HMGA2 mediates Cr (VI)-induced metabolic reprogramming through binding to mitochondrial D-Loop region.

Hexavalent chromium [Cr (VI)] exists environmentally and occupationally. It has been shown to pose a carcinogenic hazard in certain occupations. This study was to investigate the role of high mobility group A2 (HMGA2) in Cr (VI)-induced metabolism reprogramming from oxidative phosphorylation (OXPHOS) to glycolysis in A549 and HELF cells. First, knockdown of HMGA2 by siHMGA2 significantly attenuated Cr (VI)-reduced expression of OXPHOS-related proteins (COX IV and ND1) and mitochondrial mass, indicating that HMGA2 was involved in Cr (VI)-reduced OXPHOS. Overexpression of HMGA2 by transfection of HMGA2-DNA plasmids reduced the expression of COX IV, ND1 and mitochondrial mass, suggesting the negative role of HMGA2 in OXPHOS. Secondly, both CCCP, the inhibitor of mitochondrial function, and the ER stress inhibitor, 4-phenylbutyric acid (4-PBA), decreased the level of HMGA2, indicating that the interaction of mitochondrial dysfunction and ER stress resulted in Cr (VI)-induced HMGA2 expression. Further study demonstrated that ER stress/HMGA2 axis mediated the metabolism rewiring from OXPHOS to aerobic glycolysis. Notably, Cr (VI) induced the accumulation of HMGA2 proteins in mitochondria and ChIP assay demonstrated that HMGA2 proteins could bind to D-loop region of mitochondrial DNA (mtDNA), which provided the proof for HMGA2-modulating OXPHOS. Taken together, our results suggested that the interaction of mitochondria and ER stress-enhanced HMGA2 played an important role in Cr (VI)-induced metabolic reprogramming from OXPHOS to glycolysis by binding directly to D-loop region of mtDNA. This work informs on the potential mode of action for Cr (VI)-induced tumors and builds on growing evidence regarding the contribution of cellular metabolic disruption contributing to carcinogenicity.

Inhibition of ATF4-mediated elevation of both autophagy and AKT/mTOR was involved in antitumorigenic activity of curcumin.

Curcumin, a natural hydrophobic polyphenol, carries significant anticancer activity. The protein kinase B (AKT)/the mammalian target of the rapamycin (mTOR) pathway and autophagy are well known to be involved in carcinogenesis, and usually, inhibition of mTOR is the main reason to promote autophagy. In this study, however, autophagy and mTOR were found to be inhibited simultaneously by curcumin treatments, and both of them played an important role in the effect of curcumin on suppressing the growth of A549 cells. Tunicamycin (TM), the activator of Endoplasmic Reticulum (ER) stress, increased both autophagy and AKT/mTOR, while curcumin could significantly decrease TM-induced autophagy and AKT/mTOR. Furthermore, curcumin could inhibit TM-induced aerobic glycolysis in A549 cells, and decrease the level of cycle-related and migration-related proteins. Blocking activating transcription factor 4 (ATF4) by siRNA strongly reduced both the expression of autophagy-related proteins and AKT/mTOR. ChIP assay illustrated that ATF4 protein could bind to the promotor sequence of either ATG4B or AKT1. The transplantation tumor experiment showed that the weight and volume of the transplanted tumors were reduced significantly in the BALB/c mice subcutaneously injected with A549 cells treated with curcumin. Moreover, intranasal administration of curcumin decreased the protein level of autophagy, AKT/mTOR and ER stress in lung tissues of BALB/c mice. Taken together, our results demonstrated that inhibition of ER stress-dependent ATF4-mediated autophagy and AKT/mTOR pathway plays an important role in anticancer effect of curcumin.

ER stress-enhanced HMGA2 plays an important role in Cr (VI)-induced glycolysis and inhibited oxidative phosphorylation by targeting the transcription of ATF4.

