Low-dose tributyltin triggers human chondrocyte senescence and mouse articular cartilage aging.

Tributyltin (TBT) is known as an endocrine-disrupting chemical. This study investigated the effects and possible mechanisms of TBT exposure on inducing human articular chondrocyte senescence in vitro at the human-relevant concentrations of 0.01-0.5 µM and mouse articular cartilage aging in vivo at the doses of 5 and 25 µg/kg/day, which were 5 times lower than the established no observed adverse effect level (NOAEL) and equal to NOAEL, respectively. TBT significantly increased the senescence-associated ß-galactosidase activity and the protein expression levels of senescence markers p16, p53, and p21 in chondrocytes. TBT induced the protein phosphorylation of both p38 and JNK mitogen-activated protein kinases in which the JNK signaling was a main pathway to be involved in TBT-induced chondrocyte senescence. The phosphorylation of both ataxia-telangiectasia mutated (ATM) and histone protein H2AX (termed γH2AX) was also significantly increased in TBT-treated chondrocytes. ATM inhibitor significantly inhibited the protein expression levels of γH2AX, phosphorylated p38, phosphorylated JNK, p16, p53, and p21. TBT significantly stimulated the mRNA expression of senescence-associated secretory phenotype (SASP)-related factors, including IL-1ß, TGF-ß, TNF-α, ICAM-1, CCL2, and MMP13, and the protein expression of GATA4 and phosphorylated NF-κB-p65 in chondrocytes. Furthermore, TBT by oral gavage for 4 weeks in mice significantly enhanced the articular cartilage aging and abrasion. The protein expression of phosphorylated p38, phosphorylated JNK, GATA4, and phosphorylated NF-κB-p65, and the mRNA expression of SASP-related factors were enhanced in the mouse cartilages. These results suggest that TBT exposure can trigger human chondrocyte senescence in vitro and accelerating mouse articular cartilage aging in vivo.

Protective Effects of Nootkatone on Renal Inflammation, Apoptosis, and Fibrosis in a Unilateral Ureteral Obstructive Mouse Model.

Nootkatone is one of the major active ingredients of Alpiniae oxyphyllae, which has been used as both food and medicinal plants for the treatment of diarrhea, ulceration, and enuresis. In this study, we aimed to investigate whether nootkatone treatment ameliorated the progression of chronic kidney diseases (CKD) and clarified its underlying mechanisms in an obstructive nephropathy (unilateral ureteral obstructive; UUO) mouse model. Our results revealed that nootkatone treatment preventively decreased the pathological changes and significantly mitigated the collagen deposition as well as the protein expression of fibrotic markers. Nootkatone could also alleviate oxidative stress-induced injury, inflammatory cell infiltration, and renal cell apoptotic death in the kidneys of UUO mice. These results demonstrated for the first time that nootkatone protected against the progression of CKD in a UUO mouse model. It may serve as a potential therapeutic candidate for CKD intervention.

Withaferin A protects against endoplasmic reticulum stress-associated apoptosis, inflammation, and fibrosis in the kidney of a mouse model of unilateral ureteral obstruction.

BACKGROUND: Withaferin A is a functional ingredient of a traditional medicinal plant, Withania somnifera, which has been broadly used in India for protecting against chronic diseases. This bioactive steroidal lactone possesses multiple functions such as anti-oxidation, anti-inflammation, and immunomodulation. Chronic kidney disease (CKD) is one of the major health problems worldwide with the high complication, morbidity, and mortality rates. The detailed effects and underlying mechanisms of withaferin A on CKD progression still remain to be clarified. PURPOSE: We aimed to investigate whether withaferin A treatment ameliorates the development of renal fibrosis and its related mechanisms in a CKD mouse model. METHODS: A mouse model of unilateral ureteral obstruction (UUO) was used to mimic the progression of CKD. Male adult C57BL/6J mice were orally administered with 3 mg/kg/day withaferin A for 14 consecutive days after UUO surgery. Candesartan (5 mg/kg/day) was used as a positive control. RESULTS: Both Withaferin A and candesartan treatments significantly ameliorated the histopathological changes and collagen deposition in the UUO kidneys. Withaferin A could significantly reverse the increases in the protein levels of pro-fibrotic factors (fibronectin, transforming growth factor-ß, and α-smooth muscle actin), inflammatory signaling molecules (phosphorylated nuclear factor-κB-p65, interleukin-1ß, and cyclooxygenase-2), and cleaved caspase-3, apoptosis, and infiltration of neutrophils in the UUO kidneys. The protein levels of endoplasmic reticulum (ER) stress-associated molecules (GRP78, GRP94, ATF4, CHOP, phosphorylated eIF2α, and cleaved caspase 12) were increased in the kidneys of UUO mice, which could be significantly reversed by withaferin A treatment. CONCLUSION: Withaferin A protects against the CKD progression that is, at least in part, associated with the moderation of ER stress-related apoptosis, inflammation, and fibrosis in the kidneys of CKD. Withaferin A may serve as a potential therapeutic agent for the development of CKD.

Arsenic induces human chondrocyte senescence and accelerates rat articular cartilage aging.

