Redox Regulation of Protein Function via Cysteine S-Nitrosylation and Its Relevance to Neurodegenerative Diseases

Debilitating neurodegenerative diseases, such as Alzheimer's disease (AD) and Parkinson's disease (PD), can be attributed to neuronal cell damage in specific brain regions. An important hallmark of these diseases is increased oxidative and nitrosative stress that occurs via overproduction of highly reactive free radicals known as reactive oxygen species (ROS) and reactive nitrogen species (RNS). These molecules are normally removed by cellular antioxidant systems. Under physiological conditions, ROS/RNS are present at low levels, mediating several neurotrophic and neuroprotective signaling pathways. In contrast, under pathological conditions, there is a pronounced increase in ROS/RNS generation, impairing normal neurological function. Nitric oxide (NO) is one such molecule that functions as a signaling agent under physiological conditions but causes nitrosative stress under pathological conditions due to its enhanced production. As first reported by our group and colleagues, the toxic effects of NO can be in part attributed to thiol S-nitrosylation, a posttranslational modification of cysteine residues on specific proteins. Here, we review several reports appearing over the past decade showing that S-nitrosylation of an increasing number of proteins compromises important cellular functions, including mitochondrial dynamics, endoplasmic reticulum (ER) protein folding, and signal transduction, thereby promoting synaptic damage, cell death, and neurodegeneration

Cleaning Methods for Ultrasound Probes

Objective: To determine the effectiveness of three different methods of ultrasound probe cleaning for the prevention of nosocomial infections. Study Design: Experimental study. Place and Duration of Study: Radiology Department, the Aga Khan University Hospital, Karachi and Microbiology Department, JPMC, Karachi, from December 2006 to April 2007. Patients and Methods: A total of 75 culture swabs from ultrasound probes used for sonographic examinations of different body parts of patients were included in the study. Probes were prospectively randomized into three equal groups with 25 probes in each group. Culture was sent before and after using three different techniques of cleaning ultrasound probe, which included sterilized paper towel, 0.9% saline and swipe over with standard bath soap applied on group A (n=25), group B (n=25) and group C (n=25) respectively. Number of Colony Forming Unit (CFU) of bacteria were calculated on standard agar plate to find out the effectiveness of cleaning methods in reducing bacterial count from the ultrasound probe after the procedures. All samples were tested in single microbiology lab by using same bacterial growth media provided by same manufacturer. Kruskall Wallis, Jonchkheere-Terpstra and Wilcoxon sign rank tests were applied to find out statistical significance. Results: There was a significant reduction in bacterial count after applying either of all three cleaning methods for ultrasound probe compared to count on the probes before cleaning (p Conclusion: Cleaning ultrasound probe after performing each procedure is a cost-effective practice with potential of reducing nosocomial infections. Soap cleaning technique is the most effective method for reducing bacterial count acquired due to patients’ body contact with the ultrasound probes

Oligomeric Hsp33 with enhanced chaperone activity

Hsp33, an Escherichia coli cytosolic chaperone, is inactive under normal conditions but becomes active upon oxidative stress. It was previously shown to dimerize upon activation in a concentration- and temperature-dependent manner. This dimer was thought to bind to aggregation-prone target proteins, preventing their aggregation. In the present study, we report small angle x-ray scattering (SAXS), steady state and time-resolved fluorescence, gel filtration, and glutaraldehyde cross-linking analysis of full-length Hsp33. Our circular dichroism and fluorescence results show that there are significant structural changes in oxidized Hsp33 at different temperatures. SAXS, gel filtration, and glutaraldehyde cross-linking results indicate, in addition to the dimers, the presence of oligomeric species. Oxidation in the presence of physiological salt concentration leads to significant increases in the oligomer population. Our results further show that under conditions that mimic the crowded milieu of the cytosol, oxidized Hsp33 exists predominantly as an oligomeric species. Interestingly, chaperone activity studies show that the oligomeric species is much more efficient compared with the dimers in preventing aggregation of target proteins. Taken together, these results indicate that in the cell, Hsp33 undergoes conformational and quaternary structural changes leading to the formation of oligomeric species in response to oxidative stress. Oligomeric Hsp33 thus might be physiologically relevant under oxidative stress

Elective cancer surgery in COVID-19-free surgical pathways during the SARS-CoV-2 pandemic: An international, multicenter, comparative cohort study

PURPOSE As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19–free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19–free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19–free surgical pathways. Patients who underwent surgery within COVID-19–free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19–free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score–matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19–free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION Within available resources, dedicated COVID-19–free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks

Elective Cancer Surgery in COVID-19-Free Surgical Pathways During the SARS-CoV-2 Pandemic: An International, Multicenter, Comparative Cohort Study.

