Oxidative Stress-induced Senescence Research Articles

Niacinamide Down-Regulates the Expression of DKK-1 and Protects Cells from Oxidative Stress in Cultured Human Dermal Papilla Cells.

PurposeAn increasing number of people are suffering from hair loss disorders. Niacinamide has long been used as an active ingredient for anti-hair loss preparations but the exact mechanism has not been clearly elucidated yet. The effects of niacinamide were investigated in cultured human dermal papilla cells (hDPCs).MethodsTo investigate the anti-hair loss effect of niacinamide and its molecular mechanisms, Western blot analysis, ELISA, quantitative RT-PCR and immunocytochemistry were performed. To study the protective effects of niacinamide against H2O2-induced oxidative stress, ROS generation and cytotoxicity were evaluated by DCF-DA assay and LDH release assay, respectively. Minoxidil was used as a positive control.ResultsNiacinamide decreased the protein expression level of DKK-1 which promotes regression of hair follicles by inducing catagen. The protein expression levels of cell senescence markers, p21 (CDKN1A) and p16 (CDKN2A) which are related to cell cycle arrest, were decreased. The expression of versican was increased by niacinamide treatment in cultured hDPCs. We have found that niacinamide decreased the H2O2-induced intracellular ROS production in cultured hDPCs. Moreover, niacinamide decreased the protein expression levels of H2O2-induced p21 and p16 and diminished the secretion of H2O2-induced DKK-1.ConclusionOur data demonstrate that niacinamide could enhance hair growth by preventing oxidative stress-induced cell senescence and premature catagen entry of hair follicles.

Effect of Agrobacterium co-cultivation stage on explant response for subsequent genetic transformation in Soybean (Glycine max (L.) Merr.)

The establishment of an efficient in vitro genetic transformation protocol in soybean depends upon an effective interaction between the explants and Agrobacterium tumefaciens. Therefore, a study was conducted at the University of Limpopo, South Africa, between September 2019 and May 2020 to evaluate explant amenability and effects of Agrobacterium co-cultivation stage on the induction of oxidative stress. This stress potentially causes lipid peroxidation, reduction of phytochemicals and chlorophyll pigments on explant tissue targeted for genetic transformation. This study, used double cotyledonary node explants infected and co-cultured with A. tumefaciens to evaluate total phenolics, antioxidant activity, lipid peroxidation and oxidative stress-induced tissue senescence during the co-cultivation stage. The results, showed that, explant co-cultivation with Agrobacterium for 2, 4 and 6 days caused reductions in the amounts of phenolic compounds, chlorophylls and antioxidant activity due to tissue senescence, high oxidative stress and malondialdehyde contents. Percentage phenolic content of all bacteria infected explants ranged between 10.3?10.6 compared to 20.9% in the control. Chlorophyll content of about 1.49?4.00 mg/ml and malondialdehyde content ranging between 1.0?5.7 mM-1g-1 were also recorded. Overall, findings suggest that the infection of explants with A. tumefaciens can induce oxidative stress and tissue senescence depending on the period of co-cultivation. However, reduced oxidative stress and senescence of explant tissues may potentially improve soybean shoot regeneration and transformation efficiency.

Role of Aberrantly Activated Lysophosphatidic Acid Receptor 1 Signaling Mediated Inflammation in Renal Aging.

The increasing load of senescent cells is a source of aging, and chronic inflammation plays a pivotal role in cellular senescence. In addition, senescent renal tubular epithelial cells are closely associated with renal aging. Lysophosphatidic acid (LPA) is a bioactive lipid mainly produced by the catalytic action of autotaxin (ATX), and its ligation to LPA receptor-1 (LPAR1) is associated with chronic inflammation and renal fibrosis; however, its role in renal aging is unclear. Male 2-, 12-, and 24-month-old C57BL/6 mice and Human renal proximal tubular epithelial cells (HRPTEpiC) were used in the present study. DNA damage and oxidative stress-induced senescence were simulated using doxorubicin (DOXO) and H2O2, respectively. The aged kidney showed decreased renal function, increased fractional mesangial area, and tubulointerstitial fibrosis. Both aged kidney and senescent cells showed increased levels of LPAR1, Nuclear factor κB (NF-κB), and inflammatory cytokines. In addition, LPAR1-knockdown reduced NF-κB and subsequent inflammatory cytokine induction, and NF-κB-knockdown resulted in decreased LPAR1 expression. Our study revealed a positive feedback loop between LPAR1 and NF-κB, which reinforces the role of inflammatory response, suggesting that blocking of aberrantly activated LPAR1 may reduce excessive inflammation, thereby providing a new possible therapeutic strategy to attenuate renal aging.

