UCP2 as a Cancer Target through Energy Metabolism and Oxidative Stress Control

Synergistic salvation: HIIT and herbal allies reverse NAFLD damage in rats

Fatty liver disease is a build-up of fats in the liver that can damage the organ and lead to serious complications. This study aimed to investigate the effects of exercise training and supplementation (milk thistle, chicory and cumin) on liver metabolites related to its function and health in rats with non-alcoholic fatty liver disease (NAFLD). Forty adult male Wistar rats with an average weight of 215 ± 10 g were divided into a control group fed on the basal diet and four experimental groups fed with high-fat diet (HFD) for 6 weeks to induce non-alcoholic fatty liver disease (NAFLD). The 4 NAFLD groups were subdivided and treated with (a) plain HFD, (b) high-intensity interval training (HIIT), (c) supplement (milk thistle, chicory, and cumin), and (d) combined HIIT and supplementation for 4 weeks. The induction of NAFLD through HFD yielded dyslipidemia, liver tissue damage, increased malondialdehyde, uncoupling protein 2 (UCP2), and phosphatidylinositol-3 kinase (PI3K), as well as decreased superoxide dismutase (SOD) and peroxisome proliferator-activated receptor gamma co-activator 1 alpha (PGC-1α) in liver tissue (p < 0.05). The 4 weeks intervention with either HIIT, supplement or especially the combined application of both, reversed these factors (p < 0.05) through changes in their concentrations in a direction indicative of enhanced liver health and function. HIIT beside supplementation (milk thistle, chicory, and cumin) improved indices related to oxidative stress, lipid profile, and the expression of PI3K, UCP2, PGC-1α genes expression and PGC-1α protein content, making it potentially promising in the treatment of liver damage caused by HFD.

An innovative glutamine metabolism-related gene signature for predicting prognosis and immune landscape in cervical cancer

BACKGROUND

Cervical cancer (CC) is a major global malignancy affecting women. However, the precise mechanisms underlying glutamine's role in CC remain inadequately understood. This study systematically assessed the survival outcomes, immune landscape, and drug sensitivity profiles with CC patients by analyzing genes associated with glutamine metabolism.

METHODS

Transcriptomic data for the samples were sourced from the TCGA, GTEx, and GEO databases. Prognostic genes were identified through univariate, multivariate, and Least Absolute Shrinkage and Selection Operator (LASSO) regression analyses. The predictive accuracy of the model was assessed through the analysis of receiver operating characteristic (ROC) curves. A comprehensive nomogram was developed and evaluated for accuracy using calibration and Decision Curve Analysis (DCA) curves. Kaplan-Meier (K-M) survival curves were employed to estimate overall survival. The relationship between risk scores and immune infiltration was analyzed through Single-sample Gene Set Enrichment Analysis (ssGSEA) and CIBERSORT. Functional enrichment analysis and the construction of miRNA and transcription factors networks were conducted to explore the potential molecular mechanisms of the signature genes.

RESULTS

This investigation identified four signature genes associated with glutamine metabolism, UCP2, LEPR, TFRC, and RNaseH2A. We successfully developed a prognostic model with strong predictive performance. In the training set, the AUC values for 1-, 3-, and 5-year survival were 0.702, 0.719, and 0.721, respectively. In the validation set, the AUC values for these time points were 0.715, 0.696, and 0.739, respectively. Patients categorized as low-risk had notably improved survival rates than those identified as high-risk (P < 0.05). Additionally, a nomogram that combines clinical data and risk scores offered improved clinical net benefits over a broad range of threshold probabilities. Functional enrichment analysis revealed that these signature genes are strongly linked to the regulation of the cell cycle and intracellular oxygen levels. Furthermore, the gene signature displayed a significant negative correlation with the infiltration levels of most immune cell types.

CONCLUSION

This novel signature demonstrates robust predictive capability for prognostic survival probabilities and immune infiltration in CC patients, providing a fresh perspective for advancing precision treatment strategies in CC.

