scholarly journals A Putative P-Type ATPase, Apt1, Is Involved in Stress Tolerance and Virulence in Cryptococcus neoformans

2009 ◽  
Vol 9 (1) ◽  
pp. 74-83 ◽  
Author(s):  
Guanggan Hu ◽  
James W. Kronstad
Keyword(s):  
Membrane Fusion ◽  
Cryptococcus Neoformans ◽  
Virulence Factors ◽  
Molecular Mechanisms ◽  
Nitrosative Stress ◽  
Brefeldin A ◽  
Antifungal Drugs ◽  
Oxidative And Nitrosative Stress ◽  
Transport Pathways ◽  
P Type

ABSTRACT The export of virulence factors, such as the capsule polysaccharide, to the cell surface is a critical aspect of the pathogenicity of Cryptococcus neoformans. A view of capsule export via exocytosis and extracellular vesicles is emerging, but the molecular mechanisms underlying virulence factor transport pathways remain to be established. In this study, we characterized the APT1 gene, which encodes a predicted integral membrane P-type ATPase belonging to the type IV, Drs2 family of aminophospholipid translocases (flippases) (APTs). APTs maintain the phospholipid asymmetry that is critical in membrane fusion events for trafficking and in establishing cell polarity. Deletion of the APT1 gene resulted in phenotypes consistent with similar roles in C. neoformans. These included altered actin distribution, increased sensitivity to stress conditions (oxidative and nitrosative stress) and to trafficking inhibitors, such as brefeldin A and monensin, a reduction in exported acid phosphatase activity, and hypersensitivity to the antifungal drugs amphotericin B, fluconazole, and cinnamycin. However, there was no difference in growth, capsule size, or melanin production between the wild type and the apt1 mutant strains at either 30°C or 37°C. Despite the absence of an influence on these major virulence factors, Apt1 was required for survival during interactions with macrophages, and apt1 mutants exhibited attenuated virulence in a mouse inhalation model of cryptococcosis. Therefore, Apt1 contributes to virulence and the stress response in C. neoformans through apparent functions in membrane fusion and trafficking that do not influence the deposition of major virulence factors, such as capsule and melanin, outside the cell.

scholarly journals Phenotypic plasticity in the productions of virulence factors within and among serotypes in the Cryptococcus neoformans species complex

2021 ◽  
Author(s):  
Yajur Iyengar ◽  
J. P. Xu
Keyword(s):  
Phenotypic Plasticity ◽  
Cryptococcus Neoformans ◽  
Virulence Factors ◽  
Species Complex ◽  
Nitrosative Stress ◽  
Capsular Polysaccharide ◽  
Melanin Production ◽  
Oxidative And Nitrosative Stress ◽  
Polysaccharide Production ◽  
Fungal Meningitis

Abstract The Cryptococcus neoformans species complex (CNSC) is a common opportunistic human fungal pathogen and the most frequent cause of fungal meningitis. There are three major serotypes in CNSC: A, D, and their hybrids AD, and they have different geographic distributions and medical significance. Melanin pigment and a polysaccharide capsule are the two major virulence factors in CNSC. However, the relationships between serotype and virulence factor production and how environmental factors might impact their relationships are not known. This study investigated the expressions of melanin and capsular polysaccharide in a genetically diverse group of CNSC strains and how their phenotypic expressions were influenced by oxidative and nitrosative stress levels. We found significant differences in melanin and capsular polysaccharide productions among serotypes and across stress conditions. Under oxidative stress, the laboratory hybrids exhibited the highest phenotypic plasticity for melanin production while serotype A showed the highest for capsular polysaccharide production. In contrast, serotype D exhibited the highest phenotypic plasticity for capsular polysaccharide production and clinical serotype AD the highest phenotypic plasticity for melanin production under nitrosative stress. These results demonstrated that different serotypes have different environmental condition-specific mechanisms to modulate the expression of virulence factors.

