Tudor-SN promotes cardiomyocyte proliferation and neonatal heart regeneration through regulating the phosphorylation of YAP.

BACKGROUND: The neonatal mammalian heart exhibits considerable regenerative potential following injury through cardiomyocyte proliferation, whereas mature cardiomyocytes withdraw from the cell cycle and lose regenerative capacities. Therefore, investigating the mechanisms underlying neonatal cardiomyocyte proliferation and regeneration is crucial for unlocking the regenerative potential of adult mammalian heart to repair damage and restore contractile function following myocardial injury. METHODS: The Tudor staphylococcal nuclease (Tudor-SN) transgenic (TG) or cardiomyocyte-specific knockout mice (Myh6-Tudor-SN -/-) were generated to investigate the role of Tudor-SN in cardiomyocyte proliferation and heart regeneration following apical resection (AR) surgery. Primary cardiomyocytes isolated from neonatal mice were used to assess the influence of Tudor-SN on cardiomyocyte proliferation in vitro. Affinity purification and mass spectrometry were employed to elucidate the underlying mechanism. H9c2 cells and mouse myocardia with either overexpression or knockout of Tudor-SN were utilized to assess its impact on the phosphorylation of Yes-associated protein (YAP), both in vitro and in vivo. RESULTS: We previously identified Tudor-SN as a cell cycle regulator that is highly expressed in neonatal mice myocardia but downregulated in adults. Our present study demonstrates that sustained expression of Tudor-SN promotes and prolongs the proliferation of neonatal cardiomyocytes, improves cardiac function, and enhances the ability to repair the left ventricular apex resection in neonatal mice. Consistently, cardiomyocyte-specific knockout of Tudor-SN impairs cardiac function and retards recovery after injury. Tudor-SN associates with YAP, which plays important roles in heart development and regeneration, inhibiting phosphorylation at Ser 127 and Ser 397 residues by preventing the association between Large Tumor Suppressor 1 (LATS1) and YAP, correspondingly maintaining stability and promoting nuclear translocation of YAP to enhance the proliferation-related genes transcription. CONCLUSION: Tudor-SN regulates the phosphorylation of YAP, consequently enhancing and prolonging neonatal cardiomyocyte proliferation under physiological conditions and promoting neonatal heart regeneration after injury.

Xiaoyao Pill Improves the Affective Dysregulation of Sleep-deprived Female Mice by Inhibiting Brain Injury and Regulating the Content of Monoamine Neurotransmitter.

BACKGROUND: Sleep curtailment is a serious problem in many societies. Clinical evidence has shown that sleep deprivation is associated with mood dysregulation, formation of false memory, cardio-metabolic risk factors and outcomes, inflammatory disease risk, and all-cause mortality. The affective disorder dysregulation caused by insufficient sleep has become an increasingly serious health problem. However, to date, not much attention has been paid to the mild affective dysregulation caused by insufficient sleep, and there is no clear and standard therapeutic method to treat it. The Xiaoyao Pill is a classic Chinese medicinal formula, with the effect of dispersing stagnated hepatoqi, invigorating the spleen, and nourishing the blood. Therefore, it is most commonly used to treat gynecological diseases in China. In the present study, the effects of the Xiaoyao Pill on affective dysregulation of sleep-deprived mice and its underlying molecular mechanisms were investigated. METHODS: Forty adult female mice were used in the present study. The sleep deprivation model was established by improving the multi-platform water environment method. After 7 consecutive days of sleep deprivation, the mice were administrated low (LXYP, 0.32mg/kg) and high (HXYP, 0.64 mg/kg) doses of the Xiaoyao Pill for two weeks. Then, the body weight, behavioral deficits, and histopathology were evaluated. Meanwhile, the expression of c-fos protein and the concentrations of monoamine neurotransmitters in the hippocampus and prefrontal cortex were determined after two weeks of treatment. RESULTS: Xiaoyao Pill treatment significantly increased body weight and sucrose consumption and decreased the irritability scores of the sleep-deprived mice. Meanwhile, Xiaoyao Pill treatment prevented brain injury and inhibited the expression of c-fos protein in the hippocampus and prefrontal cortex. In addition, HXYP treatment significantly upregulated the levels of NE in the hippocampus and prefrontal cortex (p < 0.01). LXYP treatment significantly up-regulated the levels of 5-HT in the prefrontal cortex. Meanwhile, both HXYP and LXYP treatment significantly upregulated the levels of DA in the prefrontal cortex (p < 0.05 or p < 0.01) of sleep-deprived mice. CONCLUSION: The present study demonstrates that Xiaoyao Pill treatment prevented the behavioral deficits of mice induced by sleep deprivation by promoting the recovery of brain tissue injury and up-regulating the levels of NE, 5-HT, and DA in the brain tissue.

Translation of Tudor-SN, a novel terminal oligo-pyrimidine (TOP) mRNA, is regulated by the mTORC1 pathway in cardiomyocytes.

The mechanisms that regulate cell-cycle arrest of cardiomyocytes during heart development are largely unknown. We have previously identified Tudor staphylococcal nuclease (Tudor-SN) as a cell-cycle regulator and have shown that its expression level was closely related to cell-proliferation capacity. Herein, we found that Tudor-SN was highly expressed in neonatal mouse myocardia, but it was lowly expressed in that of adults. Using Data Base of Transcription Start Sites (DBTSS), we revealed that Tudor-SN was a terminal oligo-pyrimidine (TOP) mRNA. We further confirmed that the translational efficiency of Tudor-SN mRNA was controlled by the mammalian target of rapamycin complex 1 (mTORC1) pathway, as revealed via inhibition of activated mTORC1 in primary neonatal mouse cardiomyocytes and activation of silenced mTORC1 in adult mouse myocardia; additionally, this result was recapitulated in H9c2 cells. We also demonstrated that the downregulation of Tudor-SN in adult myocardia was due to inactivation of the mTORC1 pathway to ensure that heart growth was in proportion to that of the rest of the body. Moreover, we revealed that Tudor-SN participated in the mTORC1-mediated regulation of cardiomyocytic proliferation, which further elucidated the correlation between Tudor-SN and the mTORC1 pathway. Taken together, our findings suggest that the translational efficiency of Tudor-SN is regulated by the mTORC1 pathway in myocardia and that Tudor-SN is involved in mTORC1-mediated regulation of cardiomyocytic proliferation and cardiac development.