Stromal Cell-Derived Factor 1 Protects Brain Vascular Endothelial Cells from Radiation-Induced Brain Damage

The Role of Sirtuin-1 (SIRT1) in the Physiology and Pathophysiology of the Human Placenta

Sirtuins, especially SIRT1, play a significant role in regulating inflammatory response, autophagy, and cell response to oxidative stress. Since their discovery, sirtuins have been regarded as anti-ageing and longevity-promoting enzymes. Sirtuin-regulated processes seem to participate in the most prevalent placental pathologies, such as pre-eclampsia. Furthermore, more and more research studies indicate that SIRT1 may prevent pre-eclampsia development or at least alleviate its manifestations. Having considered this, we reviewed recent studies on the role of sirtuins, especially SIRT1, in processes determining normal or abnormal development and functioning of the placenta.

Role of Orai3-Mediated Store-Operated Calcium Entry in Radiation-Induced Brain Microvascular Endothelial Cell Injury

Radiation-induced brain injury is a serious complication with complex pathogenesis that may accompany radiotherapy of head and neck tumors. Although studies have shown that calcium (Ca²⁺) signaling may be involved in the occurrence and development of radiation-induced brain injury, the underlying molecular mechanisms are not well understood. In this study, we used real-time quantitative polymerase chain reaction and Western blotting assays to verify our previous finding using next-generation sequencing that the mRNA and protein expression levels of Orai3 in rat brain microvascular endothelial cells (rBMECs) increased after X-ray irradiation. We next explored the role of Orai3 and Orai3-mediated store-operated Ca²⁺ entry (SOCE) in radiation-induced brain injury. Primary cultured rBMECs derived from wild-type and Orai3 knockout (Orai3^(-/-)) Sprague-Dawley rats were used for in vitro experiments. Orai3-mediated SOCE was significantly increased in rBMECs after X-ray irradiation. However, X-ray irradiation-induced SOCE increase was markedly reduced in Orai3 knockout rBMECs, and the percentage of BTP2 (a nonselective inhibitor of Orai channels)-inhibited SOCE was significantly decreased in Orai3 knockout rBMECs. Functional studies indicated that X-ray irradiation decreased rBMEC proliferation, migration, and tube formation (a model for assessing angiogenesis) but increased rBMEC apoptosis, all of which were ameliorated by BTP2. In addition, occurrences of all four functional deficits were suppressed in X-ray irradiation-exposed rBMECs derived from Orai3^(-/-) rats. Cerebrovascular damage caused by whole-brain X-ray irradiation was much less in Orai3^(-/-) rats than in wild-type rats. These findings provide evidence that Orai3-mediated SOCE plays an important role in radiation-induced rBMEC damage and brain injury and suggest that Orai3 may warrant development as a potential therapeutic target for reducing or preventing radiation-induced brain injury.

Allosteric Regulation of G-Protein-Coupled Receptors: From Diversity of Molecular Mechanisms to Multiple Allosteric Sites and Their Ligands

Allosteric regulation is critical for the functioning of G protein-coupled receptors (GPCRs) and their signaling pathways. Endogenous allosteric regulators of GPCRs are simple ions, various biomolecules, and protein components of GPCR signaling (G proteins and β-arrestins). The stability and functional activity of GPCR complexes is also due to multicenter allosteric interactions between protomers. The complexity of allosteric effects caused by numerous regulators differing in structure, availability, and mechanisms of action predetermines the multiplicity and different topology of allosteric sites in GPCRs. These sites can be localized in extracellular loops; inside the transmembrane tunnel and in its upper and lower vestibules; in cytoplasmic loops; and on the outer, membrane-contacting surface of the transmembrane domain. They are involved in the regulation of basal and orthosteric agonist-stimulated receptor activity, biased agonism, GPCR-complex formation, and endocytosis. They are targets for a large number of synthetic allosteric regulators and modulators, including those constructed using molecular docking. The review is devoted to the principles and mechanisms of GPCRs allosteric regulation, the multiplicity of allosteric sites and their topology, and the endogenous and synthetic allosteric regulators, including autoantibodies and pepducins. The allosteric regulation of chemokine receptors, proteinase-activated receptors, thyroid-stimulating and luteinizing hormone receptors, and beta-adrenergic receptors are described in more detail.

miR-301a Deficiency Attenuates the Macrophage Migration and Phagocytosis through YY1/CXCR4 Pathway

