Candida albicans cell wall mannoprotein synergizes with lipopolysaccharide to affect RAW264.7 proliferation, phagocytosis and apoptosis

D-Limonene Inhibits Pichia kluyveri Y-11519 in Sichuan Pickles by Disrupting Metabolism

The Pichia kluyveri, a proliferation commonly found in Sichuan pickles (SCPs), can accelerate the growth and reproduction of spoilage bacteria, causing off-odor development and decay. Although D-limonene, a common natural preservative, effectively restricts P. kluyveri, its inhibitory mechanism remains unclear. This study aimed to elucidate this molecular mechanism by investigating the impact on basic P. kluyveri metabolism. The findings revealed that D-limonene inhibited P. kluyveri growth and disrupted the transcription of the genes responsible for encoding the enzymes involved in cell wall and membrane synthesis, oxidative phosphorylation, glycolysis, and the tricarboxylic acid (TCA) cycle pathway. The results indicated that these events disrupted crucial metabolism such as cell wall and membrane integrity, adenosine triphosphate (ATP) synthesis, and reactive oxygen species (ROS) balance. These insights provided a comprehensive understanding of the inhibitory effect of D-limonene on the growth and reproduction of P. kluyveri while highlighting its potential application in the SCP industry.

The Yeast and Hypha Phases of Candida krusei Induce the Apoptosis of Bovine Mammary Epithelial Cells via Distinct Signaling Pathways

Infection with Candida spp. is a significant cause of bovine mastitis globally. We previously found that C. krusei was the main pathogen causing mycotic mastitis in dairy cows in Yinchuan, Ningxia, China. However, whether the infection of this pathogen could induce apoptosis in BMECs remained unclear. In this report, we explored the apoptosis and underlying mechanism of BMECs induced by C. krusei yeast and hypha phases using a pathogen/host cell co-culture model. Our results revealed that both the yeast and hypha phases of C. krusei could induce BMEC apoptosis; however, the yeast phase induced more cell apoptosis than the hypha phase, as assessed via electronic microscopy and flow cytometry assays. This finding was further corroborated via the measurement of the mitochondrial membrane potential (MMP) and the TUNEL test. Infection by both the yeast and hypha phases of C. krusei greatly induced the expression of proteins associated with cell death pathways and important components of toll-like receptor (TLR) signaling, including TLR2 and TLR4 receptors, as determined via a Western blotting assay. BMECs mainly underwent apoptosis after infection by the C. krusei yeast phase through a mitochondrial pathway. Meanwhile, BMEC apoptosis induced by the C. krusei hypha phase was regulated by a death ligand/receptor pathway. In addition, C. krusei-induced BMEC apoptosis was regulated by both the TLR2/ERK and JNK/ERK signaling pathways. These data suggest that the yeast phase and hypha phase of C. krusei induce BMEC apoptosis through distinct cell signaling pathways. This study represents a unique perspective on the molecular processes underlying BMEC apoptosis in response to C. krusei infection.

Development of a new generation of miniemulsion based on cottonseed oil with α-tocopherol and ZnO and evaluation of its adjuvant activity

Background

Emulsions have been widely used as immunological adjuvants. But the use of materials derived from plants such as cottonseed oil, alpha-tocopherol, or minerals such as zinc, as well as their use at the nanometric scale has been little explored. In this study, we develop a new miniemulsion and evaluated its antioxidant and phagocytic capacity, as well as parameters related to immune response stimulation by cytokine expression and antibodies production in a mice model.

Methods

Formulated CN (cottonseed oil miniemulsion) and CNZ (cottonseed oil miniemulsion whit zinc oxide nanoparticles) miniemulsions were characterized by scanning electronic microscopy SEM, DLS and FT-IR. In murine macrophages, splenocytes and thymocytes primary cultures safety and cytotoxicity were determined by MTT. In macrophages the antioxidant and phagocytic capacity was evaluated. In BALB/c mice, the stimulation of the immune system was determined by the expression of cytokines and the production of antibodies.

Results

The CN and CNZ presented stability for 90 days. Immediately after preparation, the CN presented a higher particle size (543.1 nm) than CNZ (320 nm). FT-IR demonstrated the correct nanoparticle synthesis by the absence of sulfate groups. CN and CNZ (1.25 to 10 µL/mL) had no toxic effect on macrophages (p = 0.108), splenocytes (p = 0.413), and thymocytes (p = 0.923). All CN and CNZ doses tested induced nitric oxide and antioxidants production in dose dependent manner when compared with control. CN-ovalbumin and CNZ-ovalbumin treatments in femoral subcutaneous tissue area showed inflammation with higher leukocyte infiltration compared with FCA. The intraperitoneal administration with CN, CNZ, and FCA showed a higher total intraperitoneal cells recruitment (CD14⁺) after 24 h of inoculation than control (p = 0.0001). CN and CNZ increased the phagocyte capacity with respect to untreated macrophages in the Candida albicans-phagocytosis assay. The evaluation of residual CFU indicated that only CN significantly decreased (p = 0.004) this value at 3 h. By other side, only CN increased (p = 0.002) the nitric oxide production. CNZ stimulated a major INFγ secretion compared with FCA at day 7. A major IL-2 secretion was observed at days 7 and 14, stimulated with CN and CNZ. Both miniemulsions did not affect the antibody isotypes production (IgG1, IgG2a, IgG3, IgA and IgM) at days 7, 14, 28, and 42. CN induced a significant IgG production against OVA, but lesser than FCA.

