Effect of progesterone on colonic motility and fecal output in mice with diarrhea

Gastrointestinal pathophysiology in long COVID: Exploring roles of microbiota dysbiosis and serotonin dysregulation in post-infectious bowel symptoms

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) triggered an unprecedented public health crisis known as the coronavirus disease 2019 (COVID-19) pandemic. Gastrointestinal (GI) symptoms develop in patients during acute infection and persist after recovery from airway distress in a chronic form of the disease (long COVID). A high incidence of irritable bowel syndrome (IBS) manifested by severe abdominal pain and defecation pattern changes is reported in COVID patients. Although COVID is primarily considered a respiratory disease, fecal shedding of SARS-CoV-2 antigens positively correlates with bowel symptoms. Active viral infection in the GI tract was identified by human intestinal organoid studies showing SARS-CoV-2 replication in gut epithelial cells. In this review, we highlight the key findings in post-COVID bowel symptoms and explore possible mechanisms underlying the pathophysiology of the illness. These mechanisms include mucosal inflammation, gut barrier dysfunction, and microbiota dysbiosis during viral infection. Viral shedding through the GI route may be the primary factor causing the alteration of the microbiome ecosystem, particularly the virome. Recent evidence in experimental models suggested that microbiome dysbiosis could be further aggravated by epithelial barrier damage and immune activation. Moreover, altered microbiota composition has been associated with dysregulated serotonin pathways, resulting in intestinal nerve hypersensitivity. These mechanisms may explain the development of post-infectious IBS-like symptoms in long COVID. Understanding how coronavirus infection affects gut pathophysiology, including microbiome changes, would benefit the therapeutic advancement for managing post-infectious bowel symptoms.

Clostridium innocuum, an opportunistic gut pathogen, inactivates host gut progesterone and arrests ovarian follicular development

\Levels of progesterone, an endogenous female hormone, increase after ovulation; progesterone is crucial in the luteal phase to maintain successful pregnancy and prevent early miscarriage. Both endogenous and exogenous progesterone are recycled between the liver and gut; thus, the gut microbiota regulate host progesterone levels by inhibiting enterohepatic progesterone circulation. Our data indicated Clostridium innocuum as a major species involved in gut progesterone metabolism in women with infertility. C. innocuum converts progesterone into the neurosteroid epipregnanolone (with negligible progestogenic activity). We purified and characterized the corresponding enzyme, namely NADPH-dependent 5β-dihydroprogesterone reductase, which is highly oxygen sensitive and whose corresponding genes are prevalent in C. innocuum. Moreover, C. innocuum-administered female C57BL/6 mice (aged 7 weeks) exhibited decreased plasma progesterone levels (~35%). Clostridium-specific antibiotics (metronidazole) restored low plasma progesterone levels in these mice. Furthermore, prolonged C. innocuum administration (12 weeks) arrested ovarian follicular development in female mice. Cytological and histological analyses indicated that C. innocuum may cause luteal phase insufficiency and affect menstrual regularity. Our findings suggest C. innocuum as a causal factor of progesterone resistance in women taking progesterone.

Impact of progesterone on the gastrointestinal tract: a comprehensive literature review

Women are more prone to gastrointestinal symptoms than men. A comprehensive literature search was performed to assess the impact of sex steroid hormone, especially progesterone, on the (healthy and diseased) gastrointestinal tract. Overall, 37 articles were identified. Based on these we conclude that progesterone has a dose-dependent and sex-dependent effect on gastric emptying (especially in mammals), slows down gastrointestinal motility, reduces the gallbladder's response to contractile stimulants, may support gastroesophageal reflux by reducing the esophageal sphincter pressure, may protect from Helicobacter pylori infection gastrointestinal sequelae (especially in mammals) and does not affect inflammatory bowel disease-specific symptoms. However, for several gastrointestinal symptoms and diseases no studies have yet been performed addressing the impact of sex hormone steroids.

