Krystyna Skwarlo-Sonta

Evidence for melatonin synthesis in mouse and human bone marrow cells

Recently, it was demonstrated that inbred strains of mice have a clearcut circadian rhythm of pineal and serum melatonin. Moreover, it is known that melatonin is involved in many immunoregulatory functions. Among them, hematopoiesis is influenced by the action of melatonin via melatonin‐induced opioids on kappa‐opioid receptors, which are present on stromal bone marrow cells. Therefore, the present study was carried out to investigate the presence of melatonin in the bone marrow in which immunocompetent cells are generated. Specifically, we aimed at answering the following question: are bone marrow cells involved in melatonin synthesis? In the present study, we demonstrate that (1) bone marrow cells contain high concentrations of melatonin; (2) bone marrow cells have a N‐acetyltransferase activity and they express the mRNA encoding hydroxy‐O‐methyltransferase and (3) bone marrow cells cultured for a prolonged period exhibited high levels of melatonin. Results presented here suggest that mouse and human bone marrow and bone marrow cells are capable of de novo synthesis of melatonin, which may have intracellular and/or paracrine functions.

Composition differences between organic and conventional meat: a systematic literature review and meta-analysis

Demand for organic meat is partially driven by consumer perceptions that organic foods are more nutritious than non-organic foods. However, there have been no systematic reviews comparing specifically the nutrient content of organic and conventionally produced meat. In this study, we report results of a meta-analysis based on sixty-seven published studies comparing the composition of organic and non-organic meat products. For many nutritionally relevant compounds (e.g. minerals, antioxidants and most individual fatty acids (FA)), the evidence base was too weak for meaningful meta-analyses. However, significant differences in FA profiles were detected when data from all livestock species were pooled. Concentrations of SFA and MUFA were similar or slightly lower, respectively, in organic compared with conventional meat. Larger differences were detected for total PUFA and n-3 PUFA, which were an estimated 23 (95 % CI 11, 35) % and 47 (95 % CI 10, 84) % higher in organic meat, respectively. However, for these and many other composition parameters, for which meta-analyses found significant differences, heterogeneity was high, and this could be explained by differences between animal species/meat types. Evidence from controlled experimental studies indicates that the high grazing/forage-based diets prescribed under organic farming standards may be the main reason for differences in FA profiles. Further studies are required to enable meta-analyses for a wider range of parameters (e.g. antioxidant, vitamin and mineral concentrations) and to improve both precision and consistency of results for FA profiles for all species. Potential impacts of composition differences on human health are discussed.

Prolactin as an immunoregulatory hormone in mammals and birds.

The immunoregulatory function of prolactin (PRL) and the mechanism of its action in mammals seem to be well documented. Reciprocal interdependence between PRL secretion and immune system function is essential for normal ontogeny, development and aging. PRL receptors in lymphocytes participate in the transduction of its regulatory signal into the intracellular enzymatic machinery including that of the nucleus, leading to the expression of some genes and to the synthesis of new proteins. Activation of phosphoinositide turnover and subsequent increase in protein kinase-C activity seems to be a possible mechanism acting in the regulatory influence of PRL on mammalian immune cells. These cells in turn, under mitogen or antigen stimulation, secrete a substance with PRL-like activity. The regulatory function of PRL within the avian immune system is less well known, but it seems to have some features in common with those in mammals. Direct mitogenic action on thymocytes and splenocytes in the chicken might indicate the existence of PRL receptors in these cells and could explain the immunostimulatory effect of PRL observed in vivo, which is dependent on the time of hormone administration. As the avian PRL stimulates mitogenesis of rat Nb2 lymphoma cells, the mechanism of direct PRL action on immune cells in mammals and birds seems to be similar. PRL in chickens also modifies the level and the diurnal rhythm of corticosterone which, in turn, influences the immunoregulatory effect exerted by PRL. Thus, PRL seems to be an important factor, influencing directly or indirectly the avian immune system.

Seasonality of pineal gland activity and immune functions in chickens.

