Axisymmetric contact problem for a flattened cell : contributions of substrate effect and cell thickness to the determination of viscoelastic properties by using AFM indentation

Nanoindentation technology has proven an effective method to investigate the viscoelastic properties of biological cells. The experimental data obtained by nanoindentation are frequently interpreted by Hertz contact model. However, in order to facilitate the application of Hertz contact model, a mass of studies assume cells have infinite thickness which does not necessarily represent the real situation. In this study, a rigorous contact model based upon linear elasticity is developed for the interpretation of indentation tests of flattened cells which represent a factual morphology. The cell, normally bonded to the petri dish, is initially treated as an elastic layer of finite thickness perfectly fixed to a rigid substrate, and the conic indenter is assumed to be frictionless. The theory of linear elasticity is utilized to solve this contact issue and then the solutions are extended to viscoelastic situation which is regarded as a good indicator for mechanical properties of biological cells. To test the present model, an AFM-based creep test has been conducted on living human hepatocellular carcinoma cell (SMMC-7721 cell) and its fullerenol-treated counterpart. The results indicate that the present model could not only describe very well the creep behavior of SMMC-7721 cells, but can also curb overestimation of the mechanical properties due to substrate effect. Moreover, the present model could identify the difference between the control and treated SMMC-7721 cells in terms of the extracted viscoelastic parameters, suggesting its potential in revealing the biomechanical effects of fullerenol-like drug treatment on cancerous cells

STAT2 signaling restricts viral dissemination but drives severe pneumonia in SARS-CoV-2 infected hamsters

Emergence of SARS-CoV-2 causing COVID-19 has resulted in hundreds of thousands of deaths. In search for key targets of effective therapeutics, robust animal models mimicking COVID-19 in humans are urgently needed. Here, we show that Syrian hamsters, in contrast to mice, are highly permissive to SARS-CoV-2 and develop bronchopneumonia and strong inflammatory responses in the lungs with neutrophil infiltration and edema, further confirmed as consolidations visualized by micro-CT alike in clinical practice. Moreover, we identify an exuberant innate immune response as key player in pathogenesis, in which STAT2 signaling plays a dual role, driving severe lung injury on the one hand, yet restricting systemic virus dissemination on the other. Our results reveal the importance of STAT2-dependent interferon responses in the pathogenesis and virus control during SARS-CoV-2 infection and may help rationalizing new strategies for the treatment of COVID-19 patients. SARS-CoV-2 infection can result in severe lung inflammation and pathology, but host response remains incompletely understood. Here the authors show in Syrian hamsters that STAT2 signaling restricts systemic virus dissemination but also drives severe lung injury, playing a dual role in SARS-CoV-2 infection

Insecticide Resistance : Importance in the transmission of chikungunya virus by Aedes aegypti mosquitoes

