Ectonucleotidases and adenosine deaminase activity in laying hens naturally infected by Salmonella Gallinarum and their effects on the pathogenesis of the disease

Purinergic signalling displays an anti-inflammatory profile in the spleen of fish experimentally infected with Aeromonas caviae: Modulation of the immune response

Extracellular adenosine triphosphate (ATP) and its metabolite adenosine (Ado) are recognized as key mediators of immune and inflammatory responses. Depending on its concentration, ATP may act as an immunostimulant or immunodepressant, while Ado levels display an anti-inflammatory profile. The aim of this study was to evaluate whether splenic purinergic signalling is capable of modulating immune and inflammatory responses in fish experimentally infected with Aeromonas caviae. Triphosphate diphosphohydrolase (NTPDase) and 5'-nucleotidase activities increased in the spleen of silver catfish (Rhamdia quelen) experimentally infected with A. caviae compared with the uninfected control group. Moreover, splenic Ado levels increased in the infected animals relative to the uninfected control group. Based on these lines of evidence, our findings revealed that adenine nucleotide hydrolysis is modified in the spleen of fish infected with A. caviae attempting to restrict the inflammatory process through the upregulation of NTPDase and 5'-nucleotidase activities, which occurs in an attempt to hydrolyse the excessive ATP in the extracellular environment and rapidly hydrolyse AMP to form Ado. In summary, purinergic signalling can modulate immune and inflammatory responses during A. caviae infection.

Purinergic signaling modulates the splenic inflammatory response in silver catfish naturally infected with Ichthyophthirius multifiliis

The spleen is an immune lymphatic organ linked with control of the immune response, which is important to fish health. Recent evidence has suggested the involvement of purinergic signaling in the modulation of immune and inflammatory responses through the nucleotide adenosine triphosphate (ATP) and the nucleoside adenosine (Ado), which are regulated by the enzymes nucleoside triphosphate diphosphohydrolase (NTPDase), 5'-nucleotidase, and adenosine deaminase (ADA). Thus, the aim of this study was to evaluate whether purinergic signaling can modulate the immune and inflammatory responses in the spleen of silver catfish (Rhamdia quelen) naturally infected with Ichthyophthirius multifiliis. Splenic NTPDase and 5'-nucleotidase activities increased in infected animals compared with uninfected animals, while the splenic ADA activity decreased. These data indicate that purinergic signaling can modulate the splenic immune and inflammatory responses through the regulation of ATP and Ado levels, which are known to participate in the physiological and pathological responses as pro-inflammatory and anti-inflammatory molecules, respectively. In summary, modulation of the splenic purinergic cascade has an anti-inflammatory role in reducing or preventing inflammatory damage.

Involvement of cholinergic and adenosinergic systems on the branchial immune response of experimentally infected silver catfish with Streptococcus agalactiae

It has been recognized that the cholinergic and adenosinergic systems have an essential role in immune and inflammatory responses during bacterial fish pathogens, such as the enzymes acetylcholinesterase (AChE) and adenosine deaminase (ADA), which are responsible for catalysis of the anti-inflammatory molecules acetylcholine (ACh) and adenosine (Ado) respectively. Thus, the aim of this study was to investigate the involvement of the cholinergic and adenosinergic systems on the immune response and inflammatory process in gills of experimentally infected Rhamdia quelen with Streptococcus agalactiae. Acetylcholinesterase activity decreased, while ACh levels increased in gills of infected animals compared to uninfected animals. On the other hand, a significant increase in ADA activity with a concomitant decrease in Ado levels was observed in infected animals compared to uninfected animals. Based on this evidence, we concluded that infection by S. agalactiae in silver catfish alters the cholinergic and adenosinergic systems, suggesting the involvement of AChE and ADA activities on immune and inflammatory responses, regulating the ACh and Ado levels. In summary, the downregulation of AChE activity exerts an anti-inflammatory profile in an attempt to reduce or prevent the tissue damage, while the upregulation of ADA activity exerts a pro-inflammatory profile, contributing to disease pathophysiology.

