Stress oxidatif

Question 1

Qu’est ce que le recepter d’electron majeur en biologie ?

Answer 1

O2

Question 2

Qu,est ce qu’on appel des ROS (molecules) free radical

Answer 2

Des molécules qui contiennent un ou plus d’electrons non pairés. Cela donne une reactivité aux molecules.

Question 3

Que se passe-til quand des molecules free radical partagent des electrons impairées ?

Answer 3

Ce fait des non radical

Answer 4

-

Question 5

exlique Redox cycling (Cycle redox

Answer 5

An oxidation–reduction or redox reaction is a reaction that involves the transfer of electrons between chemical species (the atoms, ions, or molecules involved in the reaction).

Oxidation and reduction (Redox) reactions represent the transfer of electrons from an electron donor (reducing agent) to an electron acceptor (oxidizing agent

Question 6

quels metaux passent par le redox cycle

Answer 6

iron, copper,
chromium, and vanadium

Question 7

que sont les métaux redox active et redox inactive ? de quoi ça dépend ?

Que font les redox inactifs

Answer 7

-Redox-active metals, like iron (Fe), copper (Cu) [3], and chromium (Cr)

• redox-inactive metals like lead and cadmium
• based on their ability to participate in redox reactions.
• redox-inactive metals like lead and cadmium can cause oxidative stress by depleting of cellular antioxidants, especially thiol-containing compounds such as glutathione

Question 8

que sont les cellular mechanisms involved in metal-induced oxidative stress

Answer 8

One crucial mechanism is the disruption of mitochondrial function [19, 20]. Metals can impair mitochondrial electron transport, leading to electron leakage and the formation of superoxide radical. This dysfunction of the mitochondria can result in an overproduction of ROS, thereby aggravating oxidative stress

Another important mechanism is the activation of NADPH oxidase, an enzyme complex that generates superoxide radicals. Metals have the ability to activate NADPH oxidase, which increases ROS production and oxidative damage. Additionally, metals can interfere with cellular signaling pathways, such as those involving nuclear transcription factors like NF-κB and AP-1, which are sensitive to redox changes

Question 9

que sont les Biochemical responses to metal exposure

Answer 9

+ lipid peroxidation
+ meltallothionein,
+ antioxidant defense mecanism
+ heat shock Proteines
+ Nrf2 Keap1 Pathway
+ Apoptosis and carcinogenesis
+ Enzyme activity alteration
+ Lipid peroxidation

Question 10

what is Lipid peroxidation ? What are the consequences ?

Answer 10

Lipid peroxidation can be described generally as a process under which oxidants such as free radicals attack lipids containing carbon-carbon double bond(s), especially polyunsaturated fatty acids
Lipid peroxidation refers to the attack of free radicals on lipids that contain carbon-carbon double bond(s), particularly in cell membranes. This process ultimately causes damage to cells and increases their permeability.

Question 11

Que sont les mellationeines

Answer 11

Metallothioneins (MTs) are low molecular weight proteins that are rich in cysteine. They have the ability to bind heavy metals and are crucial for maintaining metal detoxification and homeostasis.

Question 12

comment un metal lourd peut mener à l’apoptose

Answer 12

augmente le ros. High doses of ROS activate cell death signalling pathways: apoptosis and necroptosis.
*
ROS activate mitochondrial, death receptor and ER pathways of apoptosis., Both intrinsic (mitochondria-mediatedpathway) and extrinsic (death-receptor-mediated) mechanisms induce apoptosis.
Intrinsicapoptosis
is a process that the cell starts on its own, frequently as a reaction to cellular stresses
such as DNA damage. On the other hand, extrinsic apoptosis is brought on by signals fromoutside cells. The executioner
caspases
or the
effector caspases
(Caspase-3 and 7) that cause celldeath are the points of convergence for both routes.