The Role of Mitochondrial Solute Carriers SLC25 in Cancer Metabolic Reprogramming: Current Insights and Future Perspectives

Cancer cells undergo remarkable metabolic changes to meet their high energetic and biosynthetic demands. The Warburg effect is the most well-characterized metabolic alteration, driving cancer cells to catabolize glucose through aerobic glycolysis to promote proliferation. Another prominent metabolic hallmark of cancer cells is their increased reliance on glutamine to replenish tricarboxylic acid (TCA) cycle intermediates essential for ATP production, aspartate and fatty acid synthesis, and maintaining redox homeostasis. In this context, mitochondria, which are primarily used to maintain energy homeostasis and support balanced biosynthesis in normal cells, become central organelles for fulfilling the heightened biosynthetic and energetic demands of proliferating cancer cells. Mitochondrial coordination and metabolite exchange with other cellular compartments are crucial. The human SLC25 mitochondrial carrier family, comprising 53 members, plays a pivotal role in transporting TCA intermediates, amino acids, vitamins, nucleotides, and cofactors across the inner mitochondrial membrane, thereby facilitating this cross-talk. Numerous studies have demonstrated that mitochondrial carriers are altered in cancer cells, actively contributing to tumorigenesis. This review comprehensively discusses the role of SLC25 carriers in cancer pathogenesis and metabolic reprogramming based on current experimental evidence. It also highlights the research gaps that need to be addressed in future studies. Understanding the involvement of these carriers in tumorigenesis may provide valuable novel targets for drug development.

Mitochondrial uncoupling protein 2: a central player in pancreatic disease pathophysiology

Pancreatic diseases pose considerable health challenges due to their complex etiology and limited therapeutic options. Mitochondrial uncoupling protein 2 (UCP2), highly expressed in pancreatic tissue, participates in numerous physiological processes and signaling pathways, indicating its potential relevance in these diseases. Despite this, UCP2's role in acute pancreatitis (AP) remains underexplored, and its functions in chronic pancreatitis (CP) and pancreatic steatosis are largely unknown. Additionally, the mechanisms connecting various pancreatic diseases are intricate and not yet fully elucidated. Given UCP2's diverse functionality, broad expression in pancreatic tissue, and the distinct pathophysiological features of pancreatic diseases, this review offers a comprehensive analysis of current findings on UCP2's involvement in these conditions. We discuss recent insights into UCP2's complex regulatory mechanisms, propose that UCP2 may serve as a central regulatory factor in pancreatic disease progression, and hypothesize that UCP2 dysfunction could significantly contribute to disease pathogenesis. Understanding UCP2's role and mechanisms in pancreatic diseases may pave the way for innovative therapeutic and diagnostic approaches.

Repurposed genipin targeting UCP2 exhibits antitumor activity through inducing ferroptosis in glioblastoma

Uncoupling protein-2 (UCP2) controls the antioxidant response and redox homeostasis in cancer and is considered a potent molecular target for cancer treatment. However, the specific mechanism of UCP2 inhibition and its role in glioblastoma (GBM) have not yet been elucidated. Here, we attempt to identify a UCP2 inhibitor and study the underlying molecular mechanism in GBM. Bioinformatics analysis and immunohistochemistry are used to validate the high expression of UCP2 in GBM and its prognostic significance. Drug intervention and tumor xenograft experiments are conducted to determine the inhibitory effect of genipin, a UCP2 inhibitor, on UCP2. The mitochondrial membrane potential and key ferroptosis genes are examined to determine the occurrence of ferroptosis. High expression of UCP2 in GBM is associated with poor prognosis, and inhibiting UCP2 can alleviate the malignant behavior of GBM tumors. Genipin can downregulate the expression of GPX4 and upregulate the expression of ACSL4 by inhibiting UCP2, leading to ferroptosis and alleviating the malignant behavior of tumors. In summary, UCP2 is a potential therapeutic target for GBM. Genipin, which targets UCP2, effectively inhibits GBM development by inducing ferroptosis in vivo and in vitro. These findings indicate that genipin treatment based on UCP2 targeting has potential therapeutic applications with a clinical perspective for the treatment of GBM patients.

