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Background: Bone marrow mesenchymal stem cells (BMSCs) can undergo inadequate osteogenesis or excessive adipogenesis as they age due to changes in the bone microenvironment, ultimately resulting in decreased bone density and elevated risk of fractures in senile osteoporosis. This study aims to investigate the effects of osteocyte senescence on the bone microenvironment and its influence on BMSCs during aging. Results: Primary osteocytes were isolated from 2-month-old and 16-month-old mice to obtain young osteocyte-derived extracellular vesicles (YO-EVs) and senescent osteocyte-derived EVs (SO-EVs), respectively. YO-EVs were found to significantly increase alkaline phosphatase activity, mineralization deposition, and the expression of osteogenesis-related genes in BMSCs, while SO-EVs promoted BMSC adipogenesis. Neither YO-EVs nor SO-EVs exerted an effect on the osteoclastogenesis of primary macrophages/monocytes. Our constructed transgenic mice, designed to trace osteocyte-derived EV distribution, revealed abundant osteocyte-derived EVs embedded in the bone matrix. Moreover, mature osteoclasts were found to release osteocyte-derived EVs from bone slices, playing a pivotal role in regulating the functions of the surrounding culture medium. Following intravenous injection into young and elderly mouse models, YO-EVs demonstrated a significant enhancement of bone mass and biomechanical strength compared to SO-EVs. Immunostaining of bone sections revealed that YO-EV treatment augmented the number of osteoblasts on the bone surface, while SO-EV treatment promoted adipocyte formation in the bone marrow. Proteomics analysis of YO-EVs and SO-EVs showed that tropomyosin-1 (TPM1) was enriched in YO-EVs, which increased the matrix stiffness of BMSCs, consequently promoting osteogenesis. Specifically, the siRNA-mediated depletion of Tpm1 eliminated pro-osteogenic activity of YO-EVs both in vitro and in vivo. Conclusions: Our findings suggested that YO-EVs played a crucial role in maintaining the balance between bone resorption and formation, and their pro-osteogenic activity declining with aging. Therefore, YO-EVs and the delivered TPM1 hold potential as therapeutic targets for senile osteoporosis. [ABSTRACT FROM AUTHOR]

Background: Emerging evidence continues to highlight the significant role of microRNAs (miRNAs) in the regulation of cancer growth and metastasis. Herein, the current study aimed to elucidate the role of exosomal miR-183 in prostate cancer development. Methods: Initially, public microarray-based gene expression profiling of prostate cancer was employed to identify differentially expressed miRNAs. The putative target gene TPM1 of miR-183 was subsequently predicted, followed by the application of a luciferase reporter assay and examination of the expression patterns in prostate cancer patients and cell lines. The effects of miR-183 and TPM1 on processes such as cell proliferation, invasion and migration were evaluated using in vitro gain- and loss-of-function experiments. The effect of PC3 cells-derived exosomal miR-183 was validated in LNCaP cells. In vivo experiments were also performed to examine the effect of miR-183 on prostate tumor growth. Results: High expression of miR-183 accompanied with low expression of TPM1 was detected in prostate cancer. Our data indicated that miR-183 could target and downregulate TPM1, with the overexpression of miR-183 and exosomal miR-183 found to promote cell proliferation, migration, and invasion in prostate cancer. Furthermore, the tumor-promoting effect of exosome-mediated delivery of miR-183 was subsequently confirmed in a tumor xenograft model. Conclusions: Taken together, the key findings of our study demonstrate that prostate cancer cell-derived exosomal miR-183 enhance prostate cancer cell proliferation, invasion and migration via the downregulation of TPM1, highlighting a promising therapeutic target against prostate cancer. [ABSTRACT FROM AUTHOR]

Tropomyosin-1 (TPM1), a widely expressed actin-binding protein, is downregulated in many tumors and associated with cancer progression. A previous study from our group suggested that TPM1 could be involved in renal cell carcinoma (RCC) apoptosis, but the mechanisms and details remained unknown. The present study aimed to further examine the proapoptotic effects of TPM1 and investigate the underlying mechanisms in RCC cell lines. Results from cell viability, DAPI staining and apoptosis assays demonstrated that TPM1 upregulation inhibited cell proliferation and promoted cell apoptosis in both 786-O and ACHN RCC cell lines. However, TPM1 knockdown in the two RCC cell lines did not result in the opposite effects on cell proliferation or cell apoptosis. Comet assay and western blotting results demonstrated that TPM1 overexpression induced DNA damage and decreased the expression levels of the antiapoptotic factor BCL2 apoptosis regulator, while increasing the expression levels of the proapoptotic factors BCL2 associated X, Caspase-3 and p53 in 786-O and ACHN cells. The present findings suggest that TPM1 overexpression in RCC cell lines can induce tumor cell apoptosis via the p53-mediated mitochondrial pathway. Further studies are needed to fully elucidate the potential of TPM1 as a candidate for RCC targeted therapy in the future. [ABSTRACT FROM AUTHOR]

