A two-clock model of circadian timing in the immune system of mammals

Role of Neurotransmitters in Steady State Hematopoiesis, Aging, and Leukemia

Haematopoiesis within the bone marrow (BM) represents a complex and dynamic process intricately regulated by neural signaling pathways. This delicate orchestration is susceptible to disruption by factors such as aging, diabetes, and obesity, which can impair the BM niche and consequently affect haematopoiesis. Genetic mutations in Tet2, Dnmt3a, Asxl1, and Jak2 are known to give rise to clonal haematopoiesis of intermediate potential (CHIP), a condition linked to age-related haematological malignancies. Despite these insights, the exact roles of circadian rhythms, sphingosine-1-phosphate (S1P), stromal cell-derived factor-1 (SDF-1), sterile inflammation, and the complement cascade on various BM niche cells remain inadequately understood. Further research is needed to elucidate how BM niche cells contribute to these malignancies through neural regulation and their potential in the development of gene-corrected stem cells. This literature review describes the updated functional aspects of BM niche cells in haematopoiesis within the context of haematological malignancies, with a particular focus on neural signaling and the potential of radiomitigators in acute radiation syndrome. Additionally, it underscores the pressing need for technological advancements in stem cell-based therapies to alleviate the impacts of immunological stressors. Recent studies have illuminated the microheterogeneity and temporal stochasticity of niche cells within the BM during haematopoiesis, emphasizing the updated roles of neural signaling and immunosurveillance. The development of gene-corrected stem cells capable of producing blood, immune cells, and tissue-resident progeny is essential for combating age-related haematological malignancies and overcoming immunological challenges. This review aims to provide a comprehensive overview of these evolving insights and their implications for future therapeutic strategies.

Chronophysiology of domestic animals

This review highlights recent findings on biological rhythms and discusses their implications for the management and production of domestic animals. Biological rhythms provide temporal coordination between organs and tissues in order to anticipate environmental changes, orchestrating biochemical, physiological and behavioural processes as the right process may occur at the right time. This allows animals to adapt their internal physiological functions, such as sleep-wake cycles, body temperature, hormone secretion, food intake and regulation of physical performance to environmental stimuli that constantly change. The study and evaluation of biological rhythms of various physiological parameters allows the assessment of the welfare status of animals. Alteration of biological rhythms represents an imbalance of the state of homeostasis that can be found in different management conditions.

The Autonomic Nervous System Pulls the Strings to Coordinate Circadian HSC Functions

As for many other adult stem cells, the behavior of hematopoietic stem and progenitor cells (HSPCs) is subjected to circadian regulatory patterns. Multiple HSPC functions, such as proliferation, differentiation or trafficking exhibit time-dependent patterns that require a tight coordination to ensure daily blood cell production. The autonomic nervous system, together with circulating hormones, relay circadian signals from the central clock-the suprachiasmatic nucleus in the brain-to synchronize HSC niche physiology according to light/darkness cycles. Research over the last 20 years has revealed how specific neural signals modulate certain aspects of circadian HSC biology. However, only recently some studies have started to decipher the cellular and molecular mechanisms that orchestrate this complex regulation in a time-dependent fashion. Here we firstly review some of the recent key findings illustrating how different neural signals (catecholaminergic or cholinergic) regulate circadian HSC egress, homing, maintenance, proliferation, and differentiation. In particular, we highlight the critical role of different neurotransmitter receptors in the bone marrow microenvironment to channel these neural signals and regulate antagonistic processes according to circadian cues and organismal demands. Then, we discuss the potential biological meaning of HSC circadian regulation and its possible utility for clinical purposes. Finally, we offer our perspective on emerging concepts in HSC chronobiology.

