Role of hypoxia-inducible factor-1α in autophagic cell death in microglial cells induced by hypoxia

Abstract

Microglial cells are phagocytic cells of the central nervous system (CNS) and have been proposed to be a primary component of the innate immune response and maintain efficient CNS homeostasis. Microglial cells are activated during various phases of tissue repair and participate in various pathological conditions in the CNS. Following spinal cord injury (SCI), anoxemia is a key problem that results in tissue destruction. Hypoxia-inducible factor 1-α (HIF-1α) may protect hypoxic cells from apoptosis or necrosis under ischemic and anoxic conditions. However, numerous studies have revealed that hypoxia upregulates HIF-1α expression leading to the death of microglial cells. The present study investigated the alterations in HIF-1α expression levels and the mechanism of autophagic cell death mediated by HIF-1α in microglial cells induced by hypoxia. Hypoxia was demonstrated to induce HIF-1α expression and autophagic cell death in microglial cells. Enhanced autophagy reduced cell death during the initial stages by restraining the functions of autophagy-associated genes (microtubule-associated protein 1A/1B-light chain 3 phosphatidylethanolamine conjugate and Beclin-1) and modulating the expression of inflammatory cytokines (tumor necrosis factor-α and interleukin-1β). Target value was determined by Cell Counting Kit 8 and cell death by flow cytometry. Transmission electron microscopy, immunohistochemical staining, reverse transcription-quantitative polymerase chain reaction, western blotting, and ELISA were used for further analysis. However, increased expression of HIF-1α induced cell death and autophagic cell death in microglial cells. Furthermore, the effects of the HIF-1α inhibitor 2-methoxyestradiol and HIF-1α small interfering RNA on the death and autophagy of microglial cells in vitro were investigated. These investigations revealed the suppression of autophagy, the decrease of cell viability and the increase of inflammatory cytokines results from HIF-1α inhibition or HIF-1α silencing. In conclusion, the results indicated that appropriate expression of HIF-1α can ameliorate autophagic cell death of microglial cells associated with hypoxia, and may provide a novel therapeutic approach for SCI associated with microglial cell activation.

Necrosulfonamide Ameliorates Neurological Impairment in Spinal Cord Injury by Improving Antioxidative Capacity

“…Factors such as free radicals, glutamate, tumour necrosis factor (TNF), ischemia, and hypoxia cause delayed neuronal death (Oyinbo, 2011;Zhang et al, 2012). Studies have reported that anoxemia after SCI leads to tissue destruction, while hypoxia gradually induces cell death alongside inflammation (Wang et al, 2017). Other data indicate that anoxemia also can lead to a variety of vascular pathologies that lead to acute arterial occlusion, ischemia, and shock (Fleming et al, 2006;Webb et al, 2010).…”

Bone marrow stromal cells‑derived exosomes target DAB2IP to induce microglial cell autophagy, a new strategy for neural stem cell transplantation in brain injury

“…All reagents and chemicals were purchased and used directly without further purification. The bone marrow stromal cell line was collected from the rat model of our team (28)(29)(30), whilst the BV-2 microglial cell line was provided by CHI Scientific Inc. (cat. no.…”

“…The fixative was removed, the sample was rinsed three times with PBS and fixed with 1% osmic acid solution for 2 h at 37˚C. The sample was subsequently dehydrated using an ascending ethanol gradient (30,50,70,80, 90 and 95%) and treated with pure acetone for 20 min at 25˚C. The sample was treated with a mixture of epikote resin and acetone (v/v=1/1) for 1 h, followed by the same mixture but at a higher concentration of the embedding agent (v/v=3/1) for 3 h before incubation with 100% embedding agent overnight at 25˚C.…”

“…However, progress has been slow regarding investigation into the treatment of brain injury using neural stem cell transplantation, which may be due to changes in the intracranial microenvironment following brain injury (26). A series of studies have reported that the autophagy of microglia serves an important role in brain injury, involving cranial nerve inflammation, cerebral ischemia and cerebral hypoxia (28)(29)(30). Stem cells that are transplanted into the body frequently fail and do not result in tissue repair (31).…”

“…Observation and study on this series of problems are therefore urgently required for future clinical work on cell transplantation. To expand on previous studies assessing bone marrow-derived neural progenitor cell-mediated tissue repair (28)(29)(30)32), the present study systematically characterized the structure and size of bone marrow-derived neural progenitor exosomes using optical technology, analyzed its content using second-generation sequencing technology and investigated the molecular mechanism underlying microglia autophagy induced by the exosomes from bone marrow-derived neural progenitor cells using molecular and cell biology techniques. The present study provided theoretical information on neural progenitor cell survival and differentiation following the transplantation of bone marrow-derived neural progenitor cells, in addition to offering mechanistic and experimental support for the future clinical application of cell transplantation.…”