Mitochondrial ADP/ATP Carrier 1 Is Important for the Growth of Toxoplasma Tachyzoites.

Metabolism associated with energy production is highly compartmentalized in eukaryotic cells. During this process, transporters that move metabolites across organelle membranes play pivotal roles. The highly conserved ADP/ATP carrier (AAC) involved in ATP and ADP exchange between the mitochondria and cytoplasm is key to linking the metabolic activities in these 2 compartments. The ATP produced in mitochondria can be exchanged with cytoplasmic ADP by AAC, thus satisfying the energy needs in the cytoplasm. Toxoplasma gondii is an obligate intracellular parasite with a wide range of hosts. Previous studies have shown that mitochondrial metabolism helps Toxoplasma to parasitize diverse host cells. Here, we identified 2 putative mitochondria ADP/ATP carriers in Toxoplasma with significant sequence similarity to known AACs from other eukaryotes. We examined the ATP transport function of TgAACs by expressing them in Escherichia coli cells and found that only TgAAC1 had ATP transport activity. Moreover, knockdown of TgAAC1 caused severe growth defects of parasites and heterologous expression of mouse ANT2 in the TgAAC1 depletion mutant restored its growth, revealing its importance for parasite growth. These results verified that TgAAC1 functions as the mitochondrial ADP/ATP carrier in T. gondii and the functional studies demonstrated the importance of TgAAC1 for tachyzoites growth. IMPORTANCE T. gondii has an efficient and flexible energy metabolism system to meet different growth needs. ATP is an energy-carrying molecule and needs to be exchanged between organelles with the assistance of transporters. However, the function of TgAACs has yet to be characterized. Here, we identified 2 putative AACs of T. gondii and verified that only TgAAC1 had ATP transport activity with expression in the intact E. coli cells. Detailed analyses found that TgAAC1 is critical for the growth of tachyzoites and TgAAC2 is dispensable. Moreover, complementation with mouse ANT2 restored the growth speed of iTgAAC1, further suggesting TgAAC1 functions as a mitochondrial ADP/ATP carrier. Our research demonstrated the importance of TgAAC1 for tachyzoites growth.

A negative feedback loop involving NF-κB/TIR8 regulates IL-1ß-induced epithelial- myofibroblast transdifferentiation in human tubular cells.

Renal tubular epithelial-myofibroblast transdifferentiation (EMT) plays a central role in the development of renal interstitial fibrosis (RIF). The profibrotic cytokine interleukin (IL)-1 and the IL-1 receptor (IL-1R) also participate in RIF development, and Toll/IL-1R 8 (TIR8), a member of the Toll-like receptor superfamily, has been identified as a negative regulator of IL-1R signaling. However, the functions of TIR8 in IL-1-induced RIF remain unknown. Here, human embryonic kidney epithelial cells (HKC) and unilateral ureteric obstruction (UUO)-induced RIF models on SD rats were used to investigate the functions of TIR8 involving IL-1ß-induced EMT. We showed that IL-1ß primarily triggers TIR8 expression by activating nuclear factor-κB (NF-κB) in HKC cells. Conversely, high levels of TIR8 in HKC cells repress IL-1ß-induced NF-κB activation and inhibit IL-1ß-induced EMT. Moreover, in vitro and in vivo findings revealed that TIR8 downregulation facilitated IL-1ß-induced NF-κB activation and contributed to TGF-ß1-mediated EMT in renal tubular epithelial cells. These results suggested that TIR8 exerts a protective role in IL-1ß-mediated EMT and potentially represents a new target for RIF treatment.

Estimating PM2.5 concentrations via random forest method using satellite, auxiliary, and ground-level station dataset at multiple temporal scales across China in 2017.

Fine particulate matter with aerodynamic diameters less than 2.5 µm (PM2.5) poses adverse impacts on public health and the environment. It is still a great challenge to estimate high-resolution PM2.5 concentrations at moderate scales. The current study calibrated PM2.5 concentrations at a 1 km resolution scale using ground-level monitoring data, Aerosol Optical Depth (AOD), meteorological data, and auxiliary data via Random Forest (RF) model across China in 2017. The three ten-folded cross-validations (CV) methods including sample-based, time-based, and spatial-based validation combined with Coefficient Square (R2), Root-Mean-Square Error (RMSE), and Mean Predictive Error (MPE) have been used for validation at different temporal scales in terms of daily, monthly, heating seasonal, and non-heating seasonal. Finally, the distribution map of PM2.5 concentrations was illustrated based on the RF model. Some findings were achieved. The RF model performed well, with a relatively high sample-based cross-validation R2 of 0.74, a low RMSE of 16.29 µg × m-3, and a small MPE of -0.282 µg × m-3. Meanwhile, the performance of the RF model in inferring the PM2.5 concentrations was well at urban scales except for Chengyu (CY). North China, the CY urban agglomeration, and the northwest of China exhibited relatively high PM2.5 pollution features, especially in the heating season. The robustness of the RF model in the present study outperformed most statistical regression models for calibrating PM2.5 concentrations. The outcomes can supply an up-to-date scientific dataset for epidemiological and air pollutants exposure risk studies across China.

Interleukin-1ß-Induced Senescence Promotes Osteoblastic Transition of Vascular Smooth Muscle Cells.

