A comprehensive study of the genotoxic and anti-genotoxic effects of homocysteine in HUVECs and mouse bone marrow cells

Safety and efficacy evaluation of halicin as an effective drug for inhibiting intestinal infections

Halicin, the first antibacterial agent discovered by artificial intelligence, exerts broad-spectrum antibacterial effects and has a unique structure. Our study found that halicin had a good inhibitory effect on clinical isolates of drug-resistant strains and Clostridium perfringens (C. perfringens). The safety of halicin was evaluated by acute oral toxicity, genotoxicity and subchronic toxicity studies. The results of acute toxicity test indicated that halicin, as a low-toxicity compound, had an LD50 of 2018.3 mg/kg. The results of sperm malformation, bone marrow chromosome aberration and cell micronucleus tests showed that halicin had no obvious genotoxicity. However, the results of the 90-day subchronic toxicity test indicated that the test rats exhibited weight loss and slight renal inflammation at a high dose of 201.8 mg/kg. Teratogenicity of zebrafish embryos showed that halicin had no significant teratogenicity. Analysis of intestinal microbiota showed that halicin had a significant effect on the intestinal microbial composition, but caused a faster recovery. Furthermore, drug metabolism experiments showed that halicin was poorly absorbed and quickly eliminated in vivo. Our study found that halicin had a good therapeutic effect on intestinal infection model of C. perfringens. These results show the feasibility of developing oral halicin as a clinical candidate drug for treating intestinal infections.

Telomere length and micronuclei trajectories in APP/PS1 mouse model of Alzheimer's disease: Correlating with cognitive impairment and brain amyloidosis in a sexually dimorphic manner

Although studies have demonstrated that genome instability is accumulated in patients with Alzheimer's disease (AD), the specific types of genome instability linked to AD pathogenesis remain poorly understood. Here, we report the first characterization of the age- and sex-related trajectories of telomere length (TL) and micronuclei in APP/PS1 mice model and wild-type (WT) controls (C57BL/6). TL was measured in brain (prefrontal cortex, cerebellum, pituitary gland, and hippocampus), colon and skin, and MN was measured in bone marrow in 6- to 14-month-old mice. Variation in TL was attributable to tissue type, age, genotype and, to a lesser extent, sex. Compared to WT, APP/PS1 had a significantly shorter baseline TL across all examined tissues. TL was inversely associated with age in both genotypes and TL shortening was accelerated in brain of APP/PS1. Age-related increase of micronuclei was observed in both genotypes but was accelerated in APP/PS1. We integrated TL and micronuclei data with data on cognition performance and brain amyloidosis. TL and micronuclei were linearly correlated with cognition performance or Aβ40 and Aβ42 levels in both genotypes but to a greater extent in APP/PS1. These associations in APP/PS1 mice were dominantly driven by females. Together, our findings provide foundational knowledge to infer the TL and micronuclei trajectories in APP/PS1 mice during disease progression, and strongly support that TL attrition and micronucleation are tightly associated with AD pathogenesis in a female-biased manner.

Endocrine modulation of brain-skeleton axis driven by neural stem cell-derived perilipin 5 in the lipid metabolism homeostasis for bone regeneration

Factors released from the nervous system always play crucial roles in modulating bone metabolism and regeneration. How the brain-driven endocrine axes maintain bone homeostasis, especially under metabolic disorders, remains obscure. Here, we found that neural stem cells (NSCs) residing in the subventricular zone participated in lipid metabolism homeostasis of regenerative bone through exosomal perilipin 5 (PLIN5). Fluorescence-labeled exosomes tracing and histological detection identified that NSC-derived exosomes (NSC-Exo) could travel from the lateral ventricle into bone injury sites. Homocysteine (Hcy) led to osteogenic and angiogenic impairment, whereas the NSC-Exo were confirmed to restore it. Mecobalamin, a clinically used neurotrophic drug, further enhanced the protective effects of NSC-Exo through increased PLIN5 expression. Mechanistically, NSC-derived PLIN5 reversed excessive Hcy-induced lipid metabolic imbalance and aberrant lipid droplet accumulation through lipophagy-dependent intracellular lipolysis. Intracerebroventricular administration of mecobalamin and/or AAV-shPlin5 confirmed the effects of PLIN5-driven endocrine modulations on new bone formation and vascular reconstruction in hyperhomocysteinemic and high-fat diet models. This study uncovered a novel brain-skeleton axis that NSCs in the mammalian brain modulated bone regeneration through PLIN5-driven lipid metabolism modulation, providing evidence for lipid- or bone-targeted medicine development.

Effects of dietary restriction on genome stability are sex and feeding regimen dependent

Preserving genome stability is essential to prevent aging and cancer. Dietary restriction (DR) is the most reproducible non-pharmacological way to improve health and extend lifespan in various species. Whether DR helps to preserve genome stability and whether this effect is altered by experimental variables remain unclear. Moreover, DR research relies heavily on experimental animals, making the development of reliable in vitro mimetics of great interest. Therefore, we tested the effects of sex and feeding regimen (time-restricted eating, alternate day fasting and calorie restriction) on genome stability in CF-1 mice and whether these effects can be recapitulated by cell culture paradigms. Here, we show that calorie restriction significantly decreases the spontaneous micronuclei (MN), a biomarker of genome instability, in bone marrow cells of females instead of males. Alternate day fasting significantly decreases cisplatin-induced MN in females instead of males. Unexpectedly, daily time-restricted eating significantly exacerbates cisplatin-induced MN in males but not in females. Additionally, we design several culture paradigms that are able to faithfully recapitulate the key effects of these DR regimens on genome stability. In particular, 30% reduction of serum, a mimetic of calorie restriction, exhibits a strong ability to decrease spontaneous and cisplatin-induced MN in immortalized human umbilical vein endothelial cells. We conclude that the effects of different DR regimens on genome stability are not universal and females from each diet regimen sustain a more stable genome than males. Our results provide novel insight into the understanding of how DR influences genome stability in a sex and regimen dependent way, and suggest that our in vitro DR mimetics could be adopted to study the underlying molecular mechanisms.

High-dose metformin induces a low-glucose dependent genotoxic stress

Epidemiological studies have demonstrated that metformin (a cornerstone of diabetes treatment) has anticancer activity, but the underlying mechanism remains elusive. We aimed to investigate whether metformin elicits anticancer activity via increasing genotoxic stress, a state of increased genome damage that becomes tumor-suppressing if it goes beyond an intolerable threshold. We found that metformin (1-16 mM) suppressed proliferation and colony formation in a panel of cancer cell lines (HeLa, A375, A549 and QGY). Metformin induced a dose-dependent increase of genotoxic stress (including micronucleus, nucleoplasmic bridge and nuclear bud) and the increase of genotoxic stress correlated well with metformin's anticancer potential. Metformin deregulated the expression of BUBR1 and MAD2, two core genes of spindle assembly checkpoint (SAC) that surveillances chromosome segregation. Metformin had weakened antiproliferative effect and a corresponding attenuated genotoxic effect in HeLa cells cultured in high glucose (16 mg/ml). Meanwhile, metformin significantly increased genotoxicity in non-cancer cells (NCM460 and HUVECs). Metformin became non-genotoxic to HUVECs in high-glucose (8 and 16 mg/ml) conditions and reduced the genotoxicity of high glucose. Overall, these results infer a new mechanism of high-dose metformin, whereby low-glucose dependent genotoxic stress derived from SAC dysfunction might mediate some of the anticancer effect of this drug.