Potential Antifungal Targets against a Candida Biofilm Based on an Enzyme in the Arachidonic Acid Cascade-A Review

Can nonsteroidal anti-inflammatory drugs (NSAIDs) be repurposed for fungal infection?

Nonsteroidal anti-inflammatory drugs (NSAIDs) are an important class of anti-inflammatory drugs widely used for the treatment of musculoskeletal disorders, mild-to-moderate pain, and fever. This review aimed to explain the functional role and possible mechanisms of the antifungal effects of NSAIDs alone or in combination with antifungal drugs in vitro and in vivo. Several studies reported that NSAIDs such as aspirin, ibuprofen, diclofenac, indomethacin, ketorolac, celecoxib, flurbiprofen, and nimesulide had antifungal activities in vitro, either fungistatic or fungicidal, against different strains of Candida, Aspergillus, Cryptococcus, Microsporum, and Trichophyton species. These drugs inhibited biofilm adhesion and development, and yeast-to-hypha conversion which may be related to a prostaglandin E2 (PGE2)/PGEx-dependent mechanism. Modulating PGE2 levels by NSAIDs during fungal infection can be introduced as a possible mechanism to overcome. In addition, some important mechanisms of the antifungal activities of NSAIDs and their new derivatives on fungi and host immune responses are summarized. Overall, we believe that using NSAIDs along with classical antifungal drugs has the potential to be investigated as a novel therapeutic strategy in clinical studies. Furthermore, combination therapy can help manage resistant strains, increase the efficacy of antifungal drugs, and reduce toxicity.

Strategies of targeting CYP51 for IFIs therapy: Emerging prospects, opportunities and challenges

CYP51, a monooxygenase associated with the sterol synthesis pathway, is responsible for the catalysis of the 14-methyl hydroxylation reaction of lanosterol precursors. This enzyme is widely present in microorganisms, plants, and mammals. In mammals, CYP51 plays a role in cholesterol production, oligodendrocyte formation, oocyte maturation, and spermatogenesis. In fungal cells, CYP51 is an enzyme that synthesizes membrane sterols. By inhibiting fungal CYP51, ergosterol synthesis can be inhibited and ergosterol membrane fluidity is altered, resulting in fungal cell apoptosis. Thus, targeting CYP51 is a reliable antifungal strategy with important implications for the treatment of invasive fungal infections (IFIs). Many CYP51 inhibitors have been approved by the FDA for clinical treatment. However, several limitations of CYP51 inhibitors remain to be resolved, including fungal resistance, hepatotoxicity, and drug-drug interactions. New broad-spectrum, anti-resistant, highly selective CYP51 inhibitors are expected to be developed to enhance clinical efficacy and minimize adverse effects. Herein, we summarize the structural features and biological functions of CYP51 and emphatically analyze the structure-activity relationship (SAR) and therapeutic potential of different chemical types of small-molecule CYP51 inhibitors. We also discuss the latest progress of novel strategies, providing insights into new drugs targeting CYP51 for clinical practice.

In Vitro Effect of Three-Antibiotic Combinations plus Potential Antibiofilm Agents against Biofilm-Producing Mycobacterium avium and Mycobacterium intracellulare Clinical Isolates

Patients with chronic pulmonary diseases infected by Mycobacterium avium complex (MAC) often develop complications and suffer from treatment failure due to biofilm formation. There is a lack of correlation between in vitro susceptibility tests and the treatment of clinical isolates producing biofilm. We performed susceptibility tests of 10 different three-drug combinations, including two recommended in the guidelines, in biofilm forms of eight MAC clinical isolates. Biofilm developed in the eight isolates following incubation of the inoculum for 3 weeks. Then, the biofilm was treated with three-drug combinations with and without the addition of potential antibiofilm agents (PAAs). Biofilm bactericidal concentrations (BBCs) were determined using the Vizion lector system. All selected drug combinations showed synergistic activity, reducing BBC values compared to those treated with single drugs, but BBC values remained high enough to treat patients. However, with the addition of PAAs, the BBCs steadily decreased, achieving similar values to the combinations in planktonic forms and showing synergistic activity in all the combinations and in both species. In conclusion, three-drug combinations with PAAs showed synergistic activity in biofilm forms of MAC isolates. Our results suggest the need for clinical studies introducing PAAs combined with antibiotics for the treatment of patients with pulmonary diseases infected by MAC.