Le moustique Aedes aegypti est le vecteur principal du Chikungunya, en l'absence de vaccins efficaces et de traitements disponibles, la lutte anti-vectorielle reste la stratégie principale de prévention et de défense pour le contrôle de la maladie. Néanmoins le problème de la résistance aux insecticides est en train de s'aggraver, notamment à cause de l’augmentation de la fréquence des luttes chimiques contre les intenses épidémies d’arbovirus, frappant partout dans le monde. Nous voulons comprendre l’importance de la résistance à l’insecticide dans le contexte de la transmission du virus Chikungunya par les moustiques Aedes aegypti.A partir de la population de moustiques de l’Ile Royale considérée comme la population la moins résistante en Guyane, 4 lignées de moustiques IR03, IR05, IR13 et IR 36 présentant différents profils de résistance à l’insecticide deltaméthrine ont été isolées, des tests biologiques et moléculaires ont été réalisés pour caractériser les mécanismes de résistance au niveau de leur phénotype et de leur génotype. Les résultats montrent que IR03 n'a qu'une résistance métabolique, que IR05 possède à la fois les résistances kdr et métabolique, et que IR13/36 est doté d’une faible résistance métabolique.Plus de 600 femelles ont été infectées oralement par le virus Chikungunya en utilisant un système de gorgement artificiel. Pour chaque individu, 3 séries d’échantillons (l’intestin moyen, la tête et la salive) sont récoltés indépendamment pour y quantifier le virus, afin de définir sa compétence vectorielle par trois paramètres : le taux d’infection, le taux de dissémination et le taux de transmission. Les résultats montrent qu’il existe des différences significatives dans la compétence vectorielle, plus spécifiquement dans le taux de dissémination de l'intestin moyen à tout le corps du moustique au fil du temps, qui est plus bas dans la lignée la plus résistante.Ensuite, pour étudier les interactions entre les mécanismes résistants et la barrière de l’intestin moyen, les niveaux d’expression de certains gènes (CYP 6BB2, CYP 6N12, GST2, Trypsine) qui sont associés directement ou indirectement à la résistance à la deltaméthrine ont été mesurés sur des intestins moyens datant de 7 jours après le repas sanguin infectieux, que la tête soit positive ou négative. En complétant ces niveaux d’expression avec l’information du génotype kdr, les résultats montrent que la surexpression des enzymes de détoxification et l’existence des mutations kdr pourraient avoir un effet significatif sur la dissémination du virus dans le corps des moustiques.Enfin, concernant le coût de la résistance qui est un des facteurs important pour évaluer la capacité vectorielle des moustiques résistants, les lignées isofemelles se manifestent plus clairement en termes de reproduction de la population (temps de ponte, fécondité et fertilité) que de développement des stades immatures y compris avec le temps de développement larvaire, les larves et les nymphes mortes, et le sex ratio.En conclusion, toutes les données obtenues fournissent une meilleure compréhension sur l'existence des interactions entre la résistance aux insecticides et la capacité vectorielle chez les moustiques. Même si plus de manipulations concernant des validations fonctionnelles ou des recherches plus approfondies peuvent être déclenchées sur la base de ces travaux, nous avons déjà plus d’informations pour aider à adapter ou améliorer la réponse de la lutte anti-vectorielle, afin d’établir le meilleur compromis entre l’efficacité de la lutte et l’augmentation de la résistance.The mosquito Aedes aegypti is well known as the main vector of Chikungunya, in absence of effective vaccinations and available treatments, mosquito control strategy remains the principal prevention and defense measures for disease control. Nevertheless, the problem of resistance to insecticides is worsening especially because of more and more frequent chemical fights against intense arbovirus outbreaks in the world. We are interested in understanding the effects of resistance in the context of transmission of the disease, and struggle to establish the reasonable compromise between the effectiveness of the vector control strategy and the increase in resistance.From the mosquito population of Ile Royale which was considered as the least resistant population in French Guiana, 4 mosquito lines IR03, IR05, IR13 and IR36 with different resistance profiles to the deltamethrin insecticide have been isolated successfully, biologic and molecular tests were carried out to characterize the resistance mechanisms between them in regarding with their phenotypes and genotypes. The results indicated that IR03 presented only a metabolic resistance, that IR05 harboured both kdr and metabolic resistance, and that IR13/36 showed a moderate metabolic resistance.More than 600 females were orally infected with Chikungunya virus using an artificial engorged system. For each individual, 3 sets of samples (midgut, head and saliva) are collected independently to quantify the presence of virus, in order to define its vector competence by three parameters: the infection rate, the dissemination rate and the transmission rate. The results show that there were significant differences in vector competence, more specifically between the dissemination rate from the midgut to the head over time, which is lower in the more resistant line.Then, expression level of certain genes (CYP 6BB2, CYP 6N12, GST2, Trypsin) which were associated with deltamethrin resistance were measured on the midgut at 7 days after infectious blood meal. Combined with the information of the kdr genotype, we propose that different mechanisms of resistance can influence not only the barrier of the midgut, but also affect the entire spread pathway of the virus to develop in the mosquito body from the midgut to the saliva.Finally, regarding the cost of resistance, the isofemale lines manifested more clearly in terms of population reproduction than immature development including larval development time, larval and nymphal mortality, and the sex ratio post-emergence.Overall, although this research requires more functional validations or supporting experimentations, the data obtained could provide a better understanding of the interactions between insecticide resistance and vector capacity in mosquitoes Aedes aegypti and supply some useful information to improve the current vector control

Résistance aux insecticides : importance dans la transmission du virus chikungunya par les moustiques Aedes aegypti