1α,25-Dihydroxyvitamin D3 promotes angiogenesis by alleviating AGEs-induced autophagy

Diabetes mellitus (DM) induces abnormal angiogenesis and results in multiple chronic vascular complications. Previous studies showed that advanced glycation end products (AGEs) up-regulated in diabetic patients and induced a series of cellular effects such as oxidative stress, inflammation, and autophagy. 1α,25-Dihydroxyvitamin D3 (1,25D), a hormonal form of vitamin D, proved to be beneficial for vascular diseases. However, the underlying mechanism of 1,25D in angiogenesis in DM remains unclear. Using CCK8 assay and transwell assay, we found that 1,25D could partly ameliorate impaired proliferation and migration ability of endothelial cells (ECs) induced by AGEs (200 μg/mL). Furthermore, tube formation assay, Western blot, and real-time qPCR assay were conducted to demonstrate that AGEs impaired angiogenetic ability, and that angiogenesis-related gene expression (i.e., VEGFA, VEGFB, VEGFR1, VEGFR2, TGFβ1, MMP2, MMP9) in ECs and 1,25D could promote angiogenesis and angiogenetic markers expression. By using DCFH-DA, ELISA, and Western blot assay, we also found that AGEs-induced oxidative stress impaired angiogenic ability of ECs, and 1,25D alleviated angiogenesis dysfunction by inhibiting oxidative stress. Of note, AGEs-induced excessive autophagy was found to impair angiogenesis. We elucidated that the detrimental autophagy is modulated by 1,25D and AGEs via PI3K/Akt pathway. Observed together, our findings illustrated that AGEs-induced oxidative stress and autophagy resulted in angiogenic disorder and 1,25D improved angiogenesis by restraining excessive autophagy and oxidative stress, providing a novel insight for the treatment of vascular complications in DM.

Dietary Nucleotides Retard Oxidative Stress-Induced Senescence of Human Umbilical Vein Endothelial Cells.

Several lines of evidence suggest an inhibitory role of dietary nucleotides (NTs) against oxidative stress and inflammation, which promote senescence in age-associated cardiovascular diseases. We sought to test whether the dietary NTs could retard the hydrogen peroxide (H2O2)-induced senescence of human umbilical vein endothelial cells (HUVECs) and to elucidate the efficiency of different NTs as well as the potential mechanism. Senescence was induced in HUVECs by 4 h exposure to 200 µM H2O2 and was confirmed using senescence-associated-β-galactosidase staining (SA-β-gal), cell viability, and Western blot analyses of p16INK4A and p21Waf1/Cip1 after 24 h administration of growth medium. We find that NTs retards oxidative stress-induced HUVECs senescence, as shown by a lower percentage of SA-β-gal-positive cells, lower expression of p16INK4A, and p21Waf1/Cip1 as well as higher cell viability. GMP100 was the most excellent in delaying HUVECs senescence, which was followed by the NTs mixture, NMN, CMP50, and UMP50/100, while AMP retards HUVECs senescence by specifically reducing p15INK4b expression. NTs all have significant anti-inflammatory effects; AMP and CMP were more prominent in restoring mitochondrial function, GMP and CMP were more competent at eliminating ROS and MDA, while AMP and UMP were more efficient at enhancing antioxidant enzyme activity. The role of the NTs mixture in retarding HUVECs senescence is full-scaled. These results stated that the mechanisms of NTs retarding HUVECs senescence could be related to its antioxidant and anti-inflammation properties promoting cell proliferation and protecting mitochondrial function activities.

