Physalin A Induces Apoptosis and Autophagy in Hepatocellular Carcinoma via Inhibition of PI3K/Akt Signaling Pathway

Physalin A (PA) is a bioactive withanolide with multiple pharmacological properties and has been indicated to be cytotoxic to hepatocellular carcinoma (HCC) cell line HepG2. This study aims to explore the mechanisms underlying PA antitumor activity in HCC. HepG2 cells were exposed to various concentrations of PA. Cell counting kit-8 assay and flow cytometry were implemented for evaluating cell viability and apoptosis, respectively. Immunofluorescence staining was utilized for detecting autophagic protein LC3. Western blotting was employed for measuring levels of autophagy-, apoptosis- and phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt) signaling-related proteins. A xenograft mouse model was established to verify the antitumor activity of PA in vivo. PA impaired HepG2 cell viability, and triggered apoptosis as well as autophagy. Inhibiting autophagy augmented PA-evoked HepG2 cell apoptosis. PA repressed PI3K/Akt signaling in HCC cells and activating PI3K/Akt reversed PA-triggered apoptosis and autophagy. PA treatment inhibited tumor growth in tumor-bearing mice. PA triggers HCC cell apoptosis and autophagy by inactivating PI3K/Akt signaling.

Physalin A alleviates intervertebral disc degeneration via anti-inflammatory and anti-fibrotic effects

Background

The incidence of intervertebral disc degeneration (IVDD) is a common degenerative disease with inflammation, decreased autophagy, and progression of fibrosis as its possible pathogenesis. Physalin A (PA) is a widely studied anti-inflammatory drug. However, its therapeutic effects on IVDD remain unexplored. Therefore, we aimed to explore the therapeutic potential of PA in IVDD progression.

Materials and methods

In vivo, we investigated PA bioactivity using a puncture-induced IVDD rat model. IVDD signals and height changes were detected using X-ray, micro-CT, and MRI, and structural and molecular lesions using histological staining and immunohistochemistry of intervertebral disc sections. In vivo, interleukin-1 beta (IL-1β) and TGF-β1 were employed to establish inflammation fibrotic nucleus pulposus (NP) cells. The PA effect duration, concentration, influence pathways, and pathological changes in IVDD treatment were elucidated using western blotting, real-time PCR, and immunofluorescence.

Results

PA exerted significant effects on IVDD remission due to anti-inflammation, fibrosis reduction, and autophagy enhancement. In vitro, PA improved inflammation by blocking the NF-κB and MAPK pathways, whereas it promoted autophagy via the PI3K/AKT/mTOR pathway and affected fibrotic progression by regulating the SMAD2/3 pathway. Moreover, PA improved the disc degeneration process in IVDD model.

Conclusions

PA exhibited significant anti-inflammatory and anti-fibrotic effects and improved autophagy in vivo and in vitro IVDD models, thus effectively relieving IVDD progression, indicating it is a promising agent for IVDD treatment.

The translational potential of this article

This study successfully reveals that PA, a natural bioactive withanolide, effectively relieved IVDD progression via inflammation inhibition, fibrosis reduction, and autophagy enhancement, indicating it is a promising agent for IVDD treatment.

Anti-inflammatory action of physalin A by blocking the activation of NF-κB signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Physalis Calyx seu Fructus is typically used to treat inflammatory diseases such as upper respiratory tract infection and acute tonsillitis in clinical practice of China. Physalin A, a main active ingredient of this traditional Chinese medicine (TCM), has been reported for its significant anti-tumor activity. However, most reports focused on the studies of its anti-tumor activity, the anti-inflammatory activity of physalin A and its molecular mechanism are still not elucidated clearly.

AIM OF THE STUDY

The aim of the study was to investigate the anti-inflammatory activities both in vitro and in vivo and molecular mechanism of physalin A.

MATERIALS AND METHODS

The potential anti-inflammatory properties of physalin A were evaluated in vitro by lipopolysaccharide (LPS)-induced RAW 264.7 macrophage cells, and in vivo via two typical acute inflammation murine models. Some important inflammation-related molecules were analyzed by enzyme-linked immuno sorbent assay (ELISA) and Western blotting.

RESULTS

The results showed that physalin A inhibited carrageenan-induced paw edema of rats and capillary permeability of mice induced by acetic acid in vivo. Furthermore, physalin A also significantly reduced the release of inflammatory mediators nitric oxide (NO), prostaglandin E2 (PGE2), and tumor necrosis factor-α (TNF-α) induced by lipopolysaccharide (LPS) in RAW 264.7 in vitro. Further investigations indicated that physalin A can down-regulate the high expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in a dose-dependent manner. Physalin A remarkably blocked the degradation of inhibitor of nuclear factor kappa B alpha (IκB-α) and the nuclear translocation of nuclear factor-κB (NF-κB) p65 induced by LPS in RAW 264.7 cells. However, physalin A did not significantly inhibit the phosphorylation of mitogen-activated protein kinases (MAPKs) family proteins c-Jun N-terminal kinase (JNK) or extracellular signal-regulated kinase (ERK) or p38.

