SIRT1 activation by 2,3,5,6-tetramethylpyrazine alleviates neuroinflammation via inhibiting M1 microglia polarization

Annexin A1 protects periodontal ligament cells against lipopolysaccharide-induced inflammatory response and cellular senescence: An implication in periodontitis

Periodontitis is an inflammatory condition that affects the tooth-supporting structures, triggered by the host's immune response toward the bacterial deposits around the teeth. Annexin A1 (AnxA1), a vital member of the annexin superfamily, is known for its diverse physiological functions, particularly its anti-inflammatory and anti-senescence properties. We hypothesized that AnxA1 has a protective effect against lipopolysaccharide (LPS)-induced inflammatory responses and cellular damage in periodontal ligament cells (PDLCs). In this study, we demonstrate that LPS stimulation significantly reduced telomerase activity in PDLCs, a decline that was dose-dependently reversed by AnxA1. Importantly, AnxA1 protected the cells from LPS-induced cellular senescence and the downregulation of human telomerase reverse transcriptase (hTERT) expression. In line with this, AnxA1 suppressed the LPS-induced expression of p21 and p16 at both the mRNA and protein levels. Furthermore, AnxA1 demonstrated potent anti-inflammatory effects by inhibiting the secretion of interleukin 6 (IL-6), interleukin 8 (IL-8), and monocyte chemoattractant protein-1 (MCP-1). It also mitigated LPS-induced oxidative stress by reducing the levels of phosphorylated Foxo3a (Ser253) and restored sirtuin 1 (SIRT1) expression. Notably, SIRT1 silencing abolished AnxA1's protective effects on Foxo3a phosphorylation and cellular senescence, suggesting that SIRT1 mediates AnxA1's actions. In conclusion, AnxA1 protected PDLCs against LPS-triggered inflammation and cell senescence by activating SIRT1 signal pathway. These findings indicate that AnxA1 could serve as a promising therapeutic strategy for the treatment of periodontitis.

Synergistic effects of tetramethylpyrazine and astragaloside IV on spinal cord injury via alteration of astrocyte A1/A2 polarization through the Sirt1-NF-κB pathway

OBJECTIVE

Reactive astrocytes are hallmarks of traumatic spinal cord injury (T-SCI) and are associated with neuropathic pain (NP). Mediating the functional phenotype of reactive astrocytes helps neural repair and ameliorates NP in T-SCI. Here, we aimed to explore the role of tetramethylpyrazine (TMPZ) and astragaloside IV (AGS-IV) in astrocyte polarization and the underlying molecular mechanism in T-SCI.

METHODS

Primary cultured astrocytes from mice were treated with LPS or conditioned medium from "M1" polarized microglia (M1-CM), followed by TMPZ and/or AGS-IV administration. The expression levels of "A1" astrocyte-specific markers (including C3, GBP2, Serping1, iNOS), "A2" astrocyte-specific markers (including S100a10 and PTX3), Sirt1 and NF-κB were detected via western blotting. TNF-α and IL-1β levels were detected via ELISA. RT-PCR was used to evaluate OIP5-AS1 and miR-34a expression. si-OIP5-AS1 or the Sirt1 inhibitor EX-527 was administered to astrocytes. A spinal cord injury (SCI) model was constructed in Sprague-Dawley (SD) rats. Alterations in astrocytic "A1/A2" polarization in the spinal cord tissues were evaluated.

RESULTS

LPS and M1-CM induced "A1" polarization of primary astrocytes. TMPZ and ASG IV could substantially reduce the expression of "A1"-related biomarkers but enhance "A2"-related biomarkers. OIP5-AS1 and Sirt1 levels were reduced in "A1"-polarized astrocytes, while miR-34a and p-NF-κB p65 were elevated. TMPZ and ASG IV enhanced OIP5-AS1 and Sirt1 levels and, in contrast, attenuated the changes in miR-34a and p-NF-κB p65 levels. Notably, the TMPZ and ASG IV combination had stronger effects on astrocyte polarization than the single treatment with TMPZ or ASG IV. OIP5-AS1 knockdown and Sirt1 inhibition both reversed the regulatory effects of TMPZ and ASG IV in astrocytic polarization. According to the in vivo experiments, the expression of "A1"-associated markers was enhanced in the spinal cords of SCI rats. The TMPZ and ASG IV combination reduced astrocytic "A1" polarization and enhanced astrocytic "A2" polarization. The expression of lncRNA OIP5-AS1 and Sirt1 was enhanced by TMPZ and ASG IV, while that of miR-34a and p-NF-κB p65 was inhibited.

