ER stress decreases exosome production through adiponectin/T-cadherin-dependent and -independent pathways

The endoplasmic reticulum as a cradle for virus and extracellular vesicle secretion

Extracellular vesicles (EVs) are small membranous carriers of protein, lipid, and nucleic acid cargoes and play a key role in intercellular communication. Recent work has revealed the previously under-recognized participation of endoplasmic reticulum (ER)-associated proteins (ERAPs) during EV secretion, using pathways reminiscent of viral replication and secretion. Here, we present highlights of the literature involving ER/ERAPs in EV biogenesis and propose mechanistic parallels with ERAPs exploited during viral infections. We propose that ERAPs play an active role in the release of EVs and viral particles, and we present views on whether viruses hijack or enhance pre-existing ERAP-dependent secretory machineries or whether they repurpose ERAPs to create new secretory pathways.

Endoplasmic reticulum stress alters myelin associated protein expression and extracellular vesicle composition in human oligodendrocytes

Myelination of the central nervous system is mediated by specialized glial cells called oligodendrocytes (OLs). Multiple sclerosis (MS) is characterized by loss of myelination and subsequent clinical symptoms that can severely impact the quality of life and mobility of those affected by the disease. The major protein components of myelin sheaths are synthesized in the endoplasmic reticulum (ER), and ER stress has been observed in patients with MS. Extracellular vesicles (EVs) have been shown to carry bioactive cargo and have the potential to be utilized as noninvasive biomarkers for various diseases. In the current study, we sought to determine how ER stress in OLs affected the production of key myelination proteins and EV release and composition. To achieve this, tunicamycin was used to induce ER stress in a human oligodendroglioma cell line and changes in myelination protein expression and markers of autophagy were assessed. EVs were also separated from the conditioned cell culture media through size exclusion chromatography and characterized. Significant reductions in the expression of myelination proteins and alterations to autophagosome formation were observed in cells undergoing ER stress. EVs released from these cells were slightly smaller relative to controls, and had strong expression of LC3B. We also observed significant upregulation of miR-29a-3p in ER stress EVs when compared to controls. Taken together, these data suggest that ER stress negatively impacts production of key myelination proteins and induces cells to release EVs that may function to preemptively activate autophagic pathways in neighboring cells.

Association between COVID-19 severity and relatively high serum adiponectin levels at the time of admission

At the beginning of 2020, coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) led to epidemics worldwide. Obesity and visceral fat accumulation have been reported to be independent risk factors for severe COVID-19. Several reports have focused on the levels of adipocytokines/adipokines, including adiponectin (APN), which is exclusively secreted from adipocytes, although the importance of these factors in acute disease conditions remains unclear. Therefore, we investigated the relationship between serum adiponectin levels and COVID-19 severity. Patients with COVID-19 who were admitted to Sumitomo Hospital (Osaka, Japan) from May through October 2021 were included. A total of 107 patients were enrolled in this study. We obtained the anthropometric and clinical laboratory data of the patients at the time of admission and examined the associations between various parameters and COVID-19 severity. The mean period from onset to admission was 6.5 ± 2.8 days. We divided the patients into "non-severe" (mild, moderate-I and moderate-II) (n = 80) and "severe" (n = 27) groups. The "severe" patients were significantly older than "non-severe" patients. Additionally, no significant differences were observed in BMI, sex, or the period from onset to admission. The serum adiponectin levels of "severe" patients at the time of admission were significantly greater than those of "non-severe" patients even after adjusting for age, sex, and BMI. These results suggest that the serum APN levels at the time of admission can predict COVID-19 severity. However, further investigations on the changes in APN levels in acute diseases are needed.

The role of adiponectin and its receptor signaling in ocular inflammation-associated diseases

Ocular inflammation-associated diseases are leading causes of global visual impairment, with limited treatment options. Adiponectin, a hormone primarily secreted by adipose tissue, binds to its receptors, which are widely distributed throughout the body, exerting powerful physiological regulatory effects. The protective role of adiponectin in various inflammatory diseases has gained increasing attention in recent years. Previous studies have confirmed the presence of adiponectin and its receptors in the eyes. Furthermore, adiponectin and its analogs have shown potential as novel drugs for the treatment of inflammatory eye diseases. This article summarizes the evidence for the interplay between adiponectin and inflammatory eye diseases and provides new perspectives on the diagnostic and therapeutic possibilities of adiponectin.

Pharmacological HIF-1 activation upregulates extracellular vesicle production synergistically with adiponectin through transcriptional induction and protein stabilization of T-cadherin

Pharmacological activation of hypoxia-inducible factor 1 (HIF-1), a hypoxia-responsive transcription factor, has attracted increasing attention due to its efficacy not only in renal anemia but also in various disease models. Our study demonstrated that a HIF-1 activator enhanced extracellular vesicle (EV) production from cultured endothelial cells synergistically with adiponectin, an adipocyte-derived factor, through both transcriptional induction and posttranscriptional stabilization of an adiponectin binding partner, T-cadherin. Increased EV levels were observed in wild-type mice but not in T-cadherin null mice after consecutive administration of roxadustat. Adiponectin- and T-cadherin-dependent increased EV production may be involved in the pleiotropic effects of HIF-1 activators.