Metformin normalizes mitochondrial function to delay astrocyte senescence in a mouse model of Parkinson's disease through Mfn2-cGAS signaling.

BACKGROUND: Senescent astrocytes play crucial roles in age-associated neurodegenerative diseases, including Parkinson's disease (PD). Metformin, a drug widely used for treating diabetes, exerts longevity effects and neuroprotective activities. However, its effect on astrocyte senescence in PD remains to be defined. METHODS: Long culture-induced replicative senescence model and 1-methyl-4-phenylpyridinium/α-synuclein aggregate-induced premature senescence model, and a mouse model of PD were used to investigate the effect of metformin on astrocyte senescence in vivo and in vitro. Immunofluorescence staining and flow cytometric analyses were performed to evaluate the mitochondrial function. We stereotactically injected AAV carrying GFAP-promoter-cGAS-shRNA to mouse substantia nigra pars compacta regions to specifically reduce astrocytic cGAS expression to clarify the potential molecular mechanism by which metformin inhibited the astrocyte senescence in PD. RESULTS: We showed that metformin inhibited the astrocyte senescence in vitro and in PD mice. Mechanistically, metformin normalized mitochondrial function to reduce mitochondrial DNA release through mitofusin 2 (Mfn2), leading to inactivation of cGAS-STING, which delayed astrocyte senescence and prevented neurodegeneration. Mfn2 overexpression in astrocytes reversed the inhibitory role of metformin in cGAS-STING activation and astrocyte senescence. More importantly, metformin ameliorated dopamine neuron injury and behavioral deficits in mice by reducing the accumulation of senescent astrocytes via inhibition of astrocytic cGAS activation. Deletion of astrocytic cGAS abolished the suppressive effects of metformin on astrocyte senescence and neurodegeneration. CONCLUSIONS: This work reveals that metformin delays astrocyte senescence via inhibiting astrocytic Mfn2-cGAS activation and suggest that metformin is a promising therapeutic agent for age-associated neurodegenerative diseases.

[Phenolic constituents from Wikstroemia chamaedaphne].

The phenolic constituents of Wikstroemia chamaedaphne were investigated by various column chromatographic methods including silica gel,Sephadex LH-20,ODS and preparative HPLC,and their chemical structures were identified by physico-chemical properties and spectral analyses. Thirteen phenolic compounds were isolated and elucidated,including five flavonoids: luteolin 7-O-ß-D-glucopyranoside(1),luteolin 4'-O-ß-D-glucopyranoside(2),kaempferol 3-O-ß-D-glucopyranoside(3),chrysoeriol 4'-O-ß-D-glucopyranoside(4),chrysoeriol(5); and eight lignans:(-)-secoisolariciresinol(6),acanthosessilin A(7),(-)-nortrachelogenin(8),(+)-isolariciresinol(9),sesamin(10),syringaresinol(11),(+)-epipinoresinol(12),and [3,3',4,4'-tetrahydro-6,6'-dimethoxy-3,3'-bi-2 H-benzopyran]-4,4'-diol(13). Compounds 1, 3, 5-8, 10, 11 and 13 were obtained from the plants of W. chamaedaphne for the first time,and compounds 1,5,7,10 and 13 were obtained from the Wikstroemia genus for the first time.

Suppressing autophagy protects photoreceptor cells from light-induced injury.