PURPOSE: As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19-free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS: This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19-free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS: Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19-free surgical pathways. Patients who underwent surgery within COVID-19-free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19-free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score-matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19-free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION: Within available resources, dedicated COVID-19-free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks

Oligomeric Hsp33 with Enhanced Chaperone Activity

Hsp33, an Escherichia coli cytosolic chaperone, is inactive under normal conditions but becomes active upon oxidative stress. It was previously shown to dimerize upon activation in a concentration- and temperature-dependent manner. This dimer was thought to bind to aggregation-prone target proteins, preventing their aggregation. In the present study, we report small angle x-ray scattering (SAXS), steady state and time-resolved fluorescence, gel filtration, and glutaraldehyde cross-linking analysis of full-length Hsp33. Our circular dichroism and fluorescence results show that there are significant structural changes in oxidized Hsp33 at different temperatures. SAXS, gel filtration, and glutaraldehyde cross-linking results indicate, in addition to the dimers, the presence of oligomeric species. Oxidation in the presence of physiological salt concentration leads to significant increases in the oligomer population. Our results further show that under conditions that mimic the crowded milieu of the cytosol, oxidized Hsp33 exists predominantly as an oligomeric species. Interestingly, chaperone activity studies show that the oligomeric species is much more efficient compared with the dimers in preventing aggregation of target proteins. Taken together, these results indicate that in the cell, Hsp33 undergoes conformational and quaternary structural changes leading to the formation of oligomeric species in response to oxidative stress. Oligomeric Hsp33 thus might be physiologically relevant under oxidative stress

Anti-inflammatory activity of roots of Cichorium intybus due to its inhibitory effect on various cytokines and antioxidant activity

Background: Cichorium intybus L. commonly known as chicory is one of the important medicinal plants commonly used in Ayurvedic system of medicine. It is commonly used for the treatment of diseases involving a khapa and pitta doshas. Traditionally, C. intybus is used for the treatment of inflammatory conditions, but there are only few in vitro studies reporting the anti-inflammatory activity of roots of chicory. Objective: Evaluation of anti-inflammatory activity of roots of chicory and mechanisms involved in it using in vivo models of inflammation. Materials and Methods: Albino Wistar rats of either sex weighing 150-200 g were used. Ethanolic and aqueous extracts of roots of chicory were prepared with the help of Soxhlet′s apparatus. The anti-inflammatory activity was studied using carrageenan-induced paw edema method and cotton pellet granuloma method. Levels of cytokines such as tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), and IL-1 and activity of antioxidant enzymes such as catalase (CAT) and glutathione peroxidase (GPx) were estimated. Results: Chicory roots demonstrated significant dose-dependent decrease in paw edema in carrageenan-induced paw edema method. Chicory roots diminished the serum TNF-α, IL-6, and IL-1 levels. They also significantly attenuated the malonylaldehyde levels and increased the activities of CAT and GPx in paw tissue. Similarly, chicory roots demonstrated a significant decrease in granuloma formation in cotton pellet induced granuloma method. Conclusion: Chicory roots possess anti-inflammatory activity, and this might be due to the inhibition of various cytokines, antioxidant effects, and their free radical scavenging activity

α-Synuclein Oligomers Induce Glutamate Release from Astrocytes and Excessive Extrasynaptic NMDAR Activity in Neurons, Thus Contributing to Synapse Loss

Synaptic and neuronal loss are major neuropathological characteristics of Parkinson's disease. Misfolded protein aggregates in the form of Lewy bodies, comprised mainly of α-synuclein (αSyn), are associated with disease progression, and have also been linked to other neurodegenerative diseases, including Lewy body dementia, Alzheimer's disease, and frontotemporal dementia. However, the effects of αSyn and its mechanism of synaptic damage remain incompletely understood. Here, we show that αSyn oligomers induce Ca2+-dependent release of glutamate from astrocytes obtained from male and female mice, and that mice overexpressing αSyn manifest increased tonic release of glutamate in vivo In turn, this extracellular glutamate activates glutamate receptors, including extrasynaptic NMDARs (eNMDARs), on neurons both in culture and in hippocampal slices of αSyn-overexpressing mice. Additionally, in patch-clamp recording from outside-out patches, we found that oligomerized αSyn can directly activate eNMDARs. In organotypic slices, oligomeric αSyn induces eNMDAR-mediated synaptic loss, which can be reversed by the drug NitroSynapsin. When we expose human induced pluripotent stem cell-derived cerebrocortical neurons to αSyn, we find similar effects. Importantly, the improved NMDAR antagonist NitroSynapsin, which selectively inhibits extrasynaptic over physiological synaptic NMDAR activity, protects synapses from oligomeric αSyn-induced damage in our model systems, thus meriting further study for its therapeutic potential.SIGNIFICANCE STATEMENT Loss of synaptic function and ensuing neuronal loss are associated with disease progression in Parkinson's disease (PD), Lewy body dementia (LBD), and other neurodegenerative diseases. However, the mechanism of synaptic damage remains incompletely understood. α-Synuclein (αSyn) misfolds in PD/LBD, forming Lewy bodies and contributing to disease pathogenesis. Here, we found that misfolded/oligomeric αSyn releases excessive astrocytic glutamate, in turn activating neuronal extrasynaptic NMDA receptors (eNMDARs), thereby contributing to synaptic damage. Additionally, αSyn oligomers directly activate eNMDARs, further contributing to damage. While the FDA-approved drug memantine has been reported to offer some benefit in PD/LBD (Hershey and Coleman-Jackson, 2019), we find that the improved eNMDAR antagonist NitroSynapsin ameliorates αSyn-induced synaptic spine loss, providing potential disease-modifying intervention in PD/LBD