Trypanosoma cruzi Infection Induces Cellular Stress Response and Senescence-Like Phenotype in Murine Fibroblasts

Trypanosoma cruzi infects and replicates within a wide variety of immune and non-immune cells. Here, we investigated early cellular responses induced in NIH-3T3 fibroblasts upon infection with trypomastigote forms of T. cruzi. We show that fibroblasts were susceptible to T. cruzi infection and started to release trypomastigotes to the culture medium after 4 days of infection. Also, we found that T. cruzi infection reduced the number of fibroblasts in 3-day cell cultures, by altering fibroblast proliferation. Infected fibroblasts displayed distinctive phenotypic alterations, including enlarged and flattened morphology with a nuclei accumulation of senescence-associated heterochromatin foci. In addition, infection induced an overexpression of the enzyme senescence-associated β-galactosidase (SA-β-gal), an activation marker of the cellular senescence program, as well as the production of cytokines and chemokines involved with the senescence-associated secretory phenotype (SASP) such as IL-6, TNF-α, IL-1β, and MCP-1. Infected fibroblasts released increased amounts of stress-associated factors nitric oxide (NO) and reactive oxygen species (ROS), and the treatment with antioxidants deferoxamine (DFO) and N-acetylcysteine reduced ROS generation, secretion of SASP-related cytokine IL-6, SA-β-gal activity, and parasite load by infected fibroblasts. Taken together, our data suggest that T. cruzi infection triggers a rapid cellular stress response followed by induction of a senescent-like phenotype in NIH-3T3 fibroblasts, enabling them to act as reservoirs of parasites during the early stages of the Chagas disease

Implication of Apoptosis for the Pathogenesis of Trypanosoma cruzi Infection

Apoptosis is induced during the course of immune response to different infectious agents, and the ultimate fate is the recognition and uptake of apoptotic bodies by neighboring cells or by professional phagocytes. Apoptotic cells expose specific ligands to a set of conserved receptors expressed on macrophage cellular surface, which are the main cells involved in the clearance of the dying cells. These scavenger receptors, besides triggering the production of anti-inflammatory factors, also block the production of inflammatory mediators by phagocytes. Experimental infection of mice with the parasite Trypanosoma cruzi shows many pathological changes that parallels the evolution of human infection. Leukocytes undergoing intense apoptotic death are observed during the immune response to T. cruzi in the mouse model of the disease. T. cruzi replicate intensely and secrete molecules with immunomodulatory activities that interfere with T cell-mediated immune responses and secretion of pro-inflammatory cytokine secretion. This mechanism of immune evasion allows the infection to be established in the vertebrate host. Under inflammatory conditions, efferocytosis of apoptotic bodies generates an immune-regulatory phenotype in phagocytes, which is conducive to intracellular pathogen replication. However, the relevance of cellular apoptosis in the pathology of Chagas’ disease requires further studies. Here, we review the evidence of leukocyte apoptosis in T. cruzi infection and its immunomodulatory mechanism for disease progression

Decoding the Role of Glycans in Malaria

Complications arising from malaria are a concern for public health authorities worldwide, since the annual caseload in humans usually exceeds millions. Of more than 160 species of Plasmodium, only 4 infect humans, with the most severe cases ascribed to Plasmodium falciparum and the most prevalent to Plasmodium vivax. Over the past 70 years, since World War II, when the first antimalarial drugs were widely used, many efforts have been made to combat this disease, including vectorial control, new drug discoveries and genetic and molecular approaches. Molecular approaches, such as glycobiology, may lead to new therapeutic targets (both in the host and the parasites), since all interactions are mediated by carbohydrates or glycan moieties decorating both cellular surfaces from parasite and host cells. In this review, we address the carbohydrate-mediated glycobiology that directly affects Plasmodium survival or host resistance

Circulating Plasma MicroRNA-208a as Potential Biomarker of Chronic Indeterminate Phase of Chagas Disease

Chagas cardiomyopathy is the most severe clinical manifestation of chronic Chagas disease. The disease affects most of the Latin American countries, being considered one of the leading causes of morbidity and death in the continent. The pathogenesis of Chagas cardiomyopathy is very complex, with mechanisms involving parasite-dependent cytopathy, immune-mediated myocardial damage and neurogenic disturbances. These pathological changes eventually result in cardiac myocyte hypertrophy, arrhythmias, congestive heart failure and stroke during chronic infection phase. Herein, we show that miR-208a, a microRNA that is a key factor in promoting cardiovascular dysfunction during cardiac hypertrophy processes of heart failure, has its circulating levels increased during chronic indeterminate phase when compared to cardiac (CARD) clinical forms in patients with Chagas disease. In contrast, we have not found altered serum levels of miR-34a, a microRNA known to promote pro-apoptotic role in myocardial infarction during degenerative process of cardiac injuries thus indicating intrinsic differences in the nature of the mechanisms underlying the heart failure triggered by Trypanosoma cruzi infection. Our findings support that the chronic indeterminate phase is a progressive phase involved in the genesis of chagasic cardiopathy and point out the use of plasma levels of miR-208a as candidate biomarker in risk-prediction score for the clinical prognosis of Chagas disease

ATP-induced apoptosis involves a Ca(2+)-independent phospholipase A(2) and 5-lipoxygenase in macrophages

Macrophages express P2X(7) and other nucleotide (P2) receptors, and display the phenomena of extracellular ATP (ATP(e))-induced P2X(7)-dependent membrane permeabilization and cell death by apoptosis and necrosis. P2X7 receptors also cooperate with toll-like receptors (TLRs) to induce inflammasome activation and IL-1 beta secretion. We investigated signaling pathways involved in the induction of cell death by ATP, in intraperitoneal murine macrophages. Apoptosis (hypodiploid nuclei) and necrosis (LDH release) were detected 6 h after an induction period of 20 min in the presence of ATP Apoptosis was blocked by caspase 3 and caspase 9 inhibitors and by cyclosporin A. The MAPK inhibitors PD-98059, SB-203580 and SB-202190 provoked no significant effect oil apoptosis, but SB-203580 blocked LDH release. Neither apoptosis nor necrosis was inhibited when both intra- and extracellular Ca(2+) were chelated during the induction period. Mepacrine, a generic PLA(2) inhibitor and BEL, an inhibitor of Ca(2+)-independent PLA(2) (iPLA(2)) blocked apoptosis, while pBPB and AACOOPF(3). inhibitors of secretory and Ca(2+)-dependent PLA(2) respectively, had no significant effect. Cycloxygenase inhibitors had no effect on apoptosis, while the inhibitors of lipoxygenase (LOX) and leukotriene biosynthesis nordihydroguaiaretic acid (NDGA), zileuton, AA-861, and MK-886 significantly decreased apoptosis. Neither NDGA nor MK-886 blocked apoptosis of 5-LOX(-/-) macrophages. CP-105696 and MK-571, antagonists of leukotriene receptors, had no significant effect on apoptosis. None of the inhibitors of PLA(2) and LOX/leukotriene pathway had a significant inhibitory effect on LDH release. Our results indicate that a Ca(2+) -independent step involving an iPLA(2) and 5-LOX are involved in the triggering of apoptosis but not necrosis by P2X7 in macrophages. (C) 2008 Elsevier Inc. All rights reserved