Immunohisto- and Cytochemistry Analysis of Connexins

Expression of Connexin 43 in Granular Cell Tumors of the Skin, Tongue and Esophagus

BACKGROUND

Granular cell tumors (GCT) are rare neoplasms of Schwann cell origin occurring in the skin and in other organs. The etiopathogenesis of GCT is yet poorly understood. Connexin 43 (Cx43) is the most broadly expressed gap junction protein in humans, the tumoral role of which has been investigated in several types of tumors. Its role in GCT of the skin, oral cavity and gastrointestinal tract is as yet unknown.

METHODS

Herein, we present a study on the immunohistochemical expression of Cx43 in GCT of the skin (n = 15), tongue (n = 4) and esophagus (n = 3). Immunolabeling was scored positive (weak (+), moderate (++) or strong (+++)).

RESULTS

Cx43 was expressed by all cases of GCT of the skin, tongue and esophagus (22/22), showing moderate to strong staining. All tissue sections of GCT were characterized by a diffuse, cytoplasmic staining pattern of the tumor cells. None of those showed membranous or nuclear staining.

CONCLUSION

Our results suggest that Cx43 probably plays an important role in the development of this rare tumor entity.

Connexin Expression in Human Minor Salivary Glands: An Immunohistochemical Microscopy Study

Connexins (Cxs) are transmembrane proteins involved in the formation of hemichannels and gap junctions (GJs). GJs are involved in various physiological functions, including secretion in glandular tissue. It has been demonstrated that Cx26, Cx32, and Cx43 are mainly expressed in glands, but no data are available in human salivary glands to date. The aim of our study was to investigate the presence and the localization of Cxs in human minor labial salivary glands. Immunofluorescence and immunoelectron microscopy were employed to evaluate the Cx26, Cx32, and Cx43 protein in human labial salivary gland biopsies (hLSGBs). RT-PCR was also used to detect their mRNA expression. Cx expression was found at both the mRNA and protein levels in all hLSGBs analysed. Cxs were observed at the level of the duct and acinar cells, as well as in myoepithelial cells. The localization of the three Cx types was very similar, suggesting colocalization of these Cxs in the same connexons. These results demonstrated the presence of Cxs in human salivary glands for the first time. Moreover, the few samples with primary Sjögren’s Syndrome analysed only by immunofluorescence showed an alteration of the Cx expression, indicating that these proteins could be involved in salivary gland dysfunctions.

Expression of connexin-43 in surgical resections of primary tumor and lymph node metastases of squamous cell carcinoma and adenocarcinoma of the lung: a retrospective study

Background

Connexins are transmembrane proteins forming gap junctions between the cells, which allow intercellular communication. Significance of gap junctions and connexins in lung carcinoma is not yet understood. The objective of the study was to investigate immunohistochemical expression and the localization of connexin-43 (Cx43) in primary lung carcinoma and its lymphatic metastases.

Methods

Surgical specimens of excised tumors from 88 patients (45 men and 43 women, 61.9 ± 7.4 years) with lung carcinoma (52 adenocarcinoma (AC), 36 squamous cell carcinoma (SqCC)) who were operated on at the University Hospital "Bezanijska Kosa" in a five-year period (2012-2016) were used. We conducted immunohistochemical staining for Cx43 and measured the degree of expression (percentage of positive cells and staining intensity) as well as localization of Cx43 in primary tumor and in lymphatic metastases.

Results

Immunohistochemical analysis of the primary tumors revealed that SqCC showed significantly higher percentage of tumor cells expressing Cx43 as well as higher staining intensity than AC (p < 0.001). Almost 70% of samples with SqCC showed high Cx43 expression, whereas AC showed no expression in more than 50% of cases. Localization of Cx43 expression was most often cytoplasmic (AC and SqCC) and combined membranous and cytoplasmic (SqCC) with very rare instances of nuclear localization (AC). Almost the same pattern in distribution, intensity, and localization of Cx43 expression was observed in the lymph node metastases; however, almost a third of AC cases changed the pattern of Cx43 expression in the metastasis compared to primary tumor.

Conclusion

The results of this study showed that lung carcinomas express Cx43 in more than 65% of cases and that it was aberrantly localized (not membranous localization). We highlighted that SqCC expressed Cx43 more than did AC, both in primary tumor and lymphatic metastases. Further research is needed to establish whether Cx43 could be used as a prognostic biomarker in lung carcinoma.

Sex-specific effects of metformin and liraglutide on renal pathology and expression of connexin 45 and pannexin 1 following long-term high-fat high-sugar diet

The comparative effects of the two commonly used antidiabetic drugs metformin and liraglutide on renal pathology and expression of connexin 45 (Cx45) and pannexin 1 (Panx1) in adult obese rats fed high-fat high-sugar diet (HFHSD) were studied. Considering recent data on the profound influence of sex on metformin and liraglutide effects, we compared the effects of both drugs between male and female animals. 44-week-old Sprague-Dawley rats were separated into 4 groups that were fed: standard diet, HFHSD, HFHSD treated with metformin (s.c., 50 mg/kg/day) and HFHSD treated with liraglutide (s.c., 0.3 mg/kg/day). Treatment with metformin or liraglutide lasted for 14 weeks. Histology and immunohistochemistry were performed to quantify renal pathological changes and Cx45 and Panx1 expression. HFHSD caused thickening of the Bowman's capsule (BC). Both metformin and liraglutide failed to ameliorate the BC thickening; metformin even worsened it. Effects on the tubulointerstitial fibrosis score, BC thickness and Cx45 and Panx1 expression were sex-dependent. We found a 50% increase in mitochondria in proximal tubules of metformin- and liraglutide-treated HFHSD-fed rats, but these effects were not dependent on the sex. This is a first study showing that the effects of metformin and liraglutide on kidney pathology in rats fed HFHSD are mostly sex-dependent and that these effects are not necessarily beneficial. Both drugs changed the Cx45 and Panx 1 expression; hence their effects could be related to amelioration of disruptions in intercellular communication.

Cholestasis Differentially Affects Liver Connexins

Connexins are goal keepers of tissue homeostasis, including in the liver. As a result, they are frequently involved in disease. The current study was set up to investigate the effects of cholestatic disease on the production of connexin26, connexin32 and connexin43 in the liver. For this purpose, bile duct ligation, a well-known trigger of cholestatic liver injury, was applied to mice. In parallel, human hepatoma HepaRG cell cultures were exposed to cholestatic drugs and bile acids. Samples from both the in vivo and in vitro settings were subsequently subjected to assessment of mRNA and protein quantities as well as to in situ immunostaining. While the outcome of cholestasis on connexin26 and connexin43 varied among experimental settings, a more generalized repressing effect was seen for connexin32. This has also been observed in many other liver pathologies and could suggest a role for connexin32 as a robust biomarker of liver disease and toxicity.