scholarly journals Cryptococcus neoformans Phosphoinositide-Dependent Kinase 1 (PDK1) Ortholog Is Required for Stress Tolerance and Survival in Murine Phagocytes

2012 ◽  
Vol 12 (1) ◽  
pp. 12-22 ◽  
Author(s):  
Yeissa Chabrier-Roselló ◽  
Kimberly J. Gerik ◽  
Kristy Koselny ◽  
Louis DiDone ◽  
Jennifer K. Lodge ◽  
...  
Keyword(s):  
Cell Wall ◽  
Stress Tolerance ◽  
Cryptococcus Neoformans ◽  
Nitrosative Stress ◽  
Galleria Mellonella ◽  
Mapk Pathway ◽  
Mitogen Activated Protein Kinase ◽  
Oxidative And Nitrosative Stress ◽  
Independent Manner ◽  
Content Type

ABSTRACTCryptococcus neoformansPKH2-01andPKH2-02are orthologous to mammalian PDK1 kinase genes. Although orthologs of these kinases have been extensively studied inS. cerevisiae, little is known about their function in pathogenic fungi. In this study, we show thatPKH2-02but notPKH2-01is required forC. neoformansto tolerate cell wall, oxidative, nitrosative, and antifungal drug stress. Deletion ofPKH2-02leads to decreased basal levels of Pkc1 activity and, consequently, reduced activation of the cell wall integrity mitogen-activated protein kinase (MAPK) pathway in response to cell wall, oxidative, and nitrosative stress.PKH2-02function also is required for tolerance of fluconazole and amphotericin B, two important drugs for the treatment of cryptococcosis. Furthermore, OSU-03012, an inhibitor of human PDK1, is synergistic and fungicidal in combination with fluconazole. Using aGalleria mellonellamodel of low-temperature cryptococcosis, we found thatPKH2-02is also required for virulence in a temperature-independent manner. Consistent with the hypersensitivity of thepkh2-02Δ mutant to oxidative and nitrosative stress, this mutant shows decreased survival in murine phagocytes compared to that of wild-type (WT) cells. In addition, we show that deletion ofPKH2-02affects the interaction betweenC. neoformansand phagocytes by decreasing its ability to suppress production of tumor necrosis factor alpha (TNF-α) and reactive oxygen species. Taken together, our studies demonstrate that Pkh2-02-mediated signaling inC. neoformansis crucial for stress tolerance, host-pathogen interactions, and both temperature-dependent and -independent virulence.

Altered plasma proteome during an early phase of peritonitis-induced sepsis

2009 ◽  
Vol 116 (9) ◽  
pp. 721-730 ◽  
Author(s):  
Visith Thongboonkerd ◽  
Wararat Chiangjong ◽  
Jan Mares ◽  
Jiri Moravec ◽  
Zdenek Tuma ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Nitrosative Stress ◽  
Inflammatory Responses ◽  
Sepsis Syndrome ◽  
Host Responses ◽  
Plasma Proteome ◽  
Oxidative And Nitrosative Stress ◽  
Two Dimensional Gel Electrophoresis ◽  
Human Sepsis ◽  
Altered Proteins

Sepsis is a systemic response to infection commonly found in critically ill patients and is associated with multi-organ failure and high mortality rate. Its pathophysiology and molecular mechanisms are complicated and remain poorly understood. In the present study, we performed a proteomics investigation to characterize early host responses to sepsis as determined by an altered plasma proteome in a porcine model of peritonitis-induced sepsis, which simulated several clinical characteristics of human sepsis syndrome. Haemodynamics, oxygen exchange, inflammatory responses, oxidative and nitrosative stress, and other laboratory parameters were closely monitored. Plasma samples were obtained from seven pigs before and 12 h after the induction of sepsis, and plasma proteins were resolved with two-dimensional gel electrophoresis (n=7 gels/group; before being compared with during sepsis). The resolved proteins were stained with the SYPRO Ruby fluorescence dye and subjected to quantitative and comparative analyses. From approx. 1500 protein spots visualized in each gel, levels of 36 protein spots were significantly altered in the plasma of animals with sepsis (sepsis/basal ratios or degrees of change ranged from 0.07 to 21.24). Q-TOF (quadrupole–time-of-flight) MS and MS/MS (tandem MS) identified 30 protein forms representing 22 unique proteins whose plasma levels were increased, whereas six forms of five unique proteins were significantly decreased during sepsis. The proteomic results could be related to the clinical features of this animal model, as most of these altered proteins have important roles in inflammatory responses and some of them play roles in oxidative and nitrosative stress. In conclusion, these findings may lead to a better understanding of the pathophysiology and molecular mechanisms underlying the sepsis syndrome.

