Vitamin D3-VDR-PTPN6 axis mediated autophagy contributes to the inhibition of macrophage foam cell formation.

Macrophage derived foam cells in atherosclerotic plaques are the major factor responsible for the pathogenesis of atherosclerosis (AS). During advanced AS, macrophage-specific macroautophagy/autophagy is dysfunctional. 1, 25-dihydroxy vitamin D3 (VitD3) and its receptor VDR (vitamin D receptor) are reported to inhibit foam cell formation and induce autophagy; however, the role of VitD3-VDR-induced autophagy and foam cell formation in AS has not been explored. Here we find that VitD3 significantly recovered oxidized low-density lipoprotein-impaired autophagy, as well as increased autophagy-mediated lipid breakdown in mouse bone marrow-derived macrophages and human monocyte-derived macrophages, thus inhibiting the conversion of macrophages into foam cells. Importantly, VitD3 functions through its receptor VDR to upregulate autophagy and attenuate the accumulation of lipids in macrophages. Moreover, this study is the first occasion to report the interesting link between VitD3 signaling and PTPN6/SHP-1 (protein tyrosine phosphatase non-receptor type 6) in macrophages. VitD3-induced autophagy was abrogated in the presence of the PTPN6/Ptpn6 shRNA or inhibitor. VDR along with RXRA (retinoid X receptor alpha), and NCOA1 (nuclear receptor coactivator 1), are recruited to a specific response element located on the gene promoter and induce PTPN6 expression. PTPN6 contributes to VitD3-mediated autophagy by regulating autophagy-related genes via activation of MAPK1 (mitogen-activated protein kinase 1) and CEBPB (CCAAT enhancer binding protein beta). Furthermore, expression of PTPN6 is also crucial for VitD3-mediated inhibition of macrophage foam cell formation through autophagy. Thus, VitD3-VDR-PTPN6 axis-regulated autophagy attenuates foam cell formation in macrophages.

BECN2 (beclin 2)-mediated non-canonical autophagy in innate immune signaling and tumor development.

BECN2 (beclin 2) is a newly identified mammalian-specific macroautophagy/autophagy family member, and plays a critical role in the control of obesity and insulin sensitivity. However, its role in innate immune signaling and inflammation remains elusive. In our recent study, we show that BECN2 functions as a negative regulator in innate immune signaling and tumor development through non-canonical autophagy. Loss of Becn2 causes splenomegaly, lymphadenopathy, elevated proinflammatory cytokine production and spontaneous lymphoma development in mice. Mechanistically, BECN2 mediates the degradation of MAP3K7/TAK1 and MAP3K3/MEKK3 through an ATG9A- and ULK1-dependent but ATG16L1-BECN1-MAP1LC3B/LC3B-independent autophagy pathway to control systemic inflammation. BECN2 interacts with MAP3K7 and MAP3K3 through the engagement of ATG9A+ vesicles upon ULK1 activation, and promotes the fusion of MAP3K3- or MAP3K7-associated ATG9A+ vesicles with phagophores for subsequent degradation. Our findings have identified a previously unrecognized role of BECN2 in innate immune signaling and tumor development through non-canonical autophagy, thus providing a potential target for inflammatory disease and cancer therapy.

miR-141-5p regulate ATF2 via effecting MAPK1/ERK2 signaling to promote preeclampsia.

