Extracellular PKM2 facilitates organ-tissue fibrosis progression

Therapeutic potential of natural arginase modulators: mechanisms, challenges, and future directions

Arginase (Arg) plays a pivotal role in numerous pathological processes, with its dysregulated expression being intricately associated with tumor progression and immune evasion. This review comprehensively examines the diversity, mechanisms, and clinical potential of natural Arg modulators, encompassing polyphenols, flavonoids, and terpenoids. These bioactive compounds exert their modulatory effects on Arg activity through multiple mechanisms, including direct enzyme interaction, regulation of signaling pathways, and modulation of cellular metabolism. The therapeutic potential of these metabolites spans across various medical domains, notably in cardiovascular diseases, oncology, neurological disorders, and inflammatory conditions. Specifically, polyphenol metabolites such as resveratrol and curcumin have demonstrated significant benefits in cardiovascular health and neuroprotection, while flavonoids including rutin and quercetin have shown promising effects on intracellular inflammatory factors and tumor cell proliferation. Similarly, terpenoids like perillyl alcohol and triptolide have been found to influence cell polarization processes. However, despite their substantial therapeutic potential demonstrated in experimental studies, the development of natural Arg modulators faces several significant challenges. These include complexities in drug design attributed to the intricate structure and multiple isoforms of Arg, difficulties in elucidating precise mechanisms due to Arg's multifaceted roles in various metabolic pathways, and limitations in current drug delivery systems. To overcome these challenges, future research should focus on continuous optimization of experimental design paradigms, enhancement of experimental models and data quality, thorough evaluation of therapeutic efficacy, and strategic integration of natural Arg modulators with precision medicine approaches.

Extracellular PKM2 Preserves Cardiomyocytes and Reduces Cardiac Fibrosis During Myocardial Infarction

Substantial loss of cardiomyocytes during heart attacks and onset of other cardiovascular diseases is a major cause of mortality. Preservation of cardiomyocytes during cardiac injury would be the most effective strategy to manage these diseases in clinic. However, there is no effective treatment strategy that is able to prevent cardiomyocyte loss. We demonstrate here that the systemic administration of a recombinant PKM2 mutant (G415R) preserves cardiomyocytes and reduces cardiac fibrosis during myocardial infarction. G415R preserves cardiomyocytes by protecting the cardiomyocytes from dying and by promoting cardiomyocyte proliferation. Preservation of cardiomyocytes by extracellular PKM2 (EcPKM2) reduces cardiac fibrosis because of the decreased activation of cardiac fibroblasts. Our experiments show that EcPKM2 (G415R) exerts its action by interacting with integrin avb3 on cardiomyocytes. EcPKM2(G415R) activates the integrin-FAK-PI3K signaling axis, which subsequently suppresses PTEN expression and consequently regulates cardiomyocyte apoptosis resistance and proliferation under hypoxia and oxidative stress conditions. Our studies uncover an important cardiomyocyte protection mechanism. More importantly, the activity/action of EcPKM2 (G415R) in preserving cardiomyocyte suggesting a possible therapeutic strategy and target for the treatment of heart attacks and other cardiovascular diseases.

Modulating Tumor Immunity by Targeting Tumor Fibrotic Stroma and Angiogenic Vessels for Lung Cancer Treatment

Fibrotic stroma and angiogenic tumor vessels play an important role in modulating tumor immunity. We previously reported a rationally designed protein (ProAgio) that targets integrin αvβ3 at a novel site. ProAgio induces the apoptosis of cells that express high levels of the integrin. Both activated cancer-associated fibroblasts (CAFs) and angiogenic endothelial cells (aECs) in tumors express high levels of integrin αvβ3. ProAgio simultaneously and specifically induces apoptosis in CAFs and aECs in tumors. We provide evidence here that the depletion of CAFs and the elimination of leaky tumor angiogenic vessels by ProAgio alter tumor immunity. ProAgio reduces CD4+ Treg and Myeloid-derived suppressor cells (MDSCs), increases CD8+ T-cells, and increases the M1/M2 macrophage ratio in the tumor. The depletion of dense fibrotic stroma (CAFs) by ProAgio decreases the Programmed Death Ligand 1 (PDL-1) levels in the stroma areas surrounding the tumors, and thus strongly increases the delivery of anti-PDL-1 antibody to the target cancer cells. The impact of ProAgio on tumor immunity provides strong synergistical effects of checkpoint inhibitors on lung cancer treatment.

