Loganin Prevents Hepatic Steatosis by Blocking NLRP3 Inflammasome Activation

Activation of the NLRP3 inflammasome is a necessary process to induce fibrosis in nonalcoholic fatty liver disease (NAFLD). Nonalcoholic steatohepatitis (NASH) is a kind of NAFLD that encompasses the spectrum of liver disease. It is characterized by inflammation and ballooning of hepatocytes during steatosis. We tested whether inhibiting the NLRP3 inflammasome could prevent the development and pathology of NASH. We identified loganin as an inhibitor of the NLRP3 inflammasome and investigated whether in vivo administration of loganin prevented NASH symptoms using a methionine-choline deficient (MCD) diet model in mice. We found that loganin inhibited the NLRP3 inflammasome activation triggered by ATP or nigericin, as shown by suppression of the production of interleukin (IL)-1β and caspase-1 (p10) in mouse primary macrophages. The speck formation of apoptosisassociated speck-like protein containing a caspase recruitment domain (ASC) was blocked by loganin, showing that the assembly of the NLRP3 inflammasome complex was impaired by loganin. Administration of loganin reduced the clinical signs of NASH in mice fed the MCD diet, including hepatic inflammation, fat accumulation, and fibrosis. In addition, loganin reduced the expression of NLRP3 inflammasome components in the liver. Our findings indicate that loganin alleviates the inflammatory symptoms associated with NASH, presumably by inhibiting NLRP3 inflammasome activation. In summary, these findings imply that loganin may be a novel nutritional and therapeutic treatment for NASH-related inflammation.

F-box Protein βTrCP1 Is a Substrate of Extracellular Signal-regulated Kinase 2

F-box proteins, consisting of 69 members which are organized into the three subclasses FBXW, FBXL, and FBXO, are the substrate specific recognition subunits of the SKP1-Cullin 1-F-box protein E3 ligase complex. Although βTrCP 1 and 2, members of the FBXW subfamily, are known to regulate some protein stability, molecular mechanisms by which these proteins can recognize proper substrates are unknown. In this study, it was found that βTrCP1 showed strong interaction with members of mitogen-activated protein kinases. Although extracellular signal-regulated kinase (ERK) 3, p38β, and p38δ showed weak interactions, ERK2 specifically interacted with βTrCP1 as assessed by immunoprecipitation. In interaction domain determination experiments, we found that ERK2 interacted with two independent ERK docking sites located in the F-box domain and linker domain, but not the WD40 domain, of βTrCP1. Notably, mutations of βTrCP1 at the ERK docking sites abolished the interaction with ERK2. βTrCP1 underwent phosphorylation by EGF stimulation, while the presence of the mitogen-activated protein kinase kinases inhibitor U0126, genetic silencing by sh-ERK2, and mutation of the ERK docking site of βTrCP1 inhibited phosphorylation. This inhibition of βTrCP1 phosphorylation resulted in a shortened half-life and low protein levels. These results suggest that ERK2-mediated βTrCP1 phosphorylation may induce the destabilization of βTrCP1.

F-box Protein βTrCP1 Is a Substrate of Extracellular Signal-regulated Kinase 2

F-box proteins, consisting of 69 members which are organized into the three subclasses FBXW, FBXL, and FBXO, are the substrate specific recognition subunits of the SKP1-Cullin 1-F-box protein E3 ligase complex. Although βTrCP 1 and 2, members of the FBXW subfamily, are known to regulate some protein stability, molecular mechanisms by which these proteins can recognize proper substrates are unknown. In this study, it was found that βTrCP1 showed strong interaction with members of mitogen-activated protein kinases. Although extracellular signal-regulated kinase (ERK) 3, p38β, and p38δ showed weak interactions, ERK2 specifically interacted with βTrCP1 as assessed by immunoprecipitation. In interaction domain determination experiments, we found that ERK2 interacted with two independent ERK docking sites located in the F-box domain and linker domain, but not the WD40 domain, of βTrCP1. Notably, mutations of βTrCP1 at the ERK docking sites abolished the interaction with ERK2. βTrCP1 underwent phosphorylation by EGF stimulation, while the presence of the mitogen-activated protein kinase kinases inhibitor U0126, genetic silencing by sh-ERK2, and mutation of the ERK docking site of βTrCP1 inhibited phosphorylation. This inhibition of βTrCP1 phosphorylation resulted in a shortened half-life and low protein levels. These results suggest that ERK2-mediated βTrCP1 phosphorylation may induce the destabilization of βTrCP1.

Repurposing Auranofin, an Anti-Rheumatic Gold Compound, to Treat Acne Vulgaris by Targeting the NLRP3 Inflammasome

Activation of the NLRP3 inflammasome is critical for host defense as well as the progression of inflammatory diseases through the production of the proinflammatory cytokine IL-1β, which is cleaved by active caspase-1. It has been reported that overactivation of the NLRP3 inflammasome contributes to the development and pathology of acne vulgaris. Therefore, inhibiting activation of the NLRP3 inflammasome may provide a new therapeutic strategy for acne vulgaris. In this study, we investigated whether auranofin, an anti-rheumatoid arthritis agent, inhibited NLRP3 inflammasome activation, thereby effectively treating acne vulgaris.Auranofin suppressed NLRP3 inflammasome activation induced by Propionibacterium acnes, reducing the production of IL-1β in primary mouse macrophages and human sebocytes. In a P. acnes-induced acne mouse model, injection of P. acnes into the ears of mice induced acne symptoms such as redness, swelling, and neutrophil infiltration. Topical application of auranofin (0.5 or 1%) to mouse ears significantly reduced the inflammatory symptoms of acne vulgaris induced by P. acnes injection. Topical application of auranofin led to the downregulation of the NLRP3 inflammasome activated by P. acnes in mouse ear skin. These results show that auranofin inhibits the NLRP3 inflammasome, the activation of which is associated with acne symptoms. The results further suggest that topical application of auranofin could be a new therapeutic strategy for treating acne vulgaris by targeting the NLRP3 inflammasome.

Mitochondria-targeting drug conjugates for cytotoxic, anti-oxidizing and sensing purposes: current strategies and future perspectives

Mitochondrial targeting is a promising approach for solving current issues in clinical application of chemotherapy and diagnosis of several disorders. Here, we discuss direct conjugation of mitochondrial-targeting moieties to anticancer drugs, antioxidants and sensor molecules. Among them, the most widely applied mitochondrial targeting moiety is triphenylphosphonium (TPP), which is a delocalized cationic lipid that readily accumulates and penetrates through the mitochondrial membrane due to the highly negative mitochondrial membrane potential. Other moieties, including short peptides, dequalinium, guanidine, rhodamine, and F16, are also known to be promising mitochondrial targeting agents. Direct conjugation of mitochondrial targeting moieties to anticancer drugs, antioxidants and sensors results in increased cytotoxicity, anti-oxidizing activity and sensing activity, respectively, compared with their non-targeting counterparts, especially in drug-resistant cells. Although many mitochondria-targeted anticancer drug conjugates have been investigated and , further clinical studies are still needed. On the other hand, several mitochondria-targeting antioxidants have been analyzed in clinical phases I, II and III trials, and one conjugate has been approved for treating eye disease in Russia. There are numerous ongoing studies of mitochondria-targeted sensors.