Conclusions

The two new miniemulsions with adjuvant and antioxidant capacity, were capable of generating leukocyte infiltration and increased cytokines and antibodies production.

Oxidative stress-triggered pyroptosis mediates Candida albicans susceptibility in diabetic foot

An accumulating trend of research demonstrates that diabetic patients are susceptible to skin infections with Candida albicans, but the mechanism still remains unclear. The intense oxidative stress (OS) responses were occurred in the lesion of diabetic mice footpads after C. albicans infection. Localised skin infections would lead to more severe complications while the severity of the condition worsens or the inadequate treatment. Notably, in this study, through the investigation of murine diabetic footpad C. albicans infection model and molecular biotechnology, including histopathological staining, immunofluorescence (IF) staining, quantitative real-time PCR (qPCR), western blot (WB), flow cytometry (FCM), sandwich enzyme-linked immunosorbent assay (ELISA) assays, we found that intense OS responses in the footpad tissue not only mediated the activation of NF-κB protein complex, but also triggered downstream pyroptosis and apoptosis through NLRP3 inflammasome, which is one of the potential reasons for the severe condition of infectious skin injuries in diabetic mice. Caspase-1, a classical signal pathway protein in pyroptosis, could promote pore formation on cell membranes and the release of the cytokine after NLRP3 inflammasome activation. With intense immune-inflammatory responses, the organism also stimulates immune organs such as the spleen and lymph nodes to produce negative feedback regulation and generate CD4⁺CD25⁺Foxp3⁺ Treg cells to rectify the process. Therefore, combined with the results of this work, it is possible to design and screen relevant drugs for NLRP3 inflammasomes as core targets to keep the OS response at a low level in the footpad tissues.

Candida albicans induces upregulation of programmed death ligand 1 in oral squamous cell carcinoma

BACKGROUND

The potential association between Candida albicans (C. albicans) infection and oral squamous cell carcinoma (OSCC) has been noticed for a long time. Programmed death ligand-1 (PD-L1) is a key molecule of tumor immune escape and tumor progression. This study aimed to explore whether C. albicans could influence PD-L1 expression in OSCC in vitro and in mouse model.

METHODS

OSCC cell lines (Cal27 and HN6) were infected with C. albicans for 2 and 24 h, then PD-L1 expression was detected by quantitative real-time polymerase chain reaction (RT-qPCR), western blot (WB), and flow cytometry (FCM). To identify the underlying mechanisms, PD-L1 expression in OSCC cells treated with heat-inactivated C. albicans or with biofilm metabolites derived from C. albicans were explored respectively. Meanwhile, signaling pathways involved in PD-L1 regulation were explored by RT-qPCR, and the candidate genes were verified by WB. Moreover, an OSCC mouse model induced by 4-nitroquinoline-1 oxide was used to further explore the role of C. albicans infection in PD-L1 expression in vivo.

RESULTS

C. albicans and heat-inactivated C. albicans upregulated the PD-L1 expression in Cal27 and HN6 cells. Various signaling pathways involved in PD-L1 regulation were influenced by C. albicans infection. Among them, TLR2/MyD88 and TLR2/NF-κB pathways might participate in this process. Furthermore, PD-L1 expression in oral mucosa epithelium was upregulated by C. albicans infection in both normal and OSCC mice.

CONCLUSIONS

This study suggests that C. albicans could induce upregulation of PD-L1 in OSCC in vitro and in mouse model, which might due to the activation of TLR2/MyD88 and TLR2/NF-κB pathways.

Replicative Aging Remodels the Cell Wall and Is Associated with Increased Intracellular Trafficking in Human Pathogenic Yeasts

Replicative aging is an underexplored field of research in medical mycology. Cryptococcus neoformans (Cn) and Candida glabrata (Cg) are dreaded fungal pathogens that cause fatal invasive infections. The fungal cell wall is essential for yeast viability and pathogenesis. In this study, we provide data characterizing age-associated modifications to the cell wall of Cn and Cg. Here, we report that old yeast cells upregulate genes of cell wall biosynthesis, leading to cell wall reorganization and increased levels of all major components, including glucan, chitin, and its derivatives, as well as mannan. This results in a significant thickening of the cell wall in aged cells. Old-generation yeast cells exhibited drastic ultrastructural changes, including the presence of abundant vesicle-like particles in the cytoplasm, and enlarged vacuoles with altered pH homeostasis. Our findings suggest that the cell wall modifications could be enabled by augmented intracellular trafficking. This work furthers our understanding of the cell phenotype that emerges during aging. It highlights differences in these two fungal pathogens and elucidates mechanisms that explain the enhanced resistance of old cells to antifungals and phagocytic attacks. IMPORTANCE Cryptococcus neoformans and Candida glabrata are two opportunistic human fungal pathogens that cause life-threatening diseases. During infection, both microorganisms have the ability to persist for long periods, and treatment failure can occur even if standard testing identifies the yeasts to be sensitive to antifungals. Replicative life span is a trait that is measured by the number of divisions a cell undergoes before death. Aging in fungi is associated with enhanced tolerance to antifungals and resistance to phagocytosis, and characterization of old cells may help identify novel antifungal targets. The cell wall remains an attractive target for new therapies because it is essential for fungi and is not present in humans. This study shows that the organization of the fungal cell wall changes remarkably during aging and becomes thicker and is associated with increased intracellular trafficking as well as the alteration of vacuole morphology and pH homeostasis.

