TGF-β3/Smad3 Contributes to Isoflurane Postconditioning Against Cerebral Ischemia–Reperfusion Injury by Upregulating MEF2C

The influence of ferroptosis on the in vitro OGD/R model in rat microglia

OBJECTIVE

We aimed to explore the influence of ferroptosis on an oxygen-glucose deprivation/reoxygenation (OGD/R) model in primary rat microglia.

METHODS

Primary microglia were extracted from rats and cultured in vitro. The cells were subjected to a hypoxic environment for 6 h in a glucose-free medium, and then re-oxygenated for 24 h in DMEM/F12. Rat microglia were pretreated with the ferroptosis activator erastin and the ferroptosis inhibitor ferrostatin 1 for 24 h, followed by detection of cell cycle progression and apoptosis by flow cytometry. Intracellular total iron levels were measured. In addition, the relative levels of reactive oxygen species (ROS), malondialdehyde (MDA), and superoxide dismutase (SOD) were determined using enzyme-linked immunosorbent assay. The protein levels of 15-lox2, GPX4, SLC7A11, ACSL4, and TFR1 were examined by western blotting.

RESULTS

Compared with rat microglia subjected to OGD/R, pretreatment with erastin did not influence cell apoptosis but significantly enhanced total iron levels, MDA, and ROS levels, whereas it reduced SOD levels. Moreover, it upregulated ACSL4, TFR1, and 15-lox2 and downregulated GPX4 and SLC7A11. Pretreatment with ferrostatin 1 significantly inhibited cell apoptosis and cell cycle arrest in the G0/G1 phase. It significantly reduced total iron levels, MDA, and ROS levels and enhanced SOD levels, which also downregulated ACSL4, TFR1, and 15-lox2, and upregulated GPX4 and SLC7A11.

CONCLUSION

Our study showed that inhibition of ferroptosis is favorable against potential OGD/R-induced damage in rat microglia.

Isoflurane Enhances Autophagy by Activating AMPK/ULK1, Inhibits NLRP3, and Reduces Cognitive Impairment After Cerebral Ischemia-Reperfusion Injury in Rats

Cerebral ischemic stroke (CIS) has become the second leading cause of death worldwide, which is largely related to cerebral ischemia reperfusion injury (CIRI). Surgical intervention is a reliable treatment for CIS, which predictably causes cerebral reperfusion. Therefore, the choice of anesthetic drugs has important clinical significance. Isoflurane (ISO), one of the most used anesthetics, attenuates cognitive impairment and has brain protective effects. However, the role of isoflurane in regulating autophagy and its regulatory mechanism on inflammation in CIRI are still unclear. The middle cerebral artery occlusion (MCAO) method was used to establish a rat model of CIRI. After 24 h of reperfusion, all rats were evaluated by mNSS scoring and dark avoidance experiment. Western blotting and immunofluorescence were used to examine the expression of key proteins. Compared with the sham group, the MCAO group showed increased neurobehavioral scores and decreased cognitive memory function (P < 0.05). As for the ISO-treated MCAO rats, the neurobehavioral score was significantly decreased, the expression of AMPK, ULK1, Beclin1, and LC3B was significantly increased, and the cognitive and memory functions were also significantly improved (P < 0.05). After inhibition of autophagy pathway or key protein AMPK in autophagy, neurobehavioral scores and protein expression of NLRP3, IL-1β, and IL-18 were significantly increased (P < 0.05). Isoflurane post-treatment may enhance autophagy by activating the AMPK/ULK1 signaling pathway and further inhibit the release of inflammatory factors from NLRP3 inflammasomes, thereby ameliorating neurological function and cognitive impairment and exerting a protective effect on the brain in CIRI rats.

