Role of B-Cell Lymphoma 2 Ovarian Killer (BOK) in Acute Toxicity of Human Lung Epithelial Cells Caused by Cadmium Chloride

Multi-Effects of Acute Salinity Stress on Osmoregulation, Physiological Metabolism, Antioxidant Capacity, Immunity, and Apoptosis in Macrobrachium rosenbergii

Salinity stress can trigger a series of physiological changes. However, the mechanism underlying the response to acute salinity stress in Macrobrachium rosenbergii remains poorly understood. In this study, osmoregulation, physiological metabolism, antioxidant capacity, and apoptosis were examined over 96 h of acute salinity stress. Hemolymph osmolality increased with increasing salinity. After 48 h of salinity exposure, the glucose, triglycerides, total protein, and total cholesterol contents in two salinity stress groups (13 and 26‱ salinity) were significantly lower than those in the 0‱ salinity group. The highest levels of these parameters were detected at 6 h; however, superoxide dismutase (SOD), total antioxidant capacity (T-AOC), and malondialdehyde (MDA) were the lowest at 96 h in the 13‱ salinity group. The activity of immunity-related enzyme alkaline phosphatase (AKP) showed a decreasing trend with increasing salinity and remained at a low level in the 26‱ salinity group throughout the experiment. No significant differences were observed in aspartate aminotransferase (AST), alanine aminotransferase (ALT), or lysozyme (LZM) among the three treatments at 96 h. After 96 h of salinity treatments, the gill filament diameter significantly decreased, and a more pronounced terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive signal was detected in the 13‱ and 26‱ groups compared to that in the 0‱ group. Expression levels of apoptosis-related genes, including Cysteine-aspartic acid protease 3 (Caspase 3), Cysteine-aspartic acid protease 8 (Caspase 8), Cytochrome c (Cyt-c), tumor suppressor gene (P53), Nuclear factor kappa-B (NF-κB), and B cell lymphoma 2 ovarian killer (Bok) were significantly higher in the 26‱ salinity group than in the other groups at 24 h, but lower than those in the 0‱ salinity group at 96 h. Cyt-c and P53 levels exhibited a significantly positive relationship with MDA, AST, and LZM activity during salinity stress. In the 13‱ salinity group, Bok expression was significantly correlated with SOD, T-AOC, AKP, acid phosphatase, and LZM activity, whereas in the 26‱ group, the AST content was positively correlated with Caspase 8, Cyt-c, and P53 expression. A significant negative relationship was observed between Caspase 3 expression and catalase (CAT) activity. These findings provide insight into the mechanisms underlying the response to acute salinity stress and will contribute to improving M. rosenbergii aquaculture and management practices.

Necrostatin-1 prevents skeletal muscle ischemia reperfusion injury by regulating Bok-mediated apoptosis

BACKGROUND

Receptor interacting serine/threonine kinase 1 (RIPK1) mediates apoptosis by regulating the classic proapoptotic effectors Bcl-2-associated X protein (Bax) and Bcl-2 homologous antagonist/killer (Bak). Although Bcl-2-related ovarian killer (Bok) is structurally similar to Bak and Bax, it is unclear whether it mediates apoptosis in skeletal muscle ischemia reperfusion (IR) injury. We hypothesized that by regulating Bok-mediated apoptosis, inhibiting RIPK1 with necrostatin-1 would reduce skeletal muscle IR injury.

METHODS

Rats were randomized into four groups: sham (SM), IR, IR treated with necrostatin-1 (NI), or vehicle dimethyl sulfoxide (DI). For the IR group, the right femoral artery was clamped for 4 hours and then reperfused for 4 hours, and for the NI and DI groups, necrostatin-1 (1.65 mg/kg) and the equal volume of dimethyl sulfoxide were intraperitoneally administered prior to IR induction. The structural damage of muscle tissue and protein expression of Bok, Bcl-2, and cleaved caspase-3 were investigated, and apoptotic cells were identified with terminal dUTP nick-end labeling (TUNEL) staining. In vitro, human skeletal muscle cells (HSMCs) were exposed to 6 hours of oxygen-glucose deprivation followed by normoxia for 6 hours to establish an oxygen-glucose deprivation/reoxygenation (OGD/R) model. To determine the role of Bok, cell viability, lactate dehydrogenase (LDH) release, and flow cytometry were examined to demonstrate the effects of necrostatin-1 and Bok knockdown on the OGD/R insult of HSMCs.