CONCLUSIONS

All the results clearly illustrated that the anti-inflammatory action of physalin A is due to the inactivation of NF-κB signal pathway, but is irrelevant to the MAPKs pathway.

Physalin A regulates the Nrf2 pathway through ERK and p38 for induction of detoxifying enzymes

Background

Physalin A isolated from Physalis alkekengi var. franchetii has been known to have many pharmacological properties. However, its effect through the Nrf2 pathway has not yet been elucidated. In the present study, we determined the effects of physalin A on cancer chemoprevention via the Nrf2 pathway.

Methods

Experiments were performed in Hepa-1c1c7 and HepG2 cells. The quinone reductase (QR) activity assay was used to assess the activity of physalin A and other compounds isolated from P. alkekengi. The antioxidant response element (ARE) reporter assay was used to determine physalin A induced transcription of Nrf2 target genes, whereas the oligonucleotide pull-down assay was used to investigate Nrf2 binding to the AREs post physalin A treatment. Real-time PCR and western blotting were performed to determine the expression of Nrf2 target genes. Immunocytochemistry was used to determine Nrf2 localization after treatment with physalin A. Kinase inhibitors were used to test the involvement of Nrf2-targeting kinases and the role of ERK and p38 phosphorylation was confirmed using western blotting.

Results

Physalin A significantly induced QR activity. As an upstream effector of QR, Nrf2 induced genes containing the ARE, which encode various antioxidants and detoxification enzymes. We observed that physalin A increased the expression of Nrf2 and its target genes in HepG2 cells. Moreover, we observed that physalin A-induced Nrf2 activation was regulated by ERK and p38 kinase in HepG2 cells.

Conclusions

Taken together, we showed that physalin A increased detoxifying enzyme expression via activation of Nrf2 and its target genes. These results imply that physalin A could be a potential chemopreventive agent for liver diseases, as well as cancer.

Two sulfonate metabolites of physalin A in rats

1. Physalin A is a bioactive withanolide isolated from the natural plant Physalis alkekengi var. franchetii (Solanaceae), a common traditional Chinese herbal medicine. This study aims to investigate the metabolites of physalin A in vivo. 2. Two metabolites (M1 and M2) were characterized as sulfonate metabolites in the feces obtained from rats treated with physalin A orally at a dose of 15 mg/kg/day for 3 days, by application of a UPLC-Q/TOF-MS method. Furthermore, formation of the two sulfonate metabolites was verified by chemical synthesis and NMR, including ¹H NMR, ¹³C NMR and two-dimensional NMR. The structures of M1 and M2 were identified to be 3α-sulfo-2,25β,27-trihydrophysalin A and 3α,27-disulfo-2,25α-dihydrophysalin A, respectively. 3. In summary, this study indicated that physalin A could be biotransformed to sulfonate metabolites with strong polarity, which contributed to the elimination of physalin A. A rare metabolic pathway has been revealed in this study.

Physalin A induces G2/M phase cell cycle arrest in human non-small cell lung cancer cells: involvement of the p38 MAPK/ROS pathway

Physalin A (PA) is an active withanolide isolated from Physalis alkekengi var. franchetii, a traditional Chinese herbal medicine named Jindenglong, which has long been used for the treatment of sore throat, hepatitis, and tumors in China. In the present study, we firstly investigated the effects of PA on proliferation and cell cycle distribution of the human non-small cell lung cancer (NSCLC) A549 cell line, and the potential mechanisms involved. Here, PA inhibited cell growth in dose- and time-dependent manners. Treatment of A549 cells with 28.4 μM PA for 24 h resulted in approximately 50 % cell death. PA increased the amount of intracellular ROS and the proportion of cells in G2/M. G2/M arrest was attenuated by the addition of ROS scavenger NAC. ERK and P38 were triggered by PA through phosphorylation in a time-dependent manner. The phosphorylation of ERK and P38 were not attenuated by the addition of NAC, but the use of the p38 inhibitor could reduce, at least in part, PA-induced ROS and the proportion of cells in G2/M. PA induces G2/M cell cycle arrest in A549 cells involving in the p38 MAPK/ROS pathway. This study suggests that PA might be a promising therapeutic agent against NSCLC.