INTRODUCTION: Interleukin (IL)-1ß, as a key biomarker and mediator of vascular calcification in patients with end-stage renal disease (ESRD), may be involved in the process of premature senescence of vascular smooth muscle cells (VSMCs). This work sought to investigate whether IL-1ß-induced premature senescence contributes to the process of osteoblastic transition and vascular calcification in VSMCs. METHODS: Eighty-eight patients with ESRD (aged 25-81 years), 11 healthy individuals, and 15 cases of lesion-free distal radial arteries from dialysis ESRD patients with angiostomy were collected in this study. Immunohistochemical analysis was performed to detect expression of IL-1ß, p21, and bone morphogenetic protein-2 (BMP2) in the distal radial arteries. Primary human VSMCs from healthy neonatal umbilical cords were incubated with test agents for 1-3 days. Intracellular levels of reactive oxygen species (ROS) and senescence-associated-ß-galactosidase (SA-ß-gal) staining were used to detect senescent cells. Alizarin red staining and the calcium content of the cell layer were used to detect mineral deposition in VSMCs. RESULTS: Coincident with positive staining of IL-1ß, p21, and BMP2 in the lesion-free distal radial arteries, 66.67% patients showed mineral deposition. Serum IL-1ß was 0.24 ± 0.57, 1.20 ± 2.95, and 9.41 ± 40.52 pg/mL in 11 healthy individuals, 20 patients without calcification, and 53 patients with calcification, respectively. Analysis of the cross-table chi-square test showed cardiovascular calcification is not correlated with levels of serum IL-1ß in patients with ESRD (p = 0.533). In response to IL-1ß, VSMCs showed a senescence-like phenotype, such as flat and enlarged morphology, increased expression of p21, an increased activity of SA-ß-gal, and increased levels of ROS. IL-1ß-induced senescence of VSMCs was required for the activation of IL-1ß/NF-κB/p53/p21 signaling pathway. IL-1ß-induced senescent VSMCs underwent calcification due to osteoblastic transition mainly depending upon the upregulation of BMP2. Resveratrol, an activator of sirtuin-1, postponed the IL-1ß-induced senescence through blocking the NF-κB/p53/p21 pathway and attenuated the osteoblastic transition and calcification in VSMCs. CONCLUSIONS: High levels of IL-1ß in medial smooth muscles of arteries may play roles in inducing senescence-associated calcification. IL-1ß-induced senescence depending on the activation of the NF-κB/p53/p21 signaling pathway and contributing to osteoblastic transition of VSMCs.

The synergistic action of phosphate and interleukin-6 enhances senescence-associated calcification in vascular smooth muscle cells depending on p53.

Cardiovascular calcification is associated with cardiovascular morbidity and mortality of patients with end-stage renal diseases (ESRD). Hyperphosphatemia and many of the inflammatory markers and mediators, including interleukin-6 (IL-6), are considered as the major risk factors of cardiovascular calcification. Although cellular senescence may be involved in cardiovascular calcification caused by phosphate overload and (or) IL-6 in patients with ESRD, less is known about the underlying mechanisms for phosphate- and IL-6-induced senescence-associated calcification of vascular smooth muscle cells (VSMCs). In the present study, we investigated the correlation between cellular senescence and vascular calcification induced by loading phosphate and (or) IL-6 in VSMCs. Our findings show that p53 plays a major role in senescence-associated vascular calcification induced by phosphate overload. IL-6 induces senescence-associated calcification in VSMCs depending upon activation of the IL-6/soluble IL-6 receptor (sIL-6R)/signal transducer and activator of transcription 3 (STAT3)/p53/p21 pathway. We demonstrate that the synergistic action of phosphate overload and IL-6 enhances senescence-associated calcification in a p53-dependent manner and is inhibited by an anti-aging agent (resveratrol) in a dose-dependent manner.

Molecular link between glucose and glutamine consumption in cancer cells mediated by CtBP and SIRT4.

Glucose and Glutamine are two essential ingredients for cell growth. However, it remains open for investigation whether there is a general mechanism that coordinates the consumption of glucose and glutamine in cancer cells. Glutamine is mainly metabolized through the glutaminolysis pathway and our previous report indicated that CtBP increases GDH activity and promotes glutaminolysis through repressing the expression of SIRT4, a well-known mitochondrion-located factor that inhibits glutaminolysis pathway. CtBP is known to be a sensor of intracellular metabolic status; we thus hypothesized that a consensus CtBP-SIRT4-GDH axis may mediate the crosstalk between glycolysis and glutaminolysis. Herein, supporting this hypothesis, we observed the coordinated consumption of glucose and glutamine across different cell lines. This coordination was found to be related to CtBP repression activity on SIRT4 expression under high level of glucose but not low glucose level. Low level of glucose supply was found to decrease GDH activity via blocking CtBP dimerization. Mechanically, low glucose also abolished CtBP binding to SIRT4 promoter and the repression of SIRT4 expression. Consistently, the CtBP dimerization inhibitor MTOB mimicked low glucose effects on SIRT4 expression, and GDH activity suggest that CtBP requires high glucose supply to act as a suppressor of SIRT4 gene. In conclusion, we propose that a general molecular pathway composed by CtBP-SIRT4-GDH coordinating the metabolism of glucose and glutamine in cancer cells.