Melatonin attenuated inflammatory reaction by inhibiting the activation of p38 and NF‑κB in taurocholate‑induced acute pancreatitis

The aim of the present study was to investigate the protective mechanism underlying of melatonin in severe acute pancreatitis (SAP). A total of 64 male Sprague‑Dawley rats were randomly divided into four groups: The sham operation (SO) group, SAP group, melatonin treatment (MLT) group and p38 inhibitor (SB203580) treatment (SB) group. Acute pancreatitis was induced by 5% taurocholate through retrograde infusion into the biliopancreatic ducts. The melatonin and SB203580 treatment groups were administered with MLT and SB 30 min before operation the induction of SAP. Rats in each group were euthanized at 6 and 12 h following SAP induction. Blood and pancreatic tissues were removed for inflammatory examination. Peripheral blood mononuclear cells (PBMCs) were isolated following sacrifice to measure the phosphorylation of p38 and nuclear factor‑κB (NF‑κB was measured as p65 and phosphorylation of p65). The pretreatment of melatonin significantly attenuated the severity of pancreatitis. In addition, melatonin also reduced serum amylase and proinflammatory cytokine levels, including tumor necrosis factor‑α, interleukin (IL)‑1 and IL‑6. The mean pathological scores for pancreatic tissues in the MLT group were higher than those for samples in the SO group, but were lower than those for samples in the SAP group at each time-point. Phosphorylation of p38 and p65 levels in the melatonin treatment group were lower than that in the SAP group, and higher in the SAP group than in the SO group, and the SB203580 treatment group. Furthermore, melatonin significantly inhibited the activation of p38 and NF‑κB in PBMCs. The authors revealed that melatonin may attenuate inflammatory reactions by inhibiting the activation of p38 MAPK and NF‑κB in both acute pancreatitis rats and PBMCs. SAP is a severe disease with a high risk of morbidity and mortality. It is important to attenuated inflammatory reaction in acute pancreatitis. Thus, the authors studied melatonin, which is synthesized by the pineal gland and released into the blood. Previous studies have shown that melatonin serves a protective role in the early course of human acute pancreatitis, and melatonin concentration variations are closely related to the severity of acute pancreatitis. It may be concluded that melatonin may attenuates inflammatory reactions by inhibiting the activation of p38 MAPK and NF‑κB in both acute pancreatitis rats and PBMCs.

Avian biological clock - Immune system relationship

Biological rhythms in birds are driven by the master clock, which includes the suprachiasmatic nucleus, the pineal gland and the retina. Light/dark cycles are the cues that synchronize the rhythmic changes in physiological processes, including immunity. This review summarizes our investigations on the bidirectional relationships between the chicken pineal gland and the immune system. We demonstrated that, in the chicken, the main pineal hormone, melatonin, regulates innate immunity, maintains the rhythmicity of immune reactions and is involved in the seasonal changes in immunity. Using thioglycollate-induced peritonitis as a model, we showed that the activated immune system regulates the pineal gland by inhibition of melatonin production at the level of the key enzyme in its biosynthetic pathway, arylalkylamine-N-acetyltransferase (AANAT). Interleukin 6 and interleukin 18 seem to be the immune mediators influencing the pineal gland, directly inhibiting Aanat gene transcription and modulating expression of the clock genes Bmal1 and Per3, which in turn regulate Aanat.

Circadian Control of Antibacterial Immunity: Findings from Animal Models

Most of the biological functions, including the immune system, are linked to circadian rhythms in living organisms. Changes occurring to biological parameters as the result of these circadian rhythms can therefore affect the outcome of a disease. For decades, model organisms have proven to be a great tool to understanding biological mechanisms such as circadian cycle and immunity. In this review, we created an inventory of the use of model organisms in order to decipher the relation between circadian rhythms and antibacterial immunity.

Molecular cloning and functional characterization of the NFIL3/E4BP4 transcription factor of grass carp, Ctenopharyngodon idella

NFIL3 (nuclear factor interleukin 3-regulated) is an important bZIP transcription factor in the immune response and immune cells' development. Here, we identified the NFIL3 gene from grass carp (Ctenopharyngodon idella; gcNFIL3). The deduced amino acid sequence of gcNFIL3 is 468 residues with a typical bZIP domain. Phylogenetics demonstrated that gcNFIL3 clustered closely with NFIL3 of zebrafish. Real-time PCR revealed gcNFIL3 is constitutively expressed in all tissues examined. Its expression was significantly upregulated in head kidney and trunk kidney after stimulation by bacteria. Immunofluorescence microscopy revealed that gcNFIL3 is mainly expressed in the nucleus. Overexpression of gcNFIL3 reduces Aeromonas hydrophila invasion and proliferation. In CIK cells, gcNFIL3 could induce the activation of NF-kappa B and upregulates the expression of IL10 and IFN. These results indicated that gcNFIL3 has immunoregulatory properties and might play a role in the immune response of fish.

