Phosphocreatine Promotes Osteoblastic Activities in H2O2-Induced MC3T3-E1 Cells by Regulating SIRT1/FOXO1/PGC-1α Signaling Pathway

Sirtuins mediate mitochondrial quality control mechanisms: a novel therapeutic target for osteoporosis

Mitochondria plays a role in cell differentiation and apoptosis processes. Maintaining mitochondrial function is critical, and this involves various aspects of mitochondrial quality control such as protein homeostasis, biogenesis, dynamics, and mitophagy. Osteoporosis, a metabolic bone disorder, primarily arises from two factors: the dysregulation between lipogenic and osteogenic differentiation of aging bone marrow mesenchymal stem cells, and the imbalance between osteoblast-mediated bone formation and osteoclast-mediated bone resorption. Mitochondrial quality control has the potential to mitigate or even reverse the effects. Among the Sirtuin family, consisting of seven Sirtuins (SIRT1-7), SIRT1-SIRT6 play a crucial role in maintaining mitochondrial quality control. Additionally, SIRT1, SIRT3, SIRT6, and SIRT7 are directly involved in normal bone development and homeostasis by modulating bone cells. However, the precise mechanism by which these Sirtuins exert their effects remains unclear. This article reviews the impact of various aspects of mitochondrial quality control on osteoporosis, focusing on how SIRT1, SIRT3, and SIRT6 can improve osteoporosis by regulating mitochondrial protein homeostasis, biogenesis, and mitophagy. Furthermore, we provide an overview of the current state of clinical and preclinical drugs that can activate Sirtuins to improve osteoporosis. Specific Sirtuin-activating compounds are effective, but further studies are needed. The findings of this study may offer valuable insights for future research on osteoporosis and the development of clinical prevention and therapeutic target strategies.

LITAF inhibits colorectal cancer stemness and metastatic behavior by regulating FOXO1-mediated SIRT1 expression

Lipopolysaccharide-induced tumor necrosis factor alpha factor (LITAF) is a transcription factor that activates the transcription of TNF-α and regulates the inflammatory response. LITAF has been found to have potential anti-cancer effects of in several tumors. However, the role of LITAF in colorectal cancer (CRC) remains unclear. Through a comprehensive pan-cancer analysis of the Cancer Genome Atlas (TCGA), LITAF was identified as a differentially downregulated gene in CRC. We hypothesized that LITAF may participate in the modulation of CRC progression. The present study was aimed to investigate the expression profile of LITAF in CRC and its effect on metastatic behavior and stemness as well as the underlying molecular mechanism. The expression profile of LITAF in CRC, and its relationship with the prognosis of CRC were explored using public databases. LITAF expression was detected by quantitative real-time PCR (qRT-PCR), western blot, and immunohistochemistry. Furthermore, the effects of overexpression or knockdown of LITAF on cell proliferation, apoptosis, migration, invasion, and stemness of CRC cells were investigated in vitro. The regulatory effect of LITAF on forkhead Box O 1 (FOXO1)-sirtuin 1 (SIRT1) signaling axis was also explored. In addition, a xenograft mouse model was used to investigate the in-vivo role of LITAF. LITAF was downregulated in tumor tissues and its expression was associated with the prognosis, pathological stage and liver metastasis. In-vitro experiments confirmed that LITAF inhibited tumor cell proliferation, migration, invasion and stemness, and induced cell apoptosis. In vivo experiments demonstrated that LITAF inhibited the tumorigenicity and liver metastasis in tumor-bearing mice. Additionally, LITAF promoted FOXO1-mediated SIRT1 inhibition, thus regulating cancer stemness and malignant phenotypes. LITAF was silenced in CRC and it participated in the progression of CRC by inhibiting CRC cell stemness, and malignant phenotypes. Therefore, LITAF may serve as a novel biomarker of CRC prognosis.

Rejuvenation of Mesenchymal Stem Cells to Ameliorate Skeletal Aging

Advanced age is a shared risk factor for many chronic and debilitating skeletal diseases including osteoporosis and periodontitis. Mesenchymal stem cells develop various aging phenotypes including the onset of senescence, intrinsic loss of regenerative potential and exacerbation of inflammatory microenvironment via secretory factors. This review elaborates on the emerging concepts on the molecular and epigenetic mechanisms of MSC senescence, such as the accumulation of oxidative stress, DNA damage and mitochondrial dysfunction. Senescent MSCs aggravate local inflammation, disrupt bone remodeling and bone-fat balance, thereby contributing to the progression of age-related bone diseases. Various rejuvenation strategies to target senescent MSCs could present a promising paradigm to restore skeletal aging.

