Altered expression of circadian clock genes in polyglandular autoimmune syndrome type III

Biological Clock Perspective in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by systemic polyarticular pain, and its main pathological features include inflammatory cell infiltration, synovial fibroblast proliferation, and cartilage erosion. Immune cells, synovial cells and neuroendocrine factors play pivotal roles in the pathophysiological mechanism underlying rheumatoid arthritis. Biological clock genes regulate immune cell functions, which is linked to rhythmic changes in arthritis pathology. Additionally, the interaction between biological clock genes and neuroendocrine factors is also involved in rhythmic changes in rheumatoid arthritis. This review provides an overview of the contributions of circadian rhythm genes to RA pathology, including their interaction with the immune system and their involvement in regulating the secretion and function of neuroendocrine factors. A molecular understanding of the role of the circadian rhythm in RA may offer insights for effective disease management.

Daily Changes in the Expression of Clock Genes in Sepsis and Their Relation with Sepsis Outcome and Urinary Excretion of 6-Sulfatoximelatonin

BACKGROUND

Whereas the circadian system controls the daily production of melatonin and the daily activity of the immune system, increasing evidences support the association between circadian misalignment with the alterations in the immune response and melatonin rhythm during sepsis. The aim of this study was to analyze the daily changes in clock genes expression and the urinary excretion of 6-SM (6-sulfatoxymelatonin, the major melatonin metabolite), and their connection with the innate immune activity, oxidative status in blood, and clinical outcome during sepsis.

METHODS

Healthy volunteers, non-septic intensive care unit (ICU) patients, and septic ICU patients, were evaluated. The expression of bmal1, per2, clock, and cry1 genes was determined by polymerase chain reaction in blood; 6-SM was assessed in urine by ELISA; plasma cytokines IL-1β, IL-6, IL-8, TNFα, and IL-10 were determined by a multiplex array method, and lipid peroxidation (LPO) and protein oxidation (AOPP) by spectrophotometry. Hematological and biochemical data, and clinical scores of the patients, were also recorded.

RESULTS

Clock gene rhythm was maintained in non-septic patients but blunted in septic ones, whereas the innate immune and the oxidative stress responses were significantly higher in the latter. 6-SM excretion was also more elevated in septic than in non-septic patients, and it correlated with the degree of the immune response and oxidative status. 6-SM also correlated with SOFA and procalcitonin in the patients. Proinflammatory cytokines, LPO, and AOPP were normalized in the patients once recovered from sepsis.

CONCLUSION

Our data suggest a relationship between clock genes rhythm disruption, the immune response, and the oxidative status, with 6-SM acting as a compensatory response. ICU conditions are not a main clock disrupter because of the significant differences found in the responses of septic versus non-septic patients under the same ICU environment.

Circadian clock genes as promising therapeutic targets for autoimmune diseases

Circadian rhythm is a natural, endogenous process whose physiological functions are controlled by a set of clock genes. Disturbance of the clock genes have detrimental effects on both innate and adaptive immunity, which significantly enhance pro-inflammatory responses and susceptibility to autoimmune diseases via strictly controlling the individual cellular components of the immune system that initiate and perpetuate the inflammation pathways. Autoimmune diseases, especially rheumatoid arthritis (RA), often exhibit substantial circadian oscillations, and circadian rhythm is involved in the onset and progression of autoimmune diseases. Mounting evidence indicate that the synthetic ligands of circadian clock genes have the property of reducing the susceptibility and clinical severity of subjects. This review supplies an overview of the roles of circadian clock genes in the pathology of autoimmune diseases, including BMAL1, CLOCK, PER, CRY, REV-ERBα, and ROR. Furthermore, summarized some circadian clock genes as candidate genes for autoimmune diseases and current advancement on therapy of autoimmune diseases with synthetic ligands of circadian clock genes. The existing body of knowledge demonstrates that circadian clock genes are inextricably linked to autoimmune diseases. Future research should pay attention to improve the quality of life of patients with autoimmune diseases and reduce the effects of drug preparation on the normal circadian rhythms.

Expression of clock-related genes in benign and malignant adrenal tumors

Although the effect of the central clock system on adrenal function has been extensively studied, the role of the peripheral clock system in adrenal tumorigenesis remains largely unexplored. In this study we investigated the expression of clock-related genes in normal adrenocortical tissue and adrenocortical tumors. Twenty-seven fresh frozen human adrenal tissues including 13 cortisol secreting adenomas (CSA), seven aldosterone producing adenomas (APA), and seven adrenocortical carcinomas (ACC) were collected. CLOCK, BMAL1, PER1, CRY1, Rev-ERB, and RORα mRNA and protein expression were determined by qPCR and immunoblotting in pathological tissues and compared with the adjacent normal adrenal tissues. A significant downregulation of PER1, CRY1, and Rev-ERB compared with their normal tissue was demonstrated in CSA. All clock-related genes were overexpressed in APA compared with their normal tissue, albeit not significantly. A significant upregulation of CRY1 and PER1 and downregulation of BMAL1, RORα, and Rev-ERB compared with normal adrenal tissue was observed in ACC. BMAL1 and PER1 were significantly downregulated in APA compared with CSA. CLOCK, CRY1, and PER1 were upregulated, whereas BMAL1, RORα, and Rev-ERB were downregulated in ACC compared with CSA. Our study demonstrated the expression of CLOCK, BMAL1, PER1, CRY1, Rev-ERB, and RORα in normal and pathological human adrenal tissues. Adrenal tumors exhibited altered expression of these genes compared with normal tissue, with specific differences between benign and malignant lesions and between benign tumors arising from glomerulosa vs fasciculata zone. Further studies should clarify whether these alterations could be implicated in adrenocortical tumorigenesis.

Clock genes and cancer development in particular in endocrine tissues

Circadian rhythms at a central and peripheral level are operated by transcriptional/translational feedback loops involving a set of genes called 'clock genes' that have been implicated in the development of several diseases, including malignancies. Dysregulation of the Clock system can influence cancer susceptibility by regulating DNA damage and repair mechanisms, as well as apoptosis. A number of oncogenic pathways can be dysregulated via clock genes' epigenetic alterations, including hypermethylation of clock genes' promoters or variants of clock genes. Clock gene disruption has been studied in breast, lung and prostate cancer, and haematological malignancies. However, it is still not entirely clear whether clock gene disruption is the cause or the consequence of tumourigenesis and data in endocrine neoplasms are scarce. Recent findings suggest that clock genes are implicated in benign and malignant adrenocortical neoplasias. They have been also associated with follicular and papillary thyroid carcinomas and parathyroid adenomas, as well as pituitary adenomas and craniopharyngiomas. Dysregulation of clock genes is also encountered in ovarian and testicular tumours and may also be related with their susceptibility to chemotherapeutic agents. The most common clock genes that are implicated in endocrine neoplasms are PER1, CRY1; in most cases their expression is downregulated in tumoural compared to normal tissues. Although there is still a lot to be done for the better understanding of the role of clock genes in endocrine tumourigenenesis, existing evidence could guide research and help identify novel therapeutic targets aiming mainly at the peripheral components of the clock gene system.