Cacao powder supplementation attenuates oxidative stress, cholinergic impairment, and apoptosis in d-galactose-induced aging rat brain

Aging, a critical risk factor of several diseases, including neurodegenerative disorders, affects an ever-growing number of people. Cacao supplementation has been suggested to improve age-related neuronal deficits. Therefore, this study investigated the protective effects of raw cacao powder on oxidative stress-induced aging. Male Sprague–Dawley rats were divided into 4 groups: Control (C), d-galactose-induced aging (G), d-galactose injection with 10% (LC), and 16% (HC) cacao powder mixed diet. d-galactose (300 mg/3 mL/kg) was intraperitoneally injected into all but the control group for 12 weeks. Cacao supplemented diets were provided for 8 weeks. The levels of serum Malondialdehyde (MDA), Advanced Glycation End-products (AGEs), brain and liver MDA, the indicators of the d-galactose induced oxidative stress were significantly decreased in LC and HC but increased in G. The Acetylcholinesterase (AChE) activity of brain showed that the cholinergic impairment was significantly lower in LC, and HC than G. Furthermore, the expression levels of catalase (CAT), phospho-Akt/Akt, and procaspase-3 were significantly increased in LC and HC. In conclusion, cacao consumption attenuated the effects of oxidative stress, cholinergic impairment and apoptosis, indicating its potential in future clinical studies.

Protective Effects of Sal B on Oxidative Stress-Induced Aging by Regulating the Keap1/Nrf2 Signaling Pathway in Zebrafish.

The models of oxidative damage-induced aging were established by adding ethanol (C2H5OH), hydrogen peroxide (H2O2) and 6-hydroxydopamine (6-OHDA) to zebrafish embryos in this research. To find effective protective drugs/foods, Salvianolic acid B (Sal B) was added after the embryos were treated by these oxidative reagents. After being treated with ethanol, H2O2 and 6-OHDA, the morphological changes were obvious and the deformities included spinal curvature, heart bleeding, liver bleeding, yolk sac deformity and pericardial edema, and the expression of oxidative stress-related genes Nrf2b, sod1 and sod2 and aging-related genes myl2a and selenbp1 were significantly up-regulated compared to the control group. While after adding 0.05 μg/mL and 0.5 μg/mL Sal B to the ethanol-treated group, death rates and MDA levels decreased, the activity of antioxidant enzyme (SOD, CAT and GSH-Px) changed and Nrf2b, sod1, sod2, myl2a, selenbp1, p53 and p21 were down-regulated compared to the ethanol-treated group. The bioinformatics analysis also showed that oxidative stress-related factors were associated with a variety of cellular functions and physiological pathways. In conclusion, Sal B can protect against aging through regulating the Keap1/Nrf2 pathway as well as antioxidative genes and enzyme activity.

Oxidative stress-induced senescence in mature, post-mature and pathological placentas

Oxidative stress-induced senescence in mature, post-mature and pathological placentas

Metformin alleviates oxidative stress-induced senescence of human lens epithelial cells via AMPK activation and autophagic flux restoration.

Cataracts are the leading cause of blindness worldwide owing to the increasing proportion of elderly individuals in the population. The purpose of this study was to investigate whether metformin could alleviate the occurrence and development of age‐related cataract (ARC) and the underlying mechanism. In the present study, we established a senescence model induced by oxidative stress, which was confirmed by measuring β‐galactosidase activity, qRT‐PCR and Western blotting. In addition, we showed that metformin alleviated the oxidative stress‐induced senescence of HLE‐B3 cells via the activation of AMPK. Next, we provided evidence that oxidative stress impaired autophagic flux and induced lysosomal dysfunction. Subsequently, we found that metformin restored autophagic flux that had been impaired by oxidative stress by activating AMPK. Additionally, we found that metformin suppressed HLE‐B3 cell senescence by improving lysosomal function and inactivating mTOR. Furthermore, the inactivation of AMPK, impairment of autophagic flux and lysosomal dysfunction were observed in the human lens epithelium of ARC. In summary, our data suggest that the activation of AMPK may be a potential strategy for preventing ARC, and metformin may be an emerging candidate to alleviate the formation and development of ARC.

Licochalcone D Ameliorates Oxidative Stress-Induced Senescence via AMPK Activation.

