Subchronic mycotoxicoses in rats. Histopathological changes and modulation of the sphinganine to sphingosine (Sa/So) ratio imbalance induced by Fusarium verticillioides culture material, due to the coexistence of aflatoxin B1 in the diet.

Mycotoxicoses are diseases caused by consumption of diets contaminated with mycotoxins, a special class of fungal secondary metabolites. Fumonisin B1 (FB1) and aflatoxin B1 (AFB1), the main toxins synthesized by toxicogenic stocks of Fusarium spp. and Aspergillus spp., respectively, can coexist in grains and in its by-products. We investigated a probable synergism of a fumonisins-containing Fusarium verticillioides culture material and AFB1 in the induction of hepatocyte apoptosis in rats subchronically fed on a mixture of them. Furthermore, the possibility of modifications in the fumonisins-induced Sa/So ratio imbalance in tissues and urine from rats poisoned with this mycotoxin, due to the presence of AFB1 in the diet, was evaluated. The co-exposure to fumonisins and AFB1 produced a higher liver toxicity, with respect to their individual administration, inducing apoptosis and mitotic hepatocytes. There was an inversion of the typical Sa/So ratio in rats fed on the culture material as well as in those subjected to a diet co-contamined with fumonisins and AFB1. Moreover, the later had a synergistic effect in the induction of Sa/So variations in kidneys. Therefore, the mixture of fumonisins and AFB1 induced toxic responses which could not be considered a sum of the effects caused individually by these mycotoxins.

Cruzipaína, la principal cisteín proteasa de trypanosoma cruzi en la interrelación huésped-parásito / Cruzipain, a major Trypanosoma cruzi cystein protease in the host-parasite interplay

La enfermedad de Chagas, causada por el parásito protozoarioTrypanosoma cruzi, es endémica en América Central y Sudaméricay representa la miocarditis más frecuente a nivel mundial.El establecimiento de la infección crónica conduce a una patologíacardíaca debilitante por la cual mueren más de 50,000 personascada año. No existe consenso sobre si la causa del daño tisulares ocasionada por el parásito o está exacerbada por una respuestaautoinmune. En ambos escenarios, ha sido sugerido quecruzipaína- la principal cisteín proteasa del T. cruzi- cumple unrol importante en la progresión de la enfermedad.Cruzipaína, miembro de la superfamilia de las papaínas, seexpresa como una mezcla compleja de isoformas en los diferentesestadíos de desarrollo de todas las cepas del parásito. Esta glicoproteínaparticipa en la internalización del T. cruzi en las célulasmamíferas, lo que ha sido demostrado con inhibidores específicosde la enzima que interfieren en la invasión celular y la replicacióndel parásito. Además, cruzipaína genera una fuerte respuestaimmune en individuos infectados. Estas característicashacen de cruzipaína un potencial blanco de drogas terapéuticas.La presente revisión resume el conocimiento actual sobre elrol de cruzipaína en la patogénesis de la enfermedad, su compromisoen la invasión de células del huésped así como su participaciónen la activación y evasión de la respuesta inmune enmodelos experimentales y en pacientes chagásicos. El avance enesta área de investigación, proveerá nuevas estrategias terapéuticastendientes a incrementar la respuesta inmunoprotectiva yprevenir la respuesta deletérea producida por el parásito

The protozoan parasite Trypanosoma cruzi, etiological agentof Chagas disease, is endemic in Central and South America andproduces the most common myocarditis worldwide.Parasite persistence eventually leads to a debilitating heartdisease that kills more than 50,000 people every year. There is noconsensus as to whether tissue damage is caused entirely by theparasite or is exacerbated by an autoimmune response. In bothmodels of disease progression, cruzipain- the major cysteine proteinaseof T. cruzi- has been suggested to play an important role.Cruzipain is a member of the papain superfamily, and it isexpressed as a complex mixture of isoforms by different strains ofthe parasite, as well as in all its developmental stages. This parasiteglycoprotein plays a role in the process of T. cruzi internalizationinto mammalian cells, as proved by specific enzyme inhibitors, whichinterfere with cell invasion and inhibit parasite replication.In addition, cruzipain not only is essential for parasite survivalbut also generates a strong immune response in infected individuals.These characteristics point to cruzipain as a potential targetfor drug therapy and for the generation of immune responses.This review analyses our present knowledge of the role ofcruzipain in the disease pathogenesis, its involvement in host cellinvasion, immune activation and evasion by T. cruzi in experimentalmodels and human infection. Ongoing studies in this researcharea may provide novel therapeutic strategies that couldenhance the immunoprotective response while preventing thedeleterious parasite elicited responses observed during Chagasdisease

Apoptosis induction by glucuronoxylomannan of Cryptococcus neoformans.

