Here, we report new mechanistic insight into how chronic hypoxia increases 'stemness' in cancer cells. Using chemical inhibitors, we provide direct experimental evidence that ROS production and ...mitochondrial biogenesis are both required for the hypoxia-induced propagation of CSCs. More specifically, we show that hypoxic CSCs can be effectively targeted with i) simple mitochondrial anti-oxidants (Mito-TEMPO) and/or ii) inhibitors of mitochondrial biogenesis (Doxycycline). In this context, we discuss the idea that mitochondrial biogenesis itself may be a primary driver of "stemness" in hypoxic cancer cells, with metabolic links to fatty acid oxidation (FAO). As Doxycycline is an FDA-approved drug, we propose that it could be re-purposed to target hypoxic CSCs, either alone or in combination with chemotherapy, i.e., Paclitaxel. For example, we demonstrate that Doxycycline effectively targets the sub-population of hypoxia-induced CSCs that are Paclitaxel-resistant, overcoming hypoxia-induced drug-resistance. Finally, anti-angiogenic therapy often induces tumor hypoxia, allowing CSCs to survive and propagate, ultimately driving tumor progression. Therefore, we suggest that Doxycycline could be used in combination with anti-angiogenic agents, to actively prevent or minimize hypoxia-induced treatment failure. In direct support of this assertion, Paclitaxel is already known to behave as an angiogenesis inhibitor.
Sepsis, a major cause of morbidity/mortality in intensive care units worldwide, is commonly associated with cardiac dysfunction, which worsens the prognosis dramatically for patients. Although in ...recent years the concept of septic cardiomyopathy has evolved, the importance of myocardial structural alterations in sepsis has not been fully explored. This study offers novel and mechanistic data to clarify subcellular events that occur in the pathogenesis of septic cardiomyopathy and myocardial dysfunction in severe sepsis. Cultured neonatal mice cardiomyocytes subjected to serum obtained from mice with severe sepsis presented striking increment of Ca(2+)i and calpain-1 levels associated with decreased expression of dystrophin and disruption and derangement of F-actin filaments and cytoplasmic bleb formation. Severe sepsis induced in mice led to an increased expression of calpain-1 in cardiomyocytes. Moreover, decreased myocardial amounts of dystrophin, sarcomeric actin, and myosin heavy chain were observed in septic hearts associated with depressed cardiac contractile dysfunction and a very low survival rate. Actin and myosin from the sarcomere are first disassembled by calpain and then ubiquitinated and degraded by proteasome or sequestered inside specialized vacuoles called autophagosomes, delivered to the lysosome for degradation forming autophagolysosomes. Verapamil and dantrolene prevented the increase of calpain-1 levels and preserved dystrophin, actin, and myosin loss/reduction as well cardiac contractile dysfunction associated with strikingly improved survival rate. These abnormal parameters emerge as therapeutic targets, which modulation may provide beneficial effects on future vascular outcomes and mortality in sepsis. Further studies are needed to shed light on this mechanism, mainly regarding specific calpain inhibitors.
Energy transfer in "parasitic" cancer metabolism Martinez-Outschoorn, Ubaldo E.; Pestell, Richard G.; Howell, Anthony ...