Increased oxidative stress is a crucial factor for the progression of cellular senescence and aging. The present study aimed to investigate the effects of licochalcone D (Lico D) on oxidative stress-induced senescence, both in vitro and in vivo, and explore its potential mechanisms. Hydrogen peroxide (200 µM for double time) and D-galactose (D-Gal) (150 mg/kg) were used to induce oxidative stress in human bone marrow-mesenchymal stem cells (hBM-MSCs) and mice, respectively. We performed the SA-β-gal assay and evaluated the senescence markers, activation of AMPK, and autophagy. Lico D potentially reduced oxidative stress-induced senescence by upregulating AMPK-mediated activation of autophagy in hBM-MSCs. D-Gal treatment significantly increased the expression levels of senescence markers, such as p53 and p21, in the heart and hippocampal tissues, while this effect was reversed in the Lico D-treated animals. Furthermore, a significant increase in AMPK activation was observed in both tissues, while the activation of autophagy was only observed in the heart tissue. Interestingly, we found that Lico D significantly reduced the expression levels of the receptors for advanced glycation end products (RAGE) in the hippocampal tissue. Taken together, our findings highlight the antioxidant, anti-senescent, and cardioprotective effects of Lico D and suggest that the activation of AMPK and autophagy ameliorates the oxidative stress-induced senescence.

To study the effect of acute infrared radiation-induced alterations in human skin at cellular and molecular level using in vivo confocal Raman spectroscopy.

Solar radiations are classified in terms of wavelengths, including visible light, infrared, and ultraviolet. Infrared radiation (IR) accounts the largest proportion of solar radiations that cause oxidative stress-induced aging of human skin. This study investigates the biochemical changes in proteins, lipids, and DNA associated with acute exposure to IR radiations. In vivo confocal Raman spectroscopy was used to examine the forearms region of 20 healthy participants with phototype II skin, aged between 18 and 30years, without IR incidence (T0), with IR incidence 30minutes (T30) at day 1 and 30minutes at day 2 (T60). One-way ANOVA and two-tailed t test along with post hoc Bonferroni correction were used to detect the existence of significant differences in the timestamps of stratum corneum, stratum basale, and dermis at all IR wavenumbers under test. An increase in the Raman peaks of stratum corneum lipids, decrease in stratum basal DNA peaks, and a shift in the amide I peak of collagen in the skin dermis were observed. One-way ANOVA results showed significant differences among timestamps of stratum corneum, stratum basale, and dermis at all wavenumbers under test (P<.001). Furthermore, paired timestamps also showed significant differences (P<.016) except at two wavenumbers 1293cm-1 and 852cm-1 in stratum corneum and basale layer clusters on timestamps (T0 & T30 and T30 & T60, P>.016). This study proved that confocal Raman spectroscopy is an useful technique for early evaluation of IR-induced skin changes.

Luteolin inhibits H2O2-induced cellular senescence via modulation of SIRT1 and p53.

Luteolin, a sort of flavonoid, has been reported to be involved in neuroprotective function via suppression of neuroinflammation. In this study, we investigated the protective effect of luteolin against oxidative stress-induced cellular senescence and its molecular mechanism using hydrogen peroxide (H2O2)-induced cellular senescence model in House Ear Institute-Organ of Corti 1 cells (HEI-OC1). Our results showed that luteolin attenuated senescent phenotypes including alterations of morphology, cell proliferation, senescence-associated β-galactosidase expression, DNA damage, as well as related molecules expression such as p53 and p21 in the oxidant challenged model. Interestingly, we found that luteolin induces expression of sirtuin 1 in dose- and time-dependent manners and it has protective role against H2O2-induced cellular senescence by upregulation of sirtuin 1 (SIRT1). In contrast, the inhibitory effect of luteolin on cellular senescence under oxidative stress was abolished by silencing of SIRT1. This study indicates that luteolin effectively protects against oxidative stress-induced cellular senescence through p53 and SIRT1. These results suggest that luteolin possesses therapeutic potentials against age-related hearing loss that are induced by oxidative stress.

Oxidative stress-induced senescence mediates inflammatory and fibrotic phenotypes in fibroblasts from systemic sclerosis patients.