Search progress of pyruvate kinase M2 (PKM2) in organ fibrosis

Fibrosis is characterized by abnormal deposition of the extracellular matrix (ECM), leading to organ structural remodeling and loss of function. The principal cellular effector in fibrosis is activated myofibroblasts, which serve as the main source of matrix proteins. Metabolic reprogramming, transitioning from mitochondrial oxidative phosphorylation to aerobic glycolysis, is widely observed in rapidly dividing cells such as tumor cells and activated myofibroblasts and is increasingly recognized as a fundamental pathogenic basis in organ fibrosis. Targeting metabolism represents a promising strategy to mitigate fibrosis. PKM2, a key enzyme in glycolysis, plays a pivotal role in metabolic reprogramming through allosteric regulation, impacting both metabolic and non-metabolic pathways. Therefore, metabolic reprogramming induced by PKM2 activation is involved in the occurrence and development of fibrosis in various organs. A comprehensive understanding of the role of PKM2 in fibrotic diseases is crucial for seeking new anti-fibrotic therapeutic targets. In this context, we summarize PKM2's role in glycolysis, mediating the intricate mechanisms underlying fibrosis in multiple organs, and discuss the potential value of PKM2 inhibitors and allosteric activators in future clinical treatments, aiming to identify novel therapeutic targets for proliferative fibrotic diseases.

Extracellular pyruvate kinase M2 induces cell migration through p-Tyr42 RhoA-mediated superoxide generation and epithelial-mesenchymal transition

In the tumor microenvironment (TME), communication between cancer cells and tumor-associated macrophages (TAMs) through secreted extracellular proteins promotes cancer progression. Here, we observed that co-culturing cancer cells (4T1) and macrophage cells (Raw264.7) significantly enhanced superoxide production in both cell types. Using MALDI-TOF, we identified PKM2 as a highly secreted protein by Raw264.7 cells and bone marrow-derived monocytes. The extracellular recombinant PKM2 protein not only enhanced cancer cell migration and invasion but also increased superoxide production. Additionally, PKM2 was found to associate with the cell surface, and its binding to integrin α5/β1 receptor was inhibited by antibodies specifically targeting it. Furthermore, we investigated downstream signaling pathways involved in PKM2-induced superoxide production. We found that knock-down of RhoA and p47phox using siRNAs effectively abolished superoxide generation in response to extracellular PKM2. Notably, extracellular PKM2 triggered the phosphorylation of p47phox at Ser345 residue and RhoA at Tyr42 residue (p-Tyr42 RhoA). Moreover, extracellular PKM2 exerted regulatory control over the expression of key epithelial-mesenchymal transition (EMT) markers, including ZEB1, Snail1, vimentin, and E-cadherin. Interestingly, p-Tyr42 RhoA translocated to the nucleus, where it bound to the ZEB1 promoter region. In light of these findings, we propose that extracellular PKM2 within the TME plays a critical role in tumorigenesis by promoting cancer cell migration and invasion through RhoA/p47phox signaling pathway.

Fibrosis Development Linked to Alterations in Glucose and Energy Metabolism and Prooxidant-Antioxidant Balance in Experimental Models of Liver Injury

The development of liver fibrosis is one of the most severe and life-threatening outcomes of chronic liver disease (CLD). For targeted therapy of CLD, it is highly needed to reveal molecular targets for normalizing metabolic processes impaired in damaged liver and associated with fibrosis. In this study, we investigated the morphological and biochemical changes in rat liver models of fibrosis induced by chronic administration of thioacetamide, carbon tetrachloride, bile duct ligation (BDL), and ischemia/reperfusion (I/R), with a specific focus on carbohydrate and energy metabolism. Changes in the levels of substrates and products, as well as enzyme activities of the major glucose metabolic pathways (glycolysis, glucuronidation, and pentose phosphate pathway) were examined in rat liver tissue after injury. We examined key markers of oxidative energy metabolism, such as the activity of the Krebs cycle enzymes, and assessed mitochondrial respiratory activity. In addition, pro- and anti-oxidative status was assessed in fibrotic liver tissue. We found that 6 weeks of exposure to thioacetamide, carbon tetrachloride, BDL or I/R resulted in a decrease in the activity of glycolytic enzymes, retardation of mitochondrial respiration, elevation of glucuronidation, and activation of pentose phosphate pathways, accompanied by a decrease in antioxidant activity and the onset of oxidative stress in rat liver. Resemblance and differences in the changes in the fibrosis models used are described, including energy metabolism alterations and antioxidant status in the used fibrosis models. The least pronounced changes in glucose metabolism and mitochondrial functions in the I/R and thioacetamide models were associated with the least advanced fibrosis. Ultimately, liver fibrosis significantly altered the metabolic profile in liver tissue and the flux of glucose metabolic pathways, which could be the basis for targeted therapy of liver fibrosis in CLD caused by toxic, cholestatic, or I/R liver injury.