Cell cycle (Georgetown, Tex.),
12/15/2011, 2011/12/15, 2011-Dec-15, 2011-12-15, 20111215, Letnik:
10, Številka:
24
Journal Article
Recenzirano
Odprti dostop
It is now widely recognized that the tumor microenvironment promotes cancer cell growth and metastasis via changes in cytokine secretion and extracellular matrix remodeling. However, the role of ...tumor stromal cells in providing energy for epithelial cancer cell growth is a newly emerging paradigm. For example, we and others have recently proposed that tumor growth and metastasis is related to an energy imbalance. Host cells produce energy-rich nutrients via catabolism (through autophagy, mitophagy, and aerobic glycolysis), which are then transferred to cancer cells to fuel anabolic tumor growth. Stromal cell-derived L-lactate is taken up by cancer cells and is used for mitochondrial oxidative phosphorylation (OXPHOS) to produce ATP efficiently. However, "parasitic" energy transfer may be a more generalized mechanism in cancer biology than previously appreciated. Two recent papers in Science and Nature Medicine now show that lipolysis in host tissues also fuels tumor growth. These studies demonstrate that free fatty acids produced by host cell lipolysis are re-used via beta-oxidation (beta-OX) in cancer cell mitochondria. Thus, stromal catabolites (such as lactate, ketones, glutamine and free fatty acids) promote tumor growth by acting as high-energy onco-metabolites. As such, host catabolism, via autophagy, mitophagy and lipolysis, may explain the pathogenesis of cancer-associated cachexia and provides exciting new druggable targets for novel therapeutic interventions. Taken together, these findings also suggest that tumor cells promote their own growth and survival by behaving as a "parasitic organism." Hence, we propose the term "Parasitic Cancer Metabolism" to describe this type of metabolic coupling in tumors. Targeting tumor cell mitochondria (OXPHOS and beta-OX) would effectively uncouple tumor cells from their hosts, leading to their acute starvation. In this context, we discuss new evidence that high-energy onco-metabolites (produced by the stroma) can confer drug resistance. Importantly, this metabolic chemo-resistance is reversed by blocking OXPHOS in cancer cell mitochondria with drugs like Metformin, a mitochondrial "poison." In summary, parasitic cancer metabolism is achieved architecturally by dividing tumor tissue into at least two well-defined opposing "metabolic compartments:" catabolic and anabolic.
Cancer cells do not exist as pure homogeneous populations
in vivo. Instead they are embedded in “cancer cell nests” that are surrounded by stromal cells, especially cancer associated fibroblasts. ...Thus, it is not unreasonable to suspect that stromal fibroblasts could influence the metabolism of adjacent cancer cells, and visa versa. In accordance with this idea, we have recently proposed that the Warburg effect in cancer cells may be due to culturing cancer cells by themselves, out of their normal stromal context or tumor microenvironment. In fact, when cancer cells are co-cultured with fibroblasts, then cancer cells increase their mitochondrial mass, while fibroblasts lose their mitochondria. An in depth analysis of this phenomenon reveals that aggressive cancer cells are “parasites” that use oxidative stress as a “weapon” to extract nutrients from surrounding stromal cells. Oxidative stress in fibroblasts induces the autophagic destruction of mitochondria, by mitophagy. Then, stromal cells are forced to undergo aerobic glycolysis, and produce energy-rich nutrients (such as lactate and ketones) to “feed” cancer cells. This mechanism would allow cancer cells to seed anywhere, without blood vessels as a food source, as they could simply induce oxidative stress wherever they go, explaining how cancer cells survive during metastasis. We suggest that stromal catabolism, via autophagy and mitophagy, fuels the anabolic growth of tumor cells, promoting tumor progression and metastasis. We have previously termed this new paradigm “The Autophagic Tumor Stroma Model of Cancer Metabolism”, or the “Reverse Warburg Effect”. We also discuss how glutamine addiction (glutaminolysis) in cancer cells fits well with this new model, by promoting oxidative mitochondrial metabolism in aggressive cancer cells.
Trypanosoma cruzi, an intracellular protozoan parasite that infects humans and other mammalian hosts, is the etiologic agent in Chagas disease. This parasite can invade a wide variety of mammalian ...cells. The mechanism(s) by which T. cruzi invades its host cell is not completely understood. The activation of many signaling receptors during invasion has been reported; however, the exact mechanism by which parasites cross the host cell membrane barrier and trigger fusion of the parasitophorous vacuole with lysosomes is not understood.
In order to explore the role of the Low Density Lipoprotein receptor (LDLr) in T. cruzi invasion, we evaluated LDLr parasite interactions using immunoblot and immunofluorescence (IFA) techniques. These experiments demonstrated that T. cruzi infection increases LDLr levels in infected host cells, inhibition or disruption of LDLr reduces parasite load in infected cells, T. cruzi directly binds recombinant LDLr, and LDLr-dependent T. cruzi invasion requires PIP2/3. qPCR analysis demonstrated a massive increase in LDLr mRNA (8000 fold) in the heart of T. cruzi infected mice, which is observed as early as 15 days after infection. IFA shows a co-localization of both LDL and LDLr with parasites in infected heart.
These data highlight, for the first time, that LDLr is involved in host cell invasion by this parasite and the subsequent fusion of the parasitophorous vacuole with the host cell lysosomal compartment. The model suggested by this study unifies previous models of host cell invasion for this pathogenic protozoon. Overall, these data indicate that T. cruzi targets LDLr and its family members during invasion. Binding to LDL likely facilitates parasite entry into host cells. The observations in this report suggest that therapeutic strategies based on the interaction of T. cruzi and the LDLr pathway should be pursued as possible targets to modify the pathogenesis of disease following infection.