(1) Background: the miR-301a is well known involving the proliferation and migration of tumor cells. However, the role of miR-301a in the migration and phagocytosis of macrophages is still unclear. (2) Methods: sciatic nerve injury, liver injury models, as well as primary macrophage cultures were prepared from the miR-301a knockout (KO) and wild type (WT) mice to assess the macrophage's migration and phagocytosis capabilities. Targetscan database analysis, Western blotting, siRNA transfection, and CXCR4 inhibition or activation were performed to reveal miR301a's potential mechanism. (3) Results: the macrophage's migration and phagocytosis were significantly attenuated by the miR-301a KO both in vivo and in vitro. MiR-301a can target Yin-Yang 1 (YY1), and miR-301a KO resulted in YY1 up-regulation and CXCR4 (YY1's down-stream molecule) down-regulation. siYY1 increased the expression of CXCR4 and enhanced migration and phagocytosis in KO macrophages. Meanwhile, a CXCR4 inhibitor or agonist could attenuate or accelerate, respectively, the macrophage migration and phagocytosis. (4) Conclusions: current findings indicated that miR-301a plays important roles in a macrophage's capabilities of migration and phagocytosis through the YY1/CXCR4 pathway. Hence, miR-301a might be a promising therapeutic candidate for inflammatory diseases by adjusting macrophage bio-functions.

SIRT1: A Novel Protective Molecule in Pre-eclampsia

Pre-eclampsia is a severe pregnant complication, mainly characterized by insufficient trophoblast invasion, impaired uterine spiral artery remodeling, placental hypoxia and ischemia, and endothelial dysfunction. However, the potential mechanisms of pre-eclampsia remain unclear. SIRT1 is a NAD+-dependent deacetylase, involving in multiple biological processes, including energy metabolism, oxidative stress, inflammatory response, and cellular autophagy. Several studies showed that SIRT1 might play a vital role in the pathogenesis of pre-eclampsia. In this review, we aim to integrate the latest research on SIRT1 and pre-eclampsia to explore the comprehensive mechanisms of SIRT1 in pre-eclampsia. More specifically, SIRT1 might affect placental development and trophoblast invasion through autophagy and senescence in pre-eclampsia, and SIRT1 protects vascular endothelial cells from oxidative stress, inflammatory response, autophagy, and senescence. Furthermore, SIRT1 deficiency mice showed typical pre-eclampsia-like performances, which can be reversed via direct SIRT1 supplement or SIRT1 agonist treatment. Additionally, resveratrol, a SIRT1 agonist, attenuates vascular endothelial injury and placental dysfunction, and exerts protective effect on decreasing blood pressure. In this review, we provide new insights into the development of pre-eclampsia, which can establish a theoretical basis for prevention and treatment for pre-eclampsia. Besides, we also propose questions that still need to be further addressed in order to elucidate the comprehensive molecular mechanisms of pre-eclampsia in the future.

Inorganic nitrate alleviates irradiation-induced salivary gland damage by inhibiting pyroptosis

Over 80% of patients undergoing radiotherapy (RT) for head and neck cancer (HNC) suffer reduced saliva secretion and dry mouth symptoms due to salivary gland damage. Although therapeutic interventions to alleviate such RT-induced damage are available, long-term hypofunction remains a significant issue. Therefore, novel therapeutic solutions to prevent irradiation (IR)-induced salivary gland damage are required. This study explored the protective effect of inorganic nitrate in preventing IR-induced salivary gland injury via pyroptosis suppression, both in vivo and in vitro. In the treatment group, C57BL/6 mice were pretreated with 2 mmol/L NaNO₃ supplied in drinking water one week before a single-dose of 15 Gy IR in the submandibular gland (SMG) region. Human vein endothelial cells (HUVECs) and mice SMG cells were treated with 10 μmol/L or 100 μmol/L NaNO₃ 2 h before a single-dose of 8 Gy IR. In vivo, IR-induced decreased saliva flow rate and body weight loss could be alleviated by nitrate supplementation. Nitrate prevented acinar and microvascular endothelial cell loss. Moreover, nitrate improved mitochondrial function and significantly decreased pyroptosis-related indexes. In vitro, nitrate supplementation reduced reactive oxygen species (ROS) generation by preserving mitochondrial homeostasis to inhibit NLPR3 inflammasome-mediated pyroptosis both in HUVECs and SMG cells. Nitrate showed potential as an oral protective agent to prevent IR-induced salivary gland damage; prospective insight into the underlying molecular mechanisms is presented.

