Mast Cells in Irritable Bowel Syndrome: A Systematic Review.

BACKGROUND AND AIMS: As mast cells (MC) serve as a link between mucosal immune activity and the nervous system, it is likely they also play a role in the pathogenesis of irritable bowel syndrome (IBS). This connection might be an important factor in the development of IBS-related symptoms. METHOD: This overview comprises 36 case-control studies published from 2000 to 2018 that investigated MC in bowel biopsies of IBS patients and controls. The studies were selected from PubMed, EMBASE, Central, SemanticScholar by an electronic search, performed using RISMed R package. RESULTS: Significantly increased mucosal MC counts/or density in IBS patients compared to controls was observed in 30 studies. Five studies reported no differences and only one of the studies found a decreased amount of MC in an IBS patient. Furthermore, 15 studies made a statement regarding the correlation between the amount of MC and IBS associated symptoms. A significant positive correlation between MC count and IBS-associated symptoms was found in six investigations. A negative correlation was not reported. CONCLUSION: The results support the idea that MC are involved in IBS pathophysiology as key players in the interplay between psychological factors and the frequency and severity of IBS symptoms.

The Circadian Clock Drives Mast Cell Functions in Allergic Reactions.

Allergic diseases are known to vary in the severity of their symptoms throughout the day/night cycle. This rhythmicity is also observed in mast cell function and responsiveness. Mast cells are key effector cells of allergic reactions and release cytokines, chemokines, and important inflammatory mediators such as histamine, which have been shown to display diurnal variation. Recent research clarified that mast cells are controlled by their internal clock-which is regulated by a specific set of clock genes-as well as external factors such as light sensed by the suprachiasmatic nuclei, hormonal status, or diet. Here, we give an overview of the connections between circadian clock, mast cells, and allergic disease. Further work aimed at studying the role of chronotherapy/chronomedicine should take into account this rhythmic nature of not only mast cells but also the immune responses generated by mast cell signaling.

Karyopherin α-3 is a key protein in the pathogenesis of spinocerebellar ataxia type 3 controlling the nuclear localization of ataxin-3.

Spinocerebellar ataxia type 3 (SCA3) is a neurodegenerative disorder caused by a CAG expansion in the ATXN3 gene leading to a polyglutamine expansion in the ataxin-3 protein. The nuclear presence and aggregation of expanded ataxin-3 are critical steps in disease pathogenesis. To identify novel therapeutic targets, we investigated the nucleocytoplasmic transport system by screening a collection of importins and exportins that potentially modulate this nuclear localization. Using cell, Drosophila, and mouse models, we focused on three transport proteins, namely, CRM1, IPO13, KPNA3, and their respective Drosophila orthologs Emb, Cdm, and Kap-α3. While overexpression of CRM1/Emb demonstrated positive effects in Drosophila, KPNA3/Kap-α3 emerged as the most promising target, as knockdown via multiple RNAi lines demonstrated its ability to shuttle both truncated and full-length expanded ataxin-3, rescue neurodegeneration, restore photoreceptor formation, and reduce aggregation. Furthermore, KPNA3 knockout in SCA3 mice resulted in an amelioration of molecular and behavioral disturbances such as total activity, anxiety, and gait. Since KPNA3 is known to function as an import protein and recognize nuclear localization signals (NLSs), this work unites ataxin-3 structure to the nuclear pore machinery and provides a link between karyopherins, NLS signals, and polyglutamine disease, as well as demonstrates that KPNA3 is a key player in the pathogenesis of SCA3.

From pathways to targets: understanding the mechanisms behind polyglutamine disease.

The history of polyglutamine diseases dates back approximately 20 years to the discovery of a polyglutamine repeat in the androgen receptor of SBMA followed by the identification of similar expansion mutations in Huntington's disease, SCA1, DRPLA, and the other spinocerebellar ataxias. This common molecular feature of polyglutamine diseases suggests shared mechanisms in disease pathology and neurodegeneration of disease specific brain regions. In this review, we discuss the main pathogenic pathways including proteolytic processing, nuclear shuttling and aggregation, mitochondrial dysfunction, and clearance of misfolded polyglutamine proteins and point out possible targets for treatment.