Our recent studies have mechanistically implicated a loss of stromal Cav-1 expression and HIF1-alpha-activation in driving the cancer-associated fibroblast phenotype, through the paracrine production ...of nutrients via autophagy and aerobic glycolysis. However, it remains unknown if HIF1a-activation is sufficient to confer the cancer-associated fibroblast phenotype. To test this hypothesis directly, we stably-expressed activated HIF1a in fibroblasts and then examined their ability to promote tumor growth using a xenograft model employing human breast cancer cells (MDA-MB-231). Fibroblasts harboring activated HIF1a showed a dramatic reduction in Cav-1 levels and a shift towards aerobic glycolysis, as evidenced by a loss of mitochondrial activity, and an increase in lactate production. Activated HIF1a also induced BNIP3 and BNIP3L expression, markers for the autophagic destruction of mitochondria. Most importantly, fibroblasts expressing activated HIF1a increased tumor mass by ~2-fold and tumor volume by ~3-fold, without a significant increase in tumor angiogenesis. In this context, HIF1a also induced an increase in the lymph node metastasis of cancer cells. Similar results were obtained by driving NFκB activation in fibroblasts, another inducer of autophagy. Thus, activated HIF1a is sufficient to functionally confer the cancer-associated fibroblast phenotype. It is also known that HIF1a expression is required for the induction of autophagy in cancer cells. As such, we next directly expressed activated HIF1a in MDA-MB-231 cells and assessed its effect on tumor growth via xenograft analysis. Surprisingly, activated HIF1a in cancer cells dramatically suppressed tumor growth, resulting in a 2-fold reduction in tumor mass and a 3-fold reduction in tumor volume. We conclude that HIF1a activation in different cell types can either promote or repress tumorigenesis. Based on these studies, we suggest that autophagy in cancer-associated fibroblasts promotes tumor growth via the paracrine production of recycled nutrients, which can directly "feed" cancer cells. Conversely, autophagy in cancer cells represses tumor growth via their "self-digestion." Thus, we should consider that the activities of various known oncogenes and tumor-suppressors may be compartment and cell-type specific, and are not necessarily an intrinsic property of the molecule itself. As such, other "classic" oncogenes and tumor suppressors will have to be re-evaluated to determine their compartment specific effects on tumor growth and metastasis. Lastly, our results provide direct experimental support for the recently proposed "Autophagic Tumor Stroma Model of Cancer."
Endothelins are potent regulators of vascular tone, which also have mitogenic, apoptotic, and immunomodulatory properties (Rubanyi and Polokoff, 1994; Kedzierski and Yanagisawa, 2001; Bagnato et al., ...2011). Three isoforms of endothelin have been identified to date, with endothelin-1 (ET-1) being the best studied. ET-1 is classically considered a potent vasoconstrictor. However, in addition to the effects of ET-1 on vascular smooth muscle cells, the peptide is increasingly recognized as a pro-inflammatory cytokine (Teder and Noble, 2000; Sessa et al., 1991). ET-1 causes platelet aggregation and plays a role in the increased expression of leukocyte adhesion molecules, the synthesis of inflammatory mediators contributing to vascular dysfunction. High levels of ET-1 are found in alveolar macrophages, leukocytes (Sessa et al., 1991) and fibroblasts (Gu et al., 1991). Clinical and experimental data indicate that ET-1 is involved in the pathogenesis of sepsis (Tschaikowsky et al., 2000; Goto et al., 2012), viral and bacterial pneumonia (Schuetz et al., 2008; Samransamruajkit et al., 2002), Rickettsia conorii infections (Davi et al., 1995), Chagas disease (Petkova et al., 2000, 2001), and severe malaria (Dai et al., 2012; Machado et al., 2006; Wenisch et al., 1996a; Dietmann et al., 2008). In this minireview, we will discuss the role of endothelin in the pathogenesis of infectious processes.