Differential regulation of mitochondrial uncoupling protein 2 in cancer cells

The persistent growth of cancer cells is underscored by complex metabolic reprogramming, with mitochondria playing a key role in the transition to aerobic glycolysis and representing new therapeutic targets. Mitochondrial uncoupling protein 2 (UCP2) has attracted interest because of its abundance in rapidly proliferating cells, including cancer cells, and its involvement in cellular metabolism. However, the specific contributions of UCP2 to cancer biology remain poorly defined. Our investigation of UCP2 expression in various human and mouse cancer cell lines aimed to elucidate its links to metabolic states, proliferation, and adaptation to environmental stresses such as hypoxia and nutrient deprivation. We observed significant variability in UCP2 expression across cancer types, with no direct correlation to their metabolic activity or proliferation rates. UCP2 abundance was also differentially affected by nutrient availability in different cancer cells, but UCP2 was generally downregulated under hypoxia. These findings challenge the notion that UCP2 is a marker of malignant potential and suggest its more complex involvement in the metabolic landscape of cancer.

Transcriptome analysis provides new insights into the response of canine intestinal epithelial cells treated by sulforaphane: a natural product of cruciferous origin

This study presents a comprehensive transcriptome analysis of canine intestinal epithelial cells following treatment with sulforaphane (SFN), a naturally occurring compound found in cruciferous vegetables with established anti-inflammatory and antioxidant properties. Through high-throughput sequencing, we identified 29,993 genes, among which 1,612 were differentially expressed, with 792 up-regulated and 820 down-regulated in response to SFN treatment. Our analysis revealed significant enrichment of genes in pathways associated with the inflammatory response, lipid metabolism, oxidative stress response, and T-cell mediated immunity, suggesting SFN's potential in modulating these biological processes. Notably, the PPARγ gene, which plays a crucial role in the body's oxidative stress and inflammatory response, was highly up-regulated, indicating its possible centrality in SFN's effects. Gene-gene interaction analysis further supported SFN's role in alleviating inflammation through PPARγ, with key genes in oxidative stress and inflammatory response pathways showing significant correlations with PPARγ. Overall, our findings provide molecular evidence for SFN's protective effects on canine intestinal health, potentially through the modulation of inflammatory and oxidative stress pathways, with PPARγ emerging as a critical mediator.

Effects of photobiomodulation on colon cancer cell line HT29 according to mitochondria

BACKGROUND/AIM

Although photobiomodulation therapy (PBMt) is available to alleviate post-operative side effects of malignant diseases, its application is still controversial due to some potential of cancer recurrence and occurrence of a secondary malignancy. We investigated effect of PBMt on mitochondrial function in HT29 colon cancer cells.

METHODS

HT29 cell proliferation was determined with MTT assay after PBMt. Immunofluorescent staining was performed to determine mitochondrial biogenesis and reactive oxygen species (ROS). Mitochondrial membrane potential was measured with Mitotracker. Western blotting was executed to determine expression of fission, fusion, UCP2, and cyclin B1 and D1 proteins. In vivo study was performed by subcutaneously inoculating cancer cells into nude mice and immunohistochemistry was done to determine expression of FIS1, MFN2, UCP2, and p-AKT.

RESULTS

The proliferation and migration of HT29 cells reached maximum with PBMt (670 nm, light emitting diode, LED) at 2.0 J/cm2 compared to control (P < 0.05) with more expression of cyclin B1 and cyclin D1 (P < 0.05). Immunofluorescent staining showed that ROS and mitochondrial membrane potential were enhanced after PBMt compared to control. ATP synthesis of mitochondria was also higher in the PBMt group than in the control (P < 0.05). Expression levels of fission and fusion proteins were significantly increased in the PBMt group than in the control (P < 0.05). Electron microscopy revealed that the percentage of mitochondria showing fission was not significantly different between the two groups. Oncometabolites including D-2-hydoxyglutamate in the supernatant of cell culture were higher in the PBMt group than in the control with increased UCP2 expression (P < 0.05). Both tumor size and weight of xenograft in nude mice model were bigger and heavier in the PBMt group than in the control (P < 0.05). Immunohistologically, mitochondrial biogenesis proteins UCP2 and p-AKT in xenograft of nude mice were expressed more in the PBMt group than in the control (P < 0.05).

CONCLUSIONS

Treatment with PBM using red light LED may induce proliferation and progression of HT29 cancer cells by increasing mitochondrial activity and fission.

