Are cortisol and melatonin involved in the immune modulation by the light environment in pike perch Sander lucioperca?

Abstract

The pineal gland is the main organ involved in the transduction process converting environmental light information into a melatonin response. Since light environment was described as an important factor that could affect physiology of teleosts, and because melatonin is a crucial hormone regulating numerous physiological processes, we hypothesized that environmental light may act on both stress and circadian axes which in turn could influence the immune status of pike perch. Therefore, we investigated the effects of two light spectra (red and white) and two light intensities (10 and 100 lx) with a constant photoperiod 12L(8:00‐20:00)/12D on pike perch physiological and immune responses. Samples were collected at 04:00 and 16:00 at days 1 and 30 of the experiment. Stress markers, plasma melatonin levels, humoral innate immune markers, and expression of key immune genes in the head kidney were assessed. Light intensity clearly affected pike perch physiology. This included negative growth performances, increase in stress status, decrease in plasma melatonin levels, and immune depression. Light spectrum had only little influences. These results demonstrate that high stress status may have impacted melatonin production and secretion by the pineal organ. The drop in circulating melatonin and the increase in stress status may both be involved in the immune suppression.

Seasonal simulated photoperiods influence melatonin release and immune markers of pike perch Sander lucioperca

“…Our results defined also day-night variations of lysozyme, peroxidase, complement and phagocytic activities. Such cyclic activity has already been described in several fish species including pike perch, Nile tilapia (Oreochromis niloticus), gilthead seabream and sea bass 19,23,24,62 . The day-night variations of immune variables, as observed in the present experiment, are comparable to the variations of both plasma melatonin and cortisol 23,24 .…”

“…Such cyclic activity has already been described in several fish species including pike perch, Nile tilapia (Oreochromis niloticus), gilthead seabream and sea bass 19,23,24,62 . The day-night variations of immune variables, as observed in the present experiment, are comparable to the variations of both plasma melatonin and cortisol 23,24 . www.nature.com/scientificreports www.nature.com/scientificreports/ Considering that cortisol is a potent immunosuppressive agent with complex actions on immune cells and tissues 31,32 and that an anti-stress role for melatonin has been defined 33,35 , the present results may support that melatonin acts on immune activities through the modulation of cortisol release in plasma 3,63 .…”

“…Nevertheless, the available information supports an immune regulation by the melatonin hormone in teleosts 3,[19][20][21][22] . In pike perch, a potential dual action of cortisol and melatonin hormones on immune defenses was described 23,24 . In addition, these experiments defined a correlation between daily cyclic activities of humoral innate immune markers and the nocturnal peak of plasma melatonin.…”

“…While cortisol is known as a potent immunosuppressive agent in vertebrates 31,32 , a mutual inhibition was described between HPI and melatonin axes [33][34][35] . In addition, brain serotonergic and dopaminergic activities, which are both indicators of acute and chronic stress in teleosts, were affected by light color and intensity but no consideration of the photoperiod was made 24,[35][36][37][38] .…”

“…Pike perch is the most promising freshwater fish species for the diversification of inland aquaculture industry in Europe. The eyes of this species possess a tapetum lucidum that is a specific tissue of the retina which greatly amplify the eye sensitivity to light 24,39 . This is in agreement with behavior of pike perch since it is a crepuscular predator actively feeding during dusk and night 40,41 .…”