Hypoxic postconditioning attenuates apoptosis via inactivation of adenosine A2a receptor through NDRG3-Raf-ERK pathway

Elevated N-Myc downstream-regulated gene 3 expression indicates poor survival in epithelial ovarian cancer

N-Myc downstream-regulated gene 3 (NDRG3), a member of the NDRG family, plays an important role in the development, progression, invasiveness, and metastasis of multiple tumor types. This study focuses on NDRG3 expression in epithelial ovarian cancer (EOC) and the correlation between NDRG3 expression and prognostic indicators. First, the LinkedOmics database was used to analyze the expression of genes associated with NDRG3, and then gene ontology and Kyoto encyclopedia of genes and genomes (KEGG) functional enrichment analyses and methylation analysis of NDRG3-related genes were performed to identify co-expressed genes. A protein-protein interaction network was constructed using the STRING database. Subsequently, quantitative polymerase chain reaction was performed to determine the mRNA expression level of NDRG3 in 22 fresh EOC tissue samples. In addition, immunohistochemistry was performed to detect the expression of NDRG3 protein in 110 EOC microarray samples. Cox regression and Kaplan-Meier survival analyses were performed to assess the prognostic value of NDRG3. Bioinformatics analysis showed that NDRG3 had a broad impact on the transcriptome and that genes that were co-expressed with NDRG3 were primarily involved in organ- or tissue-specific immune response, response to chemokine, interleukin-1 production, and other related pathways. The KEGG pathway analysis suggested that genes co-expressed with NDRG3 were also enriched in signaling pathways, including the interleukin-17 signaling pathway. The mRNA expression levels of NDRG3 were significantly higher in EOC tissues than in paracancerous nontumor tissues (P < .01). NDRG3 expression in EOC was correlated with distant metastasis (P = .02), tumor-node-metastasis stage (P = .03), and patient prognosis (P = .01). Moreover, the disease-free survival and overall survival times of EOC patients decreased with increasing NDRG3 expression. High NDRG3 expression and lymph node metastasis were identified as independent prognostic factors in 110 EOC patients. NDRG3 plays a key role in ovarian cancer progression. High NDRG3 expression is correlated with multiple clinicopathologic features of EOC and may be an indicator of a poor prognosis in EOC.

Extracellular vesicles from hypoxia-pretreated adipose-derived stem cells regulate hypoxia/reoxygenation-induced human dermal microvascular endothelial apoptosis and autophagy in vitro

Recent studies suggest hypoxia can promote adipose-derived stem cells (ADSCs) to attenuate hypoxia/reoxygenation (H/R)-induced damage to human dermal microvascular endothelial cells (HDMECs). Extracellular vesicles (EVs), isolated from ADSCs, play an-important role in the fields of regenerative medicine. Here, we aimed to investigate the effect of EVs isolated from hypoxia-pretreated ADSCs (ADSC-EVs[H]) on HDMECs to attenuate ischemia/reperfusion injury of free skin flaps. First, we characterized EVs isolated from normoxia-cultured ADSCs (ADSC-EVs[N]) and ADSC-EVs(H). Experimental data indicated that EVs isolated from ADSCs consisted of lipid-bilayer vesicles that exhibited positive expression of vascular endothelial growth factor (VEGF) and marker proteins CD9, CD63 and CD81, and the mean particle size of EVs in the hypoxia-pretreated ADSCs (ADSC[H]) group was smaller (74.17 nm) than in the normoxic-cultured ADSCs (ADSC[N]) group (93.87 nm). Hypoxic pretreatment increased the number of EVs. Later, we favorably constructed the co-culture model of EVs isolated from ADSCs (ADSC-EVs) and H/R-induced HDMECs. Cell counting kit-8, Ethynyldeoxyuridine assay, western blotting and immunofluorescence staining showed that ADSC-EVs(H) promoted the survival of HDMECs and increased LC3 level. Apoptosis, reactive oxygen species (ROS) and JC-1 mitochondrial membrane potential (MMP) assays revealed that ADSC-EVs(H) reduced the apoptosis rate and ROS accumulation and increased MMP level in HDMECs, indicating that ADSC-EVs(H) effectively attenuated H/R-induced damage in HDMECs through autophagy activation and the-inhibition of apoptosis and oxidative stress. This study confirmed that ADSC-EVs(H) could effectively regulate the proliferation, apoptosis, oxidative stress, and autophagy expression of H/R-induced HDMECs in vitro, and therefore the transplantation of ADSC-EVs(H) may provide novel insights for the transplantation of free skin flaps.

