Host-Derived Reactive Oxygen Species Trigger Activation of the Candida albicans Transcription Regulator Rtg1/3

The signals that denote mammalian host environments and dictate the activation of signaling pathways in human-associated microorganisms are often unknown. The transcription regulator Rtg1/3 in the human fungal pathogen Candida albicans is a crucial determinant of host colonization and pathogenicity. Rtg1/3\u27s activity is controlled, in part, by shuttling the regulator between the cytoplasm and nucleus of the fungus. The host signal(s) that Rtg1/3 respond(s) to, however, have remained unclear. Here we report that neutrophil-derived reactive oxygen species (ROS) direct the subcellular localization of this C. albicans transcription regulator. Upon engulfment of Candida cells by human or mouse neutrophils, the regulator shuttles to the fungal nucleus. Using genetic and chemical approaches to disrupt the neutrophils\u27 oxidative burst, we establish that the oxidants produced by the NOX2 complex-but not the oxidants generated by myeloperoxidase-trigger Rtg1/3\u27s migration to the nucleus. Furthermore, screening a collection of C. albicans kinase deletion mutants, we implicate the MKC1 signaling pathway in the ROS-dependent regulation of Rtg1/3 in this fungus. Finally, we show that Rtg1/3 contributes to C. albicans virulence in the nematode Caenorhabditis elegans in an ROS-dependent manner as the rtg1 and rtg3 mutants display virulence defects in wild-type but not in ROS deficient worms. Our findings establish NOX2-derived ROS as a key signal that directs the activity of the pleiotropic fungal regulator Rtg1/3

Access-Site Complications in Transfemoral Neuroendovascular Procedures: A Systematic Review of Incidence Rates and Management Strategies

BACKGROUND: The femoral artery is the most common access route for cerebral angiography and neurointerventional procedures. Complications of the transfemoral approach include groin hemorrhages and hematomas, retroperitoneal hematomas, pseudoaneurysms, arteriovenous fistulas, peripheral artery occlusions, femoral nerve injuries, and access-site infections. Incidence rates vary among different randomized and nonrandomized trials, and the literature lacks a comprehensive review of this subject. OBJECTIVE: To gather data from 16 randomized clinical trials (RCT) and 17 nonrandomized cohort studies regarding femoral access-site complications for a review paper. We also briefly discuss management strategies for these complications based on the most recent literature. METHODS: A PubMed indexed search for all neuroendovascular clinical trials, retrospective studies, and prospective studies that reported femoral artery access-site complications in neurointerventional procedures. RESULTS: The overall access-site complication rate in RCTs is 5.13%, while in in non-RCTs, the rate is 2.78%. The most common complication in both groups is groin hematoma followed by access-site hemorrhage and femoral pseudoaneurysm. On the other hand, wound infection was the least common complication. CONCLUSION: The transfemoral approach in neuroendovascular procedures holds risk for several complications. This review will allow further studies to compare access-site complications between the transfemoral approach and other alternative access sites, mainly the transradial approach, which is gaining a lot of interest nowadays

Letter: Thrombotic Neurovascular Disease in COVID-19 Patients.

Although the respiratory system is the primary target of the coronavirus, studies have demonstrated a strong tropism to the central nervous system (CNS).1,2 The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infects cells by binding to the angiotensin-converting enzyme 2 (ACE2) receptor. This receptor is also found in the CNS and plays a crucial role in autoregulating cerebral perfusion pressure.3,4 Additionally, epidemiological data demonstrated increased mortality due to cardiovascular and cerebrovascular diseases during flu pandemics due to a hypercoagulable state.5,6 The triad of neuroinvasion of SARS-CoV-2, induction of hypercoagulable state,5-9 and the inhibition of ACE2 blocking the formation of Angiotensin (1-7) serve as the pathophysiology for neurovascular insults.3,4 We present a case series of coronavirus disease 2019 (COVID-19) patients from 2 health systems developing cerebrovascular insult

Transradial approach for diagnostic cerebral angiograms in the elderly: a comparative observational study

