involved in four key autophagic processes: induction of autophagy and phagophore formation, phagophore extension, and autophagosome formation, on the development of various types of leukemias as well as drug resistance. Autophagy may become a promising therapeutic target for treating leukemia.

Unveiling autophagy complexity in leukemia: The molecular landscape and possible interactions with apoptosis and ferroptosis

Autophagy is a self-digestion multistep process in which causes the homeostasis through degradation of macromolecules and damaged organelles. The autophagy-mediated tumor progression regulation has been a critical point in recent years, revealing the function of this process in reduction or acceleration of carcinogenesis. Leukemia is a haematological malignancy in which abnormal expansion of hematopoietic cells occurs. The current and conventional therapies from chemotherapy to cell transplantation have failed to appropriately treat the leukemia patients. Among the mechanisms dysregulated in leukemia, autophagy is a prominent one in which can regulate the hallmarks of this tumor. The protective autophagy inhibits apoptosis and ferroptosis in leukemia, while toxic autophagy accelerates cell death. The proliferation and invasion of tumor cells are tightly regulated by the autophagy. The direction of regulation depends on the function of autophagy that is protective or lethal. The protective autophagy accelerates chemoresistance and radio-resistsance. The non-coding RNAs, histone transferases and other pathways such as PI3K/Akt/mTOR are among the regulators of autophagy in leukemia progression. The pharmacological intervention for the inhibition or induction of autophagy by the compounds including sesamine, tanshinone IIA and other synthetic compounds can chance progression of leukemia.

In vitro studies for antiparasitic activities of Punica granatum extract

Because of the drug resistance, medicinal plants are used more frequently than coccidiostats to treat and control coccidiosis. Punica granatum is a powerful antioxidant with a variety of medicinal uses. This study used an in vitro experiment to investigate how different P. granatum from Yemen (Y) and Egypt (E) sources affected oocyst sporulation and served as an anthelminthic effector. In contrast to PGE and mebendazole, PGY (200 mg/mL) has the shortest time to paralyze and death the earthworm Eisenia fetida in this investigation. In addition, the treated worm groups' cuticle thickness and shrinkage in comparison to the control group were assessed and contrasted. Eimeria papillata is used as a model protozoan parasite in anticoccidial assays. This study shows that P. granatum affects oocysts sporulation in a dose-dependent manner, with maximal percentages of 100% (PGY) and 48.60% (PGE) at 96 h for P. granatum concentrations of 200 mg/mL. Inhibition (%) was compared to various detergents, as well as positive and negative controls. According to our research, the P. granatum extract had powerful anthelmintic and anticoccidial properties, with the potency changing according to the environmental conditions of each fruit source. RESEARCH HIGHLIGHTS: Habitat of the plant is useful for production and accumulation of some secondary metabolites in plants which be effective for the therapeutic uses. Different parameters in the environmental ecosystem affecting variation in chemical compositions and biological activity of P. granatum.

Punicalagin is cytotoxic to human colon cancer cells by modulating cell proliferation, apoptosis, and invasion

Purpose: The purpose of this study was to explore the anticancer effect of punicalagin, an abundant bioactive tannin compound isolated from Punica granatum L., on three colon cancer cell lines, namely, HCT 116, HT-29, and LoVo.Research Design: Normal and colon cancer cells were treated with different concentrations of punicalagin for different periods. Data Collection and Analysis: Cell viability was measured with a CCK-8 assay. Programmed cell death and invasion were analyzed using an annexin V and cell death kit and a cell invasion analysis kit. The expression of active caspase-3, MMP-2, MMP-9, Snail, and Slug were measured by Western blot.Results: The results of the cell viability analysis showed that punicalagin was cytotoxic to colon cancer cells, but it was not to normal cells in a dose- and time-dependent manner. Additionally, punicalagin induced apoptosis in colon cancer cells (shown by the cumulative percentage of colorectal cancer cells in early and late apoptosis). It was found that caspase-3 activity increased following punicalagin treatment. Western blot results also showed that punicalagin increased the expression of activated caspase-3. In contrast, punicalagin inhibited the invasion of colon cancer cells. Further, treatment of colon cancer cells with punicalagin suppressed the expression of MMP-2, MMP-9, Snail, and Slug. Conclusions: These results showed that the activation of caspase-3 and the inhibition of MMP-2, MMP-9, Snail and Slug were involved in the effects of punicalagin on colon cancer cells.

Anti-leukemic effect of menthol, a peppermint compound, on induction of apoptosis and autophagy

Background

Menthol, a natural compound in peppermint leaves, has several biological activities, including antioxidant, anti-inflammatory, antiviral, antibacterial and anticancer properties. This study revealed the anti-leukemic effects and its underlying mechanisms of the menthol related apoptosis signaling pathway and autophagy in both NB4 and Molt-4 leukemic cell lines.

