Recently studies have demonstrated that alterations

Recently, studies have demonstrated that alterations on these enzymes contribute directly to disease pathophysiology during many infectious diseases, such as those caused by Trypanosoma evansi (Baldissera et al., 2015a,b) and Fasciola hepatica (Baldissera et al., 2015a,b). However, the activities of these enzymes during P. aeruginosa infection were not evaluated so far. Thus, due to the importance of fdps metabolism to the gills, the aim of this study was to evaluate whether experimental infection by P. aeruginosa strain PA01 alters AK, PK and CK activities in gills of silver catfish, Rhamdia quelen.

Materials and methods

Results

Discussion
The present study is novel since it evaluates important alterations in the phosphoryltransfer network in gills of animals experimentally infected by P. aeruginosa strain PA01. Our findings clearly shows the inhibition of the AK, PK and the cytosolic and mitochondrial CK, indicating an imbalance of energy homeostasis in gills of infected animals.
The systemic integration of energetic and metabolic signaling networks ensure cellular energy homeostasis and an adequate response to stress conditions, such as those caused by infectious diseases (Saks et al., 2006). Thus, the measurement of phosphoryltransfer network provides new perspectives for understanding the alterations in energy metabolism due to diseases. According to Dzeja et al. (2000), the coupling of spatially separated intracellular ATP-producing and ATP-consuming is a fundamental process to the proper energetic metabolism physiology. Therefore, an enzymatic network is necessary, catalyzed by AK, CK, and in special by PK, because they support high-energy phosphoryltransfer between ATP-generating and ATP-consuming process (Dzeja and Terzic, 1998). We observed that AK, PK and cytosolic and mitochondrial CK activities were inhibited by P. aeruginosa infection, which may result in decreased availability of ATP and impairment of energy supply. These enzymes are intimately related in such a way, that a decrease in one enzyme may lead to an increase of the other, a mechanism known as energy compensation. This mechanism contributes to efficient intracellular energetic communication, maintaining the balance between cellular ATP consumption and production in attempt to preserve the energetic homeostasis (Alekssev et al., 2012). On the other hand, a concomitant decrease on these enzymes in the gills was observed in infected animals with P. aeruginosa strain PA01, contributing directly to the impairment of synthesis and release of ATP on the gills, which may be related to disease pathophysiology. Recently, a study conducted by Baldissera et al. (2015a,b) demonstrated that inhibition on hepatic, cardiac and cerebral AK, PK and CK activities contributes directly to disease pathophysiology during T. evansi infection.
Recently, studies have demonstrated that impairment on enzymes of energy metabolism is linked to the appearance of clinical signs and disease evolution, such as observed during other infectious diseases (Baldissera et al., 2015a,b). Impairment on AK activity has been associated to disturbances on cellular functions, loss of osmoprotection activity, as well as focal hemorrhage, one of the main clinical symptom caused by P. aeruginosa (Toren et al., 1994). Also, inhibition of CK activity may lead to an important dysfunction in fish respiration, since mitochondrial CK activity is a modulator of the metabolic potential localized in mitochondria connected to the respiratory chain (Brdicza et al., 1994).
In summary, we have demonstrated, for the first time, that experimental infection by P. aeruginosa inhibits key enzymes linked to the production and utilization of metabolic energy in silver catfish, and consequently, impairs the cellular energy homeostasis, contributing to disease pathogenesis.

Introduction
Since the identification of the porcine reproductive and respiratory syndrome virus (PRRSV) in 1991 as the causative agent of PRRS in Europe, several studies have demonstrated the remarkable phenotypic and genetic diversity between strains and within subtypes (Wensvoort et al., 1991; Meulenberg et al., 1993; Han et al., 2013a, 2013b, 2013c; Morgan et al., 2013; Stadejek et al., 2013; Weesendorp et al., 2014; Amarilla et al., 2015; Salguero et al., 2015). PRRSV has been recently included within the new genus Rodartevirus which comprises the species suid 1 rodartevirus and suid 2 rodartervirus, corresponding to the viruses named PRRSV-1 and PRRSV-2, respectively (Kuhn et al., 2016).