CONCLUSION

The combination of TMPZ and ASG IV can ameliorate dysregulated astrocytic polarization induced by spinal cord injury by affecting the lncRNA OIP5-AS1-Sirt1-NF-κB pathway.

NAD-Dependent Protein Deacetylase Sirtuin-1 Mediated Mitophagy Regulates Early Brain Injury After Subarachnoid Hemorrhage

Background

This study focuses on the role of SIRT1 in neuroinflammation caused by early brain injury (EBI) after subarachnoid hemorrhage (SAH), and explores its mechanism in mitophagy after SAH.

Methods

C57BL/6J mice and primary microglia SAH in vivo and in vitro models were constructed to explore the expression level of SIRT1 in neuroinflammation after SAH. Subsequently, the brain edema content, blood-brain barrier (BBB) damage and neurological function scores of the mice were observed after using the SIRT1 inhibitor EX-527. q-PCR and Western blot were used to detect relevant genes and proteins, and enzyme-linked immunosorbent assay (ELISA) was used to detect the levels of IL-6, IL-1β, and TNF-α inflammatory factors. Immunofluorescence staining was used to observe the positive level of SIRT1 and the degree of mitochondria-lysosome fusion, and transmission electron microscopy was used to observe mitochondrial damage and autophagosome levels.

Results

In in vivo and in vitro experiments, we found that SIRT1 expression increased after SAH, and neurological deficits, brain edema, and blood-brain barrier damage after SAH were aggravated. Inhibiting SIRT1 further aggravates the aforementioned damage. In addition, EX-527 can also inhibit the level of mitophagy and aggravate neuroinflammation after SAH.

Conclusion

Our results indicated that SIRT1 promotes mitophagy and alleviates neuroinflammation after SAH.

The Interplay between Ferroptosis and Neuroinflammation in Central Neurological Disorders

Central neurological disorders are significant contributors to morbidity, mortality, and long-term disability globally in modern society. These encompass neurodegenerative diseases, ischemic brain diseases, traumatic brain injury, epilepsy, depression, and more. The involved pathogenesis is notably intricate and diverse. Ferroptosis and neuroinflammation play pivotal roles in elucidating the causes of cognitive impairment stemming from these diseases. Given the concurrent occurrence of ferroptosis and neuroinflammation due to metabolic shifts such as iron and ROS, as well as their critical roles in central nervous disorders, the investigation into the co-regulatory mechanism of ferroptosis and neuroinflammation has emerged as a prominent area of research. This paper delves into the mechanisms of ferroptosis and neuroinflammation in central nervous disorders, along with their interrelationship. It specifically emphasizes the core molecules within the shared pathways governing ferroptosis and neuroinflammation, including SIRT1, Nrf2, NF-κB, Cox-2, iNOS/NO·, and how different immune cells and structures contribute to cognitive dysfunction through these mechanisms. Researchers' findings suggest that ferroptosis and neuroinflammation mutually promote each other and may represent key factors in the progression of central neurological disorders. A deeper comprehension of the common pathway between cellular ferroptosis and neuroinflammation holds promise for improving symptoms and prognosis related to central neurological disorders.