Relationship between serum NDRG3 and papillary thyroid carcinoma

BACKGROUND

In recent years, papillary thyroid carcinoma is considered to be one of the fastest increaseing cancer. NDRG family member 3 (NDRG3) has been proposed as a molecular marker of tumor, and is expected to be used in clinic.

METHODS

Enzyme-linked immunosorbent assay was used to detect the serum NDRG3 expression in 81 papillary thyroid carcinoma cases, 75 benign thyroid nodules cases and 77 healthy control cases, respectively. Electrochemiluminescence method was applied to measure the levels of triiodothyronine, tetraiodothyronine, thyrotropin, thyroglobulin antibody and thyroid peroxidase antibody. Immunohistochemical staining was used to detect the expression of NDRG3 in papillary thyroid carcinoma, benign thyroid nodules and normal tissues adjacent to cancer.

RESULTS

The expression of serum triiodothyronine, tetraiodothyronine, thyrotropin, thyroglobulin antibody and thyroid peroxidase antibody and NDRG3 were significantly different among benign thyroid nodules, papillary thyroid carcinoma cases and healthy control groups (P <0.001). Only the expression of serum NDRG3 was significantly different between benign thyroid nodules and papillary thyroid carcinoma groups (P <0.001). Immunohistochemistry showed that NDRG3 was expressed in all three groups, the lowest in papillary thyroid carcinoma, the second in benign thyroid nodules, and the highest in normal tissues adjacent to cancer. Logistic regression analysis showed that serum NDRG3 was an independent protective factor for papillary thyroid carcinoma (OR =0.964, 95%CI =0.953 to 0.974, P <0.001). The ROC curve of non-papillary thyroid carcinoma diagnosed by serum NDRG3 showed the optimal cut-off value of 481.38 pg/ml, sensitivity of 72.4%, specificity of 90.1%, and the maximum area under the curve (AUC =0.902, 95%CI =0.863 to 0.940, P <0.001). The ROC curve of benign thyroid nodules diagnosed by serum NDRG3 showed the optimal critical value of 459.28 pg/ml, sensitivity of 81.3%, and specificity of 74.1% (AUC =0.863, 95%CI =0.808 to 0.919, P <0.001). The expression level of serum NDRG3 was significantly correlated with extrathyroid extensionand (P =0.007) and lymphatic metastasis of papillary thyroid carcinoma (P =0.019).

CONCLUSIONS

The decrease of NDRG3 expression can not only differential diagnosis benign thyroid nodules and papillary thyroid carcinoma, but also serve as a molecular marker for the diagnosis of papillary thyroid carcinoma.

Hypoxia Promotes Adipose-Derived Stem Cells to Protect Human Dermal Microvascular Endothelial Cells Against Hypoxia/Reoxygenation Injury

BACKGROUND

Microcirculation is important for regulating ischemia-reperfusion (I/R) injury associated with skin flap transplantation surgery. We investigated whether co-culture with adipose-derived stem cells (ADSCs) could protect human dermal microvascular endothelial cells (HDMECs) from I/R injury by inhibiting cell apoptosis and enhancing cell proliferation. We also investigated the effects of hypoxic preconditioning on ADSCs.

MATERIALS AND METHODS

HDMECs were divided into four groups, control, HDMECs in normoxic culture conditions; hypoxia/reoxygenation (H/R), HDMECs in a hypoxic incubator for 8 h then in saturated aerobic culture medium for 24 h; H/R + ADSC(N), HDMECs treated similar to the H/R group then co-cultured with normoxic ADSCs; and H/R + ADSC(H), HDMECs treated similar to the H/R group then co-cultured with hypoxia preconditioned ADSCs.

