Vaginal Transcriptional Signatures of the Neutrophil-Driven Immune Response Correlate With Clinical Severity During Recurrent Vulvovaginal Candidiasis

PROBLEM

Recurrent vulvovaginal candidiasis (RVVC) affects 5%-10% of all women, negatively impacting their reproductive health and quality of life. Herein, we investigated the molecular effects of RVVC on the vaginal mucosa of otherwise healthy women.

METHOD OF STUDY

Gene expression analysis was performed on vaginal tissue biopsies from women with RVVC, including those with a current episode of vulvovaginal candidiasis (VVC, n = 19) and women between infections (culture negative RVVC [CNR], n = 8); women asymptomatically colonized with Candida albicans (asymptomatic [AS], n = 7); and healthy controls (n = 18). Gene expression profiles were compared between groups and correlated with clinical data retrieved from questionnaires and gynecologic examinations.

RESULTS

Of 20 171 genes identified in vaginal biopsies, 6506 were differentially expressed in the RVVC group, compared to healthy controls. Gene expression pathway analysis revealed an association between RVVC and pathways of inflammatory responses, especially genes involved in neutrophil recruitment and activation. Expression of genes involved in inflammation and neutrophil recruitment increased with increasing clinical severity of VVC, whereas expression of some genes involved in epithelial integrity decreased with increasing clinical severity of infection. Gene expression profiles of both the CNR and AS groups were comparable to those of healthy controls.

CONCLUSIONS

The clinical severity of RVVC during active infection correlates with increased expression of genes involved in molecular inflammation and neutrophil activation in the vaginal mucosa. The lack of differences between healthy controls and women with RVVC who were between acute infections indicates that the molecular effects observed in the RVVC group are only present during active infection.

Inflammatory cytokine signalling in vulvovaginal candidiasis: a hot mess driving immunopathology

Protective immunity to opportunistic fungal infections consists of tightly regulated innate and adaptive immune responses that clear the infection. Immune responses to infections of the vaginal mucosa by Candida species are, however, an exception. In the case of vulvovaginal candidiasis (VVC), the inflammatory response is associated with symptomatic disease, rather than that it results in pathogen clearance. As such VVC can be considered an inflammatory disease, which is a significant public health problem due to its predominance as a female-specific fungal infection. Particularly, women with recurrent VVC (RVVC) suffer from a significant negative impact on their quality of life and mental health. Knowledge of the inflammatory pathogenesis of (R)VVC may guide more effective diagnostic and therapeutic options to improve the quality of life of women with (R)VVC. Here, we review the immunopathogenesis of (R)VVC describing several elements that induce an inflammatory arson, starting with the activation threshold established by vaginal epithelial cells that prevent unnecessary ignition of inflammatory responses, epithelial and inflammasome-dependent immune responses. These inflammatory responses will drive neutrophil recruitment and dysfunctional neutrophil-mediated inflammation. We also review the, sometimes controversial, findings on the involvement of adaptive and systemic responses. Finally, we provide future perspectives on the potential of some unexplored cytokine axes and discuss whether VVC needs to be subdivided into subgroups to improve diagnosis and treatment.

Targeting Virulence Factors of Candida albicans with Natural Products

Natural products derived from natural resources, including nutritional functional food, play an important role in human health. In recent years, the study of anti-fungal and other properties of agri-foods and derived functional compounds has been a hot research topic. Candida albicans is a parasitic fungus that thrives on human mucosal surfaces, which are colonized through opportunistic infection. It is the most prevalent cause of invasive fungal infection in immunocompromised individuals, resulting in a wide variety of clinical symptoms. Moreover, the efficacy of classical therapeutic medications such as fluconazole is often limited by the development of resistance. There is an ongoing need for the development of novel and effective antifungal therapy and medications. Infection of C. albicans is influenced by a great quantity of virulence factors, like adhesion, invasion-promoting enzymes, mycelial growth, and phenotypic change, and among others. Furthermore, various natural products especially from food sources that target C. albicans virulence factors have been researched, providing promising prospects for C. albicans prevention and treatment. In this review, we discuss the virulence factors of C. albicans and how functional foods and derived functional compounds affect them. Our hope is that this review will stimulate additional thoughts and suggestions regarding nutritional functional food and therapeutic development for patients afflicted with C. albicans.

