The different functions of short and long thymic stromal lymphopoietin isoforms in autophagy-mediated asthmatic airway inflammation and remodeling

Asthma is a chronic respiratory disease characterized by airway inflammation and remodeling as well as hyper-responsiveness. Thymic stromal lymphopoietin (TSLP), which is a crucial inflammatory cytokine in immune homeostasis, consists of two isoforms, the long isoform lfTSLP and short isoform sfTSLP. The lfTSLP promotes inflammation and plays a pivotal role in asthma pathogenesis, while sfTSLP had been reported to have anti-asthma effects. Experiments have shown that lfTSLP could induce autophagy in hepatocytes. It is unknown whether lfTSLP or sfTSLP could influence autophagy and affect the progression of asthma. Using house dust mite (HDM)-stimulated airway smooth muscle cells as an in vitro model and HDM-induced asthma mice as in vivo model, we found that lfTSLP could induce autophagy and remodeling, while sfTSLP has the reverse effect. Strikingly, sfTSLP treatment in vivo reversed HDM-mediated activation of inflammation and airway remodeling, partly determined by autophagy change. These findings may help us understand the function of TSLP isoforms in the pathogenesis of asthma, and they support the use of drugs targeting sfTSLP and TSLP for asthma treatment.     

Cell death and autophagy in tuberculosis

Mycobacterium tuberculosis has succeeded in infecting one-third of the human race though inhibition or evasion of innate and adaptive immunity. The pathogen is a facultative intracellular parasite that uses the niche provided by mononuclear phagocytes for its advantage. Complex interactions determine whether the bacillus will or will not be delivered to acidified lysosomes, whether the host phagocyte will survive infection or die, and whether the timing and mode of cell death works to the advantage of the host or the pathogen. Here we discuss cell death and autophagy in TB. These fundamental processes of cell biology feature in all aspects of TB pathogenesis and may be exploited to the treatment or prevention of TB disease.     

High glucose-induced oxidative stress promotes autophagy through mitochondrial damage in rat notochordal cells

Purpose

Diabetes mellitus is associated with an increased risk of intervertebral disc degeneration (IDD). Reactive oxygen species (ROS), oxidative stressors, play a key role in autophagy of diabetes-associated diseases. Mitochondria are known to be the main source of endogenous ROS in most mammalian cell types. The authors therefore conducted the following study to evaluate the effects of high glucose concentrations on the induction of oxidative stress and autophagy through mitochondrial damage in rat notochordal cells.

Methods

Rat notochordal cells were isolated, cultured, and placed in either 10 % fetal bovine serum (normal control) or 10 % fetal bovine serum plus two different high glucose concentrations (0.1 M and 0.2 M) (experimental conditions) for one and three days, respectively. We identified and quantified the mitochondrial damage (mitochondrial transmembrane potential) and the generation of ROS and antioxidants (manganese superoxide dismutase [MnSOD] and catalase). We also investigated expressions and activities of autophagy markers (beclin-1, light chain3-I [LC3-I] and LC3-II, autophagy-related gene [Atg] 3, 5, 7, and 12).

Results

An enhanced disruption of mitochondrial transmembrane potential, which indicates mitochondrial damage, was identified in rat notochordal cells treated with both high glucose concentrations. Both high glucose concentrations increased production of ROS by rat notochordal cells in a dose- and time-dependent manner. The two high glucose solutions also enhanced rat notochordal cells’ compensatory expressions of MnSOD and catalase in a dose- and time-dependent manner. The proautophagic effects of high glucose concentrations were manifested in the form of enhanced rat notochordal cells’ expressions of beclin-1, LC3-II, Atg3, 5, 7, and 12 in a dose- and time-dependent manner. The ratio of LC3-II/LC3-I expression was also increased in a dose- and time-dependent manner.

Conclusions

The findings from this study demonstrate that high glucose-induced oxidative stress promotes autophagy through mitochondrial damage of rat notochordal cells in a dose- and time-dependent manner. These results suggest that preventing the generation of oxidative stress might be a novel therapeutic target by which to prevent or to delay IDD in patients with diabetes mellitus.     

Cervical Vagus Nerve Stimulation Improves Neurologic Outcome After Cardiac Arrest in Mice by Attenuating Oxidative Stress and Excessive Autophagy

BackgroundCerebral ischemia and reperfusion (I/R) induces oxidative stress and activates autophagy, leading to brain injury and neurologic deficits. Cervical vagus nerve stimulation (VNS) increases cerebral blood flow (CBF). In this study, we investigate the effect of VNS-induced CBF increase on neurologic outcomes after cardiac arrest (CA).Materials and MethodsA total of 40 male C57Bl/6 mice were subjected to ten minutes of asphyxia CA and randomized to vagus nerve isolation (VNI) or VNS treatment group. Eight mice received sham surgery and VNI. Immediately after resuscitation, 20 minutes of electrical stimulation (1 mA, 1 ms, and 10 Hz) was started in the VNS group. Electrocardiogram, blood pressure, and CBF were monitored. Neurologic and histologic outcomes were evaluated at 72 hours. Oxidative stress and autophagy were assessed at 3 hours and 24 hours after CA.ResultsBaseline characteristics were not different among groups. VNS mice had better behavioral performance (ie, open field, rotarod, and neurologic score) and less neuronal death (p < 0.05, vs VNI) in the hippocampus. CBF was significantly increased in VNS-treated mice at 20 minutes after return of spontaneous circulation (ROSC) (p < 0.05). Furthermore, levels of 8-hydroxy-2?-deoxyguanosine in the blood and autophagy-related proteins (ie, LC-3Ⅱ/Ⅰ, Beclin-1, and p62) in the brain were significantly decreased in VNS mice. Aconitase activity was also reduced, and the p-mTOR/mTOR ratio was increased in VNS mice.ConclusionsOxidative stress induced by global brain I/R following CA/ROSC leads to early excessive autophagy and impaired autophagic flux. VNS promoted CBF recovery, ameliorating these changes. Neurologic and histologic outcomes were also improved.     

Bromelain activates the AMP-activated protein kinase-autophagy pathway to alleviate hepatic lipid accumulation

Bromelain, a cysteine protease found in pineapple, is known to exert protective effects against non-alcoholic fatty liver disease (NAFLD); however, the underlying mechanism is unclear. In this study, we aimed to investigate the molecular mechanisms underlying the beneficial effects of bromelain using in vivo and in vitro models. C57BL/6 mice were fed a high-fat diet (HFD) with or without bromelain (20 mg/kg/day) for 12 weeks. We found that treatment with bromelain alleviated hepatic lipid accumulation accompanied by the activation of AMP-activated protein kinase (AMPK) and autophagy flux, as evidenced by the elevated levels of phosphorylated AMPK, ATG5, ATG7, LC3-II, and lysosome-associated membrane protein 2 (LAMP2), and the decreased levels of p62 in the liver of HFD-fed mice. In human hepatoma Huh 7 cells, bromelain prevented oleic acid (OA)-induced lipid accumulation and increased the levels of phosphorylated AMPK, ATG5, ATG7, LC3-II, and LAMP2 but decreased the levels of p62. Inhibition of AMPK and autophagy flux by specific inhibitors or small interfering RNAs suppressed bromelain-mediated protective effect on lipid accumulation. Moreover, inhibition of AMPK activity abolished the activation of autophagy flux in OA-treated hepatocytes. Collectively, these findings suggest a new molecular mechanism involving the AMPK-autophagy pathway through which bromelain confers protection against the deregulation of lipid metabolism in the liver.