The mosquito Aedes aegypti is well known as the main vector of Chikungunya, in absence of effective vaccinations and available treatments, mosquito control strategy remains the principal prevention and defense measures for disease control. Nevertheless, the problem of resistance to insecticides is worsening especially because of more and more frequent chemical fights against intense arbovirus outbreaks in the world. We are interested in understanding the effects of resistance in the context of transmission of the disease, and struggle to establish the reasonable compromise between the effectiveness of the vector control strategy and the increase in resistance.From the mosquito population of Ile Royale which was considered as the least resistant population in French Guiana, 4 mosquito lines IR03, IR05, IR13 and IR36 with different resistance profiles to the deltamethrin insecticide have been isolated successfully, biologic and molecular tests were carried out to characterize the resistance mechanisms between them in regarding with their phenotypes and genotypes. The results indicated that IR03 presented only a metabolic resistance, that IR05 harboured both kdr and metabolic resistance, and that IR13/36 showed a moderate metabolic resistance.More than 600 females were orally infected with Chikungunya virus using an artificial engorged system. For each individual, 3 sets of samples (midgut, head and saliva) are collected independently to quantify the presence of virus, in order to define its vector competence by three parameters: the infection rate, the dissemination rate and the transmission rate. The results show that there were significant differences in vector competence, more specifically between the dissemination rate from the midgut to the head over time, which is lower in the more resistant line.Then, expression level of certain genes (CYP 6BB2, CYP 6N12, GST2, Trypsin) which were associated with deltamethrin resistance were measured on the midgut at 7 days after infectious blood meal. Combined with the information of the kdr genotype, we propose that different mechanisms of resistance can influence not only the barrier of the midgut, but also affect the entire spread pathway of the virus to develop in the mosquito body from the midgut to the saliva.Finally, regarding the cost of resistance, the isofemale lines manifested more clearly in terms of population reproduction than immature development including larval development time, larval and nymphal mortality, and the sex ratio post-emergence.Overall, although this research requires more functional validations or supporting experimentations, the data obtained could provide a better understanding of the interactions between insecticide resistance and vector capacity in mosquitoes Aedes aegypti and supply some useful information to improve the current vector control.Le moustique Aedes aegypti est le vecteur principal du Chikungunya, en l'absence de vaccins efficaces et de traitements disponibles, la lutte anti-vectorielle reste la stratégie principale de prévention et de défense pour le contrôle de la maladie. Néanmoins le problème de la résistance aux insecticides est en train de s'aggraver, notamment à cause de l’augmentation de la fréquence des luttes chimiques contre les intenses épidémies d’arbovirus, frappant partout dans le monde. Nous voulons comprendre l’importance de la résistance à l’insecticide dans le contexte de la transmission du virus Chikungunya par les moustiques Aedes aegypti.A partir de la population de moustiques de l’Ile Royale considérée comme la population la moins résistante en Guyane, 4 lignées de moustiques IR03, IR05, IR13 et IR 36 présentant différents profils de résistance à l’insecticide deltaméthrine ont été isolées, des tests biologiques et moléculaires ont été réalisés pour caractériser les mécanismes de résistance au niveau de leur phénotype et de leur génotype. Les résultats montrent que IR03 n'a qu'une résistance métabolique, que IR05 possède à la fois les résistances kdr et métabolique, et que IR13/36 est doté d’une faible résistance métabolique.Plus de 600 femelles ont été infectées oralement par le virus Chikungunya en utilisant un système de gorgement artificiel. Pour chaque individu, 3 séries d’échantillons (l’intestin moyen, la tête et la salive) sont récoltés indépendamment pour y quantifier le virus, afin de définir sa compétence vectorielle par trois paramètres : le taux d’infection, le taux de dissémination et le taux de transmission. Les résultats montrent qu’il existe des différences significatives dans la compétence vectorielle, plus spécifiquement dans le taux de dissémination de l'intestin moyen à tout le corps du moustique au fil du temps, qui est plus bas dans la lignée la plus résistante.Ensuite, pour étudier les interactions entre les mécanismes résistants et la barrière de l’intestin moyen, les niveaux d’expression de certains gènes (CYP 6BB2, CYP 6N12, GST2, Trypsine) qui sont associés directement ou indirectement à la résistance à la deltaméthrine ont été mesurés sur des intestins moyens datant de 7 jours après le repas sanguin infectieux, que la tête soit positive ou négative. En complétant ces niveaux d’expression avec l’information du génotype kdr, les résultats montrent que la surexpression des enzymes de détoxification et l’existence des mutations kdr pourraient avoir un effet significatif sur la dissémination du virus dans le corps des moustiques.Enfin, concernant le coût de la résistance qui est un des facteurs important pour évaluer la capacité vectorielle des moustiques résistants, les lignées isofemelles se manifestent plus clairement en termes de reproduction de la population (temps de ponte, fécondité et fertilité) que de développement des stades immatures y compris avec le temps de développement larvaire, les larves et les nymphes mortes, et le sex ratio.En conclusion, toutes les données obtenues fournissent une meilleure compréhension sur l'existence des interactions entre la résistance aux insecticides et la capacité vectorielle chez les moustiques. Même si plus de manipulations concernant des validations fonctionnelles ou des recherches plus approfondies peuvent être déclenchées sur la base de ces travaux, nous avons déjà plus d’informations pour aider à adapter ou améliorer la réponse de la lutte anti-vectorielle, afin d’établir le meilleur compromis entre l’efficacité de la lutte et l’augmentation de la résistance