Methods

Both leukemic cells were treated with menthol in various concentration. Cell viability was assessed using MTT assay, whereas apoptosis and autophagy were analyzed by flow cytometry using Annexin V-FITC/PI and anti-LC3/FITC antibodies staining, respectively. Apoptotic and autophagic related gene and protein expression were detected using RT-qPCR and western blot analysis, respectively. Moreover, STITCH database was used to predicts the interaction between menthol and proposed proteins.

Results

Menthol significantly decreased cell viability in NB4 and Molt-4 cell lines in dose dependent manner. In combination of menthol and daunorubicin, synergistic cytotoxic effects were observed in leukemic cells. However, there was a minimal effect found on normal, peripheral blood mononuclear cells (PBMCs). Moreover, menthol significantly induced apoptosis induction via upregulation of caspase-3, BAX, p53 and downregulation of MDM2 mRNA expression. Autophagy was also induced by menthol through upregulating ATG3 and downregulating mTOR mRNA expression. For protein expression, menthol significantly increased caspase-3 whereas decreased mTOR in both leukemic cells. Conclusions. These results suggest that menthol exhibits cytotoxic activities by inhibition of cell proliferation, induction of apoptosis and autophagy through activating the caspase cascade, altering BAX and p53/MDM2, and regulating autophagy via the ATG3/mTOR signaling pathway.

Punica granatum as Anticandidal and Anti-HIV Agent: An HIV Oral Cavity Potential Drug

The oral cavity is crucial from diagnosis to adherence to HAART therapy in the HIV/AIDS population; consequently, drugs that can maintain healthy conditions in the oral cavity are necessary for patients with HIV/AIDS. Punica granatum (pomegranate) is a tree that has been employed extensively for centuries in the traditional medicine of ancient cultures for the treatment of a wide range of diseases, including oral and dental diseases. In recent decades, its potent anticandidal properties have been shown, especially on Candida albicans, the cause of the most common clinical manifestation in HIV patients. The present work contributes to the review of the anti-HIV and anticandidal properties of the plant species P. granatum as involved with the oral cavity. The literature reviewed revealed that crude extracts of pomegranate and its main isolated compounds possess inhibitory activity on different HIV targets, including binding viral proteins and the three replicative HIV enzymes. In addition, in the literature reviewed, pomegranate exhibited anticandidal effects on 10 different species. Thus, pomegranate appears to be an excellent candidate to explore and incorporate into the treatment of the oral cavity of HIV/AIDS patients, in that, in addition to its pharmacological effects such as antiviral and anticandidal, pomegranate represents an easily available, inexpensive, and safe natural source.

Unravelling the In Vitro and In Vivo Anti-Helicobacter pylori Effect of Delphinidin-3-O-Glucoside Rich Extract from Pomegranate Exocarp: Enhancing Autophagy and Downregulating TNF-α and COX2

Fruits containing antioxidants, e.g., anthocyanins, exhibit antimicrobial activities. The emergence of drug resistance represents a major challenge in eradicating H. pylori. The current study aims to explore the effect of pomegranate exocarp anthocyanin methanol extract (PEAME) against H. pylori isolates recovered from antral gastric biopsies. The UPLC-PDA-MS/MS and 1H NMR analyses indicated delphinidin-3-O-glucoside as the major anthocyanin in the extract. The PEAME showed activity against all tested resistant isolates in vitro recording minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 128 and 256 µg/mL, respectively. In vivo investigation included evaluation of the rat gastric mucosa for malondialdehyde (MDA), catalase activity, COX2, TNF-α, and key autophagy gene expression. The combination of pomegranate with metronidazole markedly reduced the viable count of H. pylori and the level of COX2, with alleviation of H. pylori-induced inflammation and oxidative stress (reduction of MDA, p-value < 0.001; and increase in catalase activity, p-value < 0.001). Autophagy gene expression was significantly upregulated upon treatment, whereas TNF-α was downregulated. In conclusion, we comprehensively assessed the effect of PEAME against H. pylori isolates, suggesting its potential in combination with metronidazole for eradication of this pathogen. The beneficial effect of PEAME may be attributed to its ability to enhance autophagy.

