Heterogeneity of foam cell biogenesis across diseases.

Foam cells are dysfunctional, lipid-laden macrophages associated with chronic inflammation of infectious and non-infectious origin. For decades, the paradigm underlying foam cell biology has been based on atherogenesis, a disease in which macrophages are cholesterol-enriched. Our previous work showed that foam cells in tuberculous lung lesions surprisingly accumulate triglycerides, suggesting multiple modalities of foam cell biogenesis. In the present study, we used matrix-assisted laser desorption/ionization mass spectrometry imaging to assess the spatial distribution of storage lipids relative to foam-cell-rich areas in murine lungs infected with the fungal pathogen Cryptococcus neoformans and in human papillary renal cell carcinoma resection tissues. We also analyzed neutral lipid content and the transcriptional program of lipid-laden macrophages generated under corresponding in vitro conditions. The in vivo data were consistent with in vitro findings showing that C. neoformans-infected macrophages accumulated triglycerides, while macrophages exposed to human renal cell carcinoma-conditioned medium accumulated both triglycerides and cholesterol. Moreover, macrophage transcriptome analyses provided evidence for condition-specific metabolic remodeling. The in vitro data also showed that although both Mycobacterium tuberculosis and C. neoformans infections induced triglyceride accumulation in macrophages, they did so by different molecular mechanisms, as evidenced by different sensitivity of lipid accumulation to the drug rapamycin and the characteristics of macrophage transcriptome remodeling. Collectively, these data demonstrate that the mechanisms of foam cell formation are specific to the disease microenvironment. Since foam cells have been regarded as targets of pharmacological intervention in several diseases, recognizing that their formation is disease-specific opens new research directions of biomedical significance.

Macrophage Mediated Immunomodulation During Cryptococcus Pulmonary Infection.

Macrophages are key cellular components of innate immunity, acting as the first line of defense against pathogens to modulate homeostatic and inflammatory responses. They help clear pathogens and shape the T-cell response through the production of cytokines and chemokines. The facultative intracellular fungal pathogen Cryptococcus neoformans has developed a unique ability to interact with and manipulate host macrophages. These interactions dictate how Cryptococcus infection can remain latent or how dissemination within the host is achieved. In addition, differences in the activities of macrophages have been correlated with differential susceptibilities of hosts to Cryptococcus infection, highlighting the importance of macrophages in determining disease outcomes. There is now abundant information on the interaction between Cryptococcus and macrophages. In this review we discuss recent advances regarding macrophage origin, polarization, activation, and effector functions during Cryptococcus infection. The importance of these strategies in pathogenesis and the potential of immunotherapy for cryptococcosis treatment is also discussed.

Development of Antifungal Peptides against Cryptococcus neoformans; Leveraging Knowledge about the cdc50Δ Mutant Susceptibility for Lead Compound Development.

Cryptococcus neoformans is a major fungal pathogen that often causes life-threatening meningitis in immunocompromised populations. This yeast pathogen is highly resistant to the echinocandin drug caspofungin. Previous studies showed that Cryptococcus lipid translocase (flippase) is required for the caspofungin resistance of that fungus. Mutants with a deleted subunit of lipid flippase, Cdc50, showed increased sensitivity to caspofungin. Here we designed an antifungal peptide targeting the P4-ATPase function. We synthesized stable peptides based on the Cdc50 loop region to identify peptides that can sensitize caspofungin by blocking flippase function and found that myristylated peptides based on the "AS15 sequence" was effective at high concentrations. A modified peptide, "AW9-Ma" showed a MIC of 64 µg/mL against H99 wild type and a fractional inhibitory concentration (FIC) index value of 0.5 when used in combination with caspofungin. Most notably, in the presence of the AW9-Ma peptide, C. neoformans wild type was highly sensitive to caspofungin with a MIC of 4 µg/mL, the same as the cdc50Δ mutant. Further assays with flow cytometry showed inhibition of the lipid flippase enzyme activity and significant accumulation of phosphatidylserine on the cell membrane surface. Using a fluorescently labeled peptide, we confirmed that the peptide co-localized with mCherry-tagged P4-ATPase protein Apt1 in C. neoformans. Structure-activity relationship studies of the AW9 sequence showed that two lysine residues on the peptide are likely responsible for the interaction with the P4-ATPase, hence critical for its antifungal activity. IMPORTANCE The authors have developed a lead compound peptide antifungal drug targeting a protein from the organism Cryptococcus neoformans. Binding of the drug to the target fungal protein causes charged lipid molecules to be retained on the surface. This peptide works in synergy with the existing antifungal drug caspofungin. Echinocandin drugs like caspofungin are one of the few classes of existing antifungals. Due to the high concentrations needed, caspofungin is rarely used to treat C. neoformans infections. The authors believe that their new compound provides a way to lower the concentration of caspofungin needed to treat such infections, thus opening the possibility for greater utility of these antifungal.