scholarly journals Thioredoxin Reductase Is Essential for Viability in the Fungal Pathogen Cryptococcus neoformans

2005 ◽  
Vol 4 (2) ◽  
pp. 487-489 ◽  
Author(s):  
Tricia A. Missall ◽  
Jennifer K. Lodge
Keyword(s):  
Cryptococcus Neoformans ◽  
Fungal Pathogen ◽  
Nitrosative Stress ◽  
Pathogenic Fungus ◽  
Thioredoxin Reductase ◽  
Mammalian Host ◽  
Low Molecular Weight ◽  
Oxidative And Nitrosative Stress ◽  
Copper Transporter ◽  
Resistance Pathway

ABSTRACT Thioredoxin reductase (TRR1) is an important component of the thioredoxin oxidative stress resistance pathway. Here we show that it is induced during oxidative and nitrosative stress and is preferentially localized to the mitochondria in Cryptococcus neoformans. The C. neoformans TRR1 gene encodes the low-molecular-weight isoform of the thioredoxin reductase enzyme, which shares little homology with that of its mammalian host. By replacing the endogenous TRR1 promoter with an inducible copper transporter promoter, we showed that Trr1 appears to be essential for viability of this pathogenic fungus, making it a potential antifungal target.

scholarly journals Genome-Wide Transcriptional Profiling of the Cyclic AMP-Dependent Signaling Pathway during Morphogenic Transitions of Candida albicans

2007 ◽  
Vol 6 (12) ◽  
pp. 2376-2390 ◽  
Author(s):  
Yong-Sun Bahn ◽  
Matthew Molenda ◽  
Janet F. Staab ◽  
Courtney A. Lyman ◽  
Laura J. Gordon ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Cyclic Amp ◽  
Signaling Pathway ◽  
Virulence Factors ◽  
Molecular Mechanisms ◽  
Nitrosative Stress ◽  
Camp Signaling ◽  
Phenotypic Traits ◽  
Null Mutant ◽  
Camp Signaling Pathway

ABSTRACT Candida albicans is an opportunistic human fungal pathogen that causes systemic candidiasis as well as superficial mucosal candidiasis. In response to the host environment, C. albicans transitions between yeast and hyphal forms. In particular, hyphal growth is important in facilitating adhesion and invasion of host tissues, concomitant with the expression of various hypha-specific virulence factors. In previous work, we showed that the cyclic AMP (cAMP) signaling pathway plays a crucial role in morphogenic transitions and virulence of C. albicans by studying genes encoding adenylate cyclase-associated protein (CAP1) and high-affinity phosphodiesterase (PDE2) (Y. S. Bahn, J. Staab, and P. Sundstrom, Mol. Microbiol. 50:391-409, 2003; and Y. S. Bahn and P. Sundstrom, J. Bacteriol. 183:3211-3223, 2001). However, little is known about the downstream targets of the cAMP signaling pathway that are responsible for morphological transitions and the expression of virulence factors. Here, microarrays were probed with RNA from strains with hypoactive (cap1/cap1 null mutant), hyperactive (pde2/pde2 null mutant), and wild-type cAMP signaling pathways to provide insight into the molecular mechanisms of virulence that are regulated by cAMP and that are related to the morphogenesis of C. albicans. Genes controlling metabolic specialization, cell wall structure, ergosterol/lipid biosynthesis, and stress responses were modulated by cAMP during hypha formation. Phenotypic traits predicted to be regulated by cAMP from the profiling results correlated with the relative strengths of the mutants when tested for resistance to azoles and subjected to heat shock stress and oxidative/nitrosative stress. The results from this study provide important insights into the role of the cAMP signaling pathway not only in morphogenic transitions of C. albicans but also for adaptation to stress and for survival during host infections.

