Estrogen-dependent induction of persistent vaginal candidosis in naïve mice

Effects of oestrogen on vulvovaginal candidosis

As a frequently occurring infectious disease mainly caused by Candida albicans, vulvovaginal candidosis (VVC) affects more than 100 million women worldwide every year. Multiple factors that influence C. albicans colonisation have been linked to the incidence of VVC, including high levels of circulating oestrogen due to pregnancy, the use of oral contraceptives, and hormone replacement therapy. This review provides an overview of the current understanding of the mechanism(s) by which oestrogen contributes to VVC, which might provide meaningful guidance to the prevention and treatment of this disease.

Exogenous Reproductive Hormones nor Candida albicans Colonization Alter the Near Neutral Mouse Vaginal pH

While human vaginal pH in childbearing-age women is conclusively acidic, the mouse vaginal pH is reported as being near neutral. However, this information appears to be somewhat anecdotal with respect to vulvovaginal candidiasis, as such claims in the literature frequently lack citations of studies that specifically address this physiological factor. Given the disparate pH between mice and humans, the role of exogenous hormones and colonization by the fungal pathogen Candida albicans in shaping vaginal pH was assessed. Use of a convenient modified vaginal lavage technique with the pH indicator dye phenol red demonstrated that indeed vaginal pH was near neutral (7.2 ± 0.24) and was not altered by delivery of progesterone or estrogen in C57BL/6 mice. These trends were conserved in DBA/2 and CD-1 mouse backgrounds, commonly used in the mouse model of vaginitis. It was also determined that vaginal colonization with C. albicans did not alter the globally neutral vaginal pH over the course of one week. Construction and validation of a C. albicans reporter strain expressing GFPy, driven by the pH-responsive PHR1 promoter, confirmed the murine vaginal pH to be at least ≥6.0. Collectively, our data convincingly demonstrate a stable and conserved near neutrality of the mouse vaginal pH during vulvovaginal candidiasis and should serve as a definitive source for future reference. Implications and rationale for disparate pH in this model system are also discussed.

In Vitro and In Vivo Inhibitory Activity of Limonene against Different Isolates of Candida spp

Commensal yeast from the genus Candida is part of the healthy human microbiota. In some cases, Candida spp. dysbiosis can result in candidiasis, the symptoms of which may vary from mild localized rashes to severe disseminated infections. The most prevalent treatments against candidiasis involve fluconazole, itraconazole, miconazole, and caspofungin. Moreover, amphotericin B associated with prolonged azole administration is utilized to control severe cases. Currently, numerous guidelines recommend echinocandins to treat invasive candidiasis. However, resistance to these antifungal drugs has increased dramatically over recent years. Considering this situation, new therapeutic alternatives should be studied to control candidiasis, which has become a major medical concern. Limonene belongs to the group of terpene molecules, known for their pharmacological properties. In this study, we evaluated in vitro the limonene concentration capable of inhibiting the growth of yeast from the genus Candida susceptible or resistant to antifungal drugs and its capacity to induce fungal damage. In addition, intravaginal fungal infection assays using a murine model infected by Candida albicans were carried out and the fungal burden, histopathology, and scanning electron microscopy were evaluated. All of our results suggest that limonene may play a protective role against the infection process by yeast from the genus Candida.

Vulvovaginal Candidiasis: A Current Understanding and Burning Questions

Candida albicans, along with other closely related Candida species, are the primary causative agents of vulvovaginal candidiasis (VVC)-a multifactorial infectious disease of the lower female reproductive tract resulting in pathologic inflammation. Unlike other forms of candidiasis, VVC is a disease of immunocompetent and otherwise healthy women, most predominant during their child-bearing years. While VVC is non-lethal, its high global incidence and profound negative impact on quality-of-life necessitates further understanding of the host and fungal factors that drive disease pathogenesis. In this review, we cover the current state of our understanding of the epidemiology, host response, fungal pathogenicity mechanisms, impact of the microbiome, and novel approaches to treatment of this most prevalent human candidal infection. We also offer insight into the latest advancements in the VVC field and identify important questions that still remain.