Sex- and Gender-Related Differences in Common Functional Gastroenterologic Disorders

Functional gastrointestinal (GI) disorders (FGIDs) result from central and peripheral mechanisms, cause chronic remitting-relapsing symptoms, and are associated with comorbid conditions and impaired quality of life. This article reviews sex- and gender-based differences in the prevalence, pathophysiologic factors, clinical characteristics, and management of functional dyspepsia (FD) and irritable bowel syndrome (IBS) that together affect approximately 1 in 4 people in the United States. These conditions are more common in women. Among patients with IBS, women are more likely to have severe symptoms and coexistent anxiety or depression; constipation or bloating and diarrhea are more common in women and men, respectively, perhaps partly because defecatory disorders, which cause constipation, are more common in women. Current concepts suggest that biological disturbances (eg, persistent mucosal inflammation after acute gastroenteritis) interact with other environmental factors (eg, abuse) and psychological stressors, which influence the brain and gut to alter GI tract motility or sensation, thereby causing symptoms. By comparison to a considerable understanding of sex-based differences in the pathogenesis of visceral hypersensitivity in animal models, we know less about the contribution of these differences to FGID in humans. Slow gastric emptying and colon transit are more common in healthy women than in men, but effects of gonadal hormones on colon transit are less important than in rodents. Although increased visceral sensation partly explains symptoms, the effects of sex on visceral sensation, colonic permeability, and the gut microbiome are less prominent in humans than rodents. Whether sex or gender affects response to medications or behavioral therapy in FD or IBS is unclear because most patients in these studies are women.

Involvement of proBDNF in Monocytes/Macrophages with Gastrointestinal Disorders in Depressive Mice

Major depressive disorders (MDD) are often comorbid with the gastrointestinal (GI) disorders. Brain-derived neurotrophic factor precursor (proBDNF) has been reported to contribute to the development of depression in mouse models. However, the role of proBDNF in depression-associated GI disorders is still unrevealed. Mice experienced unpredictable chronic mild stress (UCMS) procedure and were then intraperitoneally injected with fluoxetine (20 mg/kg). Open field test (OFT), forced swimming test (FST), and sucrose preference test (SPT) were performed to evaluate the severity of depression. Oral administration of food dye gel and histological staining were performed to assess GI transit and morphological alterations. QPCR was performed to assess the mRNA levels of inflammatory cytokines. Additionally, flow cytometry, immunohistochemistry, and immunofluorescence were performed to examine the expression and cellular localization of proBDNF. It was found that (a) in the peripheral blood, the expression of proBDNF and its receptor pan neurotrophin receptor 75 (p75^NTR) in CD11b⁺ cells in depressive mice was higher than in controls; (b) the GI motility was decreased after the UCMS procedure and partly reversed by fluoxetine treatment; (c) proBDNF/p75^NTR was highly expressed in macrophages in the intestinal lamina propria; (d) the upregulated proBDNF/p75^NTR and the activated cytokines, including IL (interleukin)-1β, IL-6, IL-10, and IFN (interferon)-γ, were positively correlated with the depression and GI disorders, and were inhibited by fluoxetine treatment. UCMS procedure upregulated the expression of proBDNF and p75^NTR in monocytes/macrophages of peripheral blood and intestinal lamina propria, which may be involved in the pathogenesis of depression-associated GI disorders. Fluoxetine reversed the GI dysfunction, infiltration of macrophages, and upregulation of proBDNF signaling in the depressive mice.

The menstrual cycle may not be limited to the endometrium but also may impact gut permeability

OBJECTIVE

To examine associations between IgA responses to Gram-negative gut commensal bacteria and peri-menstrual symptoms and sex hormone levels during the menstrual cycle in women with and without premenstrual symptoms.

METHODS

Forty women aged 18-45 years completed the Daily Record of Severity of Problems (DRSP) during all 28 consecutive days of the menstrual cycle. We assayed, in plasma, IgA responses to six Gram-negative bacteria, that is, Hafnei alvei, Pseudomonas aeruginosa, Morganella morganii, Klebsiella pneumoniae, Pseudomonas putida and Citobacter koseri, progesterone and oestradiol at days 7, 14, 21 and 28 of the menstrual cycle.