scholarly journals The Parasympathetic Nervous System in the Quest for Stroke Therapeutics

2011 ◽  
Vol 31 (5) ◽  
pp. 1187-1195 ◽  
Author(s):  
Cletus Cheyuo ◽  
Asha Jacob ◽  
Rongqian Wu ◽  
Mian Zhou ◽  
Gene F Coppa ◽  
...  
Keyword(s):  
Nervous System ◽  
Molecular Mechanisms ◽  
Nitrosative Stress ◽  
Parasympathetic Nervous System ◽  
Brain Disorders ◽  
Stroke Therapy ◽  
Successful Development ◽  
Oxidative And Nitrosative Stress ◽  
Anatomical Basis ◽  
Further Development

Stroke is a devastating neurovascular disease with limited therapeutic options. The pathogenesis of stroke involves complex interrelated molecular mechanisms including excitotoxicity, oxidative and nitrosative stress, cortical spreading depolarizations, inflammation, necrosis, and apoptosis. Successful development of stroke therapeutics depends on understanding these molecular mechanisms and how to counteract them to limit tissue damage during stroke. Activation of the parasympathetic nervous system (PNS) has been shown to antagonize a multiplicity of pathologic mechanisms. Elements of parasympathetic activation such as vagus nerve stimulation have already been used successfully in treating brain disorders such as epilepsy and depression. This review discusses the anatomical basis and molecular mechanisms involved in activation of the PNS, and assesses the strength of available evidence for the further development of this modality into a stroke therapy.

scholarly journals Distinct Stress Responses of Two Functional Laccases in Cryptococcus neoformans Are Revealed in the Absence of the Thiol-Specific Antioxidant Tsa1

2005 ◽  
Vol 4 (1) ◽  
pp. 202-208 ◽  
Author(s):  
Tricia A. Missall ◽  
Jason M. Moran ◽  
John A. Corbett ◽  
Jennifer K. Lodge
Keyword(s):  
Nitric Oxide ◽  
Cryptococcus Neoformans ◽  
Stress Responses ◽  
Fungal Pathogens ◽  
Nitrosative Stress ◽  
Fluorescent Protein ◽  
Resistance Mechanisms ◽  
Radical Scavenger ◽  
Homologous Gene ◽  
Oxidative And Nitrosative Stress

ABSTRACT Laccases are thought to be important to the virulence of many fungal pathogens by producing melanin, a presumed oxygen radical scavenger. A laccase in Cryptococcus neoformans has been shown to synthesize melanin and contributes to the virulence and the survival in macrophages of this fungal pathogen. One C. neoformans laccase gene, LAC1, previously called CNLAC1, has been extensively studied, and we describe a homologous gene, LAC2, that is found 8 kb away from LAC1 in the genome. In this study we report a role for both laccases, in addition to the thiol peroxidase, Tsa1, in oxidative and nitrosative stress resistance mechanisms of C. neoformans. With use of real-time PCR, similar changes in expression of the two laccase genes occur in response to oxidative and nitrosative stresses, but only the regulation of the LAC2 gene during stress is influenced by Tsa1. Both laccases contribute to melanin production using L-dopa as a substrate and are differentially localized in the cell based on green fluorescent protein fusions. A single deletion of either LAC1 or LAC2 alone had no effect on sensitivity to H2O2 or nitric oxide. However, deletion of either LAC1 or LAC2 in combination with a TSA1 deletion resulted in a slight peroxide sensitivity, and a lac2Δ tsa1Δ deletion strain was sensitive to nitric oxide stress. In addition, the deletion of both laccases reduces survival of C. neoformans in primary macrophages. Based on our expression and functional analysis, we propose a novel model for the interaction of these two systems, which are both important for virulence.

scholarly journals Antidepressant Like Effect of Sodium Orthovanadate in A Mouse Model of Chronic Unpredictable Mild Stress.