Analysis of colchicine-induced effects on hepatoma and hepatpcyte cells by atomic force microscopy

Biomechanical properties of cells are altered by many diseases. Cancer cell metastasis is related to the properties such as the cell stiffness that influences cell proliferation, differentiation and migration. In this paper, we used an atomic force microscope to analyze the colchicine-induced effects on the mechanical properties of hepatocyte (HL-7702 cells) and hepatoma cells (SMCC-7721 cells) in culture at the nanoscale. The cells were exposed to a solution with a normal dose of colchicine for two, four and six hours. Surface topographic images showed that colchicine decreased the stability of the cytoskeleton. After the same six-hour treatment in a solution with a normal dose of colchicine, the biomechanical properties of HL-7702 cells were almost unchanged. However, the stiffness and the adhesion force of the SMCC-7721 cells were clearly increased (more than twofold of the normal values), especially after four hours. The deformability of SMCC-7721 cancer cells was significantly decreased within the six-hour treatment in the solution with a normal dose of colchicine. Analysis of the biomechanical properties of post-treatment hepatoma cells provided a complementary explanation for the mechanism of action of colchicine on cells at the nanoscale. This method is expected to allow the monitoring of potential metastatic cancer cell changes, thus preventing the emergence and the transmission of disease, and improving the diagnosis of cancer

5α-Hydroxycostic acid inhibits choroidal neovascularization in rats through a dual signalling pathway mediated by VEGF and angiopoietin 2

Abstract Background 5α-Hydroxycostic acid is a eudemane sesquiterpene that is isolated from the natural plant, Laggera alata. It exerts anti-inflammatory and anti-angiogenic effects on human breast cancer cells, but its role and underlying mechanism in choroidal neovascularization (CNV) are still unclear. We conducted a study to verify that 5α-Hydroxycostic acid can inhibit the formation and leakage of CNV, and describe the possible dual pathway by which it exerts its inhibitory effects in this process. Methods An in vitro model of choroidal neovascularization was established using VEGF164, while a rat model of choroidal neovascularization was established using a 532 nm laser. In both models, the effects of 5α-Hydroxycostic acid in vivo and in vitro were evaluated to determine its inhibitory effect on abnormal cell proliferation, migration and tubule formation, as well as its effect on pathological changes in choroidal tissues and the area of neovascularization leakage in rats. The levels of components in the VEGF/VEGFR and Ang2/Tie2 signaling pathways were measured in tissues and cells. Results In vitro experiments have shown that 5α-Hydroxycostic acid can inhibit abnormal cell proliferation, migration and angiogenesis. Additionally, 5α-Hydroxycostic acid enhances cell adhesion by inhibiting the phosphorylation pathways of VEGFR2 and Tie2. In vivo experiments demonstrated that 5α-Hydroxycostic acid has a positive therapeutic effect on choroidal neovascularization in rats. It can effectively reduce vascular leakage, consistent with the results of the cell experiments. Conclusion 5α-Hydroxycostic acid can inhibit choroidal neovascularization by interfering with the VEGF- and Ang2/Tie2-related pathways, and it may be a good candidate drug for treating CNV

Successes and failures of sixty years of vector control in French Guiana: what is the next step?