RESULTS

Significant changes in Δ (actual - 1 week earlier) IgA to lipopolysaccharides (LPS) of the six Gram-negative bacteria during the menstrual cycle were observed with peak IgA levels at T4 (day 28) and lows at T1 or T2 (day 7 or 14). The ΔIgA changes in H. alvei, M. Morganii, P. putida during the menstrual cycle were significantly and positively associated with changes in the total DRSP score, and severity of physio-somatic, anxiety and breast-craving, but not depressive, symptoms. The changes in IgA responses to LPS were largely predicted by changes in progesterone and steady-state levels of progesterone averaged over the luteal phase.

DISCUSSION

Menstrual cycle-associated changes in IgA directed against LPS and by inference bacterial translocation may be driven by the effects of progesterone on transcellular, paracellular and vascular pathways (leaky gut) thereby contributing to the severity of physio-somatic and anxiety symptoms as well as fatigue, breast swelling and food cravings.

Isobaric tags for relative and absolute quantification-based proteomic analysis that reveals the roles of progesterone receptor, inflammation, and fibrosis for slow-transit constipation

BACKGROUND AND AIM

Progesterone receptor, inflammation, neurotransmitter expression, and fibrosis are involved in slow-transit constipation. The aim of the present study was to examine whether patients with slow-transit constipation have an overexpression of progesterone receptor and serotonin, which may impair the fibrosis of muscularis propria in colorectal wall.

METHODS

High-resolution colon manometry was used to record the colorectal peristaltic contractions of the proximal ascending and sigmoid colon in patients. Protein samples prepared from frozen sigmoid colon tissue and the proximal margin of the ascending colon of four female patients were compared using isobaric tags for relative and absolute quantification labeling technique coupled to 2D liquid chromatography-tandem mass spectrometry analysis. Immunohistochemical staining of progesterone receptor, serotonin, and fibronectin was performed in paraffin-embedded sigmoid colon tissues and the proximal margin of the ascending colon or ileum from 43 patients with slow-transit constipation.

RESULTS

Among these differentially regulated proteins based on isobaric tags for relative and absolute quantification and liquid chromatography-tandem mass spectrometry analysis, 56 proteins involved in the response to progesterone, inflammation, matrix remodeling, fibrosis, and muscle metabolism. Immunohistochemical staining confirmed that there was significantly higher expression of progesterone receptor (t = 19.19, P = 0.000) and serotonin (t = 13.52, P = 0.004) in sigmoid colon than in the proximal margin of the ascending colon and ileum. Progesterone receptor and fibronectin expression in the outer layer of muscularis propria were higher than in the middle layer.

CONCLUSIONS

These results demonstrate that progesterone receptor, along with inflammation and fibrosis, may take part in slow-transit constipation development.

五羟色胺信号系统与胃肠道疾病的研究进展

五羟色胺(5-hydroxytryptamine, 5-HT)是脑肠轴调控路径中的一个重要组成部分. 5-HT信号系统在多种胃肠道疾病的发病机制中扮演重要的角色, 参与调节胃肠运动、感觉及分泌等功能. 5-HT的合成、释放、与特异性受体结合及再摄取过程中任意一个环节发生异常, 均与胃肠道功能紊乱的发生密切相关, 其不仅在功能性疾病中存在作用, 与器质性疾病也有很大的关系. 临床上5-HT受体激动剂、拮抗剂及选择性再摄取抑制剂已被广泛运用到多种胃肠道疾病的治疗中. 本文阐述了5-HT信号系统与胃肠道疾病病理生理的关系, 从而研究5-HT受体在胃肠道中的作用及其相关药物的临床效用, 为胃肠道疾病的防治提供理论依据.

