Luteolin inhibits herpes simplex virus 1 infection by activating cyclic guanosine monophosphate-adenosine monophosphate synthase-mediated antiviral innate immunity.

BACKGROUND: The successive outbreaks of large-scale infectious diseases due to virus infection have been a major threat to human health in recent decades. Herpes simplex virus I (HSV-1) is a widely-disseminated DNA virus that infects the central nervous system to cause herpes labialis, keratitis and herpes simplex virus encephalitis (HSE), resulting in recurrent lifelong clinical or subclinical episodes. Luteolin is a plant flavone that has been extensively used in the treatment of various human diseases, including carcinogenesis, inflammation and chronic degenerative diseases. PURPOSE: The aim of this study was to investigate the antiviral molecular mechanism of luteolin against HSV-1 infection in vitro and in vivo. METHODS: The antiviral effect of luteolin in cell lines was examined by viral plaque assay, RT-qPCR, Western blot and time-of-addition assay. The interaction between luteolin and cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) was evaluated by molecular modeling and semi-denaturing detergent agarose gel electrophoresis. The efficacy of luteolin on HSE was evaluated in the HSE mouse model by analyzing weight loss, neurodegenerative symptoms and histopathological scores. Cytokine expression and protein levels were examined by RT-qPCR, Western blot and ELISA. RESULTS: Luteolin inhibited the early process of HSV-1 infection, without affecting the infection of acyclovir-resistant HSV-1 strains. In addition, luteolin enhanced antiviral type I interferon production and activated the cytoplasmic DNA-sensing cGAS-stimulator of interferon gene (STING) pathway. Luteolin directly bound the active substrate binding site and promoted the oligomerization of cGAS. Luteolin also inhibited HSE-related weight loss, neurodegeneration and neuroinflammation in mice caused by HSV-1 infection. Furthermore, luteolin enhanced type I interferon expression and stimulated the cGAS-STING signaling pathway in vivo. CONCLUSION: Luteolin inhibited the post-entry process of HSV-1 by activating the cGAS-STING pathway to promote antiviral interferon production. These results provided the rationale for luteolin as a potent cGAS activator and antiviral agent.

In vitro cytotoxic potential of extracts from Aristolochia foetida Kunth against MCF-7 and bMECs cell lines.

The aim of this study was to evaluate the cytotoxic potential of Aristolochia foetida Kunth. Stems and leaves of A. foetida Kunth (Aristolochiaceae) have never been investigated pharmacologically. Recent studies of species of the Aristolochiaceae family found significant cytotoxic activities. Hexane, dichloromethane, ethyl acetate and methanol extracts were analyzed by 1H NMR and GC-MS to know the metabolites in each extract. In GC-MS analysis, the main compounds were methyl hexadecanoate (3); hexadecanoic acid (4); 2-butoxyethyl dodecanoate (9); ethyl hexadecanoate (20); methyl octadeca-9,12,15-trienoate (28) and (9Z,12Z,15Z)-octadeca-9,12,15-trienoic acid (40). The results showed a significant reduction in cell viability of the MCF-7 (breast cancer) cell line caused by organic extracts in a dose-dependent manner. The cytotoxicity activity of the dichloromethane extract from the stems (DSE) showed IC50 values of 45.9 µg/mL and the dichloromethane extract of the leaves (DLE) showed IC50 values of 47.3 µg/mL. DSE and DLE had the highest cytotoxic potential in an in vitro study against the MCF-7 cell line and non-tumor cells obtained from the bovine mammary epithelial (bMECs). DSE and DLE induced a loss in mitochondrial membrane potential (ΔΨm) and can cause cell death by apoptosis through the intrinsic pathway in the MCF-7 cell line. DSE and DLE are cytotoxic in cancer cells and cause late apoptosis. Higher concentrations of DSE and DLE are required to induce a cytotoxic effect in healthy mammary epithelial cells. This is the first report of the dichloromethane extract of A. foetida Kunth that induces late apoptosis in MCF-7 cancer cells and may be a candidate for pharmacological study against breast cancer.

Polyphenols and non-alcoholic fatty liver disease: impact and mechanisms.