TGF-β3 Protects Neurons Against Intermittent Hypoxia-Induced Oxidative Stress and Apoptosis Through Activation of the Nrf-2/KEAP1/HO-1 Pathway via Binding to TGF-βRI

Intermittent hypoxia (IH) is the primary pathological manifestation of obstructive sleep apnea (OSA) and the main cause of OSA-induced cognitive impairment. Hippocampal neurons are considered to be critical cells affected by IH. Transforming growth factor-β3 (TGF-β3) is a cytokine with a neuroprotective effect, which plays a crucial role in resisting hypoxic brain injury, while its role in IH-induced neuronal injury is still unclear. Here, we aimed to clarify the mechanism of TGF-β3 protecting IH-exposed neurons by regulating oxidative stress and secondary apoptosis. Morris water maze results revealed that IH exposure was unable to affect the vision and motor ability of rats, but significantly affected their spatial cognition. Second-generation sequencing (RNA-seq) and subsequent experiments supported that IH decreased TGF-β3 expression and stimulated reactive oxygen species (ROS)-induced oxidative stress and apoptosis in rat hippocampus. In vitro, IH exposure significantly activated oxidative stress within HT-22 cells. Exogenous administration of Recombinant Human Transforming Growth Factor-β3 (rhTGF-β3) prevented ROS surge and secondary apoptosis in HT-22 cells caused by IH, while TGF-β type receptor I (TGF-βRI) inhibitor SB431542 blocked the neuroprotective effect of rhTGF-β3. Nuclear factor erythroid 2-related factor 2 (Nrf-2) is a transcription factor preserving intracellular redox homeostasis. rhTGF-β3 improved the nuclear translocation of Nrf-2 and activated downstream pathway. However, Nrf-2 inhibitor ML385 suppressed the activation of the Nrf-2 mechanism by rhTGF-3 and restored the effects of oxidative stress damage. These results indicate that TGF-β3 binding to TGF-βRI activates the intracellular Nrf-2/KEAP1/HO-1 pathway, reduces ROS creation, and attenuates oxidative stress and apoptosis in IH-exposed HT-22 cells.

Protective effect of isoflurane preconditioning on neurological function in rats with HIE

Hypoxic-ischemic encephalopathy (HIE) is an important cause of neonatal death and disability, which can lead to long-term neurological and motor dysfunction. Currently, inhalation anesthetics are widely used in surgery, and some studies have found that isoflurane (ISO) may have a positive effect on neuroprotection. In this paper, we investigated whether ISO pretreatment has a neuroprotective effect on the neurological function of HIE rats. Here, 7-day-old neonatal rats were randomly divided into a sham group, a hypoxic-ischemic (HI) group, and an ISO pretreatment (pretreatment) group. The pretreatment group was pretreated with 2% ISO for 1 h, followed by the HI group to establish an HI animal model. The HI‑induced neurological injury was evaluated by Zea‑Longa scores and triphenyltetrazolium (TTC) staining. Neuronal number and histomorphological changes were observed with Nissl staining and Hematoxylin-eosin (HE) staining. In addition, motor learning memory function was evaluated by the Morris water maze (MWM), the Y-maze, and the rotarod tests. HI induced severe neurological dysfunction, brain infarction, and cell apoptosis as well as obvious neuron loss in neonatal rats. In the MWM, the rats in the pretreatment group showed a decrease in escape latency (p = 0.042), indicating that pretreatment with ISO could improve the learning ability of HI rats. The results of Nissl staining showed that in the HI group, there was an irregular arrangement of neurons and nuclear fixation; however, the cell damage was significantly reduced and the total number of neurons was increased after ISO pretreatment (p < 0.001). In conclusion, ISO pretreatment improved cognitive function and attenuated HI-induced reduction of Nissl-positive cells and spatial memory impairment, suggesting that pretreatment with ISO before HI modeling could reduce neuronal cell death in the hippocampus after HI.

BMP2 as a promising anticancer approach: functions and molecular mechanisms

Bone morphogenetic protein 2 (BMP2), a pluripotent factor, is a member of the transforming growth factor-beta (TGF-β) superfamily and is implicated in embryonic development and postnatal homeostasis in tissues and organs. Experimental research in the contexts of physiology and pathology has indicated that BMP2 can induce macrophages to differentiate into osteoclasts and accelerate the osteolytic mechanism, aggravating cancer cell bone metastasis. Emerging studies have stressed the potent regulatory effect of BMP2 in cancer cell differentiation, proliferation, survival, and apoptosis. Complicated signaling networks involving multiple regulatory proteins imply the significant biological functions of BMP2 in cancer. In this review, we comprehensively summarized and discussed the current evidence related to the modulation of BMP2 in tumorigenesis and development, including evidence related to the roles and molecular mechanisms of BMP2 in regulating cancer stem cells (CSCs), epithelial-mesenchymal transition (EMT), cancer angiogenesis and the tumor microenvironment (TME). All these findings suggest that BMP2 may be an effective therapeutic target for cancer and a new marker for assessing treatment efficacy.

