Overexpressed SIRT6 ameliorates doxorubicin-induced cardiotoxicity and potentiates the therapeutic efficacy through metabolic remodeling.

Since the utilization of anthracyclines in cancer therapy, severe cardiotoxicity has become a major obstacle. The major challenge in treating cancer patients with anthracyclines is minimizing cardiotoxicity without compromising antitumor efficacy. Herein, histone deacetylase SIRT6 expression was reduced in plasma of patients treated with anthracyclines-based chemotherapy regimens. Furthermore, overexpression of SIRT6 alleviated doxorubicin-induced cytotoxicity in cardiomyocytes, and potentiated cytotoxicity of doxorubicin in multiple cancer cell lines. Moreover, SIRT6 overexpression ameliorated doxorubicin-induced cardiotoxicity and potentiated antitumor efficacy of doxorubicin in mice, suggesting that SIRT6 overexpression could be an adjunctive therapeutic strategy during doxorubicin treatment. Mechanistically, doxorubicin-impaired mitochondria led to decreased mitochondrial respiration and ATP production. And SIRT6 enhanced mitochondrial biogenesis and mitophagy by deacetylating and inhibiting Sgk1. Thus, SIRT6 overexpression coordinated metabolic remodeling from glycolysis to mitochondrial respiration during doxorubicin treatment, which was more conducive to cardiomyocyte metabolism, thus protecting cardiomyocytes but not cancer cells against doxorubicin-induced energy deficiency. In addition, ellagic acid, a natural compound that activates SIRT6, alleviated doxorubicin-induced cardiotoxicity and enhanced doxorubicin-mediated tumor regression in tumor-bearing mice. These findings provide a preclinical rationale for preventing cardiotoxicity by activating SIRT6 in cancer patients undergoing chemotherapy, but also advancing the understanding of the crucial role of SIRT6 in mitochondrial homeostasis.

Astrocytic SIRT6 is a potential anti-depression and anti-anxiety target.

Sirtuin 6 (SIRT6) is a nuclear silencing information regulator that is widely expressed in brain. Inhibition of SIRT6 in the brain induced antidepressant effects in rodents. However, SIRT6 knockout in neurons induced developmental retardation and cognitive impairments. In this study, a mouse strain of astrocyte conditional knockout SIRT6 (AKO) was constructed. Unlike whole brain SIRT6 knockout mice, AKO mice did not show growth retardation. We showed that SIRT6 knockout in astrocytes did not impair the learning and memory ability of mice. Chronic unpredictable mild stress (CUMS) was used to evaluate the anti-depression and anti-anxiety effects in mice. In tail suspension test and forced swimming test, AKO mice did not show depression like phenotype induced by CUMS. In addition, knockout of SIRT6 in astrocytes alleviated the high anxiety level induced by CUMS in light and dark box test, open field test and elevated cross maze test. Three box social test showed that the deletion of SIRT6 in astrocytes changed the social preference of mice. Re-expression of SIRT6 in astrocytes mediated by adeno-associated virus reversed the social preference of AKO mice, but the re-expression also eliminated the anti-depression and anti-anxiety effects in AKO mice. Deletion of SIRT6 in astrocytes change the purine metabolic homeostasis of medial prefrontal cortex in mice. The results of transcriptomics and metabolomics analysis showed that the deletion of SIRT6 would change the purine metabolic pathway of cultured astrocytes and increase the contents of inosine and the second messenger cyclic adenosine monophosphate in astrocytes. In conclusion, knockout of SIRT6 in astrocytes induced anti-depression and anti-anxiety effects in mice without impairing the development and cognitive ability of mice.

Ample dietary fat reduced the risk of primary vesical calculi by inducing macrophages to engulf budding crystals in mice.

Although primary vesical calculi is an ancient disease, the mechanism of calculi formation remains unclear. In this study, we established a novel primary vesical calculi model with d,l-choline tartrate in mice. Compared with commonly used melamine and ethylene glycol models, our model was the only approach that induced vesical calculi without causing kidney injury. Previous studies suggest that proteins in the daily diet are the main contributors to the prevention of vesical calculi, yet the effect of fat is overlooked. To assay the relationship of dietary fat with the formation of primary vesical calculi, d,l-choline tartrate-treated mice were fed a high-fat, low-fat, or normal-fat diet. Genetic changes in the mouse bladder were detected with transcriptome analysis. A high-fat diet remarkably reduced the morbidity of primary vesical calculi. Higher fatty acid levels in serum and urine were observed in the high-fat diet group, and more intact epithelia in bladder were observed in the same group compared with the normal- and low-fat diet groups, suggesting the protective effect of fatty acids on bladder epithelia to maintain its normal histological structure. Transcriptome analysis revealed that the macrophage differentiation-related gene C-X-C motif chemokine ligand 14 (Cxcl14) was upregulated in the bladders of high-fat diet-fed mice compared with those of normal- or low-fat diet-fed mice, which was consistent with histological observations. The expression of CXCL14 significantly increased in the bladder in the high-fat diet group. CXCL14 enhanced the recruitment of macrophages to the crystal nucleus and induced the transformation of M2 macrophages, which led to phagocytosis of budding crystals and prevented accumulation of calculi. In human bladder epithelia (HCV-29) cells, high fatty acid supplementation significantly increased the expression of CXCL14. Dietary fat is essential for the maintenance of physiological functions of the bladder and for the prevention of primary vesical calculi, which provides new ideas for the reduction of morbidity of primary vesical calculi.