2021 ◽  
Author(s):  
Angel Joshi ◽  
Ansab Akhtar ◽  
Priyanka Saroj ◽  
Anurag Kuhad ◽  
Sangeeta Pilkhwal Sah
Keyword(s):  
Molecular Mechanisms ◽  
Nitrosative Stress ◽  
Tyrosine Phosphatase ◽  
Preference Test ◽  
Tail Suspension Test ◽  
Mild Stress ◽  
Chronic Unpredictable Mild Stress ◽  
Sodium Orthovanadate ◽  
Behavioral Tests ◽  
Oxidative And Nitrosative Stress

Abstract Depression is a psychiatric disorder characterized by low esteem, anhedonia, social deficit, and lack of interest. Decreased BDNF and impaired TrKB signaling be associated with depression. In our study, depressive-like behavior was induced in mice by chronic unpredictable mild stress (CUMS) model. Various behavioral tests like tail suspension test (TST), open field test (OFT), and sucrose preference test (SPT); biochemical analyses for corticosterone, reduced glutathione (GSH), lipid peroxidation (LPO), superoxide dismutase (SOD), nitric oxide (NO) and ELISA for BDNF were performed. Body weight was measured every week. Depressive-like behavior was associated with increased oxidative stress in the brain and subsequent reduction of BDNF. Further, sodium orthovanadate (SOV), a protein tyrosine phosphatase inhibitor was used as a test drug as it is reported to stimulate BDNF levels. Sodium orthovanadate (SOV-5 mg/kg, 10 mg/kg) and fluoxetine (10 mg/kg) was given to mice orally for 21 days before 30 minutes of stress induction. The behavioral tests reflected depressive-like behavior in CUMS, which was attenuated by both SOV and fluoxetine. SOV at 10 mg/kg has demonstrated significant results in our study by decreasing malondialdehyde levels (MDA/LPO), NO levels, and increasing GSH and SOD in both the cortex and hippocampus. Besides, ELISA revealed the elevation of BDNF levels in the treatment groups (SOV-5 mg/kg, 10 mg/kg, and FLX-10 mg/kg) as compared with the disease group (CUMS). Therefore, the treatment with SOV appeared to reverse both oxidative and nitrosative stress. Decreased serum corticosterone levels (SOV-5 mg/kg, 10 mg/kg); FLX (10 mg/kg) + SOV (5 mg/kg); FLX-10 mg/kg and per-se) and elevated BDNF level (SOV-5 mg/kg, 10 mg/kg and FLX-10 mg/kg) were associated with attenuation of depressive-like behavior. The findings of this preliminary study indicate that SOV has the potential to restore antidepressant-like effect or prevention of stress-induced anhedonia and so further molecular mechanisms will be warranted for clinical translation.

scholarly journals DIABETIC NEUROPATHY: MOLECULAR MECHANISMS OF DEVELOPMENT AND POSSIBILITIES FOR PATHOGENETIC THERAPY

2019 ◽  
pp. 8-12
Author(s):  
N.V. Hudiakova ◽  
N.V. Ivanov ◽  
I. Yu. Pchelin ◽  
A.N. Shishkin ◽  
N.V. Vorokhobina ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
Diabetic Neuropathy ◽  
Molecular Mechanisms ◽  
Nitrosative Stress ◽  
Treatment Options ◽  
Neurological Complications ◽  
Diabetic Patients ◽  
Oxidative And Nitrosative Stress ◽  
Pathogenetic Therapy ◽  
Mechanisms Of Development