Nkx1.2 deletion decreases fat production in zebrafish

OBJECTIVE

This study aimed to investigate the role of Nkx1-2, a transcription factor with the NK homeobox domain, in the regulation of fat production.

METHODS

Gene expression was analyzed using quantitative real-time polymerase chain reaction or transcriptome sequencing. CRISPR/Cas9 technology was employed to generate nkx1.2 knockout zebrafish and nkx1.2-deleted 3T3-L1 cells. Lipid droplet production in zebrafish larvae was visually quantified using Nile red staining, whereas lipid droplets in 3T3-L1 cells were stained with Oil red O. The binding of Nkx1-2 to the promoter was verified through an electrophoretic mobility shift assay experiment.

RESULTS

Nkx1-2 plays crucial roles in the regulation of fat production in zebrafish. Knockout of nkx1.2 in zebrafish leads to weight loss, accompanied by significantly reduced lipid droplet production and decreased visceral and liver fat content. Furthermore, genes related to lipid biosynthesis are significantly downregulated. In 3T3-L1 preadipocytes, Nkx1-2 induces differentiation into mature adipocytes by binding to the cebpa promoter, thereby activating its transcription. Additionally, the expression of nkx1.2 is regulated by the p38 MAPK, JNK, or Smad2/3 signaling pathways in 3T3-L1 cells.

CONCLUSIONS

Our findings suggest that Nkx1-2 functions as a positive regulator of fat production, playing a critical role in adipocyte differentiation and lipid biosynthesis.

Genipin's potential as an anti-cancer agent: from phytochemical origins to clinical prospects

This comprehensive review delves into the multifaceted aspects of genipin, a bioactive compound derived from medicinal plants, focusing on its anti-cancer potential. The review begins by detailing the sources and phytochemical properties of genipin, underscoring its significance in traditional medicine and its transition into contemporary cancer research. It then explores the intricate relationship between genipin's chemical structure and its observed anti-cancer activity, highlighting the molecular underpinnings contributing to its therapeutic potential. This is complemented by a thorough analysis of preclinical studies, which investigates genipin's efficacy against various cancer cell lines and its mechanisms of action at the cellular level. A crucial component of the review is the examination of genipin's bioavailability and pharmacokinetics, providing insights into how the compound is absorbed, distributed, metabolized, and excreted in the body. Then, this review offers a general and updated overview of the anti-cancer studies of genipin and its derivatives based on its basic molecular mechanisms, induction of apoptosis, inhibition of cell proliferation, and disruption of cancer cell signaling pathways. We include information that complements the genipin study, such as toxicity data, and we differentiate this review by including commercial status, disposition, and regulation. Also, this review of genipin stands out for incorporating information on proposals for a technological approach through its load in nanotechnology to improve its bioavailability. The culmination of this information positions genipin as a promising candidate for developing novel anti-cancer drugs capable of supplementing or enhancing current cancer therapies.

UCP2, a Member of the Mitochondrial Uncoupling Proteins: An Overview from Physiological to Pathological Roles

UCP2 is an uncoupling protein homolog to UCP1. Unlike UCP1, which participates in non-shivering thermogenesis by uncoupling oxidative phosphorylation (OXPHOS), UCP2 does not perform a canonical H+ leak, consuming the protonmotive force (Δp) through the inner mitochondrial membrane. The UCP2 biological role is elusive. It can counteract oxidative stress, acting with a "mild uncoupling" process to reduce ROS production, and, in fact, UCP2 activities are related to inflammatory processes, triggering pathological conditions. However, the Δp dissipation by UCP2 activity reduces the mitochondrial ATP production and rewires the bioenergetic metabolism of the cells. In all likelihood, UCP2 works as a carrier of metabolites with four carbon atoms (C4), reversing the anaerobic glycolysis-dependent catabolism to OXPHOS. Indeed, UCP2 can perform catalysis in dual mode: mild uncoupling of OXPHOS and metabolite C4 exchange of mitochondria. In vivo, the UCP2 features in the biology of mitochondria promote healthy ageing, increased lifespan, and can assure cerebro- and cardiovascular protection. However, the pathological conditions responsible for insulin secretion suppression are dependent on UCP2 activity. On balance, the uncertain biochemical mechanisms dependent on UCP2 do not allow us to depict the protective role in mitochondrial bioenergetics.