Research progress on mechanism and imaging of temporal lobe injury induced by radiotherapy for head and neck cancer

Radiotherapy (RT) is an effective treatment for head and neck cancer (HNC). Radiation-induced temporal lobe injury (TLI) is a serious complication of RT. Late symptoms of radiation-induced TLI are irreversible and manifest as memory loss, cognitive impairment, and even temporal lobe necrosis (TLN). It is currently believed that the mechanism of radiation-induced TLI involves microvascular injury, neuron and neural stem cell injury, glial cell damage, inflammation, and the production of free radicals. Significant RT-related structural changes and dose-dependent changes in gray matter (GM) and white matter (WM) volume and morphology were observed through computed tomography (CT) and magnetic resonance imaging (MRI) which were common imaging assessment tools. Diffusion tensor imaging (DTI), dispersion kurtosis imaging (DKI), susceptibility-weighted imaging (SWI), resting-state functional magnetic resonance (rs-fMRI), magnetic resonance spectroscopy (MRS), and positron emission tomography (PET) can be used for early diagnosis and prognosis evaluation according to functional, molecular, and cellular processes of TLI. Early diagnosis of TLI is helpful to reduce the incidence of TLN and its related complications. This review summarizes the clinical features, mechanisms, and imaging of radiation-induced TLI in HNC patients. KEY POINTS: • Radiation-induced temporal lobe injury (TLI) is a clinical complication and its symptoms mainly include memory impairment, headache, and cognitive impairment. • The mechanisms of TLI include microvascular injury, cell injury, and inflammatory and free radical injury. Significant RT-related structural changes and dose-dependent changes in TL volume and morphology were observed through CT and MRI. • SWI, MRS, DTI, and DKI and other imaging examinations can detect anatomical and functional, molecular, and cellular changes of TLI.

Stem-Cell Therapy as a Potential Strategy for Radiation-Induced Brain Injury

Radiation therapy is a standard and effective non-surgical treatment for primary brain tumors and metastases. However, this strategy inevitably results in damage of normal brain tissue, causing severe complications, especially the late-delayed cognitive impairment. Due to the multifactorial and complex pathological effects of radiation, there is a lack of effective preventative and restorative treatments for the irradiated brain. Stem-cell therapy has held considerable promise for decades in the treatment of central nervous system (CNS) disorders because of its unique capacity for tissue repair and functional integrity. Currently, there is growing interest in using stem cells as a novel option to attenuate the adverse effects of irradiation. In the present review, we discuss recent studies evaluating stem-cell therapies for the irradiated brain and their therapeutic effects on ameliorating radiation-related brain injury as well as their potential challenges in clinical applications. We discuss these works in context of the pathogenesis of radiation-induced injury to CNS tissue in an attempt to elucidate the potential mechanisms of engrafted stem cells to reverse radiation-induced degenerative processes.

MiR-217 promotes endothelial cell senescence through the SIRT1/p53 signaling pathway

Studies have shown that miR-217 can induce cell senescence, but its mechanism of action in vascular endothelial cell senescence is less reported. Therefore, this study aimed to investigate how miR-217 plays a role in endothelial cell senescence. Human umbilical vein endothelial cells (HUVECs) were used to replicate the aging model, and the population doubling levels (PDLs) during cell passage were counted. Senescence-associated β-galactosidase (SA-β-gal) staining, Real-time quantitative PCR (RT-qPCR), MTT assay, Transwell, and tube formation were used to detect the effects of miR-217 on young and senescent HUVECs. Targetscan7.2 and luciferase assay predicted and verified the relationship between miR-217 and the target gene, and the expression of silent information regulator 1 (SIRT1) and p53 was detected by RT-qPCR and western blot. In addition, SA-β-gal staining detected the effects of miR-217 inhibitor and SIRT1 on senescent HUVECs. MiR-217 was upregulated in senescent endothelial cells. Overexpression of miR-217 promoted the increase of SA-β-gal positive cells, and inhibited proliferation, migration and angiogenesis during endothelial cell growth. Furthermore, SIRT1 was a target gene of miR-217. Simultaneous silencing of SIRT1 reversed the effect of miR-217 inhibitor on the reduction of SA-β-gal positive-staining cells. Our data suggest that overexpression of miR-217 promoted vascular endothelial cell senescence by targeting the SIRT1/p53 signaling pathway, which may provide a new basis for studying the mechanism of action in vascular endothelial cell senescence.

Medical prevention and treatment of radiation-induced carotid injury

Radiotherapy has significantly improved the survival of cancer patients but is also associated with several adversities, including radiation-induced carotid injury (RICI). The RICI mechanisms are complex, including vessel inflammatory injury, carotid atherosclerosis, intimal proliferation, media necrosis, and peri-adventitial fibrosis. The main manifestation and adverse consequence of RICI is carotid artery stenosis (CAS), which can lead to stroke and transient ischemic attack. Currently, carotid artery injury is primarily diagnosed via color-coded duplex sonography. Early detection of traumatic changes in the carotid artery depends on measurements of carotid intima-media thickness; serum biomarker testing also shows great potential. CAS is mainly treated with carotid endarterectomy or carotid angioplasty and stent implantation. Notably, bone marrow mesenchymal stem cells are advantageous in RICI treatment and reduce carotid inflammation, oxidative stress, and delaying atherosclerosis. This review summarizes the mechanisms, examination methods, and latest treatments for RICI to provide data for its clinical prevention and treatment.