Anti-inflammatory effects of melatonin in a rat model of caerulein-induced acute pancreatitis

The purpose of our study was to evaluate the protective effect of melatonin in a rat model of caerulein-induced acute pancreatitis. For the induction of experimental acute pancreatitis, four subcutaneous injections of caerulein (20 mgkg–1 body weight) were given to Wistar rats at 2-h intervals. Melatonin was injected intraperitoneally (25 mg kg–1 body weight) 30 min before each caerulein injection. After 12 h, rats were sacrificed by decapitation. Blood and pancreas samples were collected and processed for serological and histopathological studies,respectively. Lipase, a-amylase, corticosterone, total antioxidant power and cytokines interleukin (IL)-1b, IL-4 and tumour necrosis factor(TNF)-a were determined using commercial kits. ANOVA and Tukey tests (P<0.05) were performed for the statistical analysis of the results.Results showed that the administration of melatonin reduced histological damage induced by caerulein treatment as well as the hyperamylasemia and hyperlipidemia. Corticosterone and antioxidant total power were also reverted to basal activities. Furthermore, melatonin pre-treatment reduced pro-inflammatory cytokines IL-1b and TNF-a and increased the serum levels of anti-inflammatory cytokine IL-4. In conclusion,the findings suggest that the protective effect of melatonin in caerulein-induced acute pancreatitis is mediated by the anti-inflammatory ability of this indolamine. Thus, melatonin may have a protective effect against acute pancreatitis.

Expression of cell cycle regulatory factors hus1, gadd45a, rb1, cdkn2a and mre11a correlates with expression of clock gene per2 in human colorectal carcinoma tissue

Deregulated expression of clock gene per2 has previously been associated with progression of cancer. The aim of the present study was to identify genes related to per2 expression and involved in cell cycle control. Patients surgically treated for colorectal carcinoma with up-regulated and down-regulated per2 expression in cancer versus adjacent tissue were studied. Total RNA from cancer tissue of these patients was used to specify genes associated with altered per2 expression using the Human Cell Cycle RT(2) profiler PCR array system. We identified seven genes positively correlated (hus1, gadd45α, rb1, cdkn2a, cdk5rp1, mre11a, sumo1) and two genes negatively correlated (cdc20, birc5) with per2 expression. Expression of these seven genes was subsequently measured by real time PCR in all patients of the cohort. Patients were divided into three groups according to TNM classification. We observed an increase in gene expression in cancer tissue compared to adjacent tissue in the first group of patients in all genes measured. Expression of genes positively associated with per2 gene expression was dependent on tumor staging and changes were observed preferentially in cancer tissue. For genes negatively associated with per2 expression we also detected changes in expression dependent on tumor staging. Expression of cdc20 and birc5 was increasing in the proximal tissue and decreasing in the cancer tissue. These results implicate functional involvement of per2 in the process of carcinogenesis via newly uncovered genes. The relevancy of gene expression for determination of diagnosis and prognosis should be considered in relation to tumor staging.

Peripheral circadian clocks--a conserved phenotype?