RESULTS

Necrostatin-1 pretreatment markedly reduced IR-induced muscle damage and RIPK1, Bok, and cleaved caspase-3 expression, whereas upregualted Bcl-2 expression (p < 0.05). Furthermore, necrostatin-1 prevented mitochondrial damage and decreased TUNEL-positive muscle cells (p < 0.05). In vitro, HSMCs treated with necrostatin-1 showed reduced Bok expression, increased cell viability, and reduced LDH release in response to OGD/R (p < 0.05), and Bok knockdown significantly blunted the OGD/R insult in HSMCs.

CONCLUSION

Necrostatin-1 prevents skeletal muscle from IR injury by regulating Bok-mediated apoptosis.

Endogenous Bok is stable at the endoplasmic reticulum membrane and does not mediate proteasome inhibitor-induced apoptosis

Controversy surrounds the cellular role of the Bcl-2 family protein Bok. On one hand, it has been shown that all endogenous Bok is bound to inositol 1,4,5-trisphosphate receptors (IP3Rs), while other data suggest that Bok can act as a pro-apoptotic mitochondrial outer membrane permeabilization mediator, apparently kept at very low and non-apoptotic levels by efficient proteasome-mediated degradation. Here we show that 1) endogenous Bok is expressed at readily-detectable levels in key cultured cells (e.g., mouse embryonic fibroblasts and HCT116 cells) and is not constitutively degraded by the proteasome, 2) proteasome inhibitor-induced apoptosis is not mediated by Bok, 3) endogenous Bok expression level is critically dependent on the presence of IP3Rs, 4) endogenous Bok is rapidly degraded by the ubiquitin-proteasome pathway in the absence of IP3Rs at the endoplasmic reticulum membrane, and 5) charged residues in the transmembrane region of Bok affect its stability, ability to interact with Mcl-1, and pro-apoptotic activity when over-expressed. Overall, these data indicate that endogenous Bok levels are not governed by proteasomal activity (except when IP3Rs are deleted) and that while endogenous Bok plays little or no role in apoptotic signaling, exogenous Bok can mediate apoptosis in a manner dependent on its transmembrane domain.

SARS-CoV-2 membrane protein causes the mitochondrial apoptosis and pulmonary edema via targeting BOK

Deaths caused by coronavirus disease 2019 (COVID-19) are largely due to the lungs edema resulting from the disruption of the lung alveolo-capillary barrier, induced by SARS-CoV-2-triggered pulmonary cell apoptosis. However, the molecular mechanism underlying the proapoptotic role of SARS-CoV-2 is still unclear. Here, we revealed that SARS-CoV-2 membrane (M) protein could induce lung epithelial cells mitochondrial apoptosis. Notably, M protein stabilized B-cell lymphoma 2 (BCL-2) ovarian killer (BOK) via inhibiting its ubiquitination and promoted BOK mitochondria translocation. The endodomain of M protein was required for its interaction with BOK. Knockout of BOK by CRISPR/Cas9 increased cellular resistance to M protein-induced apoptosis. BOK was rescued in the BOK-knockout cells, which led to apoptosis induced by M protein. M protein induced BOK to trigger apoptosis in the absence of BAX and BAK. Furthermore, the BH2 domain of BOK was required for interaction with M protein and proapoptosis. In vivo M protein recombinant lentivirus infection induced caspase-associated apoptosis and increased alveolar-capillary permeability in the mouse lungs. BOK knockdown improved the lung edema due to lentivirus-M protein infection. Overall, M protein activated the BOK-dependent apoptotic pathway and thus exacerbated SARS-CoV-2 associated lung injury in vivo. These findings proposed a proapoptotic role for M protein in SARS-CoV-2 pathogenesis, which may provide potential targets for COVID-19 treatments.