Vulvovaginal Candida albicans Clinical Isolates’ Resistance to Phagocytosis In-Vitro

Previous studies have revealed that Candida albicans isolates involved in chronic vulvovaginal candidosis (cVVC) phenotypically express less virulent traits than clinical isolates involved in sporadic infections. In this study, we aimed to further explore this finding by studying the behaviour of those same clinical isolates in in-vitro models of infection. Eighteen clinical Candida albicans isolates were collected from women suffering sporadic (eight isolates) or chronic infections (ten isolates). Adhesion to HeLa cells (human cervical cancer epithelial cell line) and resistance to phagocytosis by RAW 264.7 cells (murine macrophages cell line) were tested in-vitro. In addition, phenotypic expression of virulence factors related with either adhesion or resistance to phagocytosis was tested in-vitro. Results indicated that yeast isolates involved in sporadic infection adhered in a higher proportion of HeLa cells than those of chronic infections, which was related with their ability to produce biofilm (p < 0.05). The ability to evade phagocytosis was related to an elevated production of proteases (p < 0.05) by chronic isolates, while sporadic isolates’ resistance to phagocytosis was related to a higher hydrophobicity of cell walls (p < 0.05). We conclude that the evasion of macrophage-mediated phagocytosis related to the production of proteases might be an important factor involved in the recurrence of vulvovaginal candidosis infection.

Kangbainian Lotion Ameliorates Vulvovaginal Candidiasis in Mice by Inhibiting the Growth of Fluconazole-Resistant Candida albicans and the Dectin-1 Signaling Pathway Activation

Vulvovaginal candidiasis (VVC) is an infectious disease caused by Candida species, which affects millions of women worldwide every year. The resistance to available antifungal drugs for clinical treatment is a growing problem. The treatment of refractory VVC caused by azole-resistant Candida is still facing challenges. However, research on new antifungal drugs is progressing slowly. Although a lot of reports on new antifungal drugs, only three new antifungal drugs (Isavuconazole, ibrexafungerp, and rezafungin) and two new formulations of posaconazole were marketed over the last decade. Chinese botanical medicine has advantages in the treatment of drug-resistant VVC, such as outstanding curative effects and low adverse reactions, which can improve patients’ comfort and adherence to therapy. Kangbainian lotion (KBN), a Chinese botanical formulation, has achieved very good clinical effects in the treatment of VVC. In this study, we investigated the antifungal and anti-inflammatory effects of KBN at different doses in fluconazole-resistant (FLC-resistant) VVC model mice. We further studied the antifungal mechanism of KBN against FLC-resistant Candida albicans (C. albicans) and the anti-inflammatory mechanism correlated with the Dectin-1 signaling pathway. In vivo and in vitro results showed that KBN had strong antifungal and anti-inflammatory effects in FLC-resistant VVC, such as inhibiting the growth of C. albicans and vaginal inflammation. Further studies showed that KBN inhibited the biofilm and hypha formation, reduced adhesion, inhibited ergosterol synthesis and the expression of ergosterol synthesis-related genes ERG11, and reduced the expression of drug-resistant efflux pump genes MDR1 and CDR2 of FLC-resistant C. albicans in vitro. In addition, in vivo results showed that KBN reduced the expression of inflammatory factor proteins TNF-α, IL-1β, and IL-6 in vaginal tissues, and inhibited the expression of proteins related to the Dectin-1 signaling pathway. In conclusion, our study revealed that KBN could ameliorate vaginal inflammation in VVC mice caused by FLC-resistance C. albicans. This effect may be related to inhibiting the growth of FLC-resistance C. albicans and Dectin-1 signaling pathway activation.

Trichomonas vaginalis induces apoptosis via ROS and ER stress response through ER-mitochondria crosstalk in SiHa cells

Background

Trichomonas vaginalis causes lesions on the cervicovaginal mucosa in women; however, its pathogenesis remains unclear. We have investigated the involvement of the endoplasmic reticulum (ER) in the induction of apoptosis by T. vaginalis and its molecular mechanisms in human cervical cancer SiHa cells.