LncRNA H19 inhibits oxidative stress injury of cochlear hair cells by regulating miR-653-5p/SIRT1 axis

Oxidative stress is one of the important mechanisms of inner ear cell damage, which can lead to age-related hearing loss (ARHL). LncRNA H19 is significantly downregulated in the cochlea of old mouse, however, the role of H19 in the development of ARHL remains unclear. In this study, we aim to investigate the expression and function of H19 in oxidative stress injury of cochlear hair cells induced by HO. RT-qPCR and western blot analysis confirms that HEI-OC1 cells stimulated with HO decreases the expressions of H19 and SIRT1, but increases the expression of miR-653-5p. Overexpression of H19 could increase cell viability, ATP level and mitochondrial membrane potential, but reduce mitochondrial ROS generation and cell apoptosis ratio in HO-stimulated HEI-OC1 cells. MiR-653-5p is a target of H19, which can bind to the 3'-UTR of SIRT1. H19 is found to regulate the expression of SIRT1 through miR-653-5p. Further experiments demonstrates that H19 regulates HEI-OC1 cell viability, ATP level, mitochondrial membrane potential, mitochondrial ROS generation, and cell apoptosis ratio via the miR-653-5p/SIRT1 axis. In conclusion, lncRNA H19 inhibits oxidative stress injury of cochlear hair cells via the miR-653-5p/SIRT1 axis.

CD38 activation by monosodium urate crystals contributes to inflammatory responses in human and murine macrophages

Cluster of differentiation (CD) 38, a major enzyme for nicotinamide adenine dinucleotide (NAD⁺) degradation, plays a key role in inflammation. Meanwhile, intracellular NAD⁺ decline is also associated with inflammatory responses. However, whether CD38 activation is involved in gouty inflammation has not been elucidated. The present study aimed to clarify the role of CD38 in monosodium urate crystals (MSU)-triggered inflammatory responses. The results showed that MSU crystals increased the protein expression of CD38 in time- and concentration-dependent manner in THP-1 macrophages and mouse bone marrow-derived macrophages (BMDMs). Moreover, intracellular NAD⁺ levels were reduced by MSU crystals along with the increased IL-1β release. However, CD38 inhibition by 78c elevated intracellular NAD⁺ levels and suppressed IL-1β release in MSU crystals-treated THP-1 macrophages and BMDMs. Interestingly, CD38 inhibition without significant elevation of intracellular NAD⁺ also decreased IL-1β release driven by MSU crystals in THP-1 macrophages. In conclusion, the present study revealed that MSU crystals could activate CD38 with the ensuing intracellular NAD⁺ decline to promote inflammatory responses in THP-1 macrophages and BMDMs, while CD38 inhibition could suppress MSU crystals-triggered inflammatory responses, indicating that CD38 is a potential therapeutic target for gout.

Metabolomics and cytokine profiling of mesenchymal stromal cells identify markers predictive of T-cell suppression

BACKGROUND AIMS

Mesenchymal stromal cells (MSCs) have shown great promise in the field of regenerative medicine, as many studies have shown that MSCs possess immunomodulatory function. Despite this promise, no MSC therapies have been licensed by the Food and Drug Administration. This lack of successful clinical translation is due in part to MSC heterogeneity and a lack of critical quality attributes. Although MSC indoleamine 2,3-dioxygnease (IDO) activity has been shown to correlate with MSC function, multiple predictive markers may be needed to better predict MSC function.

METHODS

Three MSC lines (two bone marrow-derived, one induced pluripotent stem cell-derived) were expanded to three passages. At the time of harvest for each passage, cell pellets were collected for nuclear magnetic resonance (NMR) and ultra-performance liquid chromatography mass spectrometry (MS), and media were collected for cytokine profiling. Harvested cells were also cryopreserved for assessing function using T-cell proliferation and IDO activity assays. Linear regression was performed on functional data against NMR, MS and cytokines to reduce the number of important features, and partial least squares regression (PLSR) was used to obtain predictive markers of T-cell suppression based on variable importance in projection scores.

RESULTS

Significant functional heterogeneity (in terms of T-cell suppression and IDO activity) was observed between the three MSC lines, as were donor-dependent differences based on passage. Omics characterization revealed distinct differences between cell lines using principal component analysis. Cell lines separated along principal component one based on tissue source (bone marrow-derived versus induced pluripotent stem cell-derived) for NMR, MS and cytokine profiles. PLSR modeling of important features predicted MSC functional capacity with NMR (R² = 0.86), MS (R² = 0.83), cytokines (R² = 0.70) and a combination of all features (R² = 0.88).

CONCLUSIONS

The work described here provides a platform for identifying markers for predicting MSC functional capacity using PLSR modeling that could be used as release criteria and guide future manufacturing strategies for MSCs and other cell therapies.

The mechanisms of vascular aging

Vascular senescence is one of the hotspots in current research. With global average life expectancy increasing, delaying or reducing aging and age-related diseases has become a pressing issue for improving quality of life. Vascular senescence is an independent risk factor for age-related cardiovascular diseases (CVD) and results in the deterioration of CVD. Nevertheless, the underlying mechanisms of the vascular senescence have not been expressly illustrated. In this review, we attempt to summarize the recent literature in the field and discuss the major mechanisms involved in vascular senescence. We also underline key molecular aspects of aging-associated vascular dysfunction in the attempt to highlight potential innovative therapeutic targets to delay the onset of age-related diseases.