bims-lypmec 2024-12-08 papers

Exp Mol Med. 2024 Dec 04.

TIGAR coordinates senescence-associated secretory phenotype via lysosome repositioning and α-tubulin deacetylation.

Hae Yun Nam, Seung-Ho Park, Geun-Hee Lee, Eun-Young Kim, SangEun Lee, Hyo Won Chang, Eun-Ju Chang, Kyung-Chul Choi, Seong Who Kim.

TP53-induced glycolysis and apoptosis regulator (TIGAR) regulates redox homeostasis and provides the intermediates necessary for cell growth by reducing the glycolytic rate. During cellular senescence, cells undergo metabolic rewiring towards the glycolytic pathway, along with the development of the senescence-associated secretory phenotype (SASP), also known as the secretome. We observed that TIGAR expression increased during replicative senescence following the in vitro expansion of human mesenchymal stromal cells (MSCs) and that TIGAR knockout (KO) decreased SASP factors and triggered premature senescence with decelerated progression. Additionally, TIGAR KO impaired flexible lysosomal movement to the perinuclear region and decreased the autophagic flux of MSCs. Research on the mechanism of lysosomal movement revealed that, while native senescent MSCs presented low levels of Ac-α-tubulin (lysine 40) and increased sirtuin 2 (SIRT2) activity compared with those in growing cells, TIGAR KO-MSCs maintained Ac-α-tubulin levels and exhibited decreased SIRT2 activity despite being in a senescent state. The overexpression of SIRT2 reduced Ac-α-tubulin as a protein target of SIRT2 and induced the positioning of lysosomes at the perinuclear region, restoring the cytokine secretion of TIGAR KO-MSCs. Furthermore, TIGAR expression was positively correlated with SIRT2 activity, indicating that TIGAR affects SIRT2 activity partly by modulating the NAD+ level. Thus, our study demonstrated that TIGAR provides a foundation that translates the regulation of energy metabolism into lysosome positioning, affecting the secretome for senescence development. Considering the functional value of the cell-secretome in aging-related diseases, these findings suggest the feasibility of TIGAR for the regulation of secretory phenotypes.

DOI: https://doi.org/10.1038/s12276-024-01362-4

Cardiovasc Diabetol. 2024 Dec 04. 23(1): 432

PACS2/CPT1A/DHODH signaling promotes cardiomyocyte ferroptosis in diabetic cardiomyopathy.

Hong Xiang, Qi Lyu, Shuhua Chen, Jie Ouyang, Di Xiao, Quanjun Liu, HaiJiao Long, Xinru Zheng, Xiaoping Yang, Hongwei Lu.

OBJECTIVES: The pathophysiology of diabetic cardiomyopathy (DCM) is a phenomenon of great interest, but its clinical problems have not yet been effectively addressed. Recently, the mechanism of ferroptosis in the pathophysiology of various diseases, including DCM, has attracted widespread attention. Here, we explored the role of PACS2 in ferroptosis in DCM through its downregulation of PACS2 expression.
METHODS AND RESULTS: Cardiomyocytes were treated with high glucose and palmitic acid (HGPA), and the detection of cardiomyocyte iron ions, lipid peroxides, and reactive oxygen species (ROS) revealed clear ferroptosis during these treatments. Silencing PACS2 downregulated CPT1A expression and upregulated DHODH expression significantly, reversing HGPA-induced ferroptosis. Further silencing of PACS2 with a CPT1A agonist exacerbated cardiomyocyte ferroptosis while promoting mitochondrial damage in cardiomyocytes. Using a mouse model of type 2 diabetes induced by streptozotocin (STZ) and a high-fat diet (HFD), we found that PACS2 deletion reversed these treatment-induced increases in cellular iron ions, impaired cardiac function, mitochondrial damage and ferroptosis in cardiac muscle tissues.
CONCLUSIONS: The PACS2/CPT1A/DHODH signalling pathway may be involved in ferroptosis in DCM by regulating cardiomyocyte mitochondrial function.

Keywords: Diabetic cardiomyopathy; Ferroptosis; Mitochondria

DOI: https://doi.org/10.1186/s12933-024-02514-6

Elife. 2024 Dec 06. pii: RP97255. [Epub ahead of print]13

Reversing protonation of weakly basic drugs greatly enhances intracellular diffusion and decreases lysosomal sequestration.

Debabrata Dey, Shir Marciano, Anna Poryval, Ondřej Groborz, Lucie Wohlrabova, Tomás Slanina, Gideon Schreiber.