SSc is an autoimmune connective tissue disorder characterized by inflammation and fibrosis. Although constitutive activation of fibroblasts is proposed to be responsible for the fibrotic and inflammatory features of the disease, the underlying mechanism remains elusive, and effective therapeutic targets are still lacking. The aim of this study was to evaluate the role of oxidative stress-induced senescence and its contribution to the pro-fibrotic and pro-inflammatory phenotypes of fibroblasts from SSc patients. Dermal fibroblasts were isolated from SSc (n = 13) and healthy (n = 10) donors. Fibroblasts' intracellular and mitochondrial reactive oxygen species (ROS) were determined by flow cytometry. Mitochondrial function was measured by Seahorse XF24 analyser. Fibrotic and inflammatory gene expressions were assessed by qPCR and key pro-inflammatory components of the fibroblasts' secretome (IL-6 and IL-8) were quantified by ELISA. Compared with healthy fibroblasts, SSc fibroblasts displayed higher levels of both intracellular and mitochondrial ROS. Oxidative stress in SSc fibroblasts induced the expression of fibrotic genes and activated the TGF-β-activated kinase 1 (TAK1)-IκB kinase β (IKKβ)-IFN regulatory factor 5 (IRF5) inflammatory signalling cascade. These cellular responses paralleled the presence of a DNA damage response, a senescence-associated secretory phenotype and a fibrotic response. Treatment of SSc fibroblasts with ROS scavengers reduced their pro-inflammatory secretome production and fibrotic gene expression. Oxidative stress-induced cellular senescence in SSc fibroblasts underlies their pro-inflammatory and pro-fibrotic phenotypes. Targeting redox imbalance of SSc fibroblasts enhances their in vitro functions and could be of relevance for SSc therapy.

Outcomes of Deferoxamine Action on H2O2-Induced Growth Inhibition and Senescence Progression of Human Endometrial Stem Cells.

Mesenchymal stem cells (MSCs) are broadly applied in regenerative therapy to replace cells that are lost or impaired during disease. The low survival rate of MSCs after transplantation is one of the major limitations heavily influencing the success of the therapy. Unfavorable microenvironments with inflammation and oxidative stress in the damaged regions contribute to MSCs loss. Most of the strategies developed to overcome this obstacle are aimed to prevent stress-induced apoptosis, with little attention paid to senescence—another common stress reaction of MSCs. Here, we proposed the strategy to prevent oxidative stress-induced senescence of human endometrial stem cells (hMESCs) based on deferoxamine (DFO) application. DFO prevented DNA damage and stress-induced senescence of hMESCs, as evidenced by reduced levels of reactive oxygen species, lipofuscin, cyclin D1, decreased SA-β-Gal activity, and improved mitochondrial function. Additionally, DFO caused accumulation of HIF-1α, which may contribute to the survival of H2O2-treated cells. Importantly, cells that escaped senescence due to DFO preconditioning preserved all the properties of the initial hMESCs. Therefore, once protecting cells from oxidative damage, DFO did not alter further hMESCs functioning. The data obtained may become the important prerequisite for development of a new strategy in regenerative therapy based on MSCs preconditioning using DFO.

Laminar Shear Stress Protects Against Premature Endothelial Senescence by SIRT1-Dependent Mechanisms

PURPOSE:Accumulation of senescent endothelial cells (ECs) and development of vascular aging have been implicated in the etiology of vascular dysfunction and disease. Aerobic exercise has been recognized as the single most effective non-pharmacological anti-aging intervention via increased laminar shear stress (LSS). This study aimed to determine the protective effects of LSS against premature senescence and the underlying mechanism.METHODS: Carotid artery partial ligation surgery was performed on the left carotid arteries (LCAs) of C57BL/6J male mice to determine the effect of disturbed flow on the development of endothelial senescence. Senescence-associated β-galactosidase (SA-β-gal) staining was performed to measure cellular senescence. Expression levels of protein markers for cell senescence including p21, p16, and p53 were measured by western blotting.RESULTS: &lt;i&gt;En face&lt;/i&gt; SA-β-gal staining was identified only in the partially ligated LCAs of voluntary wheel-running mice, suggesting a direct relevance of LSS on the prevention of vascular senescence. In the &lt;i&gt;in vitro&lt;/i&gt; H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt;-induced premature senescence model, preconditioning of high-flow LSS (20 dyne/cm2, 36 hours) induced significant reduction in the percentage of SA-β-gal positive ECs. Expression of the molecular markers of cellular senescence such as p21, p16, and p53 was significantly decreased by LSS pretreatment. However, the protective effects of LSS against premature senescence were completely abolished by SIRT1 inhibition.CONCLUSIONS: The results suggest that high-flow LSS has protective effects against oxidative stress-induced premature endothelial senescence through a SIRT1-dependent mechanism.