Nanocarriers Provide Sustained Antifungal Activity for Amphotericin B and Miltefosine in the Topical Treatment of Murine Vaginal Candidiasis

Topical drug administration is frequently used for the treatment of vaginal candidiasis; however, most formulations using this route do not provide prolonged drug release. Our aim was to evaluate the antifungal efficacy of amphotericin B (AMB) and miltefosine (MFS) incorporated in nanocarriers for sustained drug release, in a murine model of vaginal candidiasis. AMB and MFS were incorporated in different topical formulations, namely: conventional vaginal cream (daily dose for 6 days; MFS-CR and AMB-CR groups), microemulsion that transforms into a liquid crystalline gel in situ (single dose, or in three doses, every 48 h; AMB-ME and MFS-ME groups) and alginate nanoparticles (single dose; MFS-AN group). Formulations were administered intravaginally in BALB/c female mice 24 h post-infection by Candida albicans yeasts. On the 7th day post-infection the animals were euthanized for mycological and histological analyses. Formulation persistence in the vaginal canal was assessed for 7 days by in vivo imaging, using nanocarriers labeled with Alexa-Fluor 647. AMB-ME(3×), MFS-ME(3×), and MFS-AN(1×) formulations were able to control fungal infection at comparable levels to those vaginal cream formulations. Notably, a single dose of MFS-AN was sufficient to reduce the fungal burden as effectively as MFS-ME(3×) and MFS-CR(6×). In vivo imaging showed that nanocarriers allowed prolonged antifungal activity by intravaginal administration reducing drug administration frequency. Therefore, AMB and MFS incorporated into a microemulsion and MFS encapsulated in alginate nanoparticles could be effective therapeutic alternatives for vaginal candidiasis, likely due to the sustained antifungal activity provided by these nanocarriers.

Proanthocyanidin polymeric tannins from Stryphnodendron adstringens are effective against Candida spp. isolates and for vaginal candidiasis treatment

ETHNOPHARMACOLOGICAL RELEVANCE

The stem bark of Stryphnodendron adstringens (Mart.) Coville is popularly used as anti-inflammatory, astringent and in the treatment of wounds and vaginal infections. Several pharmacological activities have been scientifically proven by in vitro and in vivo experimental assays for antibacterial, antiviral, antiprotozoan, anti-inflammatory and antioxidant.

AIM OF THE STUDY

We investigated whether proanthocyanidin polymeric tannins from the Stryphnodendron adstringens stem bark with antifungal activity against Candida albicans in vitro are also active against planktonic and biofilm cells of Candida non-albicans (CNA, including fluconazole-resistant isolates) and are capable of controlling Candida vaginitis in vivo.

MATERIALS AND METHODS

A total of 46 clinical isolates and 5 reference Candida spp. strains were used in this study. The antifungal effects in vitro of tannins (F2 and sub-fraction F2.4) from S. adstringens stem bark were evaluated using a broth microdilution assay (for planktonic yeasts and biofilm dispersion cells) or by XTT assay (for biofilm sessile cells). For in vivo antifungal activity analysis, mice with vaginal infection by C. albicans or C. glabrata were treated with a topical gel containing F2 (alone or combined with oral fluconazole), and the vaginal histopathology and fungal burden (by CFU counts from vaginal homogenates) were analyzed.

RESULTS

F2 and F2.4 inhibited the proliferation of planktonic cells of Candida spp., especially that of fluconazole- and/or amphotericin B-resistant isolates. F2 and F2.4 also inhibited the proliferation of Candida biofilm dispersion cells. Moreover, a gel containing F2 efficiently controlled vaginal infection by C. albicans and C. glabrata in mice, with no noticeable toxicity to vaginal tissue.

CONCLUSIONS

Our data show that proanthocyanidin polymeric tannins obtained from S. adstringens have antifungal activity in vitro against C. albicans and CNA (including fluconazole-resistant isolates) and presented efficacy in the control of candidiasis in murine model. Therefore, these tannins have potential use in the treatment of vaginal candidiasis, representing interesting alternatives to current antifungals.