Methods

Apoptosis, reactive oxygen species (ROS) production, mitochondrial membrane potential (MMP), ER stress response and Bcl-2 family protein expression were evaluated using immunocytochemistry, flow cytometry, 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethyl-imidacarbocyanine iodide dye staining and western blotting.

Results

Trichomonas vaginalis induced mitochondrial ROS production, apoptosis, the ER stress response and mitochondrial dysfunction, such as MMP depolarization and an imbalance in Bcl-2 family proteins, in SiHa cells in a parasite burden- and infection time-dependent manner. Pretreatment with N-acetyl cysteine (ROS scavenger) or 4-phenylbutyric acid (4-PBA; ER stress inhibitor) significantly alleviated apoptosis, mitochondrial ROS production, mitochondrial dysfunction and ER stress response in a dose-dependent manner. In addition, T. vaginalis induced the phosphorylation of apoptosis signal regulating kinase 1 (ASK1) and c-Jun N-terminal kinases (JNK) in SiHa cells, whereas 4-PBA or SP600125 (JNK inhibitor) pretreatment significantly attenuated ASK1/JNK phosphorylation, mitochondrial dysfunction, apoptosis and ER stress response in SiHa cells, in a dose-dependent manner. Furthermore, T. vaginalis excretory/secretory products also induced mitochondrial ROS production, apoptosis and the ER stress response in SiHa cells, in a time-dependent manner.

Conclusions

Trichomonas vaginalis induces apoptosis through mitochondrial ROS and ER stress responses, and also promotes ER stress-mediated mitochondrial apoptosis via the IRE1/ASK1/JNK/Bcl-2 family protein pathways in SiHa cells. These data suggest that T. vaginalis-induced apoptosis is affected by ROS and ER stress response via ER–mitochondria crosstalk.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-05098-2.

Different expression levels of ALS and SAP genes contribute to recurrent vulvovaginal candidiasis by Candida albicans

Aim: To study the behavior of Candida albicans in women with vulvovaginal candidiasis (VVC), recurrent VVC (RVVC) and asymptomatic (AS), regarding adhesion on HeLa cells and their ability to express secreted aspartic proteinases (SAP) genes, agglutinin-like sequence (ALS) genes and HWP1. Materials & methods: The adhesion of Candida albicans to HeLa cells was evaluated by colony-forming units, and the expressed genes were evaluated by qRT-PCR. Results: AS and VVC isolates showed greater ability to adhere HeLa cells when compared with RVVC isolate. Nevertheless, RVVC isolate exhibited upregulation of a large number of genes of ALS and SAP gene families and HWP1 gene. Conclusion: The results demonstrated that RVVC isolate expressed significantly important genes for invasion and yeast-host interactions.

Identification of Candida albicans regulatory genes governing mucosal infection

The fungus Candida albicans thrives on a variety of human mucosae, yet the fungal determinants that contribute to fitness on these surfaces remain underexplored. Here, by screening a collection of C. albicans deletion strains in a mouse model of oral infection (oropharyngeal candidiasis), we identify several novel regulatory genes that modulate the fitness of the fungus in this locale. We investigate in detail the interplay between the host mucosa and one of the identified mutants and establish that the C. albicans transcription regulator CUP9 is a key determinant of mucosal colonisation. Deletion of cup9 resulted in the formation of more foci of colonisation and heightened persistence in infected tongues. Furthermore, the cup9 mutant produced longer and denser filaments in the oral mucosa without eliciting an enhanced local immune response. Consistent with its role in oral colonisation, we show that CUP9's top target of regulation is a major effector of Candida's adherence to buccal cells. Finally, we establish that CUP9 also governs the interplay of the fungus with vaginal epithelial cells and has a role in vaginal infections, another common mucosal disease associated with Candida. Thus, our findings reveal a mechanism whereby C. albicans can regulate proliferation on mucosal surfaces.