Slowing Alzheimer's disease progression through probiotic supplementation

The lack of affordable and effective therapeutics against cognitive impairment has promoted research toward alternative approaches to the treatment of neurodegeneration. In recent years, a bidirectional pathway that allows the gut to communicate with the central nervous system has been recognized as the gut-brain axis. Alterations in the gut microbiota, a dynamic population of trillions of microorganisms residing in the gastrointestinal tract, have been implicated in a variety of pathological states, including neurodegenerative disorders such as Alzheimer's disease (AD). However, probiotic treatment as an affordable and accessible adjuvant therapy for the correction of dysbiosis in AD has not been thoroughly explored. Here, we sought to correct the dysbiosis in an AD mouse model with probiotic supplementation, with the intent of exploring its effects on disease progression. Transgenic 3xTg-AD mice were fed a control or a probiotic diet (Lactobacillus plantarum KY1032 and Lactobacillus curvatus HY7601) for 12  weeks, with the latter leading to a significant increase in the relative abundance of Bacteroidetes. Cognitive functions were evaluated via Barnes Maze trials and improvements in memory performance were detected in probiotic-fed AD mice. Neural tissue analysis of the entorhinal cortex and hippocampus of 10-month-old 3xTg-AD mice demonstrated that astrocytic and microglial densities were reduced in AD mice supplemented with a probiotic diet, with changes more pronounced in probiotic-fed female mice. In addition, elevated numbers of neurons in the hippocampus of probiotic-fed 3xTg-AD mice suggested neuroprotection induced by probiotic supplementation. Our results suggest that probiotic supplementation could be effective in delaying or mitigating early stages of neurodegeneration in the 3xTg-AD animal model. It is vital to explore new possibilities for palliative care for neurodegeneration, and probiotic supplementation could provide an inexpensive and easily implemented adjuvant clinical treatment for AD.

Sirtuins as Players in the Signal Transduction of Citrus Flavonoids

Sirtuins (SIRTs) belong to the family of nicotine adenine dinucleotide (NAD+)-dependent class III histone deacetylases, which come into play in the regulation of epigenetic processes through the deacetylation of histones and other substrates. The human genome encodes for seven homologs (SIRT1-7), which are localized into the nucleus, cytoplasm, and mitochondria, with different enzymatic activities and regulatory mechanisms. Indeed, SIRTs are involved in different physio-pathological processes responsible for the onset of several human illnesses, such as cardiovascular and neurodegenerative diseases, obesity and diabetes, age-related disorders, and cancer. Nowadays, it is well-known that Citrus fruits, typical of the Mediterranean diet, are an important source of bioactive compounds, such as polyphenols. Among these, flavonoids are recognized as potential agents endowed with a wide range of beneficial properties, including antioxidant, anti-inflammatory, hypolipidemic, and antitumoral ones. On these bases, we offer a comprehensive overview on biological effects exerted by Citrus flavonoids via targeting SIRTs, which acted as modulator of several signaling pathways. According to the reported studies, Citrus flavonoids appear to be promising SIRT modulators in many different pathologies, a role which might be potentially evaluated in future therapies, along with encouraging the study of those SIRT members which still lack proper evidence on their support.

Overexpress miR-132 in the Brain Parenchyma by a Non-invasive Way Improves Tissue Repairment and Releases Memory Impairment After Traumatic Brain Injury

Traumatic brain injury (TBI) is a serious public health problem worldwide, which could lead to an extremely high percentage of mortality and disability. Current treatment strategies mainly concentrate on neuronal protection and reconstruction, among them, exogenous neural stem cell (NSC) transplantation has long been regarded as the most effective curative treatment. However, due to secondary trauma, transplant rejection, and increased incidence of brain malignant tumor, a non-invasive therapy that enhanced endogenous neurogenesis was more suitable for TBI treatment. Our previous work has shown that miR-132 overexpression could improve neuronal differentiation of NSCs in vitro and in vivo. So, we engineered a new kind of AAV vector named AAV-PHP.eB which can transfect brain parenchyma through intravenous injection to overexpress miR-132 in brain after TBI. We found that miR-132 overexpression could reduce impact volume, promote neurogenesis in the dentate gyrus (DG), accelerate neuroblast migrating into the impact cortex, ameliorate microglia-mediated inflammatory reaction, and ultimately restore learning memory function. Our results revealed that AAV-PHP.eB-based miR-132 overexpression could improve endogenous tissue repairment and release clinical symptoms after traumatic brain injury. This work would provide a new therapeutic strategy for TBI treatment and other neurological disorders characterized by markable neuronal loss and memory impairment. miR-132 overexpression accelerates endogenous neurogenesis and releases TBI-induced tissue repairment and memory impairment. Controlled cortical impact onto the cortex would induce serious cortical injury and microglia accumulation in both cortex and hippocampus. Moreover, endogenous neuroblast could migrate around the injury core. miR-132 overexpression could accelerate neuroblast migration toward the injury core and decreased microglia accumulation in the ipsilateral cortex and hippocampus. miR-132 could be a suitable target on neuroprotective therapy after TBI.