Antifungal Activity of the Biphosphinic Cyclopalladate C7a against Candida albicans Yeast Forms In Vitro and In Vivo

Vulvovaginal and invasive candidiasis are frequent conditions in immunosuppressed individuals caused by Candida albicans and non-albicans Candida spp. Fluconazole and Amphotericin B are the main drugs used to fight the infection. However, resistance to fluconazole and other azole antifungal drugs is an important clinical problem that encourages the search for new therapeutic alternatives. In this work, we evaluate the antifungal activity of the biphosphinic cyclopalladate C7a in the in vitro and in vivo model. Our results showed fungicidal activity, with low values of minimal inhibitory concentrations and minimum fungicidal concentrations, even for fluconazole and/or miconazole resistant Candida isolates. Fluorescence microscopy and transmission electron microscopy revealed that the compound was able to inhibit the formation of hyphae/pseudohyphae and, moreover, promoted morphological alterations in cellular organelles and structures, such as disruption of cell wall, apparent mitochondrial swelling, chromatin marginalization into the nuclei and increased numbers of electron-lucent vacuoles. C7a significantly decreased the biofilm formation and reduced the viability of yeast cells in mature biofilms when tested against a virulent C. albicans strain. In vivo assays demonstrated a significant decrease of fungal burden in local (vaginal canal) and disseminated (kidneys) infection. In addition, we observed a significant increase in the survival of the systemically infected animals treated with C7a. Our results suggest C7a as a novel therapeutic agent for vaginal and disseminated candidiasis, and an alternative for conventional drug-resistant Candida.

Feasibility of histological scoring and colony count for evaluating infective severity in mouse vaginal candidiasis

Qualitative measurement of the infective level is relatively difficult in experimental vaginal candidiasis. Female BALB/c mice aged 8 to 10 weeks were randomly divided into E1, E2 and E0 groups, which received subcutaneous injection of 0.05 mg, 0.1 mg of estradiol benzoate or 0.1 ml soybean oil 3 days before vaginal inoculation, respectively, and hormone treatment continued every other day thereafter. Each group was further divided into infected and noninfected subgroups. The infected mice were inoculated intravaginally with 10 µl (5 × 10⁴ conidia) of Candida albicans suspension, while the noninfected mice were inoculated with 10 µl phosphate-buffered saline. Direct microscopic examination, colony count and vaginal histopathology including infection degree and inflammation extent were performed at 3, 7 and 14 days post inoculation. Estrogen treatment increased the vaginal fungal burden and extent of infection and inflammation compared with the control group, and 0.3 mg/week estrogen generally induced more severe infection and inflammation than 0.15 mg/week estrogen did. Colony count peaked on day 3 and decreased remarkably after 7 days. Infection score increased gradually during the first 7 days and decreased on day 14, while inflammation extent exacerbated progressively over the course of 14 days. This study demonstrates that the modified histological scoring system might be more feasible than colony count for evaluation of infectivity and dynamic change in experimental vaginal candidiasis.

Estrogen treatment predisposes to severe and persistent vaginal candidiasis in diabetic mice

Background

Increased levels of estrogen and diabetes mellitus separately predispose to vaginal candidiasis (VC). However, the compounding effect of estrogen on the severity and persistence of VC in diabetic females is not clear.

Methods

To address this issue, a diabetic mouse model with estrogen-maintained VC was developed and evaluated for vaginal fungal burden (VFB) and immune competence at different time points throughout the study period.

Results

Blood glucose levels in estrogen-treated diabetic mice were consistently lower than that in untreated counterparts. Estrogen-treated C. albicans-infected non-diabetic mice experienced persistent episodes of VC as compared with naïve controls (P < 0.01). However, severity and persistence of VC in estrogen-treated C. albicans-infected diabetic mice was significantly greater than that in non-diabetic counterparts (P < 0.05). Mortality rates among estrogen-treated C. albicans-infected diabetic mice were significantly higher (P < 0.05) than that in non-diabetic counterparts. Statistically significant (P < 0.05) and persistent suppression of the delayed hypersensitivity response (DTH) was evident in estrogen-treated C. albicans-infected diabetic and non-diabetic mice as compared with controls. Levels of expression of the inhibitory molecule CD152 on vaginal and splenic T cells isolated from estrogen-treated C. albicans infected mice was significantly higher than that in naive untreated controls (P < 0.01).