For drugs to be active they have to reach their targets. Within cells this requires crossing the cell membrane, and then free diffusion, distribution, and availability. Here, we explored the in-cell diffusion rates and distribution of a series of small molecular fluorescent drugs, in comparison to proteins, by microscopy and fluorescence recovery after photobleaching (FRAP). While all proteins diffused freely, we found a strong correlation between pKa and the intracellular diffusion and distribution of small molecule drugs. Weakly basic, small-molecule drugs displayed lower fractional recovery after photobleaching and 10- to-20-fold slower diffusion rates in cells than in aqueous solutions. As, more than half of pharmaceutical drugs are weakly basic, they, are protonated in the cell cytoplasm. Protonation, facilitates the formation of membrane impermeable ionic form of the weak base small molecules. This results in ion trapping, further reducing diffusion rates of weakly basic small molecule drugs under macromolecular crowding conditions where other nonspecific interactions become more relevant and dominant. Our imaging studies showed that acidic organelles, particularly the lysosome, captured these molecules. Surprisingly, blocking lysosomal import only slightly increased diffusion rates and fractional recovery. Conversely, blocking protonation by N-acetylated analogues, greatly enhanced their diffusion and fractional recovery after FRAP. Based on these results, N-acetylation of small molecule drugs may improve the intracellular availability and distribution of weakly basic, small molecule drugs within cells.

Keywords: biochemistry; chemical biology; diffusion; human; in-cell; lysosome; physics of living systems; small molecule drugs

DOI: https://doi.org/10.7554/eLife.97255

JACC Basic Transl Sci. 2024 Nov;9(11): 1287-1304

Deubiquitinase USP25 Alleviates Obesity-Induced Cardiac Remodeling and Dysfunction by Downregulating TAK1 and Reducing TAK1-Mediated Inflammation.

Bozhi Ye, Yanghao Chen, Xudong Chen, Diyun Xu, Yucheng Jiang, Wante Lin, Danhong Fang, Jiachen Xu, Jibo Han, Xue Han, Xiaohong Long, Wei Wang, Hao Zhou, Gaojun Wu, Guang Liang.

Deubiquitinating enzymes play a vital role in cardiovascular diseases. This study found that cardiomyocyte ubiquitin-specific protease 25 (USP25) expression was downregulated both in myocardial tissue of obesity cardiomyopathy and palmitic acid-stimulated cardiomyocytes. USP25 deficiency exacerbated high-fat diet-induced ventricular remodeling in mice, whereas overexpression of USP25 in cardiomyocytes reversed this pathological phenotype. Mechanistically, USP25 directly binds to TAK1 and P62, and the 178-cysteine of USP25 removes the K63 ubiquitin chain from P62, which promotes the degradation of TAK1 through the autophagy-lysosome pathway, thereby ameliorating obesity-induced ventricular remodeling by reducing inflammation through the TAK1-MAPK pathway. This finding identifies USP25 as a potential therapeutic target for obesity cardiomyopathy.

Keywords: TAK1; USP25; deubiquitinating enzyme; inflammation; obesity cardiomyopathy

DOI: https://doi.org/10.1016/j.jacbts.2024.06.001

Cardiovasc Diabetol. 2024 Dec 04. 23(1): 430

SGLT2 inhibitor downregulates ANGPTL4 to mitigate pathological aging of cardiomyocytes induced by type 2 diabetes.

Yun Wen, Xiaofang Zhang, Han Liu, Haowen Ye, Ruxin Wang, Caixia Ma, Tianqi Duo, Jiaxin Wang, Xian Yang, Meixin Yu, Ying Wang, Liangyan Wu, Yongting Zhao, Lihong Wang.

