Reduced expression of Ca2+-regulating proteins in the upper gastrointestinal tract of patients with achalasia

Downexpression of miR-200c-3p Contributes to Achalasia Disease by Targeting the PRKG1 Gene

Achalasia is an esophageal smooth muscle motility disorder with unknown pathogenesis. Taking into account our previous results on the downexpression of miR-200c-3p in tissues of patients with achalasia correlated with an increased expression of PRKG1, SULF1, and SYDE1 genes, our aim was to explore the unknown biological interaction between these genes and human miR-200c-3p and if this relation could unravel their functional role in the etiology of achalasia. To search for putative miR-200c-3p binding sites in the 3'-UTR of PRKG1, SULF1 and SYDE1, a bioinformatics tool was used. To test whether PRKG1, SULF1, and SYDE1 are targeted by miR-200c-3p, a dual-luciferase reporter assay and quantitative PCR on HEK293 and fibroblast cell lines were performed. To explore the biological correlation between PRKG1 and miR-200c-3p, an immunoblot analysis was carried out. The overexpression of miR-200c-3p reduced the luciferase activity in cells transfected with a luciferase reporter containing a fragment of the 3'-UTR regions of PRKG1, SULF1, and SYDE1 which included the miR-200c-3p seed sequence. The deletion of the miR-200c-3p seed sequence from the 3'-UTR fragments abrogated this reduction. A negative correlation between miR-200c-3p and PRKG1, SULF1, and SYDE1 expression levels was observed. Finally, a reduction of the endogenous level of PRKG1 in cells overexpressing miR-200c-3p was detected. Our study provides, for the first time, functional evidence about the PRKG1 gene as a direct target and SULF1 and SYDE1 as potential indirect substrates of miR-200c-3p and suggests the involvement of NO/cGMP/PKG signaling in the pathogenesis of achalasia.

Alterations of protein expression of phospholamban, ZASP and plakoglobin in human atria in subgroups of seniors

The mature mammalian myocardium contains composite junctions (areae compositae) that comprise proteins of adherens junctions as well as desmosomes. Mutations or deficiency of many of these proteins are linked to heart failure and/or arrhythmogenic cardiomyopathy in patients. We firstly wanted to address the question whether the expression of these proteins shows an age-dependent alteration in the atrium of the human heart. Right atrial biopsies, obtained from patients undergoing routine bypass surgery for coronary heart disease were subjected to immunohistology and/or western blotting for the plaque proteins plakoglobin (γ-catenin) and plakophilin 2. Moreover, the Z-band protein cypher 1 (Cypher/ZASP) and calcium handling proteins of the sarcoplasmic reticulum (SR) like phospholamban, SERCA and calsequestrin were analyzed. We noted expression of plakoglobin, plakophilin 2 and Cypher/ZASP in these atrial preparations on western blotting and/or immunohistochemistry. There was an increase of Cypher/ZASP expression with age. The present data extend our knowledge on the expression of anchoring proteins and SR regulatory proteins in the atrium of the human heart and indicate an age-dependent variation in protein expression. It is tempting to speculate that increased expression of Cypher/ZASP may contribute to mechanical changes in the aging human myocardium.

TGF-β1-induced phospholamban expression alters esophageal smooth muscle cell contraction in patients with eosinophilic esophagitis

BACKGROUND

Eosinophilic esophagitis (EoE) is a chronic antigen-mediated disease characterized by esophageal eosinophilia, remodeling, and fibrosis. TGF-β1 is a central regulator of EoE remodeling and increases esophageal smooth muscle (ESM) cell contraction.

OBJECTIVE

In this study we aimed to understand the molecular mechanisms by which TGF-β1 could induce ESM cell contraction.

METHODS

We used primary human ESM cells and esophageal myofibroblasts (EMFs) to assess the mechanisms of TGF-β1-induced contraction. We analyzed the expression, phosphorylation, and function of phospholamban (PLN), a sarcoendoplasmic reticulum regulatory protein induced by TGF-β1. Expression of PLN, phospho-PLN, and its regulatory pathway was analyzed in the ESM of biopsy specimens from patients with EoE and control subjects. Gene silencing in EMFs from patients with EoE was used to understand the role of PLN in contraction.

RESULTS

TGF-β1 induced and phosphorylated PLN in primary human ESM cells and EMFs from patients with EoE. PLN and phospho-PLN levels were increased in smooth muscle from patients with EoE compared with that seen in smooth muscle from control subjects in vivo. PLN inhibition significantly diminished TGF-β1-induced EMF contraction in patients with EoE. PLN expression and ESM/EMF contraction depended on TGF-β receptor I signals.

CONCLUSION

We describe a previously unrecognized mechanism for ESM cell contraction that depends on TGF-β1, its receptors, and PLN. Because PLN levels are increased in smooth muscle from patients with EoE and PLN silencing diminishes contraction, we provide a novel potential mechanistic framework and therapeutic target for ESM dysfunction in patients with EoE.

Sarcoplasmic reticulum function in smooth muscle

The sarcoplasmic reticulum (SR) of smooth muscles presents many intriguing facets and questions concerning its roles, especially as these change with development, disease, and modulation of physiological activity. The SR's function was originally perceived to be synthetic and then that of a Ca store for the contractile proteins, acting as a Ca amplification mechanism as it does in striated muscles. Gradually, as investigators have struggled to find a convincing role for Ca-induced Ca release in many smooth muscles, a role in controlling excitability has emerged. This is the Ca spark/spontaneous transient outward current coupling mechanism which reduces excitability and limits contraction. Release of SR Ca occurs in response to inositol 1,4,5-trisphosphate, Ca, and nicotinic acid adenine dinucleotide phosphate, and depletion of SR Ca can initiate Ca entry, the mechanism of which is being investigated but seems to involve Stim and Orai as found in nonexcitable cells. The contribution of the elemental Ca signals from the SR, sparks and puffs, to global Ca signals, i.e., Ca waves and oscillations, is becoming clearer but is far from established. The dynamics of SR Ca release and uptake mechanisms are reviewed along with the control of luminal Ca. We review the growing list of the SR's functions that still includes Ca storage, contraction, and relaxation but has been expanded to encompass Ca homeostasis, generating local and global Ca signals, and contributing to cellular microdomains and signaling in other organelles, including mitochondria, lysosomes, and the nucleus. For an integrated approach, a review of aspects of the SR in health and disease and during development and aging are also included. While the sheer versatility of smooth muscle makes it foolish to have a "one model fits all" approach to this subject, we have tried to synthesize conclusions wherever possible.

Recent developments in esophageal motor disorders

PURPOSE OF REVIEW

Every year more insight into the pathogenesis and treatment of esophageal motor disorders is obtained. This review highlights some interesting literature published in this area during the last year.

RECENT FINDINGS

Longitudinal and circular muscle contractions act in a well coordinated fashion to allow normal peristalsis. Techniques such as intraluminal impedance, high-resolution manometry and intraluminal ultrasound provide useful additional information on esophageal function both in the normal and abnormal situation. The dynamics of the gastroesophageal junction can be studied with a newly developed probe, and the mechanism behind transient lower esophageal sphincter relaxations is still being unravelled. New manometric criteria for nutcracker esophagus have been proposed, whereas further evidence is reported supporting an association between diabetes mellitus and cardiovascular disease and esophageal dysmotility and spasm, respectively. Finally, several long-term follow-up results of surgical myotomy and pneumodilatation have been reported.

SUMMARY

Due to the perfection of esophageal measuring techniques, our knowledge of esophageal function continues to increase. The studies reviewed here provide interesting information on the pathogenesis and treatment of several esophageal motor disorders.