Autophagy, a conserved cellular self-degradation process, not only serves to protect cells at critical times during development and nutrient stress, but also contributes to cell death. Photoreceptor cells are unique neurons which when directly exposed to the light, transduces light stimuli into visual signal. However, intense light exposure can be cytotoxic to the retina. So far, the precise mechanism underlying retina light injury remains unknown, and the effective therapy is still unavailable. Here, we found that visible light exposure activated the mitogen-activated protein kinases (MAPK) pathway and led to remarkable autophagy in photoreceptor cells (661W cells). Directly blocking autophagy with 3MA or LY294002 markedly attenuated light-induced death in 661W cells. Among the activated downstream factors of MAPK pathway, ERK, not JNK or p-38, played a critical role in light-induced death mechanism. Inhibiting the activation of ERK with its specific inhibitor PD98059 significantly suppressed light-induced autophagy and protected 661W cells from light injury. These results indicate that autophagy is an essential event in light-induced photoreceptor death and that directly blocking autophagy or suppressing autophagy by inhibiting the ERK pathway could effectively attenuates light-induced damage. These observations may have a potential application in the treatment of retinal light injury.

Potential HIV latency-reversing agents with STAT1-activating activity from the leaves of Wikstroemia chamaedaphne.

Developing highly effective HIV latency-reversing agent is an inportmant approach for the treatment of AIDS via the "shock and kill" of latent HIV. In this study, two unreported modified daphnane-type diterpenes (chamaedaphnelide A and epi-chamaedaphnelide A) and one unreported tigliane-type diterpene (chamaedaphnelide B), along with four known daphnane-type diterpenes and one known tigliane-type diterpene were obtained from the leaves of Wikstroemia chamaedaphne. Chamaedaphnelide A and epi-chamaedaphnelide A represents the first A ring cleavage daphnane-type backbone. Chamaedaphnelide A, epi-chamaedaphnelide A, chamaedaphnelide B, and 6α,7α-epoxy-5ß-hydroxy-12-deoxyphorbol-13-decanoate showed HIV latency-reversing activity, especially chamaedaphnelide B and 6α,7α-epoxy-5ß-hydroxy-12-deoxyphorbol-13-decanoate displayed equally potential to positive drugs prostratin with reversing latent HIV on more than 100-fold compared to unstimulated cells. Furthermore, the activation of STAT1 was involved in the HIV latency-reversing activity of these diterpenes, firstly demonstrating that daphnane- and tigliane-type diterpenes can rapidly activate STAT1 activity. Indeed, these results also supported that activating STAT1 activity is a pathway for reversing latent HIV.

Study on Network Pharmacological Analysis and Preliminary Validation to Understand the Mechanisms of Plantaginis Semen in Treatment of Gouty Nephropathy.

Plantaginis Semen (PS) has been used to promote diuresis and clear away dampness. Recent reports have shown that PS can be used to treat gouty nephropathy (GN). However, the action and mechanism of PS have not been well defined in treating GN. The present study aimed to define the molecular mechanisms of PS as a potential therapeutic approach to treat GN. A combination of network pharmacology and validation experiments in GN is used to understand the potential mechanism. Information on pharmaceutically active compounds in PS and gene information related to GN was obtained from public databases. The compound target network and protein-protein interaction network were constructed to study the mechanism of action of PS in the treatment of GN. The mechanism of action of PS in the treatment of GN was analyzed via Gene Ontology (GO) biological process annotation and Kyoto Gene and Genomics Encyclopedia (KEGG) pathway enrichment. Validation experiments were performed to verify the core targets. The GN rat model was prepared by the method of combining yeast and adenine. Hematoxylin-eosin (HE) staining was used to observe the morphology of renal tissue in rats. ELISA was applied to detect TGF-ß1, TNF-α, and IL-1ß levels in renal tissue. The expressions of TGF-ß1, TNF-α, and IL-1ß were determined using immunohistochemistry. Through the results of network pharmacology, we obtained 9 active components, 118 predicted targets, and 149 GN targets from the public database. Based on the protein-protein interaction (PPI), 26 hub genes for interaction with PS treating for GN were screened, including MMP9, TNF, IL1ß, and IL6. The enrichment analysis results showed that the treatment of GN with PS was mainly involved in the TGF-ß1 signaling pathway, MAPK signaling pathway, TNF signaling pathway, NF-κB signaling pathway, and PI3K Akt signaling pathway. Validation experiment results showed that PS could reduce the content of urinary protein and UA and deregulate the expression of TGF-ß1, TNF-α, and IL-1ß in the treatment of GN. The molecular mechanism of PS in the treatment of GN indicated the synergistic features of multicomponent, multitarget, and multipathway of traditional Chinese medicine, which provided an essential scientific basis for further elucidating the mechanism of PS in the treatment of GN.