Conclusions

These findings suggest that estrogen treatment in diabetic females may protect against the progression of DM on the one hand and predispose to severe and persistent VC on the other. The later outcome could be related to the immunosuppressed status of the host.

Estrogen-dependent changes in serum iron levels as a translator of the adverse effects of estrogen during infection: a conceptual framework

Elevated levels of estrogen often associate with increased susceptibility to infection. This has been attributed to the ability of estrogen to concomitantly enhance the growth and virulence of pathogens and suppress host immunity. But the exact mechanism of how estrogen mediates such effects, especially in cases where the pathogen and/or the immune components in question do not express estrogen receptors, has yet to be elucidated. Here we propose that translating the adverse effects of estrogen during infection is dependent to a significant degree upon its ability to manipulate iron homeostasis. For elevated levels of estrogen alter the synthesis and/or activity of several factors involved in iron metabolism including hypoxia inducible factor 1α (HIF-1α) and hepcidin among others. This leads to the inhibition of hepcidin synthesis in hepatocytes and the maintenance of ferroportin (FPN) integrity on the surface of iron-releasing duodenal enterocytes, hepatocytes, and macrophages. Intact FPN permits the continuous efflux of dietary and stored iron into the circulation, which further enhances pathogen growth and virulence on the one hand and suppresses host immunity on the other. This new conceptual framework may help explain a multitude of disparate clinical and experimental observations pertinent to the relationship between estrogen and infection.

Characteristics of Lactobacillus and Gardnerella vaginalis from women with or without bacterial vaginosis and their relationships in gnotobiotic mice

The objectives of the present study were to evaluate in vitro the production of antagonistic compounds against Gardnerella vaginalis by Lactobacillus strains isolated from women with or without bacterial vaginosis (BV), and to select one of the better Lactobacillus producers of such a substance to be tested in vivo using a gnotobiotic animal model challenged with one of the more sensitive G. vaginalis isolates. A total of 24 isolates from women with and without BV were identified as G. vaginalis. A higher frequency (P<0.05) of this bacterium was observed in women with BV (56.7%) when compared to healthy women (17.6%). A total of 86 strains of Lactobacillus were obtained from healthy women and women with BV. Lactobacillus strains were more frequently present (P<0.05) in healthy women (97.5%) than in women with BV (76.7%). Lactobacillus crispatus was the predominating strain in both healthy women and women with BV. Lactobacillus jensenii, Lactobacillus johnsonii, Lactobacillus gasseri and Lactobacillus vaginalis were isolated with an intermediate frequency in the two groups. In vitro antagonism assays were performed using as indicators 17 reference strains and the G. vaginalis strains isolated from women with BV and from healthy women. Lactobacillus isolated from healthy women showed the higher antagonistic activity against all the indicator strains when compared with isolates from women with BV. Concerning the indicator strains, G. vaginalis found in women with BV was more resistant to the antagonism, particularly when Lactobacillus isolates from women with BV were used as producer strains. A high vaginal population level of G. vaginalis was obtained by intravaginal inoculation of germ-free mice, and this colonization was accompanied by vaginal histopathological lesions. A tenfold decrease in vaginal population level of G. vaginalis and a reduction of histological lesions were observed when the pathogenic challenge was performed in mice previously monoassociated with an L. johnsonii strain. Concluding, results of the present study suggest that progression of G. vaginalis-associated BV depends in part on a simultaneous presence of Lactobacillus populations with a low antagonistic capacity and of a G. vaginalis strain with a high resistance to this antagonism. The results could also explain why G. vaginalis is frequently found in the vaginal ecosystem of healthy women.