Non-alcoholic fatty liver disease (NAFLD) is considered to be the hepatic component of the metabolic syndrome and its prevalence is rapidly increasing due to its strong association with insulin resistance and obesity. At present, given that NAFLD is highly prevalent and therapies are limited, much attention is focused on identifying effective dietary strategies for the prevention and treatment of the disease. Polyphenols are a group of plant bioactive compounds whose regular consumption have been associated with a reduction in the risk of a number of metabolic disorders associated with NAFLD. Here we review the emerging and relatively consistent evidence from cell culture and rodent studies showing that select polyphenols positively modulate a variety of contributors to the NAFLD phenotype, through diverse and complementary mechanisms of action. In particular, the reduction of de novo lipogenesis (via sterol regulatory element-binding protein 1c) and increased fatty acid ß-oxidation, presumably involving AMP-activated protein kinase activation, will be discussed. The indirect antioxidant and anti-inflammatory properties of polyphenols which have been reported to contribute to the amelioration of NAFLD will also be addressed. In addition to a direct study of the liver, rodent studies have provided insight into the impact of polyphenols on adipose tissue function and whole body insulin sensitivity, which are likely to in part modulate their impact on NAFLD development. Finally an overview of the limited data from clinical trials will be given along with a discussion of the dose extrapolation from animal studies to human subjects.

Novel polymorphisms in UTR and coding region of inducible heat shock protein 70.1 gene in tropically adapted Indian zebu cattle (Bos indicus) and riverine buffalo (Bubalus bubalis).

Due to evolutionary divergence, cattle (taurine, and indicine) and buffalo are speculated to have different responses to heat stress condition. Variation in candidate genes associated with a heat-shock response may provide an insight into the dissimilarity and suggest targets for intervention. The present work was undertaken to characterize one of the inducible heat shock protein genes promoter and coding regions in diverse breeds of Indian zebu cattle and buffaloes. The genomic DNA from a panel of 117 unrelated animals representing 14 diversified native cattle breeds and 6 buffalo breeds were utilized to determine the complete sequence and gene diversity of HSP70.1 gene. The coding region of HSP70.1 gene in Indian zebu cattle, Bos taurus and buffalo was similar in length (1,926 bp) encoding a HSP70 protein of 641 amino acids with a calculated molecular weight (Mw) of 70.26 kDa. However buffalo had a longer 5' and 3' untranslated region (UTR) of 204 and 293 nucleotides respectively, in comparison to Indian zebu cattle and Bos taurus wherein length of 5' and 3'-UTR was 172 and 286 nucleotides, respectively. The increased length of buffalo HSP70.1 gene compared to indicine and taurine gene was due to two insertions each in 5' and 3'-UTR. Comparative sequence analysis of cattle (taurine and indicine) and buffalo HSP70.1 gene revealed a total of 54 gene variations (50 SNPs and 4 INDELs) among the three species in the HSP70.1 gene. The minor allele frequencies of these nucleotide variations varied from 0.03 to 0.5 with an average of 0.26. Among the 14 B. indicus cattle breeds studied, a total of 19 polymorphic sites were identified: 4 in the 5'-UTR and 15 in the coding region (of these 2 were non-synonymous). Analysis among buffalo breeds revealed 15 SNPs throughout the gene: 6 at the 5' flanking region and 9 in the coding region. In bubaline 5'-UTR, 2 additional putative transcription factor binding sites (Elk-1 and C-Re1) were identified, other than three common sites (CP2, HSE and Pax-4) observed across all the analyzed animals. No polymorphism was found within the 3'-UTR of Indian cattle or buffalo as it was found to be monomorphic. The promoter sequences generated in 117 individuals showed a rich array of sequence elements known to be involved in transcription regulation. A total of 11 nucleotide changes were observed in the promoter sequence across the analyzed species, 3 of these changes were located within the potential transcription factor binding domains. We also identified 4 microsatellite markers within the buffalo HSP70.1 gene and 3 microsatellites within bovine HSP70.1. The present study identified several distinct changes across indicine, taurine and bubaline HSP70.1 genes that could further be evaluated as molecular markers for thermotolerance.