Endoplasmic reticulum stress‐induced exosomal miR‐27a‐3p promotes immune escape in breast cancer via regulating PD‐L1 expression in macrophages

Immune escape of breast cancer cells contributes to breast cancer pathogenesis. Tumour microenvironment stresses that disrupt protein homeostasis can produce endoplasmic reticulum (ER) stress. The miRNA‐mediated translational repression of mRNAs has been extensively studied in regulating immune escape and ER stress in human cancers. In this study, we identified a novel microRNA (miR)‐27a‐3p and investigated its mechanistic role in promoting immune evasion. The binding affinity between miR‐27a‐3p and MAGI2 was predicted using bioinformatic analysis and verified by dual‐luciferase reporter assay. Ectopic expression and inhibition of miR‐27a‐3p in breast cancer cells were achieved by transduction with mimics and inhibitors. Besides, artificial modulation of MAGI2 and PTEN was done to explore their function in ER stress and immune escape of cancer cells. Of note, exosomes were derived from cancer cells and co‐cultured with macrophages for mechanistic studies. The experimental data suggested that ER stress biomarkers including GRP78, PERK, ATF6, IRE1α and PD‐L1 were overexpressed in breast cancer tissues relative to paracancerous tissues. Endoplasmic reticulum stress promoted exosome secretion and elevated exosomal miR‐27a‐3p expression. Elevation of miR‐27a‐3p and PD‐L1 levels in macrophages was observed in response to exosomes‐overexpressing miR‐27a‐3p in vivo and in vitro. miR‐27a‐3p could target and negatively regulate MAGI2, while MAGI2 down‐regulated PD‐L1 by up‐regulating PTEN to inactivate PI3K/AKT signalling pathway. Less CD4⁺, CD8⁺ T cells and IL‐2, and T cells apoptosis were observed in response to co‐culture of macrophages and CD3⁺ T cells. Conjointly, exosomal miR‐27a‐3p promotes immune evasion by up‐regulating PD‐L1 via MAGI2/PTEN/PI3K axis in breast cancer.     

The synergy of germline C634Y and V292M RET mutations in a northern Chinese family with multiple endocrine neoplasia type 2A

Genetic analysis for germline mutations of RET proto‐oncogene has provided a basis for individual management of medullary thyroid carcinoma (MTC) and pheochromocytoma. Most of compound mutations have more aggressive phenotypes than single point mutations, but the compound C634Y/V292M variant in MTC has never been reported. Thus, we retrospectively investigated synergistic effect of C634Y and V292M RET germline mutations in family members with multiple endocrine neoplasia type 2A. Nine of 14 family members in a northern Chinese family underwent RET mutation screening using next‐generation sequencing and PCR followed by direct bidirectional DNA sequencing. Clinical features of nine individuals were retrospectively carefully reviewed. In vitro, the scratch‐wound assay was used to investigate the difference between the cells carrying different mutations. We find no patients died of MTC. All 3 carriers of the V292M variant were asymptomatic and did not have biochemical or structural evidence of disease (age: 82, 62 and 58). Among 4 C634Y mutation carriers, 2 patients had elevated calcitonin with the highest (156 pg/mL) in an 87‐year‐old male. Two carriers of compound C634Y/V292M trans variant had bilateral MTC with pheochromocytoma or lymph node metastasis (age: 54 and 41 years, respectively). Further, the compound C634Y/V292M variant had a faster migration rate than either single point mutation in vitro (P < .05). In conclusion, the V292M RET variant could be classified as ‘likely benign’ according to ACMG (2015). The compound variant V292M/C634Y was associated with both more aggressive clinical phenotype and faster cell growth in vitro than was either single mutation.     