Menopausal Hormone Therapy Is Associated With Increased Risk of Fecal Incontinence in Women After Menopause

BACKGROUND & AIMS

Low estrogen levels can contribute to development of fecal incontinence (FI) in women after menopause by altering neuromuscular continence mechanisms. However, studies have produced conflicting results on the association between menopausal hormone therapy (MHT) and risk of FI.

METHODS

We studied the association between MHT and risk of FI among 55,828 postmenopausal women (mean age, 73 years) who participated in the Nurses' Health Study, were enrolled since 2008, and with no report of FI. We defined incident FI as a report of at least 1 liquid or solid FI episode per month during 4 years of follow-up from self-administered, biennial questionnaires administered in 2010 and 2012. We used Cox proportional hazard models to calculate multivariate-adjusted hazard ratios and 95% confidence intervals (CIs) for FI risk in women receiving MHT, adjusting for potential confounding factors.

RESULTS

During more than 185,000 person-years of follow-up, there were 6834 cases of incident FI. Compared with women who never used MHT, the multivariate hazard ratio for FI was 1.26 (95% CI, 1.18-1.34) for past users of MHT and 1.32 (95% CI, 1.20-1.45) for current users. The risk of FI increased with longer duration of MHT use (P trend ≤ .0001) and decreased with time since discontinuation. There was an increased risk of FI among women receiving MHT that contained a combination of estrogen and progestin (hazard ratio, 1.37; 95% CI, 1.10-1.70) compared with estrogen monotherapy.

CONCLUSIONS

Current or past use of MHT was associated with a modestly increased risk of FI among postmenopausal women in the Nurses' Health Study. These results support a potential role for exogenous estrogens in the impairment of the fecal continence mechanism.

Colonic Inertia: approach and treatment

Objective Revision of the state of the art of the knowledge regarding pathophysiology, diagnosis and treatment of Colonic Inertia, which predominantly affects young women and has a significant socio-economic impact.

Methods A search was made in “colonic inertia”, “colon inertia” and “slow transit constipation” in PubMed database for articles of the last 5 years, in Portuguese or English with available abstract and full text. 59 articles and 2013 guidelines of the American Gastroenterological Association on constipation were included.

Results The pathophysiology is not completely elucidated and the reduction of the interstitial cells of Cajal is the most consistent histological finding. Diagnosis requires the exclusion of secondary causes of constipation and obstructed defecation syndrome, to which contribute several complementary diagnostic tests. Given the frequency of failure of the medical treatment, surgery is often the only possible option. Sacral nerve stimulation seems to be a promising therapeutical alternative.

Conclusion A deeper investigation of the pathophysiological mechanisms is fundamental to acquire a more global and integrated vision. Rigorous patient selection for each treatment and the discovery of new therapeutical targets may avoid the use of surgical therapies.

In vitro spontaneous contractile activity of colonic smooth muscle in naive Lewis rats: Acute effect of gonadal hormones

OBJECTIVE

Functional gastrointestinal disorders affect females more often. Changes in colonic motility may be etiological co-factors for the clinical symptoms. The aim of the present study was to analyze the influence of gonadal hormones on colonic contractile activity.

METHODS

In vitro measurements of colonic contractile activity in longitudinal smooth muscle strips of female and male Lewis rats were performed in an organ chamber experiment. After the administration of a gonadal hormone estradiol [EST], progesterone [PROG] and testosterone [TEST]) or ethanol solution as control, stimulation with acetylcholine (ACh) or inhibition with norepinephrine (NE) was performed.

RESULTS

Compared to the smooth muscle strips of male rats, significantly higher spontaneous colonic contractile activity (SCCA) was observed in female animals. Increasing doses of ACh showed the progressive stimulation of SCCA whereas rising doses of NE resulted in a stepwise inhibition of SCCA, respectively. EST superfusion displayed an inhibitory effect on SCCA in both sexes and inhibited the ACh effect in female rats. Similarly, acute superfusion with high-dose PROG inhibited SCCA in females. Acute TEST superfusion inhibited SCCA in males and led to significant higher colonic contractile activity in males following subsequent stimulation with ACh. In female rats, the inhibitory effect of NE was reduced by prior exposure to TEST.