OBJECTIVE: Preeclampsia is a pregnancy-specific syndrome characterized by hypertension and proteinuria. Impaired trophoblast invasion partly modulated by abnormal MAPK1/ERK2 signaling played important roles in the pathological process of preeclampsia. The objective of this study is to investigate miR-141-5p regulate ATF2 via effecting MAPK1/ERK2 signaling to promote preeclampsia. STUDY DESIGN: The maternal placentae and clinical data of 30 patients with preeclampsia and 30 healthy pregnant women were collected in the Second Hospital of Shanxi Medical University from July 2015 to April 2016. Transcriptional levels of miR-141-5p in placentae were monitored using quantitative real-time reverse transcription-polymerase chain reaction. The target gene of miR-141-5p was analyzed with "TargetScanHuman Release 7.2″. To evaluate the pathways of this response, MAPK1 and ERK1/2 in placentae were detected using immunohistochemistry and Western Blot. Transfection experiment was used to verify the function of miR-141-5p regulating ATF2 to effect MAPK1/ERK2 signaling in JEG-3 cells. RESULTS: miR-141-5p was significantly down-regulated in placentae of patients with preeclampsia, in comparison to the healthy pregnant women groups. There was no difference in MAPK1 expression between placentae of patients with preeclampsia and healthy pregnant women groups. While p-MAPK1 expression was lower in preeclampsia placentae, in comparison to the healthy pregnant women groups. Moreover, inhibition and activation experiments also validate the function of miR-141-5p in effecting p-MAPK1 level in JEG-3 cells. Bioinformatic analysis identified that ATF2 was a target gene of miR-141-5p, which was one DNA-binding protein to effect phosphatase DUSP1 transcription. DUSP1 effect MAPK1/ERK2 signaling in preeclampsia. CONCLUSION: miR-141-5p up-regulated transcription factor ATF2 to promote phosphatase DUSP1 expression. DUSP1 expression reduces p-MAPK1 and ERK1/2 expression to promote preeclampsia.

RIPK1 regulates survival of human melanoma cells upon endoplasmic reticulum stress through autophagy.

Although RIPK1 (receptor [TNFRSF]-interacting protein kinase 1) is emerging as a critical determinant of cell fate in response to cellular stress resulting from activation of death receptors and DNA damage, its potential role in cell response to endoplasmic reticulum (ER) stress remains undefined. Here we report that RIPK1 functions as an important prosurvival mechanism in melanoma cells undergoing pharmacological ER stress induced by tunicamycin (TM) or thapsigargin (TG) through activation of autophagy. While treatment with TM or TG upregulated RIPK1 and triggered autophagy in melanoma cells, knockdown of RIPK1 inhibited autophagy and rendered the cells sensitive to killing by TM or TG, recapitulating the effect of inhibition of autophagy. Consistently, overexpression of RIPK1 enhanced induction of autophagy and conferred resistance of melanoma cells to TM- or TG-induced cell death. Activation of MAPK8/JNK1 or MAPK9/JNK2, which phosphorylated BCL2L11/BIM leading to its dissociation from BECN1/Beclin 1, was involved in TM- or TG-induced, RIPK1-mediated activation of autophagy; whereas, activation of the transcription factor HSF1 (heat shock factor protein 1) downstream of the ERN1/IRE1-XBP1 axis of the unfolded protein response was responsible for the increase in RIPK1 in melanoma cells undergoing pharmacological ER stress. Collectively, these results identify upregulation of RIPK1 as an important resistance mechanism of melanoma cells to TM- or TG-induced ER stress by protecting against cell death through activation of autophagy, and suggest that targeting the autophagy-activating mechanism of RIPK1 may be a useful strategy to enhance sensitivity of melanoma cells to therapeutic agents that induce ER stress.

LC3 as a potential therapeutic target in hypoxia-induced pulmonary hypertension.

Recent research suggests that microtubule-associated protein 1 light chain 3B (LC3B) confers protection against hypoxia-induced pulmonary hypertension (HPH) by inhibiting proliferation of pulmonary artery (PA) wall cells. We recently demonstrated that 17ß-estradiol (E2), a sex hormone with known protective properties in HPH, increases lung LC3-II expression in chronically hypoxic male Sprague-Dawley rats. Stimulatory E2 effects on LC3-II were recapitulated in isolated hypoxic (1% O 2 for 48 h), but not room air-exposed primary rat PA endothelial cells (PAECs), and were accompanied by hypoxia-specific inhibitory effects on other parameters involved in proproliferative signaling (MAPK3/ERK1-MAPK1/ERK2 activation, VEGF secretion), as well as inhibitory effects on PAEC proliferation. Taken together, these results suggest that E2 mediates hypoxia-specific antiproliferative effects in PAECs, and that stimulation of autophagy may be one of the underlying mechanisms of E2-mediated protection in HPH. Viewed in the context of previously published data, these results indicate that LC3 1) exerts protective effects in the pathogenesis of HPH, and 2) may represent a potential target for future therapeutic interventions in HPH.