Introduction: The transradial approach (TRA) reduces mortality, morbidity, access site complications, hospital cost, and length of stay while maximizing patient satisfaction. We aimed to assess the technical success and safety of TRA for elderly patients (aged ≥75 years). Methods: A retrospective chart review and comparative analysis was performed for elderly patients undergoing a diagnostic cerebral angiogram performed via TRA versus transfemoral approach (TFA). Also, a second comparative analysis was performed among the TRA cohort between elderly patients and their younger counterparts. Results: Comparative analysis in the elderly (TRA vs TFA) showed no significant differences for contrast dose per vessel, fluoroscopy time per vessel, procedure duration, conversion rate, and access site complications. Radiation exposure per vessel was significantly lower in the elderly TRA group. The second comparison (TRA in elderly vs TRA in the young) showed no significant differences for contrast dose per vessel, radiation exposure per vessel, procedure duration, access site complication, and conversation rate. A trend for prolonged fluoroscopy time per vessel was observed in the elderly TRA group. Conclusion/Discussion: TRA is a technically feasible and safe option for diagnostic neurointerventional procedures in the elderly. Our small elderly cohort was not powered enough to show a significant difference in terms of access site complications between TRA and TFA

NOX2 activity in neutrophils in necessary for Rtg1/3 migration to the <i>Candida</i> nucleus.

(A) DPI-ROS dose-response curve. Wild-type C57BL/6J mouse neutrophils were isolated from femurs and incubated in 96-well plates with various DPI concentrations. Percentage of ROS production was calculated relative to controls that did not contain DPI. Each DPI concentration was evaluated in triplicates. Plotted are the means ± S.D. (B and C) Subcellular localization of the GFP-Rtg3 reporter in Candida cells upon uptake by wild-type neutrophils treated with either DPI (B) or GSK2795039 [30 μM] (C). Arrowheads point to phagocytosed fungal cells displaying reporter in the Candida cytoplasm. Asterisk indicates reporter accumulation in the nucleus. (D) Quantification of phagocytosed C. albicans cells displaying accumulation of the reporter in the fungal nucleus. A minimum of 100 Candida cells were scored per experiment per condition. At least three independent experiments were performed. Plotted are the means ± SD. Statistical analysis was conducted using Student’s t-test (two-tailed, two-sample unequal variance).</p

The kinases Mkc1 and Hog1 are necessary for the ROS-dependent nuclear translocation of Rtg1/3.

(A) C. albicans kinase deletion mutant strains (from Table 1) expressing GFP- or YFP-Rtg3 reporter were incubated in medium containing hydrogen peroxide. Shown is the quantification of Candida cells displaying accumulation of the reporter in the nucleus 15 min after addition of hydrogen peroxide. A minimum of 200 Candida cells were scored per strain per experiment. At least three independent experiments were performed. (B) Subcellular localization of the Rtg3 reporter in C. albicans reference strain, mkc1, hog1, and complemented cells upon uptake by wild-type murine neutrophils. A minimum of 100 Candida cells were scored per strain per experiment. At least three independent experiments were carried out. Plotted are the means ± SD. Statistical analysis was conducted using Student’s t-test (two-tailed, two-sample unequal variance) with Bonferroni correction.</p

<i>C</i>. <i>albicans</i> kinases exhibiting susceptibility/resistance to H₂O₂ and menadione.

C. albicans kinases exhibiting susceptibility/resistance to H2O2 and menadione.</p

Oxidative stress screening of <i>C</i>. <i>albicans</i> kinase deletion collection. (Excel file).

Oxidative stress screening of C. albicans kinase deletion collection. (Excel file).</p

H₂O₂ induces Rtg1/3 nuclear localization in <i>C</i>. <i>albicans</i>.

C. albicans expressing the reporter GFP-Rtg3 was incubated in medium without or with hydrogen peroxide [10 mM]. Shown in (A) is the quantification of C. albicans cells displaying accumulation of the reporter in the nucleus 15 or 60 min after addition of hydrogen peroxide. A minimum of 200 Candida cells were scored per time point per experiment. Three independent experiments were performed. Plotted are the means ± SD. Statistical analysis was performed using Student’s t-test (two-tailed, two-sample unequal variance). (B) Representative images. Arrowheads indicate cells with nuclear accumulation of the reporter.</p

Complementation of the <i>rtg1</i> and <i>rtg3</i> virulence phenotype in nematodes.

Wild-type C. elegans nematodes were infected with the C. albicans reference strain, the rtg1 and rtg3 single deletions, and their respective gene add-backs. The data are representative of experiments repeated three times with an N = 60–90 worms for each condition. Statistical analysis was performed using the logrank test (Kaplan-Meier survival curve). (TIFF)</p