Cancer energy reprogramming and the immune responses

Cancer as an uncontrolled growth of cells due to existing mutation in host cells that may proliferate, induce angiogenesis and sometimes metastasize due to the favorable tumor microenvironment (TME). Since it kills more than any disease, biomedical science does not relent in studying the exact pathogenesis. It was believed to be a problem that lies in the nucleus of the host cells; however, recent oncology findings are shifting attention to the mitochondria as an adjuvant to cancer pathogenesis. The changes in the gene are strongly related to cellular metabolism and metabolic reprogramming. It is now understood that reprogramming the TME will have a direct effect on the immune cells' metabolism. Although there are a number of studies on immune cells' response towards tumor energy reprogramming and cancer progression, there is still no existence with the updated collation of these immune cells' response to distinct energy reprogramming in cancer studies. To this end, this mini review shed some light on cancer energy reprogramming mechanisms and enzyme degradation pathways, the cancer pathogenicity activity series involved with reduced lactate production, the specific immune cell responses due to the energy reprogramming. This study highlighted some prospects and future experiments in harnessing the host immune response towards the altered energy metabolism due to cancer.

Polyphenols: immunonutrients tipping the balance of immunometabolism in chronic diseases

Mounting evidence progressively appreciates the vital interplay between immunity and metabolism in a wide array of immunometabolic chronic disorders, both autoimmune and non-autoimmune mediated. The immune system regulates the functioning of cellular metabolism within organs like the brain, pancreas and/or adipose tissue by sensing and adapting to fluctuations in the microenvironment's nutrients, thereby reshaping metabolic pathways that greatly impact a pro- or anti-inflammatory immunophenotype. While it is agreed that the immune system relies on an adequate nutritional status to function properly, we are only just starting to understand how the supply of single or combined nutrients, all of them termed immunonutrients, can steer immune cells towards a less inflamed, tolerogenic immunophenotype. Polyphenols, a class of secondary metabolites abundant in Mediterranean foods, are pharmacologically active natural products with outstanding immunomodulatory actions. Upon binding to a range of receptors highly expressed in immune cells (e.g. AhR, RAR, RLR), they act in immunometabolic pathways through a mitochondria-centered multi-modal approach. First, polyphenols activate nutrient sensing via stress-response pathways, essential for immune responses. Second, they regulate mammalian target of rapamycin (mTOR)/AMP-activated protein kinase (AMPK) balance in immune cells and are well-tolerated caloric restriction mimetics. Third, polyphenols interfere with the assembly of NLR family pyrin domain containing 3 (NLRP3) in endoplasmic reticulum-mitochondria contact sites, inhibiting its activation while improving mitochondrial biogenesis and autophagosome-lysosome fusion. Finally, polyphenols impact chromatin remodeling and coordinates both epigenetic and metabolic reprogramming. This work moves beyond the well-documented antioxidant properties of polyphenols, offering new insights into the multifaceted nature of these compounds. It proposes a mechanistical appraisal on the regulatory pathways through which polyphenols modulate the immune response, thereby alleviating chronic low-grade inflammation. Furthermore, it draws parallels between pharmacological interventions and polyphenol-based immunonutrition in their modes of immunomodulation across a wide spectrum of socioeconomically impactful immunometabolic diseases such as Multiple Sclerosis, Diabetes (type 1 and 2) or even Alzheimer's disease. Lastly, it discusses the existing challenges that thwart the translation of polyphenols-based immunonutritional interventions into long-term clinical studies. Overcoming these limitations will undoubtedly pave the way for improving precision nutrition protocols and provide personalized guidance on tailored polyphenol-based immunonutrition plans.

Uridine diphosphate glucuronosyltransferase 1A1 prevents the progression of liver injury

BACKGROUND

Uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1) plays a crucial role in metabolizing and detoxifying endogenous and exogenous substances. However, its contribution to the progression of liver damage remains unclear.

AIM

To determine the role and mechanism of UGT1A1 in liver damage progression.

METHODS

We investigated the relationship between UGT1A1 expression and liver injury through clinical research. Additionally, the impact and mechanism of UGT1A1 on the progression of liver injury was analyzed through a mouse model study.