The circadian system of mammals regulates the timing of occurrence of behavioral and physiological events, thereby optimizing adaptation to their surroundings. This system is composed of a single master pacemaker located in the suprachiasmatic nucleus (SCN) and a population of peripheral clocks. The SCN integrates time information from exogenous sources and, in turn, synchronizes the downstream peripheral clocks. It is assumed that under normal conditions, the circadian phenotype of different peripheral clocks would be conserved with respect to its period and robustness. To study this idea, we measured the daily wheel-running activity (WRA; a marker of the SCN output) in 84 male inbred LEW/Crl rats housed under a 12 h:12 h light-dark cycle. In addition, we assessed the mRNA expression of two clock genes, rPer2 and rBmal1, and one clock-controlled gene, rDbp, in four tissues that have the access to time cues other than those emanating from the SCN: olfactory bulbs (OBs), liver, tail skin, and white blood cells (WBCs). In contrast with the assumption stated above, we found that circadian clocks in peripheral tissues differ in the temporal pattern of the expression of circadian clock genes, in the robustness of the rhythms, and possibly in the number of functional ~24-h-clock cells. Based on the tissue diversity in the robustness of the clock output, the hepatic clock is likely to house the highest number of functional ~24-h-clock cells, and the OBs, the fewest number. Thus, the phenotype of the circadian clock in the periphery is tissue specific and may depend not only on the SCN but also on the sensitivity of the tissue to non-SCN-derived time cues. In the OBs and liver, the circadian clock phenotypes seem to be dominantly shaped by the SCN output. However, in the tail skin and WBC, other time cues participate in the phenotype design. Finally, our study suggests that the basic phenotype of the circadian clock is constructed at the transcript level of the core clock genes. Yet, additional posttranscriptional and translational events can contribute to the robustness and periodicity of the clock output.

Melatonin enhances hydrogen peroxide-induced apoptosis in human promyelocytic leukaemia HL-60 cells

Melatonin is an indoleamine secreted by the pineal gland that shows multiple tasks. This ubiquitously acting free radical scavenger has recently been shown to stimulate the production of reactive oxygen species (ROS) in tumour cells, making them undergo apoptosis, whilst it prevents apoptosis in healthy cells. The mechanisms by which melatonin exerts these dual actions are, however, not yet clearly understood. Thus, the aim of this study was to further investigate how melatonin can enhance oxidative stress-induced apoptosis in a leukaemia cell line. The results show that melatonin increased the apoptotic effects of H(2)O(2) in human myeloid HL-60 cells as assessed by cellular viability, mitochondrial permeability transition induction, mitochondrial membrane depolarization, ROS generation, caspases 3, 8 and 9 activity, phosphatidylserine externalization, and DNA fragmentation techniques. When healthy leucocytes were exposed to H(2)O(2), melatonin increased the viability of the cells. Taken together, the findings indicate that melatonin is a potential physiological tool capable of protecting healthy cells from chemotherapy-induced ROS production as well as inducing tumour cell death. Because cancer cells manifest increased oxidative stress as a result of their elevated metabolism, the use of melatonin may be useful in impairing their ROS buffering capacity.

Circadian oscillators in eukaryotes

The biological clock, present in nearly all eukaryotes, has evolved such that organisms can adapt to our planet's rotation in order to anticipate the coming day or night as well as unfavorable seasons. As all modern high-precision chronometers, the biological clock uses oscillation as a timekeeping element. In this review, we describe briefly the discovery, historical development, and general properties of circadian oscillators. The issue of temperature compensation (TC) is discussed, and our present understanding of the underlying genetic and biochemical mechanisms in circadian oscillators are described with special emphasis on Neurospora crassa, mammals, and plants.

The correlation between urinary 5-hydroxyindoleacetic acid and sperm quality in infertile men and rotating shift workers

BACKGROUND

Serotonin is a neurotransmitter that modulates a wide range of neuroendocrine functions. However, excessive circulating serotonin levels may induce harmful effects in the male reproductive system. The objective of this study was to evaluate whether the levels of urinary 5-hydroxyindoleacetic acid (5-HIIA), a major serotonin metabolite, correlate with different classical seminal parameters.

METHODS

Human ejaculates were obtained from 40 men attending infertility counselling and rotating shift workers by masturbation after 4-5 days of abstinence. Urinary 5- HIIA concentration was quantified by using a commercial ELISA kit. Forward motility was assessed by a computer-aided semen analysis (CASA) system. Sperm concentration was determined using the haemocytometer method. Sperm morphology was evaluated after Diff-Quik staining, while sperm vitality was estimated after Eosin-Nigrosin vital staining.