CONCLUSION

In our in vitro study the acute exposure of colonic smooth muscle tissue to gonadal hormones led to sex-dependent changes in SCCA and translated in a modified response of smooth muscle strips to both pro-contractile and anti-contractile neurotransmitters.

Host Nectin-1 Promotes Chlamydial Infection in the Female Mouse Genital Tract, but Is Not Required for Infection in a Novel Male Murine Rectal Infection Model

Chlamydia trachomatis is the most common bacterial sexually transmitted pathogen, but more than 70% of patients fail to seek treatment due to the asymptomatic nature of these infections. Women suffer from numerous complications from chronic chlamydial infections, which include pelvic inflammatory disease and infertility. We previously demonstrated in culture that host cell nectin-1 knockdown significantly reduced chlamydial titers and inclusion size. Here, we sought to determine whether nectin-1 was required for chlamydial development in vivo by intravaginally infecting nectin-1^-/- mice with Chlamydia muridarum and monitoring chlamydial shedding by chlamydial titer assay. We observed a significant reduction in chlamydial shedding in female nectin-1^-/- mice compared to nectin-1^+/+ control mice, an observation that was confirmed by PCR. Immunohistochemical staining in mouse cervical tissue confirmed that there are fewer chlamydial inclusions in Chlamydia-infected nectin-1^-/- mice. Notably, anorectal chlamydial infections are becoming a substantial health burden, though little is known regarding the pathogenesis of these infections. We therefore established a novel male murine model of rectal chlamydial infection, which we used to determine whether nectin-1 is required for anorectal chlamydial infection in male mice. In contrast to the data from vaginal infection, no difference in rectal chlamydial shedding was observed when male nectin-1^+/+ and nectin-1^-/- mice were compared. Through the use of these two models, we have demonstrated that nectin-1 promotes chlamydial infection in the female genital tract but does not appear to contribute to rectal infection in male mice. These models could be used to further characterize tissue and sex related differences in chlamydial infection.

Gender-related differences in irritable bowel syndrome: Potential mechanisms of sex hormones

According to epidemiological studies, twice as many women as men are affected by irritable bowel syndrome (IBS) in western countries, suggesting a role for sex hormones in IBS pathophysiology. Despite growing evidence about the implications of sex hormones in IBS symptom modulation, data on mechanisms by which they influence disease development are sparse. This review aims to determine the state of knowledge about the role of sex hormones in sensorimotor dysfunctions and to address the possible interplay of sex hormones with common risk factors associated with IBS. The scientific bibliography was searched using the following keywords: irritable bowel syndrome, sex, gender, ovarian hormone, estradiol, progesterone, testosterone, symptoms, pain, sensitivity, motility, permeability, stress, immune system, brain activity, spinal, supraspinal, imaging. Ovarian hormones variations along the menstrual cycle affect sensorimotor gastrointestinal function in both healthy and IBS populations. They can modulate pain processing by interacting with neuromodulator systems and the emotional system responsible for visceral pain perception. These hormones can also modulate the susceptibility to stress, which is a pivotal factor in IBS occurrence and symptom severity. For instance, estrogen-dependent hyper-responsiveness to stress can promote immune activation or impairments of gut barrier function. In conclusion, whereas it is important to keep in mind that ovarian hormones cannot be considered as a causal factor of IBS, they arguably modulate IBS onset and symptomatology. However, our understanding of the underlying mechanisms remains limited and studies assessing the link between IBS symptoms and ovarian hormone levels are needed to improve our knowledge of the disease evolution with regard to gender. Further studies assessing the role of male hormones are also needed to understand fully the role of sex hormones in IBS. Finally, investigation of brain-gut interactions is critical to decipher how stress, ovarian hormones, and female brain processing of pain can translate into gut dysfunctions.