Abstract:  The immunomodulatory action of melatonin in different animal species is already well known, although the mechanism(s) by which the indoleamine influences the immune system have yet to be fully elucidated. Previously, we have shown both anti‐inflammatory and opioid‐mediated influence of exogenous melatonin on thioglycollate‐induced peritonitis in young chickens. In the present study, the kinetics of peritonitis and splenocyte proliferation were compared in chickens reared in both seasons under the same L:D 12:12 conditions. These two aspects of the immune response were correlated with the diurnal rhythm of pineal gland function, measured by the activity of N‐acetyltransferase (NAT), a key enzyme in melatonin biosynthesis. The results revealed seasonal changes in the circadian rhythm of pineal NAT activity occurring in parallel to the natural local geophysical seasons. These changes appeared to influence the development of peritonitis and splenocyte responsiveness to mitogenic stimulation in vitro. Moreover, the existence of bidirectional communication between the pineal gland and the activated immune system was supported by the decreased activity of pineal NAT in chickens with peritonitis compared with control birds.

Intracellular second messengers involved in melatonin signal transduction in chicken splenocytes in vitro

Abstract:  The pineal hormone melatonin exhibits immunomodulatory activity well documented in mammals and birds. The mechanism of melatonin action within the immune system is, however, poorly understood. In mammalian immune cells in vitro, melatonin acts mainly as an antiapoptotic, oncostatic and antiproliferative agent, and these effects are exerted via specific receptors or are related to its free radical scavenging activity. In previous studies we have found that in short‐term chicken splenocyte cultures in vitro melatonin stimulated basil proliferation and inhibited that stimulated with phytohemagglutinin, a T‐cell mitogen. This paper is devoted to the involvement of membrane receptors, previously characterised by us as MT2 (Mel1b) and Mel1c subtypes, in the above mentioned melatonin effects in chicken splenocyte cultures. For this purpose, in present study a nonselective melatonin receptor antagonist, luzindole, and the selective MT2 blocker, 4P‐PDOT, were used. The effect of melatonin on second messengers, cyclic adenosine‐3′,5′‐monophosphate (cAMP) and inositol‐1,4,5‐trisphosphate (IP3), involved in the regulation of proliferation, was examined. We have found that the stimulation of proliferation occurs via Mel1c receptor and is associated with the changes in intracellular second messengers concentration: a decrease in cAMP and an increase in IP3. In contrast, in mitogen‐activated splenocytes, melatonin‐induced inhibition of proliferation is mediated by MT2 receptors and is related to cAMP accumulation, as well as a decrease in IP3. In conclusion, we have demonstrated that the stimulatory and inhibitory effect of melatonin on chicken splenocytes in vitro, dependent on the magnitude of cell stimulation, resulted from two different subtypes of membrane receptors.

Mitogenic effect of prolactin on chicken lymphocytes in vitro

Lymphocytes obtained from thymus and spleens of 1-6 week old White Leghorn cockerels, untreated or immunized twice with sheep red blood cells (SRBC), were cultured with common T-cell mitogens in serial dilutions and/or different concentrations of bovine prolactin (PRL). [3H]Thymidine incorporation in newly synthesized DNA was used as a measure of lymphocyte mitogenic stimulation. Lymphocytes were stimulated by mitogens, as well as by PRL alone, in a dose-dependent way. Cell cultures prepared from immunized and non-immunized donors differed in their response to mitogens or PRL. The present results demonstrate direct PRL action on avian lymphoid cells and resemble those found in the mammalian immune system.

Melatonin inhibits PHA-stimulated chicken lymphocyte proliferation in vitro.

Many studies have shown that melatonin plays a fundamental role in neuroimmunomodulation. There are known differences between mammals and birds in immunomodulatory function of melatonin exerted in vivo. In present study the effect of exogenous melatonin on chicken lymphoid cell proliferation in vitro was examined. Melatonin alone (10−10M–10−5M) did not exert any effect on the proliferation of the chicken thymocytes, splenocytes and lymphocytes from the bursa of Fabricius. On the other hand, melatonin addition strongly inhibited the proliferation of PHA‐activated thymocytes and splenocytes from young chickens. The effect of melatonin was hormone‐ and mitogen‐(PHA) dose‐dependent; the most pronounced effect was obtained at low PHA and melatonin concentrations i.e., 1.6–3.125 μg/100 μl of PHA and 10−10M–10−7M melatonin, respectively. Prior immunization of chickens with sheep red blood cells (SRBC) inhibited the proliferative response of splenocytes to the same dose of PHA and, consequently, the effect of melatonin addition was not observed. The results reported demonstrate a direct inhibitory effect of melatonin on in vitro activated chicken lymphocytes.