Melatonin treatment delays postharvest senescence and maintains the organoleptic quality of ‘Newhall’ navel orange (Citrus sinensis (L.) Osbeck) by inhibiting respiration and enhancing antioxidant capacity

Melatonin can improve postharvest quality and strengthen resistance to oxidative stress-induced senescence of many horticultural products, however, the effects of melatonin on storage quality and physiological senescence of citrus fruit are still unclear. The objective of this study was to determine the effect of 200 μmol•L−1 melatonin on the organoleptic quality and antioxidant system of ‘Newhall’ navel orange stored under ambient conditions for 84 days post-harvest. Melatonin caused a significant decrease in respiration rate and weight loss rate, and increased in fruit firmness, total soluble solids, soluble sugar content, titratable acidity and Citrus Color Index (CCI) indicating inhibition of fruit quality deterioration. Melatonin treatment impeded the accumulation of hydrogen peroxide and malondialdehyde, suggesting an inhibition of reactive oxygen species (ROS) burst and oxidative damage. In addition, the application of melatonin enhanced ROS scavenging capacity by increasing the activity and expressions of catalase, superoxide dismutase, ascorbate peroxidase, glutathione reductase and by promoting the accumulation of ascorbate, reduced glutathione and total phenol. Moreover, the PCA (principal component analysis) demonstrated melatonin delayed postharvest senescence of orange fruit is associated with inhibition of postharvest respiration and stimulation of oxidant-defense system.

PTH Protects Osteocytes From Oxidative Stress and Cellular Senescence

Age-induced osteoporosis is characterized by a progressive decline in bone formation and increase in bone resorption with uncoupled activities of osteoblasts and osteoclasts. Parathyroid hormone (PTH) is used in the clinic to treat osteoporosis due to its anabolic actions on bone via binding to the PTH receptor (PPR). The receptor is highly expressed in cells of the osteoblastic lineage, including osteocytes. Osteocytes are the most abundant cells in bone and serve as a key regulator of bone remodeling. Despite the significant role of PPR signaling in skeletal homeostasis, its function in osteocytes during aging remains unclear. We have gathered preliminary data demonstrating that mice lacking PPR predominantly in osteocytes (Dmp1-PPRKO) have marked age-induced bone loss due to increased bone resorption and suppressed bone formation. These mice, with aging, develop characteristics of skeletal senescence: a decrease in osteoprogenitors and an increase in bone marrow adiposity and p16Ink4a/Cdkn2a expression in bone. Since senescence of cells in the bone microenvironment has been reported as a cause of age-induced bone loss, we hypothesized that PPR signaling protects osteocytes from senescence. To test this hypothesis, we generated osteocytes (Ocy454-12H), in which the PPR expression was ablated using CRISPR/Cas9 technique. Ocy454-12H-PPRKO and Ocy454-12H-PPRCtrl cells were treated with PTH followed by an exposure to hydrogen peroxide (H2O2). High levels of intracellular reactive oxygen species (ROS), including H2O2, promote protein and DNA oxidation, resulting in cell death and senescence. PTH treatment significantly suppressed the increase in H2O2-induced cell death, measured by resazurin-based assays, in PPRCtrl but not in PPRKO cells. We analyzed intracellular ROS levels using a fluorescent probe and found that PTH treatment significantly suppressed the increase in ROS upon H2O2 exposure, suggesting an antioxidant function of PTH in osteocytes. To further investigate if PTH prevents osteocytes from oxidative stress-induced senescence, we examined senescence-associated β-galactosidase (SA β-gal) activity in cells that were treated with PTH followed by an exposure to low doses of H2O2. Compared to untreated and PPRKO groups, treatment with PTH significantly decreased the number of SA β-gal positive cells, demonstrating that PPR signaling protects osteocytes, and possibly other osteoblastic cells, from H2O2-induced cellular senescence. PTH treatment reduced mRNA expression of p21/Cdkn1a. Taken together these results demonstrate that PPR signaling is important to protect osteocytes from cellular senescence.

Lithium inhibits oxidative stress-induced neuronal senescence through miR-34a.

