Hepatic and seric levels of purines in rats experimentally infected by Fasciola hepatica

Purine levels and purinergic signaling in plasma and spleen of Brycon amazonicus exposed to acute heat thermal stress: An attempt to regulate the immune response

Amazon fish are vulnerable to climate change. Several lines of evidence suggest that the temperature of Amazonian rivers will increase in the coming years. Elevated temperature disturbs homeostasis and subjects fish to physiological stress; however, the effects of temperature on immunity remain poorly understood, particularly those effects involving purinergic signaling. This system fine-tunes the inflammatory and immune responses triggered by stress. Therefore, the aims of this study were to determine whether acute heat stress induces the release of nucleotides into extracellular compartment and to determine whether purinergic enzymes modulate the proinflammatory effects of adenosine triphosphate (ATP) in plasma and spleen of matrinxã (Brycon amazonicus) exposed to acute heat stress. We exposed juvenile matrinxã to four temperature regimes (28 °C as control, 30, 32 and 34 °C) for 72 h and observed the effects on purinergic signaling. Plasma cortisol levels were significantly higher in fish exposed to 34 °C than in the control group, while spleen ATP, adenosine diphosphate (ADP) and adenosine monophosphate (AMP) levels were significantly higher in this group than in controls. Activities of spleen nucleoside triphosphate diphosphohydrolase (NTPDase) and 5'-nucleotidase were significantly higher in fish exposed to 34 °C than those of the control group, while spleen interleukin-1 (IL-1) and interleukin-6 (IL-6) levels were higher in this same group than in the control group. No significant differences were observed between the groups regarding plasma parameters. Based on these data, we concluded that acute heat stress at 34 °C caused physiological stress in matrinxã, manifesting as elevated plasma cortisol levels. The most important finding is that purinergic enzymes were modulated, though not efficiently, in response to the excessive release of nucleotides into the extracellular space. In summary, the purinergic signaling pathway may be involved in the impairment of immune and inflammatory responses in matrinxã exposed acutely to 34 °C.

Nucleotide and nucleoside involvement in immunomodulation in experimental Chagas disease

The aim of this study was to evaluate whether Trypanosma cruzi infections cause alterations in the levels of seric purines, which could contribute to host immunomodulation. Twelve mice were divided into two groups identified as control (uninfected) and infected (T. cruzi) groups. The influence of the disease on seric purine levels was verified on day 20 post-infection (PI) by HPLC. Infected mice had circulating trypomastigotes during the experiment, as well as amastigote forms in the heart associated with inflammatory infiltrates. Increases on adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine (ADO), inosine (INO), and uric acid (URIC) levels were observed in the infected animals, while the adenosine monophosphate (AMP) and xanthine (XAN) levels were reduced compared with mice of the control group, indicating a possible impairment on the purinergic system, and consequently, on the immune system during the clinical course of the disease. In summary, the T. cruzi infection alters the seric purine levels, and consequently, modulates the immune system.

Toxoplasmosis treatment with diphenyl diselenide in infected mice modulates the activity of purinergic enzymes and reduces inflammation in spleen

Toxoplasma gondii, an intracellular protozoan, may cause chronic infection in the brain tissue of the host inducing a systemic pro-inflammatory profile. Chronic infections can induce numerous physiological changes, such as alterations in the immune and oxidative profiles. Diphenyl diselenide (PhSe)₂, an organoselenium compound, has shown antioxidant and immunomodulatory activities in recent studies. So, the aim of this study was to investigate the activity of purinergic enzymes and reactive oxygen species (ROS) in serum and spleen of mice chronically infected by T. gondii, untreated and treated with (PhSe)₂. For this experiment, were divided into four groups: Group A (healthy mice), Group B (healthy mice treated with (PhSe)₂), Group C (infected mice) and Group D (infected mice treated with (PhSe)₂). Group C and group D were infected via oral route with ME49 Toxoplasma gondii strain. Groups B and D were treated subcutaneously with 5 μmol kg^-1 of (PhSe)₂. Chronic T. gondii infection induced splenomegaly and physiological changes in the spleen and raised histologic inflammatory markers, ROS levels and the activity of purinergic enzymes activity such as NTPDase, 5´nucleotidase and ADA. In serum, the infection increased 5´nucleotidase and ADA activities. (PhSe)₂per se has managed to decrease ROS levels and ADA activity and increase NTPDase and 5´nucleotidase in spleen. In infected mice, treatment with (PhSe)₂ reversed splenomegaly, reduced histological inflammatory markers, ROS levels and ADA activity in the spleen. Our results prove that chronic toxoplasmosis can induce splenomegaly, heightens ROS levels and purinergic enzyme activity in mice. These results suggest that (PhSe)₂ is a potential therapy for the alterations found in the spleen in chronic T. gondii infection.

Oxidative stress and changes in adenosine deaminase activity of cattle experimentally infected by Fasciola hepatica

The aim of this study was to evaluate the oxidative stress in serum and liver and adenosine deaminase (ADA) activity of cattle experimentally infected by Fasciola hepatica. The group A consisted of five healthy animals (uninfected), and the group B was composed of five animals orally infected with 200 metacercariae of F. hepatica. On days 20, 40, 60 and 80 post-infection (PI) serum was collected to measure oxidative stress variables. On day 100 PI, animals were humanely euthanized and liver samples were collected. Infected animals showed lower (P < 0·05) seric ADA activities on days 40 and 60 PI but higher (P < 0·05) in the liver tissue compared with uninfected animals. Seric and hepatic reactive oxygen species (ROS) were higher (P < 0·05) in infected compared with uninfected animals. Hepatic thiobarbituric acid reactive substances were higher (P < 0·05) in infected animals. Catalase and glutathione S-transferase activities were lower in liver tissue of infected animals, while glutathione peroxidase was higher compared with uninfected (P < 0·05). In summary, we conclude that oxidative stress occurs in cattle experimentally infected by F. hepatica, mainly due to excessive ROS production in the course of fasciolosis, contributing to hepatic damage, and that increased in hepatic ADA activity may contribute to the inflammatory process.