Effect of melatonin on phagocytic activity and intracellular free calcium concentration in testicular macrophages from normal and streptozotocin-induced diabetic rats

This study examined the effect of melatonin (MLT) on in vitro phagocytosis of testicular macrophages taken from control and streptozotocin (STZ)-induced diabetic rats and the possible mechanism of its action. The phagocytic activity was measured as a number of latex beads ingested by 100 macrophages (PI, phagocytic index) in consecutive time points of the incubation. Changes in intracellular free calcium level [Ca2+]i in isolated macrophages in vitro were measured with the use of ratio-image fluorescence microscopy (fluorescent dye: Fura2/AM). Phagocytic index in macrophages isolated from healthy rats was 20% higher than in those from diabetic animals. Melatonin in physiological concentration (10−7 M) significantly (p < 0.05) increased the PI in testicular macrophages from control animals (PI = 68 ± 5 with MLT compared to PI = 46 ± 7 without MLT) while no such effect was observed in the cells from diabetic rats (PI = 36 ± 23 with MLT compared to PI = 31 ± 11 without MLT). Basal [Ca2+]i was significantly (p < 0.01) higher in macrophages from diabetic rats compared to control. Stimulation of both control and diabetic testicular macrophages with 10−7 M MLT resulted in a significant (p < 0.05) increase in [Ca2+]i in cells incubated in 2.5 mM calcium solution while no such response was observed in calcium-free Tyrode solution. However, MLT evoked [Ca2+]i response in macrophages isolated from diabetic animals was much lower than in macrophages isolated from age-matched controls and the time needed for maximal response was much longer. Lack of response in calcium-free solution suggests that extracellular calcium may be necessary to trigger MLT response and in its progression.

Pineal influence on the diurnal rhythm of nonspecific immunity indices in chickens

Abstract: The effect of pinealectpmy and melatonin injections on the diurnal rhythms of serum lysozyme and blood granulocytes was examined in White Leghorn cockerels kept from time of hatching for 5 weeks in L:D 12:12 conditions and immunized twice with sheep red blood cells (SRBC). Pinealectomy or sham‐operation was made during first week of life. Pinealectomized chickens were injected daily with a melatonin dosage increased over 4 consecutive weeks (the dosage was 10, 13, 16, and 20 ng per bird daily during the 4 weeks, respectively; MEL I) at the beginning of darkness. The same treatment was performed on chickens with an intact pineal gland using additional melatonin doses increased 10 times (MEL II) and 500 times (MEL III). Intact chickens were also injected with MEL II and MEL III 4 hr before the end of light. Control birds received equivalent injections of vehicle. Five‐week‐old chickens were sacrificed during a 24‐hr period every 4 hr. The existence of diurnal rhythm was evaluated by cosinor analysis. Pinealectomy shifted the acrophase of the diurnal rhythm of granulocytes and abolished that of serum lysozyme. Both rhythms were restored in pinealectomized chickens by MEL I but not by vehicle injections. The same melatonin dose was unable to change the granulocyte rhythm but delayed the acrophase of that of serum lysozyme in chickens with an intact pineal gland. Two higher melatonin doses influenced the diurnal rhythm of granulocytes as a function of dose and time of administration. The rhythm of serum lysozyme was dependent only on the time of injection. The pineal gland seems to control, via its hormone melatonin, the diurnal rhythm of nonspecific immunity in chickens.

Effect of dose and time of melatonin injections on the diurnal rhythm of immunity in chicken

Skwado‐Solita K, Thaela M‐J, GXuchowska B, Stepien D, Jagura M. Effect of dose and time of melatonin injections on the diurnal rhythm of immunity in chicken. J Pineal Res 1991: 10:3&35.