KITENIN promotes aerobic glycolysis through PKM2 induction by upregulating the c-Myc/hnRNPs axis in colorectal cancer

PURPOSE

The oncoprotein KAI1 C-terminal interacting tetraspanin (KITENIN; vang-like 1) promotes cell metastasis, invasion, and angiogenesis, resulting in shorter survival times in cancer patients. Here, we aimed to determine the effects of KITENIN on the energy metabolism of human colorectal cancer cells.

EXPERIMENTAL DESIGN

The effects of KITENIN on energy metabolism were evaluated using in vitro assays. The GEPIA web tool was used to extrapolate the clinical relevance of KITENIN in cancer cell metabolism. The bioavailability and effect of the disintegrator of KITENIN complex compounds were evaluated by LC-MS, in vivo animal assay.

RESULTS

KITENIN markedly upregulated the glycolytic proton efflux rate and aerobic glycolysis by increasing the expression of GLUT1, HK2, PKM2, and LDHA. β-catenin, CD44, CyclinD1 and HIF-1A, including c-Myc, were upregulated by KITENIN expression. In addition, KITENIN promoted nuclear PKM2 and PKM2-induced transactivation, which in turn, increased the expression of downstream mediators. This was found to be mediated through an effect of c-Myc on the transcription of hnRNP isoforms and a switch to the M2 isoform of pyruvate kinase, which increased aerobic glycolysis. The disintegration of KITENIN complex by silencing the KITENIN or MYO1D downregulated aerobic glycolysis. The disintegrator of KITENIN complex compound DKC1125 and its optimized form, DKC-C14S, exhibited the inhibition activity of KITENIN-mediated aerobic glycolysis in vitro and in vivo.

CONCLUSIONS

The oncoprotein KITENIN induces PKM2-mediated aerobic glycolysis by upregulating the c-Myc/hnRNPs axis.

Early Detection and Staging of Lung Fibrosis Enabled by Collagen-Targeted MRI Protein Contrast Agent

Chronic lung diseases, such as idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease (COPD), are major leading causes of death worldwide and are generally associated with poor prognoses. The heterogeneous distribution of collagen, mainly type I collagen associated with excessive collagen deposition, plays a pivotal role in the progressive remodeling of the lung parenchyma to chronic exertional dyspnea for both IPF and COPD. To address the pressing need for noninvasive early diagnosis and drug treatment monitoring of pulmonary fibrosis, we report the development of human collagen-targeted protein MRI contrast agent (hProCA32.collagen) to specifically bind to collagen I overexpressed in multiple lung diseases. When compared to clinically approved Gd3+ contrast agents, hProCA32.collagen exhibits significantly better r1 and r2 relaxivity values, strong metal binding affinity and selectivity, and transmetalation resistance. Here, we report the robust detection of early and late-stage lung fibrosis with stage-dependent MRI signal-to-noise ratio (SNR) increase, with good sensitivity and specificity, using a progressive bleomycin-induced IPF mouse model. Spatial heterogeneous mapping of usual interstitial pneumonia (UIP) patterns with key features closely mimicking human IPF, including cystic clustering, honeycombing, and traction bronchiectasis, were noninvasively detected by multiple MR imaging techniques and verified by histological correlation. We further report the detection of fibrosis in the lung airway of an electronic cigarette-induced COPD mouse model, using hProCA32.collagen-enabled precision MRI (pMRI), and validated by histological analysis. The developed hProCA32.collagen is expected to have strong translational potential for the noninvasive detection and staging of lung diseases, and facilitating effective treatment to halt further chronic lung disease progression.

Extracellular Hsp90α Supports the ePKM2-GRP78-AKT Axis to Promote Tumor Metastasis

Tumor-secreted proteins can provide numerous molecular targets for cancer diagnosis and treatment. Of note, pyruvate kinase M2 (PKM2) is secreted by tumor cells to promote malignant progression, while its regulatory mechanism or the interacting network remains uncovered. In the present study, we identified extracellular heat shock protein 90 alpha (eHsp90α) as one potential interacting protein of ePKM2 by mass spectrometry (MS), which was further verified by pull-down and co-immunoprecipitation analysis. Later, we found that eHsp90α enhanced the effect of ePKM2 on migration and invasion of lung cancer cells. Blocking of Hsp90α activity, on the other hand, attenuated tumor migration or invasion induced by ePKM2. Eventually, the in vivo role of Hsp90α in regulating ePKM2 activity was validated by the mouse xenograft tumor model. Mechanistically, we found that eHsp90α binds to and stabilizes ePKM2 to protect it from degradation in the extracellular environment. Besides, eHsp90α promoted the interaction of ePKM2 with cell surface receptor GRP78, which leads to the activation of the ePKM2/GRP78/AKT axis. Collectively, we unraveled the novel molecular mechanism of eHsp90α in regulating ePKM2 activity during tumor progression, which is beneficial for the development of new treatments against lung cancer.