Therapeutic use of a cationic antimicrobial peptide from the spider Acanthoscurria gomesiana in the control of experimental candidiasis

Background

Antimicrobial peptides are present in animals, plants and microorganisms and play a fundamental role in the innate immune response. Gomesin is a cationic antimicrobial peptide purified from haemocytes of the spider Acanthoscurria gomesiana. It has a broad-spectrum of activity against bacteria, fungi, protozoa and tumour cells. Candida albicans is a commensal yeast that is part of the human microbiota. However, in immunocompromised patients, this fungus may cause skin, mucosal or systemic infections. The typical treatment for this mycosis comprises three major categories of antifungal drugs: polyenes, azoles and echinocandins; however cases of resistance to these drugs are frequently reported. With the emergence of microorganisms that are resistant to conventional antibiotics, the development of alternative treatments for candidiasis is important. In this study, we evaluate the efficacy of gomesin treatment on disseminated and vaginal candidiasis as well as its toxicity and biodistribution.

Results

Treatment with gomesin effectively reduced Candida albicans in the kidneys, spleen, liver and vagina of infected mice. The biodistribution of gomesin labelled with technetium-99 m showed that the peptide is captured in the kidneys, spleen and liver. Enhanced production of TNF-α, IFN-γ and IL-6 was detected in infected mice treated with gomesin, suggesting an immunomodulatory activity. Moreover, immunosuppressed and C. albicans-infected mice showed an increase in survival after treatment with gomesin and fluconazole. Systemic administration of gomesin was also not toxic to the mic

Conclusions

Gomesin proved to be effective against experimental Candida albicans infection. It can be used as an alternative therapy for candidiasis, either alone or in combination with fluconazole. Gomesin's mechanism is not fully understood, but we hypothesise that the peptide acts through the permeabilisation of the yeast membrane leading to death and/or releasing the yeast antigens that trigger the host immune response against infection. Therefore, data presented in this study reinforces the potential of gomesin as a therapeutic antifungal agent in both humans and animals.

Protocols for vaginal inoculation and sample collection in the experimental mouse model of Candida vaginitis

Vulvovaginal candidiasis (VVC), caused by Candida species, is a fungal infection of the lower female genital tract that affects approximately 75% of otherwise healthy women during their reproductive years. Predisposing factors include antibiotic usage, uncontrolled diabetes and disturbance in reproductive hormone levels due to pregnancy, oral contraceptives or hormone replacement therapies. Recurrent VVC (RVVC), defined as three or more episodes per year, affects a separate 5 to 8% of women with no predisposing factors. An experimental mouse model of VVC has been established and used to study the pathogenesis and mucosal host response to Candida. This model has also been employed to test potential antifungal therapies in vivo. The model requires that the animals be maintained in a state of pseudoestrus for optimal Candida colonization/infection. Under such conditions, inoculated animals will have detectable vaginal fungal burden for weeks to months. Past studies show an extremely high parallel between the animal model and human infection relative to immunological and physiological properties. Differences, however, include a lack of Candida as normal vaginal flora and a neutral vaginal pH in the mice. Here, we demonstrate a series of key methods in the mouse vaginitis model that include vaginal inoculation, rapid collection of vaginal specimens, assessment of vaginal fungal burden, and tissue preparations for cellular extraction/isolation. This is followed by representative results for constituents of vaginal lavage fluid, fungal burden, and draining lymph node leukocyte yields. With the use of anesthetics, lavage samples can be collected at multiple time points on the same mice for longitudinal evaluation of infection/colonization. Furthermore, this model requires no immunosuppressive agents to initiate infection, allowing immunological studies under defined host conditions. Finally, the model and each technique introduced here could potentially give rise to use of the methodologies to examine other infectious diseases of the lower female genital tract (bacterial, parasitic, viral) and respective local or systemic host defenses.