RESULTS

The rate of HDMECs apoptosis significantly increased in the H/R group, but decreased upon co-culture with ADSCs for 24 h, especially in the H/R + ADSC(H) group. Co-culture with ADSCs, especially hypoxia preconditioned ADSCs, significantly enhanced cell proliferation ability compared with that of the H/R group after 48 h and 72 h, but not after 24 h. Vascular endothelial growth factor levels were significantly higher in the H/R + ADSC(N) and H/R + ADSC(H) groups than in the H/R group.

CONCLUSIONS

ADSCs attenuated H/R injury in endothelial cells by promoting proliferation ability and reducing apoptosis, with an increase in Vascular endothelial growth factor level, especially in the context of hypoxic preconditioning. This approach suggests the potential for an easy and safe method to reduce I/R injury associated with skin flap transplantation surgery.

Exome hits demystified: The next frontier

Severe mental illnesses such as schizophrenia and bipolar disorder have complex inheritance patterns, involving both common and rare variants. Whole exome sequencing is a promising approach to find out the rare genetic variants. We had previously reported several rare variants in multiplex families with severe mental illnesses. The current article tries to summarise the biological processes and pattern of expression of genes harbouring the aforementioned variants, linking them to known clinical manifestations through a methodical narrative review. Of the 28 genes considered for this review from 7 families with multiple affected individuals, 6 genes are implicated in various neuropsychiatric manifestations including some variations in the brain morphology assessed by magnetic resonance imaging. Another 15 genes, though associated with neuropsychiatric manifestations, did not have established brain morphological changes whereas the remaining 7 genes did not have any previously recorded neuropsychiatric manifestations at all. Wnt/b-catenin signaling pathway was associated with 6 of these genes and PI3K/AKT, calcium signaling, ERK, RhoA and notch signaling pathways had at least 2 gene associations. We present a comprehensive review of biological and clinical knowledge about the genes previously reported in multiplex families with severe mental illness. A 'disease in dish approach' can be helpful to further explore the fundamental mechanisms.

High expression of NDRG3 in osteoarthritis patients

BACKGROUND

Osteoarthritis (OA), as a common disease, seriously affects the quality of life of the victims, but its pathogenesis remains unclear. It has been confirmed that hypoxia-induced factor (HIF)-mediated hypoxia response plays an important role in the development and progression of OA. As a member of the N-myc downstream regulatory gene families, NDRG3 has been reported to independently regulate the hypoxic response of tumour cells, but the relationship between NDRG3 and OA development has not been reported so far.

METHODS

In this study, seven OA patients were admitted to Guizhou Provincial People's Hospital from January 2017 to December 2018. The OA group included 5 patients clinically diagnosed with hip/knee OA, which required arthroplasty. The normal group included 2 patients with no previous history of OA and rheumatoid arthritis, which required amputation due to trauma or tumour. The articular cartilage samples were collected to detect the expression of HIF-1α, HIF-2α and NDRG3 using immunohistochemical (IHC), haematoxylin and eosin (HE) and toluidine blue (TB) staining.

RESULTS

HE and TB staining indicated that the cartilage surface of the normal group was smooth and intact, with a columnar arrangement of hyaline chondrocytes, while the cartilage surface of the OA group was discontinuous, with cartilage missing and fibrous soft tissue growing into the defect site. HIF-1α staining was positive in both groups. Moreover, HIF-2α and NDRG3 staining was weakly positive in the normal group, but were uniformly and strongly positive in the OA group. The positively stained areas and integral optical density for NDRG3 were significantly greater in OA group than in the normal group (p < 0.05).

CONCLUSIONS

NDRG3 might be closely related to the development and progression of OA. However, the relationship between NDRG3 and OA, which is independent of the HIF pathway, warrants further research.

