Catalpol induces apoptosis in breast cancer in vitro and in vivo: Involvement of mitochondria apoptosis pathway and post-translational modifications

Breast cancer is a fatal cancer with the highest mortality in female. New strategies for anti-breast cancer are still urgently needed. Catalpol, an iridoid glycoside extracted from the traditional Chinese medicinal plant Rehmannia glutinosa, has shown anticancer efficacy in various cancer cells. However, its effect on breast cancer remains unclear. In this study, we aim to investigate the anti-breast cancer activity of catalpol and elucidate its underlying mechanism. Cell counting kit-8 (CCK-8) and morphology change showed that catalpol could inhibit the proliferation and viability of MCF-7 cells. Catalpol administration reduced the tumor volume in xenograft model. Catalpol induced apoptosis in MCF-7 cells confirmed by Hoechst 33342 staining and Annexin V-FITC/PI double staining. In vivo, catalpol also induced apoptosis as seen from the increased level of terminal-deoxynucleoitidyl transferase mediated nick end labeling (TUNEL) in tumor. According to JC-1 and Dichlorodi-hydrofluorescein Diacetate (DCFH-DA) staining, loss of mitochondrial membrane potential (MMP) and reactive oxygen species (ROS) generation was found in MCF-7 cells treated with catalpol. Furthermore, catalpol also increased the level of cytoplasmic cytochrome c and activity of caspase-3 in MCF-7 cells. Likewise, histopathological and immunohistochemical (IHC) assay also found that catalpol enhanced the levels of cytochrome c and caspase-3 in breast cancer tissues. Ultimately, acetylation, 2-hydroxyisobutyrylation and lactylation were dramatically increased, whereas succinylation, malonylation and phosphorylation were markedly decreased in the breast cancer tumor treated with catalpol. Taken together, catalpol inhibited breast cancer in vitro and in vivo through induction of apoptosis via mitochondria apoptosis pathway and regulation of protein post-translational modifications (PTMs). Thus, it can be considered as an excellent candidate compound for treatment of breast cancer.

l-Arginine prevents 4-hydroxy-2-nonenal accumulation and depresses inflammation via inhibiting NF-κB activation

4-Hydroxy-2-nonenal (HNE) is an inducer of inflammation. The aim of this study was to elicit the link between the inhibition of HNE accumulation and the depression of inflammation whether dependent onl-arginine availability in growing rats. Male Wistar rats were fed with different levels of l-arginine at 250, 500, and 1000 mg/kg body weight for 14 days. The control group was fed with commercial pellets. After 14 days of oral administration, l-arginine significantly reduced hepatic accumulation of HNE and depressed inflammation in rats as compared with the control group. Compared to the control group, the anti-inflammatory action of l-arginine is reflected by upregulation of hepatic interleukin-10 (IL-10) and the suppression of hepatic cyclooxygenase-2, tumor necrotic factor α, IL-1β, and IL-6 expressions in growing rats. With l-arginine administration, the activation of nuclear factor-κB (NF-κB) was efficaciously inhibited through the upregulation of inhibitory κBα, and the depression of phosphoinositide 3-kinase/protein kinase B (PI3K/Akt). In conclusion, this study demonstrated that l-arginine could reduce hepatic HNE levels and depress inflammation in growing rats, revealing a link between the inhibition of HNE accumulation with the depression of inflammation, which was attributed to the availability of l-arginine. A significant finding of this study was that the anti-inflammatory mechanism exerted by l-arginine was to inhibit NF-κB activation via downregulating PI3K/Akt.

Hesperetin ameliorates lipopolysaccharide-induced acute lung injury in mice through regulating the TLR4-MyD88-NF-κB signaling pathway

Hesperetin, a major bioflavonoid in sweet oranges and lemons, exerts an anti-inflammatory effect in pulmonary diseases; however, its effect on lipopolysaccharide (LPS)-induced acute lung injury is unclear. This study investigated the effect of hesperetin on LPS-induced lung inflammatory response. Mice were intratracheally instilled with 5 mg/kg body weight LPS, and then were given hesperetin orally (10, 20, and 30 mg/kg body weight) 1 h later. Hesperetin dramatically suppressed the levels of interleukin-6 and tumor necrosis factor-α, as well as the number of inflammatory cells in bronchoalveolar lavage fluid. Besides, it reduced lung injury, wet weight/dry weight ratio, and myeloperoxidase and lactate dehydrogenase activities, and enhanced superoxide dismutase activity. In addition, hesperetin significantly downregulated the Toll-like receptor 4 (TLR4) and myeloid differentiation factor 88 (MyD88) protein expression and suppressed nuclear factor-kappa B (NF-κB) activation in lung tissue. Together, these results indicated that the anti-inflammatory effect of hesperetin is associated with the TLR4-MyD88-NF-κB pathway, and that hesperetin shows therapeutic potential for LPS-induced acute lung injury.

Bioactivities of Natural Catalpol Derivatives

Catalpol, a famous molecule of iridoids, possesses extensive pharmacological activities. Our studies found that compounds with low-polarity substituents at the 6-O position of catalpol exhibited higher NF-κB inhibitory potency than catalpol. However, catalpol derivatives are not much focused. Here this review provides extensive coverage of naturally occurring catalpol derivatives discovered from 1888 until 2018. It covers their distribution, chemotaxonomic significance, chemical structures, and bioactivities from more than 200 peer-reviewed articles, and highlights the structure-activity relationship of catalpol derivatives.