RESULTS

Our results show that urinary 5-HIIA levels obtained from a set of 20 volunteers negatively correlated with sperm concentration, forward motility, morphology normal range and sperm vitality. On the other hand, we checked the relationship between male infertility and urinary 5-HIIA levels in 20 night shift workers. Thus, urinary 5-HIIA levels obtained from 10 recently-proven fathers were significantly lower than those found in 10 infertile males. Additionally, samples from recent fathers exhibited higher sperm concentration, as well as better forward motility and normal morphology rate.

CONCLUSIONS

In the light of our findings, we concluded that high serotonin levels, indirectly measured as urinary 5-HIIA levels, appear to play a role as an infertility determinant in male subjects.

Influence of reproductive status on the daily rhythms of oxidative stress markers in Ovis aries

Changes in circadian rhythms of dROMs, Oxy-ads and SHp during reproductive stages were studied in Comisana ewes. Twelve ewes were divided in two equal groups. The experimental group consisted of ewes undergoing gestation and lactation following artificial insemination and the control group consisted of non-pregnant ewes. Blood samples were collected every 3 h over a 24 h period, 20 days before insemination, on days 100 and 140 of pregnancy, on days 10, 30 and 200 post-partum and during the dry period. In the control group, blood samples were collected on the same days and with the same procedures as those used for the experimental group. A significant effect of time on all parameters studied was observed in the experimental group. Daily rhythms of the parameters studied were observed in the control group in all experimental conditions, and in the experimental group during pre-pregnancy and dry periods. We conclude that the reproductive status of sheep affects oxidative stress markers in blood and their circadian rhythms.

Effect of melatonin and tryptophan on humoral immunity in young and old ringdoves (Streptopelia risoria)

Melatonin is involved in the regulation of both cellular and humoral immunity. In the present study we have evaluated the effect of the oral administration of melatonin and its precursor, the amino acid tryptophan, on humoral immune response in ringdoves (Streptopelia risoria) from different age groups. Male and female ringdoves of 4-5years of age (young) and 12-14years of age (old) were used in this study. The animals received a single capsule of 300mg/kg b.w. of tryptophan (old animals) for 3 consecutive days 1h after lights on or a single oral dose (0.25 or 2.5mg/kg body weight/0.1ml per animal/day, young and old animals, respectively) of melatonin, for 3 consecutive days 1h before lights off. Blood samples were taken before beginning the treatment (basal values) and at the end of the treatment. Immunoglobulins, bactericidal and haemolytic activity were measured. Our results show that in old animals the humoral immune response was reduced with respect to the young. Both melatonin and tryptophan treatment increased the immunoglobulin concentration, with the nocturnal values being significantly higher than diurnal values and with a major effect in old animals. The bactericidal activity of the S. risoria serum against Staphylococcus aureus, after the treatment with melatonin or tryptophan, was increased at night with a greater effect in old animals. No significant differences were observed in the haemolytic activity of the serum in young animals, but there was an increase in old animals, with higher values at night after treatment with melatonin. In general, the oral administration of melatonin or tryptophan produced a stimulation of humoral immune response with greater effects in old ringdoves.

Assessment of the Potential Role of Tryptophan as the Precursor of Serotonin and Melatonin for the Aged Sleep-wake Cycle and Immune Function: Streptopelia Risoria as a Model

In the present review we summarize the relationship between the amino acid, tryptophan, the neurotransmitter, serotonin, and the indole, melatonin, with the rhythms of sleep/wake and the immune response along with the possible connections between the alterations in these rhythms due to aging and the so-called “serotonin and melatonin deficiency state.” The decrease associated with aging of the brain and circulating levels of serotonin and melatonin seemingly contributes to the alterations of both the sleep/wake cycle and the immune response that typically accompany old age. The supplemental administration of tryptophan, e.g. the inclusion of tryptophan-enriched food in the diet, might help to remediate these age-related alterations due to its capacity of raise the serotonin and melatonin levels in the brain and blood. Herein, we also summarize a set of studies related to the potential role that tryptophan, and its derived product melatonin, may play in the restoration of the aged circadian rhythms of sleep/wake and immune response, taking the ringdove (Streptopeliarisoria) as a suitable model.