Kaji-Ichigoside F1 and Rosamultin Protect Vascular Endothelial Cells against Hypoxia-Induced Apoptosis via the PI3K/AKT or ERK1/2 Signaling Pathway

As a pair of differential isomers, Kaji-ichigoside F1 and Rosamultin are both pentacyclic triterpenoids isolated from the subterranean root of Potentilla anserina L., a plant used in folk medicine in western China as antihypoxia and anti-inflammatory treatments. We demonstrated that Kaji-ichigoside F1 and Rosamultin effectively prevented hypoxia-induced apoptosis in vascular endothelial cells. We established a hypoxia model, using EA.hy926 cells, to further explore the mechanisms. Hypoxia promoted the phosphorylation of AKT, ERK1/2, and NF-κB. In hypoxic cells treated with Kaji-ichigoside F1, p-ERK1/2 and p-NF-κB levels were increased, while the level of p-AKT was decreased. Treatment with Rosamultin promoted phosphorylation of ERK1/2, NF-κB, and AKT in hypoxic cells. Following the addition of LY294002, the levels of p-AKT, p-ERK1/2, and p-NF-κB decreased significantly. Addition of PD98059 resulted in reduced levels of p-ERK1/2 and p-NF-κB, while p-AKT levels were increased. Pharmacodynamic analysis demonstrated that both LY294002 and PD98059 significantly inhibited the positive effects of Kaji-ichigoside F1 on cell viability during hypoxia, consistent with the results of hematoxylin-eosin (H&E) staining, DAPI staining, and flow cytometry. The antihypoxia effects of Rosamultin were remarkably inhibited by LY294002 but promoted by PD98059. In Kaji-ichigoside F1- and Rosamultin-treated cells, Bcl2 expression was significantly upregulated, while expression of Bax and cytochrome C and levels of cleaved caspase-9 and cleaved caspase-3 were reduced. Corresponding to pharmacodynamic analysis, LY294002 inhibited the regulatory effects of Kaji-ichigoside F1 and Rosamultin on the above molecules, while PD98059 inhibited the regulatory effects of Kaji-ichigoside F1 but enhanced the regulatory effects of Rosamultin. In conclusion, Kaji-ichigoside F1 protected vascular endothelial cells against hypoxia-induced apoptosis by activating the ERK1/2 signaling pathway, which positively regulated the NF-κB signaling pathway and negatively regulated the PI3K/AKT signaling pathway. Rosamultin protected vascular endothelial cells against hypoxia-induced apoptosis by activating the PI3K/AKT signaling pathway and positively regulating ERK1/2 and NF-κB signaling pathways.

High NDRG3 expression facilitates HCC metastasis by promoting nuclear translocation of β-catenin

NDRG1 has been reported to exert pivotal roles in tumor progression and metastasis via Wnt/β-catenin signaling pathway. However, little is known about the role of NDRG3 in hepatocarcinogenesis despite its classification in the same subfamily of NDRG1. The present study was aimed to characterize the expression pattern and understand the biological roles of NDRG3 in hepatocarcinogenesis, as a means to exploit its therapeutic potential. It was observed that NDRG3 was up-regulated in HCC tissues and higher NDRG3 expression was associated with significantly shorter overall survival. Furthermore, a lower level of NDRG3 exhibited marked positive correlation with metastasis-free survival. In vitro and in vivo experiments revealed that knock-down of NDRG3 inhibits HCC metastasis and angiogenesis. We further demonstrated that activation of WNT/β-catenin signaling and enhanced CSC-like properties were responsible for NDRG3- mediated promoting effect on HCC. In conclusion, the principal findings demonstrated that high NDRG3 expression facilitates HCC metastasis via regulating the turnover of β-catenin, as well as provides a potential therapeutic target for future therapeutic interventions.

Structural and Biophysical Analyses of Human N-Myc Downstream-Regulated Gene 3 (NDRG3) Protein

The N-Myc downstream-regulated gene (NDRG) family belongs to the α/β-hydrolase fold and is known to exert various physiologic functions in cell proliferation, differentiation, and hypoxia-induced cancer metabolism. In particular, NDRG3 is closely related to proliferation and migration of prostate cancer cells, and recent studies reported its implication in lactate-triggered hypoxia responses or tumorigenesis. However, the underlying mechanism for the functions of NDRG3 remains unclear. Here, we report the crystal structure of human NDRG3 at 2.2 Å resolution, with six molecules in an asymmetric unit. While NDRG3 adopts the α/β-hydrolase fold, complete substitution of the canonical catalytic triad residues to non-reactive residues and steric hindrance around the pseudo-active site seem to disable the α/β-hydrolase activity. While NDRG3 shares a high similarity to NDRG2 in terms of amino acid sequence and structure, NDRG3 exhibited remarkable structural differences in a flexible loop corresponding to helix α6 of NDRG2 that is responsible for tumor suppression. Thus, this flexible loop region seems to play a distinct role in oncogenic progression induced by NDRG3. Collectively, our studies could provide structural and biophysical insights into the molecular characteristics of NDRG3.