Neuronal senescence, triggered by telomere shortening, oncogene activation, DNA damage, or oxidative stress, has been associated with neurodegenerative diseases' pathogenesis. Therefore, preventing neuronal senescence could be a novel treatment strategy for neurodegenerative diseases. Lithium (Li), the first-line treatment against bipolar disorder, has been shown to have neuroprotective effects in clinical, pre-clinical, and in vitro studies. Li can protect cells from senescence, and its effect on neuronal senescence was investigated in our study. Furthermore, we also investigated the effects of Li on the senescence-associated miR-34a/Sirt1/p53 pathway. In this study, hydrogen peroxide was used as an inducer for the "stress-induced premature senescence" model. In the senescence model, we have assessed Li's effects on senescence by analyzing β-galactosidase activity, Sudan Black B, and senescence-associated heterochromatin foci (SAHF) stainings, and on cell cycle arrest by BrdU staining. Furthermore, expression levels of senescence and cell cycle arrest-related proteins (p53, p21, p16INK4a, and SIRT1) by western blotting. Finally, the effects of Li on senescence-associated miR-34a levels were measured by quantitative PCR. We show via Sudan Black B staining, β-Gal activity assay, and by detecting SAHF, Li protects against senescence in neuronal cells. Then, Li's effect on signaling has also been determined on pathways involved in senescence and cell cycle arrest. Moreover, we have observed that Li has a modulatory effect on miR-34a expression. Therefore, we posit that Li suppresses senescence in neuronal cells and that this effect is mediated through miR-34a/Sirt1/p53 axis.

Senescence‐Associated Secretory Phenotype (SASP) factors down‐regulate glutamate transporter expression in human brainstem astrocytes through a paracrine fashion

Glia-neuron crosstalk in the brainstem is emerging as a critical player in the regulation of sympathetic nerve activity (SNA). Specifically, astrocytes modulate SNA by tightly regulating synaptic glutamate levels through transporter mediated re-uptake mechanisms. Pro-inflammatory mediators like TNFα have been shown to negatively affect glutamate transporter expression in astrocytes. Previous studies from our laboratory have provided evidence for oxidative stress-induced senescence and their secretory phenotype (SASP), a potential source of inflammation, in human brainstem astrocytes. Hence, in the present study we hypothesize that inflammatory mediators in SASP factors down-regulate glutamate re-uptake transporter expression in a paracrine manner. To test our hypothesis, we induced senescence in cultured human brainstem astrocytes with hydrogen peroxide (H2O2) treatment at a dose of 300 μM for 2 hours. Senescence induction was confirmed through PCR expression for senescence markers and SA-beta-gal staining 7 days after H2O2 treatment. Conditioned media collected from the senescent and control astrocytes were used to assess the paracrine effect of SASP factors on astrocytic glutamate transporter expression. Following 36 hours of treatment with conditioned media from senescent astrocytes, we observed a significant down-regulation of two of the major astrocytic glutamate re-uptake transporters, EAAT1 (GLAST-1) and EAAT2 (GLT-1) in human brainstem astrocytes. This suggests that soluble SASP factors in the secretome of senescent cells can alter the function of glutamate transporters in the astrocytes through a paracrine action. Increased activity of glutamatergic neurons in the rostral ventrolateral medulla due to reduced glutamate re-uptake at the synapse may be a possible glial mechanism underlying enhanced sympathoexcitation in obesity.

Hesperetin, a dietary flavonoid, inhibits AGEs-induced oxidative stress and inflammation in RAW264.7 cells

• Three typical structural derivatives of Naringenin were tested in this paper. • Hesperetin could significantly inhibit both AGEs-induced ROS production and inflammation. • Gene set enrichment analysis was performed and twenty-three key genes related were screened. Advanced glycation end products (AGEs) excessive accumulation in the body either by exogenous intake or endogenous formation makes individuals prone to oxidative stress and inflammation damage. In this study, DCFH-DA fluorescence test and qPCR experiment were carried out to study the effect of some dietary flavonoids on AGEs induced toxicity. Among four tested flavonoids, it was found that hesperetin could significantly inhibit both AGEs-induced ROS production and gene expressions of TNF-α, IL-1β, IL-6, MCP-1, COX-2 and iNOS. High-throughput transcriptome analysis showed that the protective effect of hesperetin against AGEs-induced toxicity might be attributed to inhibit the activation of MAPK, JAK, NF-κB-related pathways. Furthermore, gene set enrichment analysis was performed using the MSigDB database and twenty-three key genes related were screened. This study might provide new ideas for the prevention of AGEs-related diseases and lay a theoretical foundation for the application of dietary flavonoids.