A schematic illustration of ET-1 effects on different cell types. Binding of ET-1 to its cognate receptors causes activation of monocytes, neutrophils, mast cells, and endothelial cells. ET-1 contributes to cytokine production, enhanced cellular adhesion molecule expression, as well as monocyte diapedesis. Additionally, ET receptor activation on vascular smooth muscle cells results in vasoconstriction, vascular permeability, and tissue remodeling. Display omitted
Trypanosoma cruzi, the causative agent of Chagas disease, has high affinity for lipoproteins and adipose tissue. Infection results in myocarditis, fat loss and alterations in lipid homeostasis. This ...study was aimed at analyzing the effect of high fat diet (HFD) on regulating acute T. cruzi infection-induced myocarditis and to evaluate the effect of HFD on lipid metabolism in adipose tissue and heart during acute T. cruzi infection.
CD1 mice were infected with T. cruzi (Brazil strain) and fed either a regular control diet (RD) or HFD for 35 days following infection. Serum lipid profile, tissue cholesterol levels, blood parasitemia, and tissue parasite load were analyzed to evaluate the effect of diet on infection. MicroPET and MRI analysis were performed to examine the morphological and functional status of the heart during acute infection. qPCR and immunoblot analysis were carried out to analyze the effect of diet on the genes involved in the host lipid metabolism during infection. Oil red O staining of the adipose tissue demonstrated reduced lipolysis in HFD compared to RD fed mice. HFD reduced mortality, parasitemia and cardiac parasite load, but increased parasite load in adipocytes. HFD decreased lipolysis during acute infection. Both qPCR and protein analysis demonstrated alterations in lipid metabolic pathways in adipose tissue and heart in RD fed mice, which were further modulated by HFD. Both microPET and MRI analyses demonstrated changes in infected RD murine hearts which were ameliorated by HFD.
These studies indicate that Chagasic cardiomyopathy is associated with a cardiac lipidpathy and that both cardiac lipotoxicity and adipose tissue play a role in the pathogenesis of Chagas disease. HFD protected mice from T. cruzi infection-induced myocardial damage most likely due to the effects of HFD on both adipogenesis and T. cruzi infection-induced cardiac lipidopathy.
Cardiac dysfunction caused by the impairment of myocardial contractility has been recognized as an important factor contributing to the high mortality in sepsis. Calpain activation in the heart takes ...place in response to increased intracellular calcium influx resulting in proteolysis of structural and contractile proteins with subsequent myocardial dysfunction. The purpose of the present study was to test the hypothesis that increased levels of calpain in the septic heart leads to disruption of structural and contractile proteins and that administration of calpain inhibitor-1 (N-acetyl-leucinyl-leucinyl-norleucinal (ALLN)) after sepsis induced by cecal ligation and puncture prevents cardiac protein degradation. We also tested the hypothesis that calpain plays a role in the modulation of protein synthesis/degradation through the activation of proteasome-dependent proteolysis and inhibition of the mTOR pathway. Severe sepsis significantly increased heart calpain-1 levels and promoted ubiquitin and Pa28β over-expression with a reduction in the mTOR levels. In addition, sepsis reduced the expression of structural proteins dystrophin and β-dystroglycan as well as the contractile proteins actin and myosin. ALLN administration prevented sepsis-induced increases in calpain and ubiquitin levels in the heart, which resulted in decreased of structural and contractile proteins degradation and basal mTOR expression levels were re-established. Our results support the concept that increased calpain concentrations may be part of an important mechanism of sepsis-induced cardiac muscle proteolysis.
•cantonensis is the most common cause of eosinophilic meningitis in southern Asia.•cantonensis can also cause encephalitis, encephalomyelitis and ocular disease.•Eosinophilic inflammation caused by ...dead larvae in the brain explains the pathogenesis.•Main clinical features are headache, fever, stiff neck, paraesthesias and vomiting.•We also review the treatment, prevention and prognosis of A. cantonesis infection.
Over 20 species of Angiostrongylus have been described from around the world, but only Angiostrongylus cantonensis has been confirmed to cause central nervous system disease in humans. A neurotropic parasite that matures in the pulmonary arteries of rats, A. cantonensis is the most common cause of eosinophilic meningitis in southern Asia and the Pacific and Caribbean islands. The parasite can also cause encephalitis/encephalomyelitis and rarely ocular angiostrongyliasis. The present paper reviews the life cycle, epidemiology, pathogenesis, clinical features, diagnosis, treatment, prevention and prognosis of A. cantonesis infection. Emphasis is given on the spectrum of central nervous system manifestations and disease pathogenesis.
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