TIR/BB-loop mimetic AS-1 protects vascular endothelial cells from injury induced by hypoxia/reoxygenation

Morphological and functional abnormalities of vascular endothelial cells (VECs) are risk factors of ischemia-reperfusion in skin flaps. Signaling pathway mediated by interleukin-1 receptor (IL-1R) is essential to hypoxia/reoxygenation (H/R) injury of VECs. While the TIR/BB-loop mimetic (AS-1) disrupts the interaction between IL-1R and myeloid differentiation primary-response protein 88 (MyD88), its role in the VECs dysfunction under H/R is unclear. In this study, we first showed that there was an infiltration of inflammatory cells and the apoptosis of VECs by using a skin flap section from patients who received flap transplantation. We then showed that the H/R treatment induced apoptosis and loss of cell migration of endothelial cell line H926 were attenuated by AS-1. Furthermore, our data suggested that AS-1 inhibits the interaction between IL-1R and MyD88, and subsequent phosphorylation of IκB and p38 pathway, as well as the nuclear localization of NF-KB subunit p65/p50. Thus, this study indicated that the protective role of AS-1 in H/R induced cellular injury may be due to the AS-1 mediated down-regulation of IL-1R signaling pathway.

Botulinum Toxin Type A Attenuates Apoptosis in Human Dermal Microvascular Endothelial Cells Exposed to an In Vitro Model of Ischemia/Reperfusion Injury

BACKGROUND

Botulinum toxin type A (BTXA) has been reported to increase survival of critically ischemic skin flaps; however, the effect of BTXA in human dermal microvascular endothelial cells (HDMECs) remains to be investigated. This study aimed to investigate the protective effect of BTXA in HDMECs exposed to an in vitro model of ischemia/reperfusion injury.

METHODS

HDMECs were isolated from human upper eyelid tissue and were randomly divided into 3 groups: 1.

CONTROL GROUP

culture under normoxic conditions (95% air and 5% CO₂); 2. hypoxia/reoxygenation (H/R) group: culture in a hypoxic incubator (94% N₂ + 5% CO₂ + 5% O₂) for 8 hours, followed by culture in saturated aerobic culture medium for 24 hours; and 3. BTXA group: treatment with BTXA for 12 hours before exposure to hypoxic conditions. Flow cytometry was used to analyze the apoptosis of HDMECs, and western blotting was used to detect the expression of apoptosis-related proteins.

RESULTS

H/R leads to severe injury in HDMECs, as evidenced by an increase in the percentage of apoptosis and an increase in expression of apoptosis-related proteins (Bax, cleaved-caspase-3, and cytochrome C). Moreover, H/R results in a decrease in expression of anti-apoptotic protein (Bcl-2), which can be significantly attenuated with BTXA treatment.

CONCLUSION

BTXA protects against apoptosis in HDMECs exposed to an in vitro model of H/R-induced injury.

miR-1b overexpression suppressed proliferation and migration of RSC96 and increased cell apoptosis

