Therapeutic Effects of an Inhibitor of Thioredoxin Reductase on Liver Fibrosis by Inhibiting the Transforming Growth Factor-β1/Smads Pathway

TrxR/Trx inhibitor butaselen ameliorates pulmonary fibrosis by suppressing NF-κB/TGF-β1/Smads signaling

Pulmonary fibrosis is highly lethal with limited treatments. Butaselen (BS) is an inhibitor of thioredoxin reductase (TrxR)/thioredoxin (Trx) with anti-tumor activity. However, its impact on pulmonary fibrosis and the involved mechanisms remain unclear. Here, we demonstrate that BS is a potential drug for the treatment of pulmonary fibrosis. Specifically, BS can inhibit pulmonary fibrosis both in vitro and in vivo, with comparable efficacy and enhanced safety when compared with pirfenidone. BS and dexamethasone display a synergistic effect in inhibiting pulmonary fibrosis both in vitro and in vivo. Mechanistic studies reveal that BS can inhibit the TrxR activity during pulmonary fibrosis. RNA-sequencing analysis identifies that genes of ECM-related signaling pathways are notably affected by BS. BS can not only inhibit the activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and reduce pulmonary fibrosis-related inflammation, but also reduce NF-κB-activated transcriptional expression of transforming growth factor-β1 (TGF-β1), which leads to the inactivation of Smad2/Smad3 and decrease of collagen formation and fibrosis. Moreover, the knockdown of Trx1 with siRNA can also inhibit NF-κB/TGF-β1/Smads signaling. In conclusion, the TrxR/Trx inhibitor butaselen can suppress pulmonary fibrosis by inhibiting NF-κB/TGF-β1/Smads signaling.

Liver Fibrosis Resolution: From Molecular Mechanisms to Therapeutic Opportunities

The liver is a critical system for metabolism in human beings, which plays an essential role in an abundance of physiological processes and is vulnerable to endogenous or exogenous injuries. After the damage to the liver, a type of aberrant wound healing response known as liver fibrosis may happen, which can result in an excessive accumulation of extracellular matrix (ECM) and then cause cirrhosis or hepatocellular carcinoma (HCC), seriously endangering human health and causing a great economic burden. However, few effective anti-fibrotic medications are clinically available to treat liver fibrosis. The most efficient approach to liver fibrosis prevention and treatment currently is to eliminate its causes, but this approach's efficiency is too slow, or some causes cannot be fully eliminated, which causes liver fibrosis to worsen. In cases of advanced fibrosis, the only available treatment is liver transplantation. Therefore, new treatments or therapeutic agents need to be explored to stop the further development of early liver fibrosis or to reverse the fibrosis process to achieve liver fibrosis resolution. Understanding the mechanisms that lead to the development of liver fibrosis is necessary to find new therapeutic targets and drugs. The complex process of liver fibrosis is regulated by a variety of cells and cytokines, among which hepatic stellate cells (HSCs) are the essential cells, and their continued activation will lead to further progression of liver fibrosis. It has been found that inhibiting HSC activation, or inducing apoptosis, and inactivating activated hepatic stellate cells (aHSCs) can reverse fibrosis and thus achieve liver fibrosis regression. Hence, this review will concentrate on how HSCs become activated during liver fibrosis, including intercellular interactions and related signaling pathways, as well as targeting HSCs or liver fibrosis signaling pathways to achieve the resolution of liver fibrosis. Finally, new therapeutic compounds targeting liver fibrosis are summarized to provide more options for the therapy of liver fibrosis.