RESULTS

Patients with UGT1A1 gene mutations showed varying degrees of liver damage, while patients with acute-on-chronic liver failure (ACLF) exhibited relatively reduced levels of UGT1A1 protein in the liver as compared to patients with chronic hepatitis. This suggests that low UGT1A1 levels may be associated with the progression of liver damage. In mouse models of liver injury induced by carbon tetrachloride (CCl4) and concanavalin A (ConA), the hepatic levels of UGT1A1 protein were found to be increased. In mice with lipopolysaccharide or liver steatosis-mediated liver-injury progression, the hepatic protein levels of UGT1A1 were decreased, which is consistent with the observations in patients with ACLF. UGT1A1 knockout exacerbated CCl4- and ConA-induced liver injury, hepatocyte apoptosis and necroptosis in mice, intensified hepatocyte endoplasmic reticulum (ER) stress and oxidative stress, and disrupted lipid metabolism.

CONCLUSION

UGT1A1 is upregulated as a compensatory response during liver injury, and interference with this upregulation process may worsen liver injury. UGT1A1 reduces ER stress, oxidative stress, and lipid metabolism disorder, thereby mitigating hepatocyte apoptosis and necroptosis.

Regulation of UCP2 in nonalcoholic fatty liver disease: From mechanisms to natural product

Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disease associated with lipid deposition in liver cells and/or subsequent inflammation, excluding other known causes. NAFLD is a subset of metabolic syndrome that ranges from simple steatohepatitis (NASH), fibrosis to cirrhosis and hepatocellular carcinoma (HCC). At present, the pathogenesis of NAFLD remains unclear. Among the many factors that shape these transitions, uncoupling protein 2 (UCP2) may be involved in every stage of the disease. UCP2 is a carrier protein that responds to fatty acids (FAs) in mitochondrial intima and has a wide tissue distribution. However, the biological function of UCP2 has not been fully elucidated, and most of our current knowledge comes from cell and animal experiments. These data suggest that UCP2 plays a role in lipid metabolism, oxidative stress, apoptosis, and even cancer. In this review, we summarize the structure, distribution, and biological function of UCP2 and its role in the progression of NAFLD, as well as natural products targeting UCP2 to improve NAFLD.

SLC25 family with energy metabolism and immunity in malignant tumors

Solute Carrier Family 25 (SLC25) is the largest family of mitochondrial membrane proteins in the human body, consisting of 53 members. Mitochondrial phosphate carriers (MPiC), cellular iron metabolism, voltage-dependent anion channels (VDAC), and oxidative phosphorylation in the SLC25 family play dominant roles in material transport, energy metabolism, etc. SLC25 family-related proteins are involved in the regulation of the progression of a variety of cancers, including colon, gastric, and lung cancers. In addition, the SLC25 family has been implicated in endoplasmic reticulum stress (ERS) and immunity. Since SLC25 family proteins are involved in cancer progression and are associated with endoplasmic reticulum stress and immunity, exploring inhibitors of SLC25 family-related proteins is essential. However, the exact mechanism of SLC25 family-related proteins involved in cancer, as well as potential targets and SLC25 inhibitors have not been reported in the literature. This article focuses on summarizing the relevance of the SLC25 family to cancer, ERS, and immunity. This review also provides a comprehensive overview of SLC25 family-related inhibitors.

Uncoupling protein 2 modulates polarization and metabolism of human primary macrophages via glycolysis and the NF‑κB pathway