Since the 1940s, French Guiana has implemented vector control to contain or eliminate malaria, yellow fever, and, recently, dengue, chikungunya, and Zika. Over time, strategies have evolved depending on the location, efficacy of the methods, development of insecticide resistance, and advances in vector control techniques. This review summarises the history of vector control in French Guiana by reporting the records found in the private archives of the Institute Pasteur in French Guiana and those accessible in libraries worldwide. This publication highlights successes and failures in vector control and identifies the constraints and expectations for vector control in this French overseas territory in the Americas

Biomechanical measurement and analysis of colchicine-induced effects on cells by nanoindentation using an atomic force microscope

Colchicine is a drug commonly used for the treatment of gout, however, patients may sometimes encounter side-effects induced by taking colchicine, such as nausea, vomiting, diarrhea and kidney failure. In this regard, it is imperative to investigate the mechanism effects of colchicine on biological cells. In this paper, we present a method for the detection of mechanical properties of nephrocytes (VERO cells), hepatocytes (HL-7702 cells) and hepatoma cells (SMCC-7721 cells) in culture by atomic force microscope(AFM) to analyze the 0.1 μg/mL colchicine-induced effects on the nanoscalefor two, four and six hours. Compared to the corresponding control cells, the biomechanical properties of the VERO and SMCC-7721 cells changed significantly and the HL-7702 cells did not considerably change after the treatment when considering the same time period. Based on biomechanical property analyses, the colchicine solution made the VERO and SMCC-7721 cells harder. We conclude that it is possible to reduce the division rate of the VERO cells and inhibit the metastasis of the SMCC-7721 cells. The method described here can be applied to study biomechanics of many other types of cells with different drugs. Therefore, this work provides an accurate and rapid method for drug screening and mechanical analysis of cells in medical research

Understanding the Mechanisms Underlying Host Restriction of Insect-Specific Viruses

Arthropod-borne viruses contribute significantly to global mortality and morbidity in humans and animals. These viruses are mainly transmitted between susceptible vertebrate hosts by hematophagous arthropod vectors, especially mosquitoes. Recently, there has been substantial attention for a novel group of viruses, referred to as insect-specific viruses (ISVs) which are exclusively maintained in mosquito populations. Recent discoveries of novel insect-specific viruses over the past years generated a great interest not only in their potential use as vaccine and diagnostic platforms but also as novel biological control agents due to their ability to modulate arbovirus transmission. While arboviruses infect both vertebrate and invertebrate hosts, the replication of insect-specific viruses is restricted in vertebrates at multiple stages of virus replication. The vertebrate restriction factors include the genetic elements of ISVs (structural and non-structural genes and the untranslated terminal regions), vertebrate host factors (agonists and antagonists), and the temperature-dependent microenvironment. A better understanding of these bottlenecks is thus warranted. In this review, we explore these factors and the complex interplay between ISVs and their hosts contributing to this host restriction phenomenon

Understanding the Mechanisms Underlying Host Restriction of Insect-Specific Viruses

Arthropod-borne viruses contribute significantly to global mortality and morbidity in humans and animals. These viruses are mainly transmitted between susceptible vertebrate hosts by hematophagous arthropod vectors, especially mosquitoes. Recently, there has been substantial attention for a novel group of viruses, referred to as insect-specific viruses (ISVs) which are exclusively maintained in mosquito populations. Recent discoveries of novel insect-specific viruses over the past years generated a great interest not only in their potential use as vaccine and diagnostic platforms but also as novel biological control agents due to their ability to modulate arbovirus transmission. While arboviruses infect both vertebrate and invertebrate hosts, the replication of insect-specific viruses is restricted in vertebrates at multiple stages of virus replication. The vertebrate restriction factors include the genetic elements of ISVs (structural and non-structural genes and the untranslated terminal regions), vertebrate host factors (agonists and antagonists), and the temperature-dependent microenvironment. A better understanding of these bottlenecks is thus warranted. In this review, we explore these factors and the complex interplay between ISVs and their hosts contributing to this host restriction phenomenon.status: publishe