The protective effects of lncRNA ZFAS1/miR-421-3p/MEF2C axis on cerebral ischemia-reperfusion injury

LncRNA ZNFX1 antisense RNA 1 (ZFAS1) could improve neuronal damage and inhibit inflammation and apoptosis. We conducted an in-depth exploration on the protective mechanism of ZFAS1 in cerebral ischemia-reperfusion injury. Overexpressed or silenced plasmids of ZFAS1 were transfected into the cells to analyze the effects of oxygen-glucose deprivation/reperfusion (OGD/R) treatment on the viability, apoptosis and related gene expressions of Neuro-2a cell by performing MTT assay, flow cytometry, qRT-PCR, and Western blot. Bioinformatic analysis, qRT-PCR, dual-luciferase reporter assay and RNA immunoprecipitation were used to screen and verify the miRNA(s) which could competitively bind with ZFAS1 and downstream mRNA(s) targeted by the miRNA(s). The effects of ZFAS1 and the above target miRNA(s) or gene(s) on the apoptosis of OGD/R-injured cells, apoptosis-related proteins, inflammatory factors and p65/IκBα pathway were further verified via the rescue test. The results from the middle cerebral artery occlusion (MCAO) mouse model in vivo were consistent with those from the cellular experiments. The expression of lncRNA ZFAS1 in OGD/R-injured cells was inhibited, and the up-regulation of ZFAS1 protected Neuro-2a cells. MiR-421-3p was predicted to be the target miRNA of ZFAS1 and could offset the protective effect of ZFAS1 overexpression on OGD/R-injured cells following its up-regulation. MEF2C, which was the downstream target gene of miR-421-3p, reversed the OGD/R-induced enhanced cell damage caused by miR-421-3p mimic when MEF2C was overexpressed. In in vivo studies, ZFAS1 overexpression reduced brain tissue infarction, apoptosis and gene regulation caused by MCAO, while miR-421-3p mimic had the opposite effect. Collectively, the regulation of lncRNA ZFAS1/miR-421-3p/MEF2C axis showed protective effects on cerebral ischemia-reperfusion injury.

Galectin-3 participates in PASMC migration and proliferation by interacting with TGF-β1

Pulmonary vascular remodelling is one of the most important factors for pulmonary hypertension (PH). Galectin-3 (Gal-3) is a β-galactoside-binding lectin. In the latest literature, Gal-3 has been reported to be involved in pulmonary vascular remodelling, and its underlying mechanism is unclear. Our research aims to prove the effect of Gal-3 on the proliferation and migration of human pulmonary artery smooth muscle cells (HPASMC) induced by transforming growth factor β1 (TGF-β1) and to study its mechanism. In vivo experiment: In Sprague-Dawley (SD) rats, monocrotaline was injected intraperitoneally to establish a PH model, and the Gal-3 inhibitor (modified citrus pectin, MCP) 28 Ds was administered in the stomach. The results indicate that Gal-3 and TGF-β1 may be involved in the occurrence and development of PH, which may be related to the Smad2/3 signalling pathway. In vitro experiment: Human pulmonary artery smooth muscle cells were pretreated with the Gal-3 inhibitor (MCP) for 24 h, then TGF-β1 or Gal-3 was administered to the cells for 24 h. The results show that exogenous TGF-β1 and Gal-3 can activate the downstream Smad2/3 signalling pathway, and increase the proliferation and migration ability of HPASMC. However, the Gal-3 inhibitor (MCP) inhibited these effects. Further results display that TGF-β1 and Gal-3 could mutually regulate the protein and mRNA expression levels. In summary, the results of this study indicate that Gal-3 regulates the Smad2/3 signalling pathway through protein interaction with TGF-β1, in turn regulates the proliferation and migration of HPASMC, thereby regulating the occurrence and development of PH.