Aspects of the progesterone response in Hortaea werneckii: Steroid detoxification, protein induction and remodelling of the cell wall

Progesterone in sublethal concentrations temporarily inhibits growth of Hortaea werneckii. This study investigates some of the compensatory mechanisms which are activated in the presence of progesterone and are most probably contributing to escape from growth inhibition. These mechanisms lead on the one hand to progesterone biotransformation/detoxification but, on the other, are suggested to increase the resistance of H. werneckii to the steroid. Biotransformation can detoxify progesterone efficiently in the early logarithmic phase, with mostly inducible steroid transforming enzymes, while progesterone biotransformation/detoxification in the late logarithmic and stationary phases of growth is not very efficient. The relative contribution of constitutive steroid transforming enzymes to progesterone biotransformation is increased in these latter phases of growth. In the presence of progesterone, activation of the cell wall integrity pathway is suggested by the overexpression of Pck2 which was detected in the stationary as well as the logarithmic phase of growth of the yeast. Progesterone treated H. werneckii cells were found to be more resistant to cell lysis than mock treated cells, indicating for the first time changes in the yeast cell wall as a result of treatment with progesterone.

Patterns of Expression of Vaginal T-Cell Activation Markers during Estrogen-Maintained Vaginal Candidiasis

: The immunosuppressive activity of estrogen was further investigated by assessing the pattern of expression of CD25, CD28, CD69, and CD152 on vaginal T cells during estrogen-maintained vaginal candidiasis. A precipitous and significant decrease in vaginal fungal burden toward the end of week 3 postinfection was concurrent with a significant increase in vaginal lymphocyte numbers. During this period, the percentage of CD3+, CD3+CD4+, CD152+, and CD28+ vaginal T cells gradually and significantly increased. The percentage of CD3+ and CD3+CD4+ cells increased from 43% and 15% at day 0 to 77% and 40% at day 28 postinfection. Compared with 29% CD152+ vaginal T cells in naive mice, > 70% of vaginal T cells were CD152+ at day 28 postinfection. In conclusion, estrogen-maintained vaginal candidiasis results in postinfection time-dependent changes in the pattern of expression of CD152, CD28, and other T-cell markers, suggesting that T cells are subject to mixed suppression and activation signals.

Lack of aromatase improves cell-mediated immune response after burn

BACKGROUND

Persistent elevation of estrogens after injury or sepsis correlates with increased mortality and a pro-inflammatory state. Given that aromatase is elevated after injury, the enzyme's subsequent conversion of androstenedione and testosterone to estrone and estradiol may be a causative factor for this correlation.

METHODS

Aromatase knockout (ArKO) and wild type female mice were subjected to a 15% total body surface area burn. The delayed type hypersensitivity (DTH) response and splenocyte production of IL-6 and TNFalpha were examined 8 days later.

RESULTS

Injury in wild type mice is associated with an impairment in the DTH response, as well as with an increase in IL-6 and TNFalpha production by stimulated splenocytes. However, for ArKO mice, the impairment in DTH was blunted and there was no difference in IL-6 production between sham- and burn-injured mice. Sham-injured ArKO mice produced nearly 50% more TNFalpha than wild type mice, while injury did not result in a significant increase in TNFalpha production for ArKO mice.

CONCLUSION

The complete deficiency in aromatase correlated with a decrease in the production of the inflammatory cytokine IL-6 and partial restoration of the DTH response after severe burn. However, a deficiency of aromatase did not effect TNFalpha production after injury.

Utility of the oestrogen-dependent vaginal candidosis murine model in evaluating the efficacy of various therapies against vaginal Candida albicans infection

The efficacy of yogurt treatment against vaginal candidosis (VC) was examined using an oestrogen-dependent vaginal candidosis (EDVC) murine model. The EDVC mouse model was constructed by inoculating mice with viable Candida albicans cells under pseudo-oestrus conditions. Vaginal fungal burden in the various mouse groups was evaluated at several time points following the induction of VC. Untreated and yogurt-treated naïve mice exhibited background levels of VC (<6000 CFU per mouse). Candida albicans colonisation in untreated EDVC mice was significantly higher (P < 0.05) than that in yogurt-treated EDVC mice at days 20-30. Metronidazole-treated naïve mice developed persistent C. albicans vaginal colonisation at significantly lower levels (P < 0.05) than that in untreated or metronidazole-treated EDVC mice. Lactobacillus was only detected in the reproductive tracts of yogurt-treated naïve and EDVC mice. These findings suggest that the presence of Lactobacillus in the reproductive tract can suppress C. albicans growth and the antibiotics may predispose to VC.