Effect of human lactoferrin on Candida albicans infection and host response interactions in experimental oral candidiasis in mice.

OBJECTIVES: To determine the effect of human lactoferrin (hLF) in experimental oral candidiasis and examine the host-pathogen interactions in a mouse model. DESIGN: Experimental groups comprised of 4-6-week-old wild type (C57BL/6J) or lactoferrin knockout (ltf-/-) immunosuppressed mice. Six mice in each group were inoculated with C. albicans or sham infection by swabbing the oral cavity. To determine the effect of hLF on infection and host response, we added hLF (0.5 g/kg/day) to the drinking water. Candida and mice RNA were isolated from gingival tissue and analyzed by qRT-PCR for virulence genes and host expression of inflammatory mediators. RESULTS: Administration of hLF significantly reduced the C. albicans CFUs in both WT and ltf-/- mice (P < .001). Examination of the oral cavity of ltf-/-I mice revealed lesions characterized by white patches and inflammation when compared to WTI mice. Several Candida virulence genes (als, ece, efg, sap) were significantly downregulated on administration of hLF to WTI and ltf-/-I mice (P < .001). The WTI+hLF mice had significantly increased expression of toll-like receptors (TLRs) compared to other group. We observed that hLF increased expression of interleukins, IL-1ß, IL-6, IL-12, IL-17, tumor necrosis factor alpha (TNF-α), transforming growth factor beta (TGF-ß), inducible nitric oxide synthase (iNOS) and myeloperoxidase (MPO) compared to untreated gingival tissue. CONCLUSION: Our study highlights the protective effect of hLF against oral C. albicans infection by its actions on both microbial and host factors. HLF may be of therapeutic value to protect against oral candidiasis.

The effect of iron deficiency anemia on experimental dental caries in mice.

OBJECTIVE: The objective of this study was to examine the relationship between iron deficiency and caries susceptibility in a mouse model. MATERIALS AND METHODS: Three-week-old C57BL/J6 mice were fed a cariogenic diet containing either standard iron (48 ppm Fe) or low iron (4 ppm Fe) levels. Concurrently, groups of mice with both diets were orally inoculated with Streptococcus mutans (1 × 108) cells on three consecutive days. At the end of the 5th week after infection, mice were sacrificed and jaws were collected for caries scoring, rating the number and severity of lesions using a modified Keyes method applicable to mice. RESULTS: Blood analysis by the end of the 5th week revealed marked reduction in the hemoglobin and hematocrit levels of the mice fed the iron deficient diet (IDA and IDA-S. mutans). Anemic mice in both groups lacked the incisor enamel pigmentation observed in mice fed an iron deficient diet. Anemic infected mice had the highest caries severity scores reflecting extensive deep lesions (P < 0.05). S. mutans infected mice fed a standard iron diet had similar numbers of lesions and severity scores as un-infected IDA animals (p < 0.05). IDA did not alter S. mutans CFU counts in infected animals (P < 0.05). CONCLUSION: These results demonstrated that IDA mice are at a higher risk of developing deep dental caries compared to non-anemic mice; highlighting the protective role of iron against dental caries.

Caries Preventive Effect of Sodium Fluoride Varnish on Deciduous Dentition: A Clinical Trial.

AIM: The aim of the study is to evaluate the efficacy of intensive application of sodium fluoride varnish in reducing caries incidence among children aged 6 to 7 years. MATERIALS AND METHODS: The study was a randomized controlled trial conducted among 6- to 7-year-old children of Sangamner, Maharashtra, India. Nearly 200 randomly selected children were randomized into two groups: Control group and intervention (varnish) group. Dental examination to record the caries experiences was conducted at baseline and at 1-year follow-up. The fluoride varnish was applied for three times in a week for a period of 1 year. Mean decayed, missed, and filled teeth (DMFT) were compared between and within groups using t-test. RESULTS: Out of 200 participants, there were 3 dropouts for control group and 4 for intervention group. Nearly 55% study participants were males and remaining were females. There was a statistically significant difference between the baseline and follow-up caries levels in varnish group for deciduous dentition. Mean caries reduction in this study was 26%. CONCLUSION: After 1 year of study, we found significant caries reversal in deciduous dentition among the 6- to 7-year-olds after intensive fluoride application. Such a regimen can be advocated to encourage the practitioners and the caregivers alike for early caries prevention. CLINICAL SIGNIFICANCE: Intensive fluoride application (three times a week) once a year was found to be effective in reducing the incidence of detectable carious lesions and can be advocated to the dental professionals to be incorporated in their routine preventive clinical practice.