Calotropis gigantea stem bark extracts inhibit liver cancer induced by diethylnitrosamine

Several fractions of Calotropis gigantea extracts have been proposed to have potential anticancer activity in many cancer models. The present study evaluated the anticancer activity of C. gigantea stem bark extracts in liver cancer HepG2 cells and diethylnitrosamine (DEN)-induced primary liver cancer in rats. The carcinogenesis model induced by DEN administration has been widely used to study pathophysiological features and responses in rats that are comparable to those seen in cancer patients. The dichloromethane (CGDCM), ethyl acetate, and water fractions obtained from partitioning crude ethanolic extract were quantitatively analyzed for several groups of secondary metabolites and calactin contents. A combination of C. gigantea stem bark extracts with doxorubicin (DOX) was assessed in this study to demonstrate the enhanced cytotoxic effect to cancer compared to the single administration. The combination of DOX and CGDCM, which had the most potential cytotoxic effect in HepG2 cells when compared to the other three fractions, significantly increased cytotoxicity through the apoptotic effect with increased caspase-3 expression. This combination treatment also reduced ATP levels, implying a correlation between ATP and apoptosis induction. In a rat model of DEN-induced liver cancer, treatment with DOX, C. gigantea at low (CGDCM-L) and high (CGDCM-H) doses, and DOX + CGDCM-H for 4 weeks decreased the progression of liver cancer by lowering the liver weight/body weight ratio and the occurrence of liver hyperplastic nodules, fibrosis, and proliferative cells. The therapeutic applications lowered TNF-α, IL-6, TGF-β, and α-SMA inflammatory cytokines in a similar way, implying that CGDCM had a curative effect against the inflammation-induced liver carcinogenesis produced by DEN exposure. Furthermore, CGDCM and DOX therapy decreased ATP and fatty acid synthesis in rat liver cancer, which was correlated with apoptosis inhibition. CGDCM reduced cleaved caspase-3 expression in liver cancer rats when used alone or in combination with DOX, implying that apoptosis-inducing hepatic carcinogenesis was suppressed. Our results also verified the low toxicity of CGDCM injection on the internal organs of rats. Thus, this research clearly demonstrated a promising, novel anticancer approach that could be applied in future clinical studies of CGDCM and combination therapy.

Aspirin attenuates liver fibrosis by suppressing TGF‑β1/Smad signaling

Aspirin reduces the liver fibrosis index and inflammation in patients and rats. However, the specific mechanism underlying the effects of aspirin are yet to be elucidated. The present study aimed to investigate the effects of aspirin on thioacetamide (TAA)-induced liver fibrosis in rats and hepatic stellate cells (HSCs) via the TGF-β1/Smad signaling pathway. Liver fibrosis was induced in Sprague Dawley rats by intraperitoneal injection of 200 mg/kg TAA twice weekly for 8 weeks. Aspirin (30 mg/kg) was administered to rats by gavage once every morning over a period of 8 weeks. Masson's trichrome and H&E staining were used to detect and analyze the pathological changes in liver tissues. Western blot analysis and immunohistochemistry were applied to determine the protein expression levels of α-smooth muscle actin (α-SMA), collagen I, TGF-β1, phosphorylated (p)-Smad2 and p-Smad3. In addition, reverse transcription-quantitative PCR was performed to detect the mRNA expression levels of α-SMA, collagen type I α 1 chain (COL1A1) and TGF-β1. The results demonstrated that treatment with aspirin significantly reduced the serum levels of alanine aminotransferase, aspartate aminotransferase and hydroxyproline in the TAA + aspirin compared with that in the TAA group. In the rat liver fibrosis model, pathological changes in liver tissues were improved following treatment with aspirin. Similarly, a marked decrease was observed in protein expression levels of α-SMA, collagen I, TGF-β1, p-Smad2 and p-Smad3. Furthermore, aspirin administration decreased the mRNA levels of α-SMA, COL1A1 and TGF-β1. In addition, HSCs were treated with different concentrations of aspirin (10, 20 and 40 mmol/l), and the protein expression levels of α-SMA, collagen I, TGF-β1, p-Smad2 and p-Smad3 were reduced in a dose-dependent manner. Overall, the present study showed that aspirin attenuated liver fibrosis and reduced collagen production by suppressing the TGF-β1/Smad signaling pathway, thus revealing a potential mechanism of aspirin in the treatment of liver fibrosis.