Novel strategies for the prevention of cisplatin-induced ototoxicity

Cisplatin is a commonly used chemotherapeutic agent. Unfortunately, serious side effects limit its clinical use such as ototoxicity, which presents as bilateral and progressive sensorineural hearing loss. Regrettably, there is currently no treatment for cisplatin-induced ototoxicity. The pathophysiology remains unclear, however, it is believed that inflammation and oxidative stress are the main mechanisms leading to cell death. In the present thesis, various aspects of cisplatin-induced ototoxicity and potential treatment strategies are evaluated. We begin with a review of the literature in what concerns the entrance and egress of cisplatin from cochlear cells. Cisplatin has a predilection for the inner ear tissues and the reason for such an occurrence is unknown. We describe the receptors that may play a role in cisplatin-induced ototoxicity and that are present in cochlear cells. Understanding the circulating pathways of cisplatin within the inner ear can provide some insight into the mechanisms of cisplatin-induced ototoxicity. Once inside the cell, cisplatin can elicit an inflammatory response. For this reason, we decided to evaluate the potential of dexamethasone as a protective agent against cisplatin's toxic effects in vivo. It was observed that a central regulator of inflammation was decreased as a result of the therapy; however, the hearing was not preserved. An anti-inflammatory did not provide sufficient protection to preserve hearing following the cisplatin treatment. ROS have also been implicated in cisplatin-induced cytotoxicity. It appears that cisplatin can lead to an increased expression of ROS that can overwhelm the natural antioxidant response of the cochlea. Thus, the potential of an exogenous antioxidant as a protective agent was evaluated in vivo. Erdosteine, a derivative of methionine, provided protection against cisplatin-induced ototoxicity at high frequencies of hearing as well as partially prevented OHC loss. Because these two compounds provided only but partial benefits, we decided to evaluate a more specific and targeted approach, gene therapy for cisplatin-induced ototoxicity. We performed a systematic review of the literature in order to evaluate the potential of genetic manipulation in experimental animal and in vitro studies. Interestingly, a variety of genes have been evaluated as potential targets for inhibiting cisplatin-induced cytotoxicity such as apoptotic suppressors, copper transporters, regulators of the antioxidant response and neural growth factors. Consequences of genetic manipulation in the inner ear tissues remain to be assessed in order for gene therapy to become a conventional therapeutic option. Because the cochlea is embedded in bone, is fluid filled and contains various cell types, it has been a challenge to detect the expression of manipulated genes in a particular cell type of interest. While homogenization of a whole cochlea and posterior RNA extraction can provide us with the general expression levels of a certain gene, it does not allow for the determination in a cellular subpopulation of the cochlea. One possibility is the use of laser capture microdissection of cells of interest from a histological section. With this approach, the cells of interest are obtained and RNA can then be extracted and gene expression levels determined. However, the process of obtaining histological sections from cochlear samples requires fixation and decalcification steps which are known to cause RNA degradation. Hence, we decided to evaluate combinations of fixatives and decalcifying agents in order to determine which protocol would yield the greatest quantity of RNA from the cochlea and also preserve the morphology. The resulting protocol with methacarn fixation and decalcification in Morse's solution can therefore be used in future studies that aim to determine genetic expression, a regularly performed experiment, in a specific cellular subtype of interest in the cochlea.Le cisplatine est un agent chimiothérapeutique couramment utilisé. Malheureusement, de graves effets secondaires limitent son utilisation clinique telle que l'ototoxicité qui se présente comme une perte auditive neurosensorielle bilatérale et progressive. Il n'existe actuellement aucun traitement pour l'ototoxicité du cisplatine. La physiopathologie reste obscure, cependant, on croit que l'inflammation et le stress oxydant sont les principaux mécanismes conduisant à la mort des cellules. Dans cette thèse, différents aspects de l'ototoxicité du cisplatine et des stratégies thérapeutiques potentielles sont évaluées. Nous commençons par une revue générale de la littérature en ce qui concerne l'entrée et la sortie du cisplatine des cellules cochléaires. Nous décrivons les récepteurs qui peuvent jouer un rôle dans l'ototoxicité du cisplatine et qui sont présents dans les cellules cochléaires. Une fois à l'intérieur de la cellule, le cisplatine peut provoquer une réaction inflammatoire. Pour cette raison, nous avons décidé d'évaluer le potentiel de la dexaméthasone comme agent protecteur contre les effets toxiques du cisplatine in vivo. Il a été observé qu'un régulateur important de l'inflammation a été réduit, cependant, l'audition n'a pas été préservée. Un anti-inflammatoire n'a pas fourni une protection suffisante pour préserver l'audition après le traitement avec le cisplatine. Les dérivés réactifs de l'oxygène ont également été impliqués dans la cytotoxicité induite par le cisplatine. Le cisplatine peut conduire à une expression accrue des dérivés réactifs de l'oxygène et peut compromettre la réponse antioxydante naturelle de la cochlée. Ainsi, le potentiel d'un antioxydant exogène comme agent de protection a été évalué in vivo. Erdosteine, un dérivé de la méthionine, a diminué la perte d'audition au niveau des hautes fréquences ainsi qu'empêché partiellement la perte de cellules ciliées externes. Étant donné que ces deux produits ont générés uniquement une protection partielle, nous avons décidé d'évaluer une approche plus spécifique et ciblée, la thérapie génique. Puisque la thérapie génique est en phase expérimentale et n'est pas encore disponible en tant que modalité de traitement traditionnel, nous avons effectué une revue systématique de la littérature afin d'évaluer le potentiel de la manipulation génétique chez les animaux de laboratoire et les expériences in vitro. Fait intéressant, plusieurs gènes ont été évalués comme des cibles potentielles pour inhiber la cytotoxicité induite par le cisplatine. Les conséquences des manipulations génétiques doivent encore être évaluées dans le but que la thérapie génique puisse devenir une option thérapeutique conventionnelle. Parce que la cochlée est ancrée dans l'os, est remplie de fluide et contient divers types de cellules, il a été difficile de détecter l'expression des gènes manipulés dans un type cellulaire d'intérêt. Alors que l'homogénéisation de la cochlée entière et l'extraction subséquente de l'ARN peut nous fournir une idée générale des niveaux d'expression d'un gène, ceci ne permet pas la détermination dans une sous-population cellulaire de la cochlée. Une possibilité est l'utilisation de la microdissection par capture laser des cellules d'intérêt à partir d'une coupe histologique. Avec cette approche, les cellules d'intérêt sont obtenues et l'ARN peut ensuite être extrait. Cependant, le processus d'obtention de coupes histologiques à partir d'un échantillon cochléaire nécessite des étapes de fixation et de décalcification qui sont connues pour causer une dégradation de l'ARN. Donc, nous avons décidé d'évaluer des combinaisons de fixateurs et réactifs de décalcification afin de déterminer quel protocole engendrerait la quantité d'ARN la plus élevée et qui, également, préserverait la morphologie. Le protocole établi peut donc être utilisé dans de futures études visant à déterminer l'expression génétique dans un sous-type cellulaire spécifique d'intérêt dans la cochlée