Arsenic-contaminated drinking water is known to be a serious human health problem. A previous epidemiological study has indicated that arsenic levels in blood were higher in arthritis patients compared to age-matched control subjects. Bone is known as an important arsenic store compartment in the body. Arsenic exposure has been suggested to promote senescence in human mesenchymal stem cells that may affect the balance of adipogenic and osteogenic differentiation. The toxicological effect and mechanism of arsenic exposure on articular chondrocytes still remain unclear. Here, we investigated the arsenic-induced senescence in cultured human articular chondrocytes and long-term arsenic-exposed rat articular cartilage. Arsenic trioxide (As2O3; 1-5 µM) significantly induced senescence in human articular chondrocytes by increasing senescence-associated ß-galactosidase (SA-ß-Gal) activity and protein expression of p16, p53, and p21. Arsenic induced the phosphorylation of p38 and c-Jun N-terminal kinase (JNK) proteins. The inhibitors of p38 and JNK significantly reversed the arsenic-induced chondrocyte senescence. Arsenic could also trigger the induction of GATA4-NF-κB signaling and senescence-associated secretory phenotype (SASP) by increasing IL-1α, IL-1ß, TGF-ß, TNF-α, CCL2, PAI-1, and MMP13 mRNA expression. The increased cartilage senescence and abrasion were also observed in a rat model long-term treatment with arsenic (0.05 and 0.5 ppm) in drinking water for 36 weeks as compared to age-matched control rats. The phosphorylation of p38 and JNK and the induction of GATA4-NF-κB signaling and SASP were enhanced in the rat cartilages. Taken together, these findings suggest that arsenic exposure is capable of inducing chondrocyte senescence and accelerating rat articular cartilage aging and abrasion.

Low Intensity Pulsed Ultrasound Prevents Recurrent Ischemic Stroke in a Cerebral Ischemia/Reperfusion Injury Mouse Model via Brain-derived Neurotrophic Factor Induction.

The incidence of stroke recurrence is still higher despite the advanced progression of therapeutic treatment and medical technology. Low intensity pulsed ultrasound (LIPUS) has been demonstrated to possess therapeutic effects on neuronal diseases and stroke via brain-derived neurotrophic factor (BDNF) induction. In this study, we hypothesized that LIPUS treatment possessed therapeutic benefits for the improvement of stroke recurrence. Adult male C57BL/6J mice were subjected to a middle cerebral artery occlusion (MCAO) surgery and then followed to secondary MCAO surgery as a stroke recurrence occurred after nine days from the first MCAO. LIPUS was administered continuously for nine days before secondary MCAO. LIPUS treatment not only decreased the mortality but also significantly moderated neuronal function injury including neurological score, motor activity, and brain pathological score in the recurrent stroke mice. Furthermore, the administration of LIPUS attenuated the apoptotic neuronal cells and increased Bax/Bcl-2 protein expression ratio and accelerated the expression of BDNF in the brain of the recurrent stroke mice. Taken together, these results demonstrate for the first time that LIPUS treatment arouses the expression of BDNF and possesses a therapeutic benefit for the improvement of stroke recurrence in a mouse model. The neuroprotective potential of LIPUS may provide a useful strategy for the prevention of a recurrent stroke.

Methylmercury exposure induces ROS/Akt inactivation-triggered endoplasmic reticulum stress-regulated neuronal cell apoptosis.

Epidemiological studies have positively linked mercury exposure and neurodegenerative diseases (ND). Methylmercury (MeHg), an organic form of mercury, is a ubiquitous and potent environmental neurotoxicant that easily crosses the blood-brain barrier and causes irreversible injury to the central nervous system (CNS). However, the molecular mechanisms underlying MeHg-induced neurotoxicity remain unclear. Here, the present study found that Neuro-2a cells underwent apoptosis in response to MeHg (1-5 µM), which was accompanied by increased phosphatidylserine (PS) exposure on the outer cellular membrane leaflets, caspase-3 activity, and the activation of caspase cascades and poly (ADP-ribose) polymerase (PARP). Exposure of Neuro-2a cells to MeHg also triggered endoplasmic reticulum (ER) stress, which was identified via several key molecules (including: glucose-regulated protein (GRP)78, GRP94, C/EBP homologous protein (CHOP) X-box binding protein(XBP)-1, protein kinase R-like ER kinase (PERK), eukaryotic initiation factor 2α (eIF2α), inositol-requiring enzyme(IRE)-1, activation transcription factor(AFT)4, and ATF6. Transfection with GRP78-, GRP94-, CHOP-, and XBP-1-specific small interfering (si)RNA significantly suppressed the expression of these proteins, and attenuated cytotoxicity and caspase-12, -7, and -3 activation in MeHg-exposed cells. Furthermore, MeHg dramatically decreased Akt phosphorylation, and the overexpression of activation of Akt1 (myr-Akt1) could significantly prevent MeHg-induced Akt inactivation, as well as apoptotic and ER stress-related signals. Pretreatment with the antioxidant N-acetylcysteine (NAC) effectively prevented MeHg-induced neuronal cell reactive oxygen species (ROS) generation, apoptotic and ER stress-related signals, and Akt inactivation. Collectively, these results indicate that MeHg exerts its cytotoxicity in neurons by inducing ROS-mediated Akt inactivation up-regulated ER stress, which induces apoptosis and ultimately leads to cell death.