Punicalagin protects against the development of pancreatic injury and insulitis in rats with induced T1DM by reducing inflammation and oxidative stress

Pancreatic inflammation and oxidative damage remain major concerns in type 1 diabetes mellitus (T1DM). Punicalagin, a major polyphenol in pomegranates, exhibited antioxidant and protective effects on several organs in case of T1DM; however, no study has yet explored the protective effects of punicalagin on the pancreas and islets of Langerhans. T1DM was induced by injecting 40 mg/kg streptozotocin (STZ) intraperitoneally. Punicalagin (1 mg/kg ip) was injected daily for 15 days after T1DM induction. In diabetic rats, punicalagin treatment lowered the levels of inflammatory biomarkers (monocyte chemoattractant protein-1 and C-reactive protein) and adhesion molecules (E-selectin, intercellular adhesion molecule, and vascular cell adhesion molecule) while activating myeloperoxidase activity. Treatment of diabetic rats with punicalagin improved glutathione content and superoxide dismutase, catalase, and glutathione peroxidase activities; upregulated serum paraoxonase-1 activity; and prevented the elevation lipid peroxidation and protein oxidation products in the pancreas. Furthermore, punicalagin protected the pancreas against STZ-induced histopathological alterations and increased immune-reactive β-cells while reducing leucocyte infiltration into the islets of Langerhans, leading to normalized blood glucose and insulin levels. These findings indicated that punicalagin might protect against the development of insulitis in T1DM. In conclusion, punicalagin exerts a strong protective effect on the pancreas against oxidative injury and inflammation in STZ-induced experimental T1DM. The present results recommend punicalagin as a potential adjuvant for reducing diabetes-associated insulitis.

Immunomodulatory Properties of Pomegranate Peel Extract in a Model of Human Peripheral Blood Mononuclear Cell Culture

Pomegranate peel extract (PoPEx) has been shown to have antioxidant and anti-inflammatory properties, but its effect on the adaptive immune system has not been sufficiently investigated. In this study, the treatment of human peripheral blood mononuclear cells (PBMC) with PoPEx (range 6.25–400 µg/mL) resulted in cytotoxicity at concentrations of 100 µg/mL and higher, due to the induction of apoptosis and oxidative stress, whereas autophagy was reduced. At non-cytotoxic concentrations, the opposite effect on these processes was observed simultaneously with the inhibition of PHA-induced PBMC proliferation and a significant decrease in the expression of CD4. PoPEx differently modulated the expression of activation markers (CD69, CD25, ICOS) and PD1 (inhibitory marker), depending on the dose and T-cell subsets. PoPEx (starting from 12.5 µg/mL) suppressed the production of Th1 (IFN-γ), Th17 (IL-17A, IL-17F, and IL-22), Th9 (IL-9), and proinflammatory cytokines (TNF-α and IL-6) in culture supernatants. Lower concentrations upregulated Th2 (IL-5 and IL-13) and Treg (IL-10) responses as well as CD4+CD25hiFoxp3+ cell frequency. Higher concentrations of PoPEx increased the frequency of IL-10- and TGF-β-producing T-cells (much higher in the CD4+ subset). In conclusion, our study suggested for the first time complex immunoregulatory effects of PoPEx on T cells, which could assist in the suppression of chronic inflammatory and autoimmune diseases.

Punicalagin suppresses inflammation in ventilator-induced lung injury through protease-activated receptor-2 inhibition-induced inhibition of NLR family pyrin domain containing-3 inflammasome activation

Punicalagin is recorded to be a potent anti-inflammatory drug, while its effect on inflammation existing in ventilator-induced lung injury (VILI) requires further verification. Rats were pretreated with punicalagin, followed by VILI modeling. Lung histopathological examination was performed with hematoxylin-eosin staining accompanied by the lung injury score. The lung wet/dry (W/D) weight ratio and total bronchoalveolar lavage fluid (BALF) protein level were measured. After transfection with protease-activated receptor-2 (PAR2) overexpression plasmids, mouse alveolar epithelial MLE-12 cells were treated with punicalagin and then subjected to cyclic stretching. Punicalagin's cytotoxicity to MLE-12 cells were measured by MTT assay. The levels of inflammatory cytokines (tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6), PAR2, NLR family pyrin domain containing-3 (NLRP3), and apoptosis-associated speck-like protein containing a CARD (ASC) in the BALF, lung tissues or cells were analyzed by enzyme-linked immune-sorbent assay (ELISA), qRT-PCR or/and western blot. Punicalagin treatment attenuated VILI-induced lung histopathological changes and counteracted VILI-induced increases in the lung injury score, W/D weight ratio and total protein level in BALF. Also, punicalagin treatment counteracted in vivo VILI/cyclic stretching-induced increases in the levels of PAR2, inflammatory cytokines, NLRP3, and ASC. PAR2 overexpression potentiated the cyclic stretching-induced effects, while punicalagin treatment revoked this PAR2 overexpression-induced potentiation effect. In turn, PAR2 overexpression partly resisted the punicalagin treatment-induced counteractive effects on the cyclic stretching-induced effects. Punicalagin suppresses inflammation in VILI through PAR2 inhibition-induced inhibition of NLRP3 inflammasome activation.