Antimicrobial Efficiency of Pistacia lentiscus L. Derivates against Oral Biofilm-Associated Diseases-A Narrative Review

Pistacia lentiscus L. (PlL) has been used for centuries in traditional medicine. The richness in antimicrobial biomolecules of Pll derivates can represent an alternative to chemically formulated agents used against oral infections. This review summarizes the knowledge on the antimicrobial activity of PlL essential oil (EO), extracts, and mastic resin against microorganisms being of relevance in oral biofilm-associated diseases. Results demonstrated that the potential of PlL polyphenol extracts has led to increasing scientific interest. In fact, the extracts are a significantly more effective agent than the other PlL derivates. The positive findings regarding the inhibition of periodontal pathogens and C. albicans, together with the antioxidant activity and the reduction of the inflammatory responses, suggest the use of the extracts in the prevention and/or reversal of intraoral dysbiosis. Toothpaste, mouthwashes, and local delivery devices could be effective in the clinical management of these oral diseases.

Antimicrobial and Antibiofilm Effects of Combinatorial Treatment Formulations of Anti-Inflammatory Drugs-Common Antibiotics against Pathogenic Bacteria

With the spread of multi-drug-resistant (MDR) bacteria and the lack of effective antibiotics to treat them, developing new therapeutic methods and strategies is essential. In this study, we evaluated the antibacterial and antibiofilm activity of different formulations composed of ibuprofen (IBP), acetylsalicylic acid (ASA), and dexamethasone sodium phosphate (DXP) in combination with ciprofloxacin (CIP), gentamicin (GEN), cefepime (FEP), imipenem (IPM), and meropenem (MEM) on clinical isolates of Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) as well as the transcription levels of biofilm-associated genes in the presence of sub-MICs of IBP, ASA, and DXP. The minimal inhibitory concentrations (MICs), minimal biofilm inhibitory concentrations (MBICs), and minimum biofilm eradication concentrations (MBECs) of CIP, GEN, FEP, IPM, and MEM with/without sub-MICs of IBP (200 µg/mL), ASA (200 µg/mL), and DXP (500 µg/mL) for the clinical isolates were determined by the microbroth dilution method. Quantitative real-time-PCR (qPCR) was used to determine the expression levels of biofilm-related genes, including icaA in S. aureus and algD in P. aeruginosa at sub-MICs of IBP, ASA, and DXP. All S. aureus isolates were methicillin-resistant S. aureus (MRSA), and all P. aeruginosa were resistant to carbapenems. IBP decreased the levels of MIC, MBIC, and MBEC for all antibiotic agents in both clinical isolates, except for FEP among P. aeruginosa isolates. In MRSA isolates, ASA decreased the MICs of GEN, FEP, and IPM and the MBICs of IPM and MEM. In P. aeruginosa, ASA decreased the MICs of FEP, IPM, and MEM, the MBICs of FEP and MEM, and the MBEC of FEP. DXP increased the MICs of CIP, GEN, and FEP, and the MBICs of CIP, GEN, and FEP among both clinical isolates. The MBECs of CIP and FEP for MRSA isolates and the MBECs of CIP, GEN, and MEM among P. aeruginosa isolates increased in the presence of DXP. IBP and ASA at 200 µg/mL significantly decreased the transcription level of algD in P. aeruginosa, and IBP significantly decreased the transcription level of icaA in S. aureus. DXP at 500 µg/mL significantly increased the expression levels of algD and icaA genes in S. aureus and P. aeruginosa isolates, respectively. Our findings showed that the formulations containing ASA and IBP have significant effects on decreasing the MIC, MBIC, and MBEC levels of some antibiotics and can down-regulate the expression of biofilm-related genes such as icaA and algD. Therefore, NSAIDs represent appropriate candidates for the design of new antibacterial and antibiofilm therapeutic formulations.

Fluconazole-COX Inhibitor Hybrids: A Dual-Acting Class of Antifungal Azoles

When used in combination with azole antifungal drugs, cyclooxygenase (COX) inhibitors such as ibuprofen improve antifungal efficacy. We report the conjugation of a chiral antifungal azole pharmacophore to COX inhibitors and the evaluation of activity of 24 hybrids. Hybrids derived from ibuprofen and flurbiprofen were considerably more potent than fluconazole and comparable to voriconazole against a panel of Candida species. The potencies of hybrids composed of an S-configured azole pharmacophore were higher than those with an R-configured pharmacophore. Tolerance, defined as the ability of a subpopulation of cells to grow in the presence of the drug, to the hybrids was lower than to fluconazole and voriconazole. The hybrids were active against a mutant lacking CYP51, the target of azole drugs, indicating that these agents act via a dual mode of action. This study established that azole-COX inhibitor hybrids are a novel class of potent antifungals with clinical potential.

