Inhibiting ATG5 mediated autophagy to regulate endoplasmic reticulum stress and CD4+ T lymphocyte differentiation: Mechanisms of acupuncture's effects on asthma

OBJECTIVE

Asthma is characterized by airway hyperresponsiveness(AHR), inflammation and remodeling. Autophagy and endoplasmic reticulum stress(ERS) are dysregulated in asthma, and ATG5 has attracted wide attentions a representative gene of autophagy. Previous evidence shows that acupuncture may treat asthma by regulating the immune environment.However,the precise mechanism involved in acupuncture's effects on asthma is unclear. Thus, we investigated the inner-relationships of acupuncture and ATG5-mediated autophagy, ERS and CD4+ T lymphocyte differentiation in asthma.

METHODS

Ovalbumin (OVA)-sensitized and challenged ATG5+/- and ATG5-/-mice with asthma were treated by acupuncture at Dazhui(GV14),Feishu(BL13) and Zusanli(ST36),and sacrificed the next day.Then blood and bronchoalveolar lavage fluid (BALF)samples were collected to determine inflammatory cell counts and cytokine levels. Lung tissue samples were obtained for histological examination, and the spleen was harvested for flow cytometry.

RESULTS

Compared with the untreated group, acupuncture decreased BALF inflammatory cell counts and AHR in OVA-induced mice.Acupuncture decreased autophagy-related protein and mRNA (ATG5,Beclin-1,p62 and LC3B)amounts and ERS-related protein (p-PERK, p-IRE-1,Grp78, and ATF6)levels as well as autophagosome formation in lung tissue, concomitant with increased IFN-γ and decreased IL-4, IL-17 and TGF-β amounts in BALF.Consistently, the imbalance of CD4+ T lymphocyte subsets(Th1/Th2 and Treg/Th17) was also corrected by acupuncture.Meanwhile, AHR and inflammation were decreased in ATG5-/- mice compared with ATG+/-animals,without affecting the therapeutic effect of acupuncture.

CONCLUSION

Acupuncture reduces airway inflammation and AHR in asthma by inhibiting ATG5-mediated autophagy to regulate endoplasmic reticulum stress and CD4+T lymphocyte differentiation.

Autophagy regulates long-term cross-presentation by murine dendritic cells

Autophagy has been reported to be involved in supporting antigen cross-presentation by dendritic cells (DCs). We have shown that DCs have the ability to store antigen for a prolonged time in endolysosomal compartments and thereby sustain MHCI antigen cross-presentation to CD8+ T cells. In the current study, we investigated the role of autophagy in long-term antigen presentation. We show that the autophagy machinery has a negative impact on storage of antigen in DCs. Atg5-/- DCs which are deficient in autophagy or DCs treated with common autophagy inhibitors showed enhanced antigen storage and antigen cross-presentation. This augmented antigen cross-presentation effect is independent of altered proteasome enzyme activity or MHCI surface expression on DCs. We visualized that the storage compartments are in close proximity to LC3 positive autophagosomes. Our results indicate that autophagosomes disrupt antigen storage in DCs and thereby regulate long-term MHCI cross-presentation.

Grass carp ATG5 and ATG12 promote autophagy but down-regulate the transcriptional expression levels of IFN-I signaling pathway

Autophagy is an essential and conserved process that plays an important role in physiological homeostasis, adaptive response to stress and the immune response. Autophagy-related proteins (ATGs) are key components of the autophagic machinery. In the study, grass carp (Ctenopharyngodon idella) autophagy-related gene 5 (ATG5) and 12 (ATG12) were identified. In the gill and intestine, ATG5 and ATG12 were highly expressed, but after grass carp reovirus (GCRV) infection, they were decreased significantly. In Ctenopharyngodon idella kidney (CIK) cells, the sharp variation of ATG5 and ATG12 expression was observed after poly(I:C) infection. Subcellular localisation showed that ATG5 and ATG12 were evenly distributed in the cytoplasm and nucleus. However, the interaction between ATG5 and ATG12 was only found in cytoplasm in both 293T cells and CIK cells. In addition, the overexpression of ATG5 or ATG12 in 293T cells showed enhanced autophagy, and autophagic process was facilitated when ATG5 and ATG12 were simultaneously overexpressed. Dual-luciferase activity assay indicated that both ATG5 and ATG12 remarkably suppressed the promoter activity of IRF3, IRF7, and IFN-I. Further, ATG5 and ATG12 conjugate showed far stronger inhibitory affection on the expression of IFN-I than either ATG5 or ATG12 in response to poly(I:C) or GCRV infection. Taken together, the results demonstrate that grass carp ATG5 and ATG12 play an important role in innate immunity and autophagy.

Gene-gene interaction of ATG5, ATG7, BLK and BANK1 in systemic lupus erythematosus

AIM

Autophagy-related gene 5 (ATG5), ATG7, B-lymphoid tyrosine kinase (BLK) and B-cell scaffold protein with ankyrin repeats 1 (BANK1) are involved in B-cell signaling; several genome-wide association studies detected these genes as candidates involved in systemic lupus erythematosus (SLE). We aimed to replicate the association of these genes with SLE in Chinese Han and to search for possible gene-gene interactions.

METHODS

TaqMan single-nucleotide polymorphism (SNP) genotyping was used to detect rs548234, rs665791 in ATG5, rs11706903 in ATG7, rs2736340 in BLK and rs10516487 in BANK1 in 382 SLE patients and 660 healthy controls. The epistasis effect was analyzed by logistic regression, multifactor dimensionality reduction (MDR) and linear regression analysis.

RESULTS

SLE was associated with frequency of rs548234 (P = 0.010; odds ratio [OR] = 1.298), rs2736340 (P = 2.47 × 10-5 ; OR = 1.574) and rs10516487 (P = 0.002; OR = 0.642). Although no epistasis effects were found among three autophagy-related gene loci or with rs2736340 and rs10516487, BLK and BANK1 had the closest interaction effect on logistic regression analysis (P = 0.013; OR = 1.205), MDR (P < 0.0001), and linear regression analysis (P = 0.0017; R2 = 0.1806). The risk genotype TT of rs2736340 was associated with decreased messenger RNA level of BLK; BLK transcript level was lower in SLE patients than healthy controls.

CONCLUSION

We confirmed the association of rs548234, rs2736340 and rs10516487 with SLE in Chinese Han and reinforced our hypothesis of their epistasis effect in regulating B-cell signaling in SLE.

Fusobacterium nucleatum-Induced Impairment of Autophagic Flux Enhances the Expression of Proinflammatory Cytokines via ROS in Caco-2 Cells

Fusobacterium nucleatum (F. nucleatum) plays a critical role in gastrointestinal inflammation. However, the exact mechanism by which F. nucleatum contributes to inflammation is unclear. In the present study, it was revealed that F. nucleatum could induce the production of proinflammatory cytokines (IL-8, IL-1β and TNF-α) and reactive oxygen species (ROS) in Caco-2 colorectal) adenocarcinoma cells. Furthermore, ROS scavengers (NAC or Tiron) could decrease the production of proinflammatory cytokines during F. nucleatum infection. In addition, we observed that autophagy is impaired in Caco-2 cells after F. nucleatum infection. The production of proinflammatory cytokines and ROS induced by F. nucleatum was enhanced with either autophagy pharmacologic inhibitors (3-methyladenine, bafilomycin A1) or RNA interference in essential autophagy genes (ATG5 or ATG12) in Caco-2 cells. Taken together, these results indicate that F. nucleatum-induced impairment of autophagic flux enhances the expression of proinflammatory cytokines via ROS in Caco-2 Cells.