Klotho overexpression improves amyloid-ß clearance and cognition in the APP/PS1 mouse model of Alzheimer's disease.

Alzheimer's disease (AD) is the most prevalent type of dementia, characterized by the presence of amyloid-ß (Aß) plaques. We previously reported that Klotho lowered Aß levels in the brain and protected against cognitive deficits in amyloid precursor protein/presenilin 1(APP/PS1) mice. However, the underlying mechanism remains unclear. In this study, we induced intracerebral Klotho overexpression in 13-month-old APP/PS1 mice by injecting lentivirus that carried full-length mouse Klotho cDNA in the lateral ventricle of the brain. We examined the effects of Klotho overexpression on cognition, Aß burden, Aß-related neuropathology, microglia transformation, and Aß transport systems in vivo. Additionally, we investigated the effects of Klotho on Aß transport at the blood-cerebrospinal fluid barrier by knocking down Klotho in primary human choroid plexus epithelial cells (HCPEpiCs). The upregulation of Klotho levels in the brain and serum significantly ameliorated Aß burden, neuronal and synaptic loss and cognitive deficits in aged APP/PS1 mice. Klotho treatment significantly inhibited NACHT, LRR, and PYD domain-containing protein 3 (NLRP3) and the subsequent transformation of microglia to the M2 type that may enhance microglia-mediated Aß clearance. Meanwhile, Klotho overexpression also regulated Aß transporter expression, which may promote Aß transporter-mediated Aß clearance. Moreover, the ability of HCPEpiCs to transport Aß in vitro was also significantly impaired by Klotho knockdown. Given the neuroprotective effect of Klotho overexpression, the present findings suggest that Klotho should be further investigated as a potential therapeutic target for AD.

Lentiviral vector-mediated overexpression of Klotho in the brain improves Alzheimer's disease-like pathology and cognitive deficits in mice.

Alzheimer's disease (AD) is the most common type of senile dementia. The antiaging gene Klotho is reported to decline in the brain of patients and animals with AD. However, the role of Klotho in the progression of AD remains elusive. The present study explored the effects and underlying mechanism of Klotho in a mouse model of AD. The upregulation of cerebral Klotho expression was mediated by an intracerebroventricular injection of a lentiviral vector that encoded Klotho (LV-KL) in 7-month-old amyloid precursor protein/presenilin 1 transgenic mice. Three months later, LV-KL significantly induced Klotho overexpression in the brain and effectively ameliorated cognitive deficit and AD-like pathology in amyloid precursor protein/presenilin 1 mice. LV-KL induced autophagy activation and protein kinase B/mammalian target of rapamycin inhibition both in AD mice and BV2 murine microglia. These results suggest that the upregulation of Klotho expression in the brain may promote the autophagic clearance of amyloid beta and protect against cognitive deficits in AD mice. These findings highlight the preventive and therapeutic potential of Klotho for the treatment of AD.

Lentivirus-mediated klotho up-regulation improves aging-related memory deficits and oxidative stress in senescence-accelerated mouse prone-8 mice.

AIMS: Oxidative stress caused by aging aggravates neuropathological changes and cognitive deficits. Klotho, an anti-aging protein, shows an anti-oxidative effect. The aims of the present study were to determine the potential therapeutic effect of klotho in aging-related neuropathological changes and memory impairments in senescence-accelerated mouse prone-8 (SAMP8) mice, and identify the potential mechanism of these neuroprotective effects. MATERIALS AND METHODS: A lentivirus was used to deliver and sustain the expression of klotho. The lentiviral vectors were injected into the bilateral lateral ventricles of 7-month-old SAMP8 mice or age-matched SAMR1 mice. Three months later, the Y-maze alternation task and passive avoidance task were used to assess the memory deficits of the mice. In situ hybridization, immunohistochemistry, immunofluorescence, Nissl staining, quantitative real-time PCR and Western blot assays were applied in the following research. KEY FINDINGS: Our results showed that 3 months after injection of the lentiviral vectors encoding the full-length klotho gene, the expression of klotho in the brain was significantly increased in 10-month-old SAMP8 mice. This treatment reduced memory deficits, neuronal loss, synaptic damage and 4-HNE levels but increased mitochondrial manganese-superoxide dismutase (Mn-SOD) and catalase (CAT) expression. Moreover, the up-regulation of klotho expression decreased Akt and Forkhead box class O1 (FoxO1) phosphorylation. SIGNIFICANCE: The present study provides a novel approach for klotho gene therapy and demonstrates that direct up-regulation of klotho in the brain might improve aging-related memory impairments and decrease oxidative stress. The underlying mechanism of this effect likely involves the inhibition of the Akt/FoxO1 pathway.