Purinergic system displays an anti-inflammatory profile in serum of silver catfish experimentally infected with Streptococcus agalactiae: An attempt to ameliorate the inflammatory response

The purinergic system is recognized to modulate extracellular adenosine triphosphate (ATP) and related nucleotides through the activities of triphosphate diphosphohydrolase (NTPDase), 5'-nucleotidase, and adenosine deaminase (ADA), thereby playing an essential role in the immunoregulation of inflammatory and immune responses. Thus, the aim of this study was to evaluate whether the purinergic system can improve the inflammatory response in fish experimentally infected with Streptococcus agalactiae through the modulation of seric NTPDase, 5'-nucleotidase and ADA activities. Seric NTPDase (ATP as substrate) and 5'-nucleotidase activities increased in silver catfish experimentally infected with S. agalactiae compared with the uninfected control group, while seric ADA activity decreased. Based on this evidence, our findings suggest that regulation of adenine nucleotide hydrolysis occurs in an attempt to restrict the inflammatory process and improve the immune system by hydrolyzing excess extracellular ATP. On the other hand, downregulation of seric ADA activity may be an attempt to augment extracellular adenosine (a molecule with anti-inflammatory effects) levels. In summary, the purinergic system is capable of modulating the immune and inflammatory responses during fish streptococcosis.

Melaleuca alternifolia essential oil enhances the non-specific immune system and prevents oxidative damage in Rhamdia quelen experimentally infected by Aeromonas hydrophila: Effects on cholinergic and purinergic systems in liver tissue

The aim of this study was to evaluate the effects of M. alternifolia essential oil used to treat silver catfish (Rhamdia quelen) experimentally infected by Aeromonas hydrophila on oxidative stress variables, and for the first time, on hepatic enzymes of the cholinergic and adenosinergic systems. For that, fish were divided into six groups (A-F), each containing seven animals. Groups A, B and C were composed of uninfected animals, while animals in groups D, E and F were intramuscularly inoculated with A. hydrophila. Groups B and E received a prophylactic bath with M. alternifolia essential oil (50 μL/L, diluted in ethanol) for seven days, while groups C and F were exposed to ethanol. After the prophylactic baths, groups D, E and F were inoculated with 100 μL of A. hydrophila solution (2.1 × 10⁹ colony-forming unit). Two days after inoculation, the animals were euthanized and liver samples were collected. Infected animals (the group D) showed increased TBARS and protein carbonylation levels, while CAT, AChE and ADA activities decreased compared to uninfected animals (the group A). The prophylactic treatment with M. alternifolia essential oil (the group E) prevented the alterations caused by A. hydrophila, but it did not change AChE activity. Thus, the prophylactic treatment prevents damage caused by lipids and proteins, as well as alterations of the adenosinergic system, demonstrating that the anti-inflammatory effect of TTO is mediated by the adenosinergic pathway. In addition, TTO prophylactic treatment might be considered an important approach to prevent the hepatic damage caused by A. hydrophila.

Involvement of cholinergic and purinergic systems during the inflammatory response caused by Aeromonas hydrophila in Rhamdia quelen

The aim of this study was to evaluate the cholinergic (acetylcholinesterase (AChE) and butyrylcholinesterase (BChE)) and purinergic (adenosine deaminase (ADA)) systems in head kidney, spleen, total blood and serum samples in experimentally infected fish with A. hydrophila, and the involvement of these systems during the inflammatory process. Silver catfish (Rhamdia quelen) juveniles were divided into two groups with seven fish each: uninfected (negative control) and infected (positive control). On day 2 post-infection, animals were euthanized and the head kidney, spleen, total blood and serum were collected. AChE and ADA activities in head kidney and spleen decreased in infected animals compared to uninfected animals, as well as AChE in total blood and seric ADA activities. BChE activity was not expressed in the evaluated tissues. Therefore, our results lead to the hypothesis that cholinergic and purinergic systems play an important role on the immune response against A. hydrophila with an anti-inflammatory effect. In summary, AChE and ADA activities reduced probably in order to protect against tissue inflammatory damage caused by infection.