Vestibular and Oculomotor Findings in Vestibular Migraine Patients

Background: Vestibular migraine (VM) is the most frequent etiology of recurrent spontaneous episodic vertigo. Vestibular and oculomotor abnormalities have been described in VM; however, the diagnosis is currently based on symptoms. The objective of this study was to determine the most frequent abnormalities in videonystagmography (VNG), caloric testing (Cal) and video head impulse test (vHIT) in patients with VM. Methods: A retrospective cohort study was conducted, including all VM and probable VM patients seen from January 2021 to July 2022. Demographics, auditory symptoms and results via VNG, Cal and vHIT were evaluated. VNG results were compared with a control group. Results: Sixty patients, 81.7% with VM and 18.3% with probable vestibular migraine, were included. VNG revealed the following abnormalities: 21.7% spontaneous nystagmus; 33.3% positional nystagmus, mostly central; 26.7% optokinetic nystagmus; 56.7% smooth pursuit abnormalities and 70% saccade test abnormalities, mostly velocity and latency. An abnormal unilateral caloric response was seen in 22.9%, while vHIT revealed a low gain in at least one canal in 21.7%, and saccades were seen in at least one canal with normal gains in 18.3%. Concordant results between Cal and lateral vHIT were seen in 77.1% of cases. Conclusions: Although VM is a clinical diagnosis, vestibular and oculomotor abnormalities are commonly seen. The most frequent oculomotor findings were an abnormal saccade test, abnormal smooth pursuit and central positional nystagmus