Peripheral nerve injury (PNI) is a global problem that leads to severe disability and high healthcare expenditure. Accumulating evidence suggested that the phenotypes of Schwann cells (SCs) could be regulated by microRNAs (miRNAs) and expressions of various miRNAs are altered after PNI. In this study, the expression of miR-1b in the injured nerve and hypoxia-treated SCs was detected through qRT-PCR. The target genes of miR-1b were predicted by bioinformatics prediction and dual-luciferase reporter assay and verified through qRT-PCR and western blot. The effects of miR-1b and its specific target gene on the proliferation, migration and apoptosis of SCs were determined and the regulation of miR-1b on peripheral nerve regeneration after PNI was further investigated in vivo. We found that miR-1b was obviously downregulated in the injured nerve in a rat sciatic nerve transection model and directly targeted N-myc downstream-regulated gene 3 (NDRG3) by binding to its 3'-UTR and caused both mRNA degradation and translation suppression of NDRG3. Overexpression of miR-1b or knockdown of NDRG3 decreased the proliferation and migration as well as increased the apoptosis of SCs. NDRG3 reversed the effects of miR-1b overexpression on proliferation/migration/apoptosis of RSC96. In addition, injection of miR-1b antagomir promoted the expression of NDRG3 in the injured nerve following sciatic nerve injury. Compared to the model group, the rats treated with miR-1b agomir had lower functional recovery rate, and downregulation of miR-1b through injection of specific antagomir improved the functional recovery rate according to the results of sciatic functional index and nerve conduction velocity. Overall, our results will contribute to the development of novel targets for promoting nerve regeneration after PNI.

NDRG2 suppression as a molecular hallmark of photoreceptor-specific cell death in the mouse retina

Photoreceptor cell death is recognized as the key pathogenesis of retinal degeneration, but the molecular basis underlying photoreceptor-specific cell loss in retinal damaging conditions is virtually unknown. The N-myc downstream regulated gene (NDRG) family has recently been reported to regulate cell viability, in particular NDRG1 has been uncovered expression in photoreceptor cells. Accordingly, we herein examined the potential roles of NDRGs in mediating photoreceptor-specific cell loss in retinal damages. By using mouse models of retinal degeneration and the 661 W photoreceptor cell line, we showed that photoreceptor cells are indeed highly sensitive to light exposure and the related oxidative stress, and that photoreceptor cells are even selectively diminished by phototoxins of the alkylating agent N-Methyl-N-nitrosourea (MNU). Unexpectedly, we discovered that of all the NDRG family members, NDRG2, but not the originally hypothesized NDRG1 or other NDRG subtypes, was selectively expressed and specifically responded to retinal damaging conditions in photoreceptor cells. Furthermore, functional experiments proved that NDRG2 was essential for photoreceptor cell viability, which could be attributed to NDRG2 control of the photo-oxidative stress, and that it was the suppression of NDRG2 which led to photoreceptor cell loss in damaging conditions. More importantly, NDRG2 preservation contributed to photoreceptor-specific cell maintenance and retinal protection both in vitro and in vivo. Our findings revealed a previously unrecognized role of NDRG2 in mediating photoreceptor cell homeostasis and established for the first time the molecular hallmark of photoreceptor-specific cell death as NDRG2 suppression, shedding light on improved understanding and therapy of retinal degeneration.

Folic acid supplementation repressed hypoxia-induced inflammatory response via ROS and JAK2/STAT3 pathway in human promyelomonocytic cells

Hypoxia is associated with inflammation and various chronic diseases. Folic acid is known to ameliorate inflammatory reactions, but the metabolism of folic acid protecting against hypoxia-induced injury is still unclear. In our study, we examined the inflammatory signal transduction pathway in human promyelomonocytic cells (THP-1 cells) with or without treatment with folic acid under hypoxic culture conditions. Our results indicated that supplementation with folic acid significantly reduced the levels of interleukin-1β and tumor necrosis factor-α in hypoxic conditions. Treating THP-1 cells with folic acid suppressed oxidative stress and hypoxia-inducible factor-1α in a dose-dependent manner. Folic acid targeted the activation of Janus kinase 2, downregulated the phosphorylation of signal transducer and activator of transcription 3, and decreased the expression of nuclear factor-κB p65 protein in cells. However, the absence of folic acid did not make cells more vulnerable under hypoxic conditions. In conclusion, folic acid efficiently inhibited the inflammatory response of THP-1 cells under hypoxic conditions by inhibiting reactive oxygen species production and the Janus kinase 2/signal transducer and activator of transcription 3 signaling pathway. Our study supports a basis for treatment with folic acid for chronic inflammation, which correlated with hypoxia.