Neutrophil gelatinase-associated lipocalin (NGAL) is a 25-kDa protein that is secreted mostly by immune cells such as neutrophils, macrophages, and dendritic cells. Its production is stimulated in response to inflammation. The concentrations of NGAL can be measured in plasma, urine, and biological fluids such as peritoneal effluent. NGAL is known mainly as a biomarker of acute kidney injury and is released after tubular damage and during renal regeneration processes. NGAL is also elevated in chronic kidney disease and dialysis patients. It may play a role as a predictor of the progression of renal function decreases with complications and mortality due to kidney failure. NGAL is also useful in the diagnostic processes of cardiovascular diseases. It is highly expressed in injured heart tissue and atherosclerostic plaque; its serum concentrations correlate with the severity of heart failure and coronary artery disease. NGAL increases inflammatory states and its levels rise in arterial hypertension, obesity, diabetes, and metabolic complications such as insulin resistance, and is also involved in carcinogenesis. In this review, we present the current knowledge on NGAL and its involvement in different pathologies, especially its role in renal and cardiovascular diseases.

Influence of the season of hatch on the functional characteristics of the pineal gland was examined in neonatal Hi-Line male chickens. The pineal glands from 2-day-old birds hatched in summer and winter, and kept from the day of hatch in artificial lighting conditions (12L:12D), were isolated under dim red light in the middle of the day or night. The pineal glands were analyzed to characterize their melatonin biosynthetic activity: (1) expression of the Arylalkylamine-N-acetyltransferase and Hydroxyindole-O-methyltransferase genes, encoding the final two enzymes of the melatonin biosynthesis pathway; (2) the activity of AA-NAT and HIOMT; and (3) the content of the main substrates of this pathway, tryptophan (TRY) and serotonin (5-HT). Daily changes in pineal AA-NAT activity were observed in chickens hatched in both seasons, with a more pronounced nocturnal increase in summer. In contrast, the level of Aa-nat gene expression, although exhibited the same nocturnal/diurnal pattern in both seasons, was much lower in the summer. The activity of HIOMT was season-and daytime-independent. In "winter" chickens the pineal content of 5-HT was low and stable, while in "summer" birds it was correlated with levels of AA-NAT activity and Aa-nat gene expression. TRY content was very high and exhibited neither daily nor seasonal changes. The pineal gland of newly hatched chickens kept in controlled 12L:12D conditions exhibits daily variations in melatonin biosynthetic activity influenced by the season. This suggests a maternal effect on the perinatal/postnatal development of the circadian clock residing in the chicken pineal gland.

Melatonin is a neurohormone that is mainly secreted by the pineal gland. It coordinates the work of the superior biological clock and consequently affects many processes in the human body. Disorders of the waking and sleeping period result in nervous system imbalance and generate metabolic and endocrine derangements. The purpose of this review is to provide information regarding the potential benefits of melatonin use, particularly in kidney diseases. The impact on the cardiovascular system, diabetes, and homeostasis causes melatonin to be indirectly connected to kidney function and quality of life in people with chronic kidney disease. Moreover, there are numerous reports showing that melatonin plays a role as an antioxidant, free radical scavenger, and cytoprotective agent. This means that the supplementation of melatonin can be helpful in almost every type of kidney injury because inflammation, apoptosis, and oxidative stress occur, regardless of the mechanism. The administration of melatonin has a renoprotective effect and inhibits the progression of complications connected to renal failure. It is very important that exogenous melatonin supplementation is well tolerated and that the number of side effects caused by this type of treatment is low.

Immune system activity in higher vertebrates (mammals and birds) varies over the year, mainly in correlation with the external light phase duration and intensity, as well as accompanying environmental cues. Light influences immunity mainly via retina-SCN-pineal gland-melatonin pathway. Diurnal rhythm of melatonin biosynthesis, adjusted to the changing external day length, acts as a message of darkness for the target cells/organs in the body, including the immune system. Some of melatonin effects are receptor mediated, while others are receptor independent. According to the trade-off hypothesis, seasonal changes in immunity are inversely related to reproduction, as both physiological functions are energetically costly while the resources are limited, especially in adverse environmental conditions. In the present review, the examples of the seasonal changes of immunity in mammalian and avian species are described and discussed in the context of the pineal gland biosynthetic activity. Current knowledge on the communication between the pineal gland/melatonin and immune system indicates that these relationships are complex and the precise mechanism(s) involved are still under investigation.

Diet composition may influence the activity of the HPA and HPT axes, which, in turn, modulates immune system function. The aim of the present study was to investigate the response of rat hormonal and immune parameters to feeding with a standard diet supplemented with cholesterol and vitamin E. The experiment was performed on Wistar rats fed for 6 weeks on a diet without supplementation, or the same diet enriched with cholesterol and/or vitamin E. Vitamin E supplementation caused a decrease in body weight gain and an increase in thyroid peroxidase activity as well as raised plasma concentrations of thyroid hormones and corticosterone. Supplementation with both cholesterol and vitamin E attenuated these effects. The cholesterol-enriched diet decreased plasma levels of ACTH while it stimulated the activity of 11β-hydroxylase deoxycorticosterone in the adrenals. Splenocyte proliferation in vitro was modified by the cholesterol-enriched diet but additional supplementation with vitamin E reversed these effects.