BACKGROUND: Senescence is recognized as a principal risk factor for cardiovascular diseases, with a significant association between the senescence of cardiomyocytes and inferior cardiac function. Furthermore, type 2 diabetes exacerbates this aging process. Sodium-glucose co-transporter 2 inhibitor (SGLT2i) has well-established cardiovascular benefits and, in recent years, has been posited to possess anti-aging properties. However, there are no reported data on their improvement of cardiomyocytes function through the alleviation of aging. Consequently, our study aims to investigate the mechanism by which SGLT2i exerts anti-aging and protective effects at the cardiac level through its action on the FOXO1-ANGPTL4 pathway.
METHODS: To elucidate the underlying functions and mechanisms, we established both in vivo and in vitro disease models, utilizing mice with diabetic cardiomyopathy (DCM) induced by type 2 diabetes mellitus (T2DM) through high-fat diet combined with streptozotocin (STZ) administration, and AC16 human cardiomyocyte cell subjected to stimulation with high glucose (HG) and palmitic acid (PA). These models were employed to assess the changes in the senescence phenotype of cardiomyocytes and cardiac function following treatment with SGLT2i. Concurrently, we identified ANGPTL4, a key factor contributing to senescence in DCM, using RNA sequencing (RNA-seq) technology and bioinformatics methods. We further clarified ANGPTL4 role in promoting pathological aging of cardiomyocytes induced by hyperglycemia and hyperlipidemia through knockdown and overexpression of the factor, as well as analyzed the impact of SGLT2i intervention on ANGPTL4 expression. Additionally, we utilized chromatin immunoprecipitation followed by quantitative real-time PCR (ChIP-qPCR) to confirm that FOXO1 is essential for the transcriptional activation of ANGPTL4.
RESULTS: The therapeutic intervention with SGLT2i alleviated the senescence phenotype in cardiomyocytes of the DCM mouse model constructed by high-fat feeding combined with STZ, as well as in the AC16 model stimulated by HG and PA, while also improving cardiac function in DCM mice. We observed that the knockdown of ANGPTL4, a key senescence-promoting factor in DCM identified through RNA-seq technology and bioinformatics, mitigated the senescence of cardiomyocytes, whereas overexpression of ANGPTL4 exacerbated it. Moreover, SGLT2i improved the senescence phenotype by suppressing the overexpression of ANGPTL4. In fact, we discovered that SGLT2i exert their effects by regulating the upstream transcription factor FOXO1 of ANGPTL4. Under conditions of hyperglycemia and hyperlipidemia, compared to the control group without FOXO1, the overexpression of FOXO1 in conjunction with SGLT2i intervention significantly reduced both ANGPTL4 mRNA and protein levels. This suggests that the FOXO1-ANGPTL4 axis may be a potential target for the cardioprotective effects of SGLT2i.
CONCLUSIONS: Collectively, our study demonstrates that SGLT2i ameliorate the pathological aging of cardiomyocytes induced by a high glucose and high fat metabolic milieu by regulating the interaction between FOXO1 and ANGPTL4, thereby suppressing the transcriptional synthesis of the latter, and consequently restoring cardiac function.

Keywords: ANGPTL4; Cellular senescence; Diabetic cardiomyopathy; FOXO1; SGLT2i

DOI: https://doi.org/10.1186/s12933-024-02520-8

Cancer Cell Int. 2024 Dec 03. 24(1): 394

Lysosomal gene ATP6AP1 promotes doxorubicin resistance via up-regulating autophagic flux in breast cancer.

Yinjiao Fei, Xueqin Yan, Mingxing Liang, Shu Zhou, Di Xu, Lei Li, Weilin Xu, Yuxin Song, Zhen Zhu, Jian Zhang.

BACKGROUND: Breast cancer remains the most prevalent malignancy in women. Chemotherapy is the primary systemic treatment modality, and the effectiveness of treatment is often hampered by chemoresistance. Autophagy has been implicated in promoting chemoresistance, as elevated autophagic flux supports tumor cell survival under therapeutic stress. Since lysosomes are essential for the completion of autophagy, their role in autophagy-related chemoresistance has been insufficiently studied. This study aims to elucidate the role of the lysosomal gene ATP6AP1 in promoting chemoresistance in breast cancer by upregulating autophagic flux.
METHODS: Doxorubicin-induced cell death was assessed by cytotoxicity, flow cytometry, lactate dehydrogenase (LDH) release assays in various breast cancer cell lines. Autophagic flux was assessed with western blot and the mRFP-GFP-LC3 fluorescence imaging. Breast cancer cells were infected with shRNA lentivirus targeting ATP6AP1, allowing investigation its tole in doxorubicin-induced cell death. ATP6AP1 expression and its association with prognosis were evaluated using public databases and immunohistochemistry.
RESULTS: Doxorubicin-induced cell death in breast cancer cells is negatively correlated with increased autophagic flux and lysosomal acidification. The lysosomal gene ATP6AP1, which plays a role in autophagic processes, is upregulated in breast cancer tissues. Knocking down ATP6AP1 reduces autophagy-mediated doxorubicin resistance by inhibiting autophagic flux and lysosomal acidification in breast cancer cells. Data analysis from public databases and our cohort indicate that elevated ATP6AP1 expression correlates with poor response to doxorubicin-based neoadjuvant chemotherapy (NAC) and worse prognosis.
CONCLUSIONS: Doxorubicin-induced cytotoxicity is associated with autophagy flux in breast cancer. The lysosomal gene ATP6AP1 facilitates autolysosome acidification and contributes to doxorubicin resistance in breast cancer.

Keywords: ATP6AP1; Autophagy; Breast cancer; Chemoresistance; Doxorubicin

DOI: https://doi.org/10.1186/s12935-024-03579-9