Nonspectroscopic Migratory Cell Monitoring Method Using Retroreflective Janus Microparticles

This study aims to suggest a simple migratory cell monitoring method in the Transwell system by utilizing retroreflective Janus microparticles (RJPs) as an optical probe. The RJP could be internalized on cells without compromising the cell viability and can be registered as bright spots within the cell body by inducing retroreflection from nonspectroscopic light sources. Conventional optical probes (e.g., fluorophores, chromogens, and nanoparticles) have been extensively studied and applied across diverse platforms (e.g., Boyden chamber, wound closing, and microfluidic chips) for understanding in vitro kinetic cell behavior. However, the complexities of running such platforms and setting up analytical instruments are limiting. In this regard, we aimed to demonstrate a modified Transwell migration assay by introducing the retroreflection principle to the cell quantification procedures that ensure a simplified optical setup, assure easy signal acquisition, and are compatible with conventional platforms. To demonstrate retroreflection as a signaling principle, a half-metal-coated silica particle that can induce interior retroreflection was synthesized. Because the RJPs can concentrate incident light and reflect it back to the light source, retroreflection was distinctively recognizable and enabled sensitive visualization. To verify the applicability of the developed migration assay, cell quantification during the incremental progress of macrophage migration, and cell quantification under gradients of chemoattractant monocyte protein-1, was accomplished by obtaining phagocytosed RJP-mediated retroreflection signals. Considering that conventional assays are designed as endpoint measurements, we anticipate the proposed retroreflection-based cell quantification technique to be a promising solution, bypassing current limitations.

Antibiotic-induced gut metabolome and microbiome alterations increase the susceptibility to Candida albicans colonization in the gastrointestinal tract

Antibiotic-induced alterations in the gut ecosystem increases the susceptibility to Candida albicans, yet the mechanisms involved remains poorly understood. Here we show that mice treated with the broad-spectrum antibiotic cefoperazone promoted the growth, morphogenesis and gastrointestinal (GI) colonization of C. albicans. Using metabolomics, we revealed that the cecal metabolic environment of the mice treated with cefoperazone showed a significant alteration in intestinal metabolites. Levels of carbohydrates, sugar alcohols and primary bile acids increased, whereas carboxylic acids and secondary bile acids decreased in antibiotic treated mice susceptible to C. albicans. Furthermore, using in-vitro assays, we confirmed that carbohydrates, sugar alcohols and primary bile acids promote, whereas carboxylic acids and secondary bile acids inhibit the growth and morphogenesis of C. albicans. In addition, in this study we report changes in the levels of gut metabolites correlated with shifts in the gut microbiota. Taken together, our in-vivo and in-vitro results indicate that cefoperazone-induced metabolome and microbiome alterations favor the growth and morphogenesis of C. albicans, and potentially play an important role in the GI colonization of C. albicans.

Environmentally relevant doses of tetrabromobisphenol A (TBBPA) cause immunotoxicity in murine macrophages

TBBPA is one of the main brominated flame retardants and is ubiquitous in the environment. TBBPA can directly encounter immune cells via the bloodstream, posing potential immunotoxicity. To understand the immunomodulating effect of TBBPA on macrophages, the murine macrophages, RAW 264.7, were exposed to TBBPA at environmentally relevant concentrations (1-100 nM). The results showed that TBBPA at the selected concentrations did not alter cell viability of RAW 264.7 cells with or without LPS stimulation. TBBPA upregulated the expression of pro-inflammatory cytokines, including IL-1β, IL-6, and TNF-α, whereas it attenuated the LPS-stimulated expression of these pro-inflammatory cytokines, and the expression of anti-inflammatory cytokines, including IL-4, IL-10, and IL-13. In addition, TBBPA reduced the mRNA levels of antigen-presenting-related genes, including H2-K2, H2-Aa, Cd80, and Cd86. Moreover, TBBPA impaired the phagocytic activity of macrophages. Furthermore, exposure to TBBPA significantly elevated the protein levels of phosphorylated NF-κB p65 (p-p65), while it reduced LPS-stimulated p-p65 protein levels. DCFH-DA staining assays showed that TBBPA caused a slight but significant elevation in reactive oxygen species levels. The data obtained in the present study demonstrated that exposure to environmentally relevant concentrations of TBBPA posed immunotoxicity in macrophages and unveiled a potential health risk of TBBPA.