Effects of pre-operative isolation on postoperative pulmonary complications after elective surgery: an international prospective cohort study an international prospective cohort study

We aimed to determine the impact of pre-operative isolation on postoperative pulmonary complications after elective surgery during the global SARS-CoV-2 pandemic. We performed an international prospective cohort study including patients undergoing elective surgery in October 2020. Isolation was defined as the period before surgery during which patients did not leave their house or receive visitors from outside their household. The primary outcome was postoperative pulmonary complications, adjusted in multivariable models for measured confounders. Pre-defined sub-group analyses were performed for the primary outcome. A total of 96,454 patients from 114 countries were included and overall, 26,948 (27.9%) patients isolated before surgery. Postoperative pulmonary complications were recorded in 1947 (2.0%) patients of which 227 (11.7%) were associated with SARS-CoV-2 infection. Patients who isolated pre-operatively were older, had more respiratory comorbidities and were more commonly from areas of high SARS-CoV-2 incidence and high-income countries. Although the overall rates of postoperative pulmonary complications were similar in those that isolated and those that did not (2.1% vs 2.0%, respectively), isolation was associated with higher rates of postoperative pulmonary complications after adjustment (adjusted OR 1.20, 95%CI 1.05–1.36, p = 0.005). Sensitivity analyses revealed no further differences when patients were categorised by: pre-operative testing; use of COVID-19-free pathways; or community SARS-CoV-2 prevalence. The rate of postoperative pulmonary complications increased with periods of isolation longer than 3 days, with an OR (95%CI) at 4–7 days or ≥ 8 days of 1.25 (1.04–1.48), p = 0.015 and 1.31 (1.11–1.55), p = 0.001, respectively. Isolation before elective surgery might be associated with a small but clinically important increased risk of postoperative pulmonary complications. Longer periods of isolation showed no reduction in the risk of postoperative pulmonary complications. These findings have significant implications for global provision of elective surgical care. We aimed to determine the impact of pre-operative isolation on postoperative pulmonary complications after elective surgery during the global SARS-CoV-2 pandemic. We performed an international prospective cohort study including patients undergoing elective surgery in October 2020. Isolation was defined as the period before surgery during which patients did not leave their house or receive visitors from outside their household. The primary outcome was postoperative pulmonary complications, adjusted in multivariable models for measured confounders. Pre-defined sub-group analyses were performed for the primary outcome. A total of 96,454 patients from 114 countries were included and overall, 26,948 (27.9%) patients isolated before surgery. Postoperative pulmonary complications were recorded in 1947 (2.0%) patients of which 227 (11.7%) were associated with SARS-CoV-2 infection. Patients who isolated pre-operatively were older, had more respiratory comorbidities and were more commonly from areas of high SARS-CoV-2 incidence and high-income countries. Although the overall rates of postoperative pulmonary complications were similar in those that isolated and those that did not (2.1% vs 2.0%, respectively), isolation was associated with higher rates of postoperative pulmonary complications after adjustment (adjusted OR 1.20, 95%CI 1.05–1.36, p = 0.005). Sensitivity analyses revealed no further differences when patients were categorised by: pre-operative testing; use of COVID-19-free pathways; or community SARS-CoV-2 prevalence. The rate of postoperative pulmonary complications increased with periods of isolation longer than 3 days, with an OR (95%CI) at 4–7 days or ≥ 8 days of 1.25 (1.04–1.48), p = 0.015 and 1.31 (1.11–1.55), p = 0.001, respectively. Isolation before elective surgery might be associated with a small but clinically important increased risk of postoperative pulmonary complications. Longer periods of isolation showed no reduction in the risk of postoperative pulmonary complications. These findings have significant implications for global provision of elective surgical care