Hexavalent chromium [Cr (VI)] is a proven human carcinogen which is widely used in steel manufacturing and painting. Here, the involvement of high mobility group A2 (HMGA2) in Cr (VI)-mediated glycolysis and oxidative phosphorylation (OXPHOS) was investigated. First, Cr (VI) treatment induced aerobic glycolysis by increasing the expression of GLUT1, HK II, PKM2 and LDHA enzymes, and reduced OXPHOS by decreasing mitochondrial mass, the expression of COX IV and ND1, and increasing Ca2+ content in mitochondria in A549 and HELF cells. And overexpression of HMGA2 induced aerobic glycolysis and decreased OXPHOS. Secondly, using endoplasmic reticulum (ER) stress inhibitor, 4-phenylbutyric acid (4-PBA) and knockdown of activating transcription factor 4 (ATF4) gene by siRNA, we demonstrated that ER stress and ATF4 elevation mediated Cr (VI)-induced glycolysis and inhibited OXPHOS. Furthermore, using tunicamycin (Tm), siHMGA2, transfection of HMGA2 and siATF4, we demonstrated that ER stress-enhanced interaction of HMGA2 and ATF4 resulted in Cr (VI)-induced glycolysis and inhibited OXPHOS. Additionally, ChIP assay revealed that HMGA2 protein could directly bind to the promoter sequence of ATF4 gene, which modulated Cr (VI)-induced ATF4 elevation. Finally, in lung tissues of BALB/c mice injected with HMGA2 plasmids, it is verified that HMGA2 involved in regulation of ATF4, glycolysis and OXPHOS in vivo. Combining, our data discovered that ER stress-enhanced the interaction of HMGA2 and ATF4 played an important role in Cr (VI)-mediated glycolysis and OXPHOS. These results imply a root cause for the carcinogenicity of Cr (VI), and could guide development of novel therapeutics for cancers.

Autophagy induces mTOR-dependent glucose uptake and mTOR-independent lactate utilization in cadmium-treated A549 cells.

Cadmium (Cd) is a non-essential heavy metal with many harmful effects, especially tumorigenesis. Previously we established that autophagy-dependent increasing of glycolysis played an important role in Cd-induced cell growth and migration of A549 and HELF cells. In this study, we found Cd could induce autophagy and mTOR in A549 cells, HELF cells and in lung tissues of BALB/c mice. More interestingly, Cd-induced elevation of mTOR was autophagy-dependent and autophagy-induced cell growth and glycolysis was mTOR-dependent. However, in A549 cells, besides the above mTOR-dependent pathway, Cd-induced autophagy could directly induce PKM2 and LDHA independent of mTOR. Further study showed that only in A549 cells could autophagy other than mTOR enable Cd to increase MCT1 expression and MCT1 was involved in autophagy-induced PKM2 and LDHA. Sodium lactate added in the culture medium promoted Cd-induced cell growth of A549 cells, while had no effect on HELF cells. Finally, the effect of autophagy/MCT1/PKM2 pathway on lactate utilization to facilitate Cd-induced A549 cell growth was determined. Above all, we concluded that in HELF cells, autophagy induced mTOR-dependent glycolysis in which GLUT1 and HKII was elevated to promote glucose intake to accelerate cell growth. Whereas, in A549 cells, besides the above pathway to use glucose, autophagy could induce an mTOR-independent glycolysis pathway in which lactate could be used as fuel through autophagy-MCT1-PKM2 to escape glucose deficiency.

Complete chloroplast genome of the Meconopsis quintuplinervia (Papaveraceae), a traditional medicine of Tibetan.

As a medicinal herb of Tibetan, Meconopsis quintuplinervia is often utilized for treating pneumonia. In this study, the complete chloroplast genome of M. quintuplinervia was determined by next-generation sequencing technology. The overall genome was 154,997 bp in size, including a large single copy (LSC), a small single copy (SSC) and two inverted repeat (IR) regions, which were 85,153 bp, 17,876 bp, and 25,984 bp in length, respectively. The circular chloroplast genome owned 129 genes, comprising 84 protein-coding genes, 8 ribosomal RNA genes (four rRNA species), and 37 transfer RNA genes. The GC contents of the entire sequence, LSC, SSC, and IR region were 38.5%, 37.1%, 32.8%, and 43%, separately. The maximum likelihood tree revealed that M. quintuplinervia was closely related to M. racemosa with strong support value.