We studied the ability of glucuronoxylomannan (GXM), the major constituent of Cryptococcus neoformans capsular polysaccharide, to induce apoptosis in lymphocytes from normal rats. Spleen mononuclear cells (Smc) from normal rats treated with GXM for 24 h exhibited, in comparison with controls, an increased hypodiploidy in the DNA profile after staining with propidium iodide, as well as increased ladder-type DNA fragmentation in agarose gel electrophoresis and a high number of positive cells in the terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL) reaction. Furthermore, increased hypodiploidy in the DNA profile was also observed in Smc expressing T-cell receptor (TCR +). We also studied the induction of apoptosis in lungs and spleens from rats in the immunosuppressor period of disseminated cryptococcosis. TUNEL labeling of lungs and spleens from rats obtained 14 days after infection with C. neoformans showed a large number of apoptotic cells. Our results provide strong cytometric, molecular and morphological evidence that apoptosis could be a previously unrecognized immunosuppressive property of GXM in vitro. This programmed cell death may be involved in the immunosuppression observed during C. neoformans infection.

Sexual dimorphism of apoptosis in lactotrophs induced by bromocryptine.

Interruption of lactation provokes a massive degeneration of surplus lactotrophs in the rat pituitary gland. This process was determined to be non-apoptotic in nature, and this observation raised many questions as cell death by apoptosis has been described in several tissues after withdrawal of trophic hormones. In this study we explored various experimental conditions and gathered new information leading to a comprehensive interpretation of the factors involved in the induction of apoptosis in lactotrophs. With this aim, we investigated the apoptogenic role of bromocryptine on lactotrophs in several experimental models involving male and female rats. Even though bromocryptine increased the expression of P53 in all experimental models, apoptosis was only triggered in male and ovariectomised females. In both conditions the oestrogen stimulation is low or nil, and the occurrence of apoptosis can be correlated with the appearance of atypical lactotrophs and the level of P53 expression. The existence of apoptosis was validated with the observation of DNA laddering in electrophoresis. By contrast, in intact females the majority of lactotrophs present signs of an increased prolactin secretion and no DNA fragmentation was found. Endogenous oestrogens probably prevent the deep inhibitory effect of a dopamine agonist and thus block apoptosis. Besides, the morphological analysis of regressing pituitary revealed the coexistence of lactotrophs to be an important factor responsible for tissue remodelling in functional pituitary glands undergoing apoptotic and non-apoptotic cell deaths. The non-apoptotic cell death appeared to be an important factor responsible for tissue remodelling in functional pituitary glands. The present results suggest that the occurrence of apoptosis in regressing lactotrophs caused by bromocryptine is sexually dimorphic and probably associated with the survival effect of endogenous oestrogens in intact females.

Apoptotic and non-apoptotic cell death in hormone-dependent glands.

The proliferation of cells and cell death are involved in the maintenance of appropriate tissue homeostasis. In the present study, two different mechanisms of cell death were identified in the prostate and pituitary glands when morphological data, fragmentation of DNA, and TUNEL labelling of apoptotic nuclei were compared. Typical cell death by apoptosis was identified by morphological and molecular approaches in the prostate after orchidectomy. By contrast, neither DNA fragmentation nor TUNEL labelling were found in dead cells occurring in the pituitary gland after interruption of lactation. Regressing lactotrophs were characterised by condensation and disruption of the cytoplasmic matrix, but preserved intact nuclei until advanced stages of regression. Degenerating "dark" cells comparable to those described in the pituitary were also seen coexisting with typical apoptosis in the prostate epithelial lining of orchidectomised rats. Both forms of cell death could be clearly differentiated, because dark cells suffer severe alterations of cytoplasmic organelles while maintaining the integrity of the nucleus. In contrast, apoptotic cells present well-preserved cytoplasmic organelles, but grossly disrupted nuclei with fragmentation and condensation of chromatin.