Diterpenes from buds of Wikstroemia chamaedaphne showing anti-hepatitis B virus activities.

Phytochemical study of the buds of Wikstroemia chamaedaphne Meisn. led to the isolation of seven previously undescribed diterpenes, including one tigliane diterpene (wikstchalide A), two daphnane diterpenes (wikstroelides W-X), and four lathyrane diterpenes (laurifoliosides A-B and 2-epi-laurifoliosides A-B), along with four known diterpenes. The structures of these compounds were established by extensive spectroscopic evidence and electronic circular dichroism (ECD) calculations. Wikstchalide A possesses a 5,6-epoxy ring in the tigliane skeleton. Two compounds exhibited potential anti-hepatitis B virus activities, with IC50 values of 46.5 and 88.3 µg/mL against hepatitis B virus (HBV) surface antigen (HBsAg), and six compounds showed certain inhibitory effects on HBV-DNA replication with the inhibition ratios ranging from 2.0% to 33.0% at the concentrations ranging from 0.39 to 6.25 µg/mL.

Rapamycin attenuates visible light-induced injury in retinal photoreceptor cells via inhibiting endoplasmic reticulum stress.

An extended exposure of the retina to visible light may lead to photochemical damage in retinal photoreceptor cells. The exact mechanism of retinal light damage remains unknown, and an effective therapy is still unavailable. Here, we demonstrated that rapamycin, an inhibitor of the mammalian target of rapamycin (mTOR), markedly protected 661W photoreceptor cells from visible light exposure-induced damage at the nanomolar level. We also observed by transmission electron microscopy that light exposure led to severe endoplasmic reticulum (ER) stress in 661W cells as well as abnormal endomembranes and ER membranes. In addition, obvious upregulated ER stress markers were monitored by western blot at the protein level and by quantitative reverse transcription-polymerase chain reaction (RT-PCR) at the mRNA level. Interestingly, rapamycin pretreatment significantly suppressed light-induced ER stress and all three major branches of the unfolded protein response (UPR), including the RNA-dependent protein kinase-like ER kinase (PERK), inositol-requiring enzyme 1 (IRE1), and activating transcription factor 6 (ATF6) pathways both at the protein and mRNA levels. Additionally, the inhibition of ER stress by rapamycin was further confirmed with a dithiothreitol (DTT; a classical ER stress inducer)-damaged 661W cell model. Meanwhile, our results also revealed that rapamycin was able to remarkably inhibit the activation of mTOR and its downstream factors eukaryotic translation initiation factor 4E-binding protein 1 (4EBP1), p-4EBP1, p70, p-p70, and phosphorylated ribosomal protein S6 kinase (p-S6K) in the light-injured 661W cells. Thus, these data indicate that visible light induces ER stress in 661W cells; whereas the mTOR inhibitor, rapamycin, effectively protects 661W cells from light injury through suppressing the ER stress pathway.

Differential entropy feature for EEG-based vigilance estimation.

This paper proposes a novel feature called differential entropy for EEG-based vigilance estimation. By mathematical derivation, we find an interesting relationship between the proposed differential entropy and the existing logarithm energy spectrum. We present a physical interpretation of the logarithm energy spectrum which is widely used in EEG signal analysis. To evaluate the performance of the proposed differential entropy feature for vigilance estimation, we compare it with four existing features on an EEG data set of twenty-three subjects. All of the features are projected to the same dimension by principal component analysis algorithm. Experiment results show that differential entropy is the most accurate and stable EEG feature to reflect the vigilance changes.