Mechanistic Understanding of Candida albicans Biofilm Formation and Approaches for Its Inhibition

In recent years, the demand for novel antifungal therapies has increased several- folds due to its potential to treat severe biofilm-associated infections. Biofilms are made by the sessile microorganisms attached to the abiotic or biotic surfaces, enclosed in a matrix of exopolymeric substances. This results in new phenotypic characteristics and intrinsic resistance from both host immune response and antimicrobial drugs. Candida albicans biofilm is a complex association of hyphal cells that are associated with both abiotic and animal tissues. It is an invasive fungal infection and acts as an important virulent factor. The challenges linked with biofilm-associated diseases have urged scientists to uncover the factors responsible for the formation and maturation of biofilm. Several strategies have been developed that could be adopted to eradicate biofilm-associated infections. This article presents an overview of the role of C. albicans biofilm in its pathogenicity, challenges it poses and threats associated with its formation. Further, it discusses strategies that are currently available or under development targeting prostaglandins, quorum-sensing, changing surface properties of biomedical devices, natural scaffolds, and small molecule-based chemical approaches to combat the threat of C. albicans biofilm. This review also highlights the recent developments in finding ways to increase the penetration of drugs into the extracellular matrix of biofilm using different nanomaterials against C. albicans.

Leaves and Fruits Preparations of Pistacia lentiscus L.: A Review on the Ethnopharmacological Uses and Implications in Inflammation and Infection

There is an increasing interest in revisiting plants for drug discovery, proving scientifically their role as remedies. The aim of this review was to give an overview of the ethnopharmacological uses of Pistacia lentiscus L. (PlL) leaves and fruits, expanding the search for the scientific discovery of their chemistry, anti-inflammatory, antioxidative and antimicrobial activities. PlL is a wild-growing shrub rich in terpenoids and polyphenols, the oil and extracts of which have been widely used against inflammation and infections, and as wound healing agents. The more recurrent components in PlL essential oil (EO) are represented by α-pinene, terpinene, caryophyllene, limonene and myrcene, with high variability in concentration depending on the Mediterranean country. The anti-inflammatory activity of the oil mainly occurs due to the inhibition of pro-inflammatory cytokines and the arachidonic acid cascade. Interestingly, the capacity against COX-2 and LOX indicates PlL EO as a dual inhibitory compound. The high content of polyphenols enriching the extracts provide explanations for the known biological properties of the plant. The protective effect against reactive oxygen species is of wide interest. In particular, their anthocyanins content greatly clarifies their antioxidative capacity. Further, the antimicrobial activity of PlL oil and extracts includes the inhibition of Staphylococcus aureus, Escherichia coli, periodontal bacteria and Candida spp. In conclusion, the relevant scientific properties indicate PlL as a nutraceutical and also as a therapeutic agent against a wide range of diseases based on inflammation and infections.

Visible Lights Combined with Photosensitizing Compounds Are Effective against Candida albicans Biofilms

Fungal infections are increasing in prevalence worldwide, especially in immunocompromised individuals. Given the emergence of drug-resistant fungi and the fact that there are only three major classes of antifungal drugs available to treat invasive fungal infections, there is a need to develop alternative therapeutic strategies effective against fungal infections. Candida albicans is a commensal of the human microbiota that is also one of the most common fungal pathogens isolated from clinical settings. C. albicans possesses several virulence traits that contribute to its pathogenicity, including the ability to form drug-resistant biofilms, which can make C. albicans infections particularly challenging to treat. Here, we explored red, green, and blue visible lights alone and in combination with common photosensitizing compounds for their efficacies at inhibiting and disrupting C. albicans biofilms. We found that blue light inhibited biofilm formation and disrupted mature biofilms on its own and that the addition of photosensitizing compounds improved its antibiofilm potential. Red and green lights, however, inhibited biofilm formation only in combination with photosensitizing compounds but had no effects on disrupting mature biofilms. Taken together, these results suggest that photodynamic therapy may be an effective non-drug treatment for fungal biofilm infections that is worthy of further exploration.

Recognition of Candida albicans and Role of Innate Type 17 Immunity in Oral Candidiasis

Candida albicans is an opportunistic pathogenic fungus considered to be a common member of the human microflora. Similar to some other opportunistic microbes, C. albicans can invade and benefit from its host when the immune status of that host is weakened. Most often this happens to immunocompromised individuals, leading to the infection of oral and vaginal mucosae or the systemic spread of the pathogen throughout the entire body. Oropharyngeal candidiasis (OPC) occurs in up to 90 percent of patients with acquired immunodeficiency syndrome (AIDS), making it the most frequent opportunistic infection for this group. Upon first signs of fungal invasion, a range of host signaling activates in order to eliminate the threat. Epithelial and myeloid type cells detect C. albicans mainly through receptor tyrosine kinases and pattern-recognition receptors. This review provides an overview of downstream signaling resulting in an adequate immune response through the activation of various transcription factors. The study discusses recent advances in research of the interleukin-17 (IL-17) producing innate cells, including natural T helper 17 (nTh17) cells, γδ T cells, invariant natural killer T (iNKT) cells and type 3 innate lymphoid cells (ILC3) that are involved in response to oral C. albicans infections.

