NDRG2 programs tumor-associated macrophages for tumor support

Lactate attenuates astrocytic inflammation by inhibiting ubiquitination and degradation of NDRG2 under oxygen-glucose deprivation conditions

BACKGROUND

Brain lactate concentrations are enhanced in response to cerebral ischemia and promote the formation of reactive astrocytes, which are major components of the neuroinflammatory response and functional recovery, following cerebral ischemia. NDRG2 is upregulated during reactive astrocyte formation. However, its regulation and function are unclear. We studied the relationship between lactate and NDRG2 in astrocytes under conditions of ischemia or oxygen-glucose deprivation (OGD).

METHODS

We examined astrocytic NDRG2 expression after middle cerebral artery occlusion (MCAO) using western blot and immunofluorescence staining. Under hypoxia conditions, we added exogenous L-lactate sodium (lactate) to cultured primary astrocytes to explore the effects of lactate on the ubiquitination modification of NDRG2. We profiled the transcriptomic features of NDRG2 silencing in astrocytes after 8 h of OGD conditions as well as exogenous lactate treatment by performing RNA-seq. Finally, we evaluated the molecular mechanisms of NDRG2 in regulating TNFα under OGD conditions using western blot and immunohistochemistry.

RESULTS

Reactive astrocytes strongly expressed NDRG2 in a rat model of MCAO. We also showed that lactate stabilizes astrocytic NDRG2 by inhibiting its ubiquitination. NDRG2 inhibition in astrocytes increased inflammation and upregulated immune-associated genes and signaling pathways. NDRG2 knockdown induced TNFα expression and secretion via c-Jun phosphorylation.

CONCLUSIONS

We revealed that under OGD conditions, lactate plays an important anti-inflammatory role and inhibits TNFα expression by stabilizing NDRG2, which is beneficial for neurological functional recovery. NDRG2 may be a new therapeutic target for cerebral ischemia.

N-myc Downstream-Regulated Gene 2 (NDRG2) Promotes Bone Morphogenetic Protein 2 (BMP2)-Induced Osteoblastic Differentiation and Calcification by Janus Kinase 3 (JAK3)/Signal Transducer and Activator of Transcription 3 (STAT3) Signaling Pathway

Background

Osteoporosis is an osteolytic disease resulted from imbalance in bone homeostasis. Studies indicated that N-myc downstream-regulated gene 2 (NDRG2) could affect the osteoclast differentiation. However, the effect of NDRG2 on osteoblastic differentiation and calcification remains unknown. Hence, we aimed to analyze the effect of NDRG2 on the proliferation and differentiation of osteoblasts.

Material/Methods

The differentiation of bone morphogenetic protein 2 (BMP2) induced MC3T3-E1 cells was observed by the microscope. Real-time quantitative polymerase chain reaction (RT-qPCR) and western blot analysis detected the expression of BMP2, NDRG2, runt-related transcription factor 2 (Runx2), osteoprotegerin (OPG), osterix (OSX), and osteocalcin (OCN). Alkaline phosphatase (ALP) activity assay was detecting the ALP activity and alizarin red staining assay was analyzing intracellular calcium salt deposition. The cell transfection was also verified by RT-qPCR analysis.

Results

The results demonstrated that BMP2 promoted the osteoblastic differentiation with the increasing expression of Runx2, OPG, OSX, and OCN. NDRG2 expression was upregulated during osteogenic differentiation. NDRG2 overexpression promoted the expression of Runx2, OPG, OSX, and OCN, and increased the ALP activity while NDRG2 inhibition reversed the changes. NDRG2 overexpression increased the intracellular calcium salt deposition and NDRG2 inhibition reversed the changes. The role of NDRG2 in osteoblastic differentiation and calcification was played through the JAK3/STAT3 signal pathway.

Conclusions

The presented data indicated that NDRG2 promoted BMP2-induced osteoblastic differentiation and calcification by activating the JAK3/STAT3 signal pathway.