The incidence of Alzheimer's disease (AD) is higher in elderly women than in men. The molecular background of this gender-related risk, however, is largely unknown. In a previous proteomics study, we identified significantly elevated levels of monoamine oxidase-B and tropomyosin-1 in AD patients, together with significant changes of the genetic AD risk factors apolipoprotein E4 ( APOE4) and glutathione S-transferase omega 1 ( GSTO1) , in platelets - a promising source for AD blood biomarkers. The present study aimed to investigate the gender-specificity as well as the disease-stage dependency of these biomarkers in AD patients and those with mild cognitive impairment (MCI). Tropomyosin-1 and monoamine oxidase-B protein levels were quantified by 2-D DIGE and 1-D Western blotting. Here, for the first time, we revealed a significant increase of 38&39 kDa tropomyosin-1 protein levels in female but not male AD (+ 56%; p = 0.008) and MCI patients (+ 46%; p = 0.041) measured by 1-D WB. In contrast, levels of monoamine oxidase-B were, independently of gender, elevated in AD patients (+ 52%; p = 0.009) but unaltered in MCI compared to control subjects. Moreover, we confirmed that APOE4 -positive females are at a higher risk (OR = 18.7; p = 9.7E − 09) of developing AD compared to APOE4 -positive males (OR = 6.5; p = 5.9E − 04). No gender-related effects were observed for GSTO1 . Significance Platelet tropomyosin-1 constitutes a gender-related and stage-dependent protein in cognitive impairment. In contrast, platelet monoamine oxidase-B, frequently described to be increased in platelets and brains of AD patients, shows a gender-independent but stage-related increase since it is unaltered in MCI subjects. A blood biomarker test for this preceding stage of AD that considers gender-specificity is not yet available. The newly described AD-related platelet protein profiles might refine and facilitate routine diagnosis and enable early as well as tailored interventions. [ABSTRACT FROM AUTHOR]

The aim of the study was to estimate the effect of tropomyosin-1-based structural stabilization of F-actin in transformed human alveolar epithelial line H1299 cells subjected to high oxidative stress induced by cigaret smoke extract. We demonstrated here that cigaret smoke extract induces cell shrinking and detachment as a consequence of F-actin cytoskeleton degradation in H1299 cells not overexpressing tropomyosin-1. Furthermore, the treatment of these cells with cigaret smoke extract resulted in the loss of peripheral localization of ZO-1 and initiated apoptosis. In contrast, structural stabilization of F-actin, by overexpression of tropomyosin-1, preserved cell to cell interactions through the attenuation of cortical actin organization into thin fibers and thus protected these cells against oxidative stress-induced degradation of actin cytoskeleton and cell death. In conclusion, we suggest that structural stabilization of thin cortical F-actin fibers increases link between tight junctions proteins and actin cytoskeleton and thus protects H1299 cells against cigaret smoke extract. [ABSTRACT FROM AUTHOR]

Abstract: The aim of the study was to estimate the effect of cigarette smoke extract (CSE) on EA.hy926 endothelial cells in culture in the context of maintenance of cell–cell junctions through the structural stabilization of the actin cytoskeleton. In the present study, F-actin was stabilized by the overexpression of tropomyosin-1, which is known to stabilize actin filaments in muscle and non-muscle cells. Our study showed that the stabilization of F-actin significantly increased the survival of cells treated with 25% CSE. In addition, after stabilization of F-actin the migratory potential of EA.hy926 cells subjected to CSE treatment was increased. Our results also showed increased fluorescence intensity of alpha- and beta-catenin after CSE treatment in cells which had stabilized F-actin. Analysis of fluorescence intensity of Zonula occludens-1 did not reveal any significant differences when EA.hy926 cells overexpressing tropomyosin-1 were compared with those lacking overexpression. It would appear that overexpression of tropomyosin-1 preserved the structure of actin filaments in the cells treated with CSE. In conclusion, the present study demonstrates that stabilization of F-actin protects EA.hy926 cells against CSE-induced loss of both adherens and tight junctions. The data presented in this study suggest that overexpression of tropomyosin-1 stabilizes the organizational structure of actin filaments and helps preserve the endothelial barrier function under conditions of strong oxidative stress. [Copyright &y& Elsevier]

Endothelial cells are actively involved in regulating the exchanges between blood and tissues. This function is tightly dependent on actin cytoskeleton dynamics and is challenged by a wide variety of stimuli, including oxidative stress. In endothelial cells, oxidative stress quickly activates the extracellular-signal-regulated kinase (ERK) MAP kinase, which results in the phosphorylation of tropomyosin. Here, we investigated further the mechanisms of tropomyosin phosphorylation and its function in actin remodeling. We identified, for the first time, death-associated protein kinase 1 (DAP kinase 1) as the kinase that phosphorylates tropomyosin-1 in response to ERK activation by hydrogen peroxide (H2O2). We also report that the phosphorylation of tropomyosin-1 mediated by DAP kinase occurs on Ser283. Moreover, the expression of the pseudophosphorylated tropomyosin mutant Ser283Glu triggers by itself the formation of stress fibers in untreated cells, and the effect is maintained in H2O2-treated cells in which DAP kinase expression is knocked-down by siRNA. By contrast, the expression of the nonphosphorylatable tropomyosin mutant Ser283Ala is not associated with stress fibers and leads to membrane blebbing in response to H2O2. Our finding that tropomyosin-1 is phosphorylated downstream of ERK and DAP kinase and that it helps regulate the formation of stress fibers will aid understanding the role of this protein in regulating the endothelial functions associated with cytoskeletal remodeling. [ABSTRACT FROM AUTHOR]