The Pharmaceutical Ability of Pistacia lentiscus L. Leaves Essential Oil Against Periodontal Bacteria and Candida sp. and Its Anti-Inflammatory Potential

BACKGROUND

Given the increasing request for natural pharmacological molecules, this study assessed the antimicrobial capacity of Pistacia lentiscus L. essential oil (PLL-EO) obtained from the leaves of wild plants growing in North Sardinia (Italy) toward a wide range of periodontal bacteria and Candida, including laboratory and clinical isolates sp., together with its anti-inflammatory activity and safety.

METHODS

PLL-EO was screened by gas chromatography/mass spectrometry. The minimal inhibitory concentration (MIC) was determined. The anti-inflammatory activity was measured by cyclooxygenase (COX-1/2) and lipoxygenase (LOX) inhibition, while the antioxidant capacity was determined electro-chemically and by the MTT assay. The WST-1 assay was used to ascertain cytotoxicity toward four lines of oral cells.

RESULTS

According to the concentrations of terpens, PLL-EO is a pharmacologically-active phytocomplex. MICs against periodontal bacteria ranged between 3.13 and 12.5 µg/ml, while against Candida sp. they were between 6.25 and 12.5 µg/mL. Oxidation by COX-1/2 and LOX was inhibited by 80% and 20% µg/mL of the oil, respectively. Antioxidant activity seemed negligible, and no cytotoxicity arose.

CONCLUSIONS

PLL-EO exhibits a broad-spectrum activity against periodontal bacteria and Candida, with an interesting dual inhibitory capacity toward COX-2 and LOX inflammatory enzymes, and without side effects against oral cells.

From IBS to ME - The dysbiotic march hypothesis

Irritable bowel syndrome (IBS) is often associated with other unexplained complaints like chronic fatigue syndrome (CFS), fibromyalgia and myalgic encephalopathy (ME). The pathogenesis of the relationship is unknown. Intestinal dysbiosis may be a common abnormality, but based on 1100 consecutive IBS patients examined over a nine years period, we hypothesize that the development of the disease, often from IBS to ME, actually manifests a "dysbiotic march". In analogy with "the atopic march" in allergic diseases, we suggest "a dysbiotic march" in IBS; initiated by extensive use of antibiotics during childhood, often before school age. Various abdominal complaints including IBS may develop soon thereafter, while systemic symptom like CFS, fibromyalgia and ME may appear years later.

Synergistic Antifungal Effect of Fluconazole Combined with Licofelone against Resistant Candida albicans

Candida albicans (C. albicans) is one of the important opportunistic fungal pathogens that is closely associated with disseminated or chronic infections. The objective of this study is to evaluate the synergistic antifungal effect of licofelone, which is dual microsomal prostaglandin E2 synthase/lipoxygenase (mPGES-1/LOX) inhibitor in combination with fluconazole against C. albicans. Here our results showed that licofelone (16 μg/mL) can synergistically work with fluconazole (1 μg/mL) against planktonic cells of fluconazole-resistant C. albicans. The two-drug combination inhibited the C. albicans biofilm formation over 12 h, and reduced the expression of extracellular phospholipase genes, biofilm-specific genes and RAS/cAMP/PKA pathway related genes. In addition, the two-drug combination inhibited the transition from yeast to hyphal growth form, and decreased the secreted aspartyl proteinase activity, while not affecting the drug efflux pumps activity. Galleria mellonella model was also used to confirm the antifungal activity of the drug combination in vivo. This study first indicates that the combination of fluconazole and licofelone has synergistic effect against resistant C. albicans and could be a promising therapeutic strategy for the antifungal treatment.

Linear Epitopes of Paracoccidioides brasiliensis and Other Fungal Agents of Human Systemic Mycoses As Vaccine Candidates

Dimorphic fungi are agents of systemic mycoses associated with significant morbidity and frequent lethality in the Americas. Among the pathogenic species are Paracoccidioides brasiliensis and Paracoccidioides lutzii, which predominate in South America; Histoplasma capsulatum, Coccidioides posadasii, and Coccidioides immitis, and the Sporothrix spp. complex are other important pathogens. Associated with dimorphic fungi other important infections are caused by yeast such as Candida spp. and Cryptococcus spp. or mold such as Aspergillus spp., which are also fungal agents of deadly infections. Nowadays, the actual tendency of therapy is the development of a pan-fungal vaccine. This is, however, not easy because of the complexity of eukaryotic cells and the particularities of different species and isolates. Albeit there are several experimental vaccines being studied, we will focus mainly on peptide vaccines or epitopes of T-cell receptors inducing protective fungal responses. These peptides can be carried by antibody inducing β-(1,3)-glucan oligo or polysaccharides, or be mixed with them for administration. The present review discusses the efficacy of linear peptide epitopes in the context of antifungal immunization and vaccine proposition.