The present review summarizes the results of global studies and assesses contribution of hyperglycemia towards formation of neurologic complications in diabetic patients. Hyperglycemia is believed to play a leading role in the formation of neurological complications in diabetes mellitus. However, the achievement of normalization of glycemia level does not ensure the cessation of their development and progression, which indicates a lack of knowledge about the pathogenetic relationships in diabetic neuropathy. Limited understanding of these issues entails the absence of treatment options that effectively affect the course of this complication. Based on the analysis of experimental and clinical studies of recent years, data on the molecular-biological relationships of hyperglycemia with the formation of neurological complications in diabetes mellitus are summarized. The influence of the oxidative and nitrosative stress, advanced glycation end products, the activation of the polyol and hexosamine pathways on the state of the nerve fiber is analyzed. The data on molecular mechanisms of development of diabetic neuropathy are contradictory. On the basis of recent experimental and clinical data we review possibilities for pathogenetic therapy. The problem of oppositely directed effects of treatment is discussed. Clinical rationale is given for declared direction of further studies.

scholarly journals Attenuation of Oxidative Stress in HEK 293 Cells by the TCM Constituents Schisanhenol, Baicalein, Resveratrol or Crocetin and Two Defined Mixtures

2015 ◽  
Vol 18 (4) ◽  
pp. 661 ◽  
Author(s):  
John Richard Bend ◽  
Xue Yan (Iris) Xue Yan Xia ◽  
Daofeng Chen ◽  
Abudi Awaysheh ◽  
Andrea Lo ◽  
...  
Keyword(s):  
Real Time ◽  
Molecular Mechanisms ◽  
Nitrosative Stress ◽  
Fluorescent Protein ◽  
Antioxidant Properties ◽  
Oxidative And Nitrosative Stress ◽  
Hek 293 ◽  
Hek 293 Cells ◽  
293 Cells

PURPOSE:  Our working hypothesis is that single bioactive phytochemicals with antioxidant properties that are important constituents of Traditional Chinese Medicine (TCM) and their defined mixtures have potential as chemoprotective agents for chronic conditions characterized by oxidative and nitrosative stress, including Alzheimer’s. Here we evaluate the ability of baicalein, crocetin, trans-resveratrol or schisanhenol and two defined mixtures of these TCM phytochemicals to attenuate the toxicity resulting from exposure to cell permeant t-butyl hydroperoxide (tBPH) in wild-type and bioengineered (to express choline acetyltransferase) HEK 293 cells. METHODS: Endpoints of tBHP-initiated oxidative and nitrosative stress in both types of HEK 293 cells and its attenuation by TCM constituents and mixtures included cytotoxicity (LDH release); depletion of intracellular glutathione (GSH); formation of S-glutathionylated proteins; oxidative changes to the disulfide proteome; and real-time changes in intracellular redox status. RESULTS: At low µM concentrations, each of the TCM constituents and mixtures effectively attenuated intracellular toxicity due to exposure of HEK 293 cells to 50 or 250 µM tBHP for 30 min to 3 h. Confocal microscopy of HEK 293 cells transfected with mutated green fluorescent protein (roGFP2) showed effective attenuation of tBHP oxidation by baicalein in real time. Three redox-regulated proteins prominent in the disulfide proteome of HEK 293 cells were identified by MALDI-TOF mass spectrometry. CONCLUSIONS: We conclude that single TCM chemicals and their simple mixtures have potential for use in adjunct chemoprotective therapy. Advantages of mixtures compared to single TCM constituents include the ability to combine compounds with varying molecular mechanisms of cytoprotection for enhanced biological activity; and to combine chemicals with complementary pharmacokinetic properties to increase half-life and prolong activity in vivo. This article is open to POST-PUBLICATION REVIEW. Registered readers (see “For Readers”) may comment by clicking on ABSTRACT on the issue’s contents page.

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