Metabolic abnormalities, particularly the M1/M2 macrophage imbalance, play a critical role in the development of various diseases, leading to severe inflammatory responses. The present study aimed to investigate the role of uncoupling protein 2 (UCP2) in regulating macrophage polarization, glycolysis, metabolic reprogramming, reactive oxygen species (ROS) and inflammation. Primary human macrophages were first polarized into M1 and M2 subtypes, and these two subtypes were infected by lentivirus-mediated UCP2 overexpression or knockdown, followed by enzyme-linked immunosorbent assay, reverse transcription-quantitative PCR, western blotting and flow cytometry to analyze the effects of UCP2 on glycolysis, oxidative phosphorylation (OXPHOS), ROS production and cytokine secretion, respectively. The results demonstrated that UCP2 expression was suppressed in M1 macrophages and increased in M2 macrophages, suggesting its regulatory role in macrophage polarization. UCP2 overexpression decreased macrophage glycolysis, increased OXPHOS, decreased ROS production, and led to the conversion of M1 polarization to M2 polarization. This process involved NF-κB signaling to regulate the secretion profile of cytokines and chemokines and affected the expression of key enzymes of glycolysis and a key factor for maintaining mitochondrial homeostasis (nuclear respiratory factor 1). UCP2 knockdown in M2 macrophages exacerbated inflammation and oxidative stress by promoting glycolysis, which was attenuated by the glycolysis inhibitor 2-deoxyglucose. These findings highlight the critical role of UCP2 in regulating macrophage polarization, metabolism, inflammation and oxidative stress through its effects on glycolysis, providing valuable insights into potential therapeutic strategies for macrophage-driven inflammatory and metabolic diseases.

Exploring a new mechanism between lactate and VSMC calcification: PARP1/POLG/UCP2 signaling pathway and imbalance of mitochondrial homeostasis

Lactate leads to the imbalance of mitochondria homeostasis, which then promotes vascular calcification. PARP1 can upregulate osteogenic genes and accelerate vascular calcification. However, the relationship among lactate, PARP1, and mitochondrial homeostasis is unclear. The present study aimed to explore the new molecular mechanism of lactate to promote VSMC calcification by evaluating PARP1 as a breakthrough molecule. A coculture model of VECs and VSMCs was established, and the model revealed that the glycolysis ability and lactate production of VECs were significantly enhanced after incubation in DOM. Osteogenic marker expression, calcium deposition, and apoptosis in VSMCs were decreased after lactate dehydrogenase A knockdown in VECs. Mechanistically, exogenous lactate increased the overall level of PARP and PARylation in VSMCs. PARP1 knockdown inhibited Drp1-mediated mitochondrial fission and partially restored PINK1/Parkin-mediated mitophagy, thereby reducing mitochondrial oxidative stress. Moreover, lactate induced the translocation of PARP1 from the nucleus to the mitochondria, which then combined with POLG and inhibited POLG-mediated mitochondrial DNA synthesis. This process led to the downregulation of mitochondria-encoded genes, disturbance of mitochondrial respiration, and inhibition of oxidative phosphorylation. The knockdown of PARP1 could partially reverse the damage of mitochondrial gene expression and function caused by lactate. Furthermore, UCP2 was upregulated by the PARP1/POLG signal, and UCP2 knockdown inhibited Drp1-mediated mitochondrial fission and partially recovered PINK1/Parkin-mediated mitophagy. Finally, UCP2 knockdown in VSMCs alleviated DOM-caused VSMC calcification in the coculture model. The study results thus suggest that upregulated PARP1 is involved in the mechanism through which lactate accelerates VSMC calcification partly via POLG/UCP2-caused unbalanced mitochondrial homeostasis.

Role of UCP2 in the Energy Metabolism of the Cancer Cell Line A549

The uncoupling protein UCP2 is a mitochondrial carrier for which transport activity remains controversial. The physiological contexts in which UCP2 is expressed have led to the assumption that, like UCP1, it uncouples oxidative phosphorylation and thereby reduces the generation of reactive oxygen species. Other reports have involved UCP2 in the Warburg effect, and results showing that UCP2 catalyzes the export of matrix C4 metabolites to facilitate glutamine utilization suggest that the carrier could be involved in the metabolic adaptations required for cell proliferation. We have examined the role of UCP2 in the energy metabolism of the lung adenocarcinoma cell line A549 and show that UCP2 silencing decreased the basal rate of respiration, although this inhibition was not compensated by an increase in glycolysis. Silencing did not lead to either changes in proton leakage, as determined by the rate of respiration in the absence of ATP synthesis, or changes in the rate of formation of reactive oxygen species. The decrease in energy metabolism did not alter the cellular energy charge. The decreased cell proliferation observed in UCP2-silenced cells would explain the reduced cellular ATP demand. We conclude that UCP2 does not operate as an uncoupling protein, whereas our results are consistent with its activity as a C4-metabolite carrier involved in the metabolic adaptations of proliferating cells.