Aldosterone enhances high phosphate–induced vascular calcification through inhibition of AMPK‐mediated autophagy

It remains unclear whether the necessity of calcified mellitus induced by high inorganic phosphate (Pi) is required and the roles of autophagy plays in aldosterone (Aldo)‐enhanced vascular calcification (VC) and vascular smooth muscle cell (VSMC) osteogenic differentiation. In the present study, we found that Aldo enhanced VC both in vivo and in vitro only in the presence of high Pi, alongside with increased expression of VSMC osteogenic proteins (BMP2, Runx2 and OCN) and decreased expression of VSMC contractile proteins (α‐SMA, SM22α and smoothelin). However, these effects were blocked by mineralocorticoid receptor inhibitor, spironolactone. In addition, the stimulatory effects of Aldo on VSMC calcification were further accelerated by the autophagy inhibitor, 3‐MA, and were counteracted by the autophagy inducer, rapamycin. Moreover, inhibiting adenosine monophosphate‐activated protein kinase (AMPK) by Compound C attenuated Aldo/MR‐enhanced VC. These results suggested that Aldo facilitates high Pi‐induced VSMC osteogenic phenotypic switch and calcification through MR‐mediated signalling pathways that involve AMPK‐dependent autophagy, which provided new insights into Aldo excess‐associated VC in various settings.     

Ellagic acid protects dopamine neurons from rotenone‐induced neurotoxicity via activation of Nrf2 signalling

Parkinson's disease (PD) is the second most prevalent central nervous system (CNS) degenerative disease. Oxidative stress is one of key contributors to PD. Nuclear factor erythroid‐2‐related factor 2 (Nrf2) is considered to be a master regulator of many genes involved in anti‐oxidant stress to attenuate cell death. Therefore, activation of Nrf2 signalling provides an effective avenue to treat PD. Ellagic acid (EA), a natural polyphenolic contained in fruits and nuts, possesses amounts of pharmacological activities, such as anti‐oxidant stress and anti‐inflammation. Recent studies have confirmed EA could be used as a neuroprotective agent in neurodegenerative diseases. Here, mice subcutaneous injection of rotenone (ROT)‐induced DA neuronal damage was performed to investigate EA‐mediated neuroprotection. In addition, adult Nrf2 knockout mice and different cell cultures including MN9D‐enciched, MN9D‐BV‐2 and MN9D‐C6 cell co‐cultures were applied to explore the underlying mechanisms. Results demonstrated EA conferred neuroprotection against ROT‐induced DA neurotoxicity. Activation of Nrf2 signalling was involved in EA‐mediated DA neuroprotection, as evidenced by the following observations. First, EA activated Nrf2 signalling in ROT‐induced DA neuronal damage. Second, EA generated neuroprotection with the presence of astroglia and silence of Nrf2 in astroglia abolished EA‐mediated neuroprotection. Third, EA failed to produce DA neuroprotection in Nrf2 knockout mice. In conclusion, this study identified EA protected against DA neuronal loss via an Nrf2‐dependent manner.     

Reduced Sirtuin1 signalling exacerbates diabetic mice hindlimb ischaemia injury and inhibits the protective effect of a liver X receptor agonist

Diabetes mellitus causes endothelial dysfunction, which further exacerbates peripheral arterial disease (PAD). Improving endothelial function via reducing endothelial oxidative stress (OS) may be a promising therapy for diabetic PAD. Activation of liver X receptor (LXR) inhibits excessive OS and provides protective effects on endothelial cells in diabetic individuals. Therefore, we investigated the effects of LXR agonist treatment on diabetic PAD with a focus on modulating endothelial OS. We used a streptozotocin-induced diabetes mouse model combined with a hindlimb ischaemia (HLI) injury to mimic diabetic PAD, which was followed by LXR agonist treatment. In our study, the LXR agonist T0901317 protected against HLI injury in diabetic mice by attenuating endothelial OS and stimulating angiogenesis. However, a deficiency in endothelial Sirtuin1 (SIRT1) largely inhibited the therapeutic effects of T0901317. Furthermore, we found that the underlying therapeutic mechanisms of T0901317 were related to SIRT1 and non-SIRT1 signalling, and the isoform LXRβ was involved in LXR agonist-elicited SIRT1 regulation. In conclusion, LXR agonist treatment protected against HLI injury in diabetic mice via mitigating endothelial OS and stimulating cellular viability and angiogenesis by LXRβ, which elicited both SIRT1-mediated and non-SIRT1-mediated signalling pathways. Therefore, LXR agonist treatment may be a promising therapeutic strategy for diabetic PAD.