Farnesoid X receptor enhances epithelial ACE2 expression and inhibits virally induced IL-6 secretion: implications for intestinal symptoms of SARS-CoV-2

Intestinal inflammation and diarrhea are often associated with SARS-CoV-2 infection. The angiotensin converting enzyme 2 (ACE2) receptor plays a key role in SARS-CoV-2 pathogenesis, facilitating entry of the virus into epithelial cells, while also regulating mucosal inflammatory responses. Here, we investigated roles for the nuclear bile acid receptor farnesoid X receptor (FXR) in regulating ACE2 expression and virally mediated inflammatory responses in intestinal epithelia. Human colonic or ileal enteroids and cultured T84 and Caco-2 monolayers were treated with the FXR agonists, obeticholic acid (OCA) or GW4064, or infected with live SARS-CoV-2 (2019-nCoV/USA_WA1/2020). Changes in mRNA, protein, or secreted cytokines were measured by qPCR, Western blotting, and ELISA. Treatment of undifferentiated colonic or ileal enteroids with OCA increased ACE2 mRNA by 2.1 ± 0.4-fold (n = 3; P = 0.08) and 2.3 ± 0.2-fold (n = 3; P < 0.05), respectively. In contrast, ACE2 expression in differentiated enteroids was not significantly altered. FXR activation in cultured epithelial monolayers also upregulated ACE2 mRNA, accompanied by increases in ACE2 expression and secretion. Further experiments revealed FXR activation to inhibit IL-6 release from both Caco-2 cells infected with SARS-CoV-2 and T84 cells treated with the viral mimic, polyinosinic:polycytidylic acid, by 46 ± 12% (n = 3, P < 0.05) and 35 ± 6% (n = 8; P < 0.01), respectively. By virtue of its ability to modulate epithelial ACE2 expression and inhibit virus-mediated proinflammatory cytokine release, FXR represents a promising target for the development of new approaches to prevent intestinal manifestations of SARS-CoV-2.NEW & NOTEWORTHY Activation of the nuclear bile acid receptor, farnesoid X receptor (FXR), specifically upregulates ACE2 expression in undifferentiated colonic epithelial cells and inhibits virus-induced proinflammatory cytokine release. By virtue of these actions FXR represents a promising target for the development of new approaches to prevent intestinal manifestations of SARS-CoV-2 infection.

Pentacyclic triterpenes modulate farnesoid X receptor expression in colonic epithelial cells: implications for colonic secretory function

The nuclear bile acid receptor, farnesoid X receptor (FXR), is an important regulator of intestinal and metabolic function. Previous studies suggest that pentacyclic triterpenes (PCTs), a class of plant-derived bioactive phytochemical, can modulate FXR activity and may therefore offer therapeutic benefits. Here, we investigated the effects of a prototypical PCT, hederagenin (HG), on FXR expression, activity, and antisecretory actions in colonic epithelial cells. T₈₄ cells and murine enteroid-derived monolayers were employed to assess HG effects on FXR expression and activity in colonic epithelia. We measured mRNA levels by qRT-PCR and protein by ELISA and immunoblotting. Transepithelial Cl⁻ secretion was assessed as changes in short circuit current in Ussing chambers. We determined HG treatment (5–10 μM) alone did not induce FXR activation but significantly increased expression of the receptor, both in T₈₄ cells and murine enteroid-derived monolayers. This effect was accompanied by enhanced FXR activity, as assessed by FGF-15/19 induction in response to the synthetic, GW4064, or natural FXR agonist, chenodeoxycholic acid. Effects of HG on FXR expression and activity were mimicked by another PCT, oleanolic acid. Furthermore, we found FXR-induced downregulation of cystic fibrosis transmembrane conductance regulator Cl⁻ channels and inhibition of transepithelial Cl⁻ secretion were enhanced in HG-treated cells. These data demonstrate that dietary PCTs have the capacity to modulate FXR expression, activity, and antisecretory actions in colonic epithelial cells. Based on these data, we propose that plants rich in PCTs, or extracts thereof, have excellent potential for development as a new class of “FXR-targeted nutraceuticals”.

A programme for the treatment of severe dental fear. Report of three cases

This paper describes the use of a sequence of recollection and discussion, training in muscle tone control, dental imagery, audio simulation and graded re-exposure to dental procedures to eliminate a severe fear of dental treatment in three adult female patients. All three patients had abstained from regular dental visits throughout their lives and all were in need of urgent dental treatment when the therapy began. One of the patients also identified in herself other maladaptive behaviour and reported a history of mood disorder as well. The recollections of these patients reveal that the aetiology of dental fear is more complex than dental questionnaires would indicate and, in particular, they supply further evidence of the capacity for adverse medical events to initiate this fear. Although the programme specified in this paper yielded good results, it nonetheless has a number of shortcomings. It is time consuming, dental damage is likely to be well advanced when it commences and it attracts very few patients. Thus those afflicted with severe dental fear are effectively destined for only emergency dental visits and eventually are likely to be edentulous. For this reason every possible precaution against the initiation of dental fear should be taken.

Some problems of dental treatment. Part 2. Treatment avoidance: some differences between regular and irregular patients

Analysis of questionnaire data obtained from 54 irregular patients and 56 regular patients attending the Dental Department of the Lower Hutt Hospital and private practices in Lower Hutt and Wellington, New Zealand indicates that irregular patients are more anxious about dental treatment, value natural teeth less and find dental treatment more unpleasant than do regular patients. These and other survey findings on dental service utilization and dental anxiety suggest that the dental profession has a good deal of control over the way the public utilizes dental services. Most international surveys have found that less than 60 per cent of the population visits the dentist regularly, so there appears to be the potential for a substantial increase in regular use of dental services by the public. But, it is also likely that the longer an individual is remiss in regular dental care and the more teeth are lost, the more difficult conversion to regular visits will be.

Some problems of dental treatment. Part 1. Patient anxiety: some correlates and sex differences

An analysis of questionnaire data obtained from 110 adult patients attending the Dental Department of the Lower Hutt Hospital and four private dental practices in Lower Hutt and Wellington, New Zealand indicates that patient treatment anxiety is more severe in women than men and that it is correlated with patients' descriptions of dental treatment. Altogether, survey findings indicate that treatment anxiety has adverse effects and that, with few exceptions, it results directly or indirectly from unpleasant experiences during dental treatment. Two of the most common of such experiences are evidently pain arising from the stimulation of sensitive tissue and oral injections. The eradication of treatment anxiety is therefore heavily dependent on the unobtrusive induction of profound analgesia prior to painful procedures.