Etomidate Regulates miR-192-5p Expression to Reduce Hypoxia-Reoxygenation Induced Bronchial Epithelial Cell Damage

Etomidate is a new type of intravenous anesthetic that can protect bronchial epithelial cells from oxidative stress damage. miR-192-5p is upregulated in 6-hydroxydopamine-induced neurocytes. This study explored the effect of etomidate on bronchial epithelial cell apoptosis and oxidative stress induced by hypoxia and reoxygenation and its regulatory effect on miR-192-5p. The human bronchial epithelial cells BEAS-2B were cultured in vitro and then subjected to hypoxia and reoxygenation to establish a cell injury model. The cells were then treated with etomidate at different doses. Moreover, anti-miR-NC and anti-miR-192-5p were transfected into the BEAS-2B cells to treat the hypoxia-reoxygenation. Moreover, miR-NC and miR-192-5p mimics were transfected into BEAS-2B cells, followed by treatment with 90 µmol/L etomidate for 24 h and then treatment with hypoxia and reoxygenation. The 2,4-dinitrophenylhydrazine method was used to determine the level of LDH in the culture medium of cardiomyocytes. Thiobarbituric acid was used to determine the level of MDA and xanthine oxidase to determine the activity of SOD. Flow cytometry was used to measure the apoptosis rate and qRT-PCR to evaluate miR-192-5p expression. Western blotting was used to determine the Bax and Bcl-2 protein levels. Compared with the findings in the control group, the levels of LDH and MDA, the apoptosis rate, and the protein level of Bax were increased (P < 0.05) upon treatment with hypoxia and reoxygenation, while SOD activity and Bcl-2 protein level were decreased (P < 0.05). In a manner dependent on the dose, etomidate could significantly reverse the effects of hypoxia and reoxygenation on oxidative stress and apoptosis of BEAS-2B cells (P < 0.05). Hypoxia and reoxygenation could significantly increase the miR-192-5p level of BEAS-2B cells (P < 0.05), while etomidate could reduce this miR-192-5p expression (P < 0.05) in a dose-dependent manner. Transfection of anti-miR-192-5p dramatically reduced LDH, MDA, apoptosis rate, and Bax protein level (P < 0.05), but was associated with increases of SOD activity and Bcl-2 protein expression (P < 0.05). High expression of miR-192-5p could significantly reverse the influence of etomidate on apoptosis and oxidative stress of BEAS-2B cells induced by hypoxia-reoxygenation (P < 0.05). Etomidate restrained the apoptosis of bronchial epithelial cells and oxidative stress induced by hypoxia and reoxygenation by inhibiting miR-192-5p expression, thereby reducing cell damage.

Cadmium-Induced Cell Homeostasis Impairment is Suppressed by the Tor1 Deficiency in Fission Yeast

Cadmium has no known physiological function in the body; however, its adverse effects are associated with cancer and many types of organ system damage. Although much has been shown about Cd toxicity, the underlying mechanisms of its responses to the organism remain unclear. In this study, the role of Tor1, a catalytic subunit of the target of rapamycin complex 2 (TORC2), in Cd-mediated effects on cell proliferation, the antioxidant system, morphology, and ionome balance was investigated in the eukaryotic model organism Schizosaccharomyces pombe. Surprisingly, spectrophotometric and biochemical analyses revealed that the growth rate conditions and antioxidant defense mechanisms are considerably better in cells lacking the Tor1 signaling. The malondialdehyde (MDA) content of Tor1-deficient cells upon Cd treatment represents approximately half of the wild-type content. The microscopic determination of the cell morphological parameters indicates the role for Tor1 in cell shape maintenance. The ion content, determined by inductively coupled plasma optical emission spectroscopy (ICP-OES), showed that the Cd uptake potency was markedly lower in Tor1-depleted compared to wild-type cells. Conclusively, we show that the cadmium-mediated cell impairments in the fission yeast significantly depend on the Tor1 signaling. Additionally, the data presented here suggest the yet-undefined role of Tor1 in the transport of ions.

The Multifaceted Roles of the BCL-2 Family Member BOK

BCL-2-related ovarian killer (BOK) is-despite its identification over 20 years ago-an incompletely understood member of the BCL-2 family. BCL-2 family proteins are best known for their critical role in the regulation of mitochondrial outer membrane permeabilization during the intrinsic apoptotic pathway. Based on sequence and structural similarities to BAX and BAK, BOK is grouped with these "killers" within the effector subgroup of the family. However, the mechanism of how exactly BOK exerts apoptosis is not clear and controversially discussed. Furthermore, and in accordance with reports on several other BCL-2 family members, BOK seems to be involved in the regulation of a variety of other, "apoptosis-independent" cellular functions, including the unfolded protein response, cellular proliferation, metabolism, and autophagy. Of note, compared with other proapoptotic BCL-2 family members, BOK levels are often reduced in cancer by various means, and there is increasing evidence for BOK modulating tumorigenesis. In this review, we summarize and discuss apoptotic- and non-apoptotic-related functions of BOK, its regulation as well as its physiological and pathophysiological roles.