Question 14

Que sont les étapes de la necrose ? Comment est elle provoquée par les ros

Answer 14

Necrosis is a form of cell death characterized by the loss of membrane integrity, cellular swelling, and eventual rupture, leading to inflammation. Reactive oxygen species (ROS) can induce necrosis by overwhelming the cell’s antioxidant defenses, causing oxidative damage to lipids, proteins, and DNA. This damage disrupts mitochondrial function, triggers calcium overload, and impairs membrane stability, culminating in cell lysis and necrotic death—-

Question 15

Que sont les heat shock proteins ?

Answer 15

Heat shock proteins (HSPs) are a group of proteins that are upregulated in response to stress, including exposure to metals.

These proteins play a crucial role in protecting cells from stress-induced damage and maintaining cellular homeostasis

Question 16

Comment les metaux peuvent influencer la synthèse de protéines

Answer 16

The effects of metals can be either activation or inactivation. These effects can occur directly through the interaction of metals with proteins or indirectly through the generation of metal-induced ROS. Moreover, the effects of metals on signaling pathways can resemble those caused by extracellular ligands like insulin or physical conditions like hypoxia

Question 17

Que sont les effets physiologiques des métaux

Answer 17

One of the most significant impacts of metal-induced oxidative stress is observed in the nervous system. These metals can induce oxidative stress by disrupting mitochondrial function and increasing the production of ROS, leading to neuronal damage and apoptosis.

= cardiovascular system (hypertension

• Hepatotoxicity
• Renal effects
  -Reproductive toxicity
• Pulmonary toxicity

Question 18

En gros, pourquoi les metaux lourds sont toxiques pour les poissons

Answer 18

Heavy metals have the atomic density greater than 4 g/cm3 and have the chemical properties to attract and accept electrons,

Due to their non-biodegradable and long persistence nature in the environment, heavy metals cause toxicity in fish by producing oxygen reactive species through oxidizing radical production

Heavy metals are stable compounds, non-biodegradable, shows tendency to accumulate in the sediments and long half-life period in the environment making them hard to manage.

Question 19

de quoi dépend la biodisponibilité et la prise des metaux louds

Answer 19

. Bioavailability and the uptake of heavy metals depend on many factors such as concentration of heavy metals, its exposure period, interaction with other metal, age and size of the fish, detoxifying mechanisms, metabolic processes of fish, feeding behavior, physico-chemical parameters of the environment etc

Question 20

Pourquoi les poissons sont un bon outil pour être des biominiteurs

Answer 20

Fish is the top consumer in the aquatic food web and are considered as ideal organisms for toxicology and toxicogenomics studies. Fish are highly sensitive to any kind of environmental alterations that make them suitable bioindicators for aquatic ecosystem monitoring because they readily metabolize, detoxify and accumulate heavy metals within the body

Question 21

Est ce que tous les métaux sont toxiques pour les poissons ? pourquoi ? Donne un exemple

Answer 21

Heavy metals exist in several oxidation states depending on the metal types and not all forms cause toxicity in fish. For example, chromium (Cr) is present in six oxidation states (+1 to +6), and trivalent and hexavalent Cr are more stable. Trivalent Cr acts as a cofactor for insulin, which has a significant role in glucose metabolism. On the other hand, hexavalent Cr cause toxicity in fish and has potential mutagenic and teratogenic activities in living cells (Velma et al., 2009).

Question 22

explique pourquoi il a une reaction redox et quel est le resultat

Answer 22

Heavy metals such as As, Cd, Cr, Cu, Fe, Hg, Ni, Pb, Zn are redox active components and drive the redox reaction to form reactive oxygen species (ROS) which is important for certain physiological function in the fish body. The excess of ROS indicates imbalance between the productions and scavenging of ROS causes oxidative stress

Question 23

comment fonctionne le sod et catalase

Answer 23

SOD works by converting superoxide free radical to hydrogen peroxide, which is further broken down to non-toxic oxygen and water by CAT enzyme

Question 24

que provoque une perturbation dans la réaction enzymatique

Answer 24

Une perturbation dans la réaction enzymatique pourrait générer un excès de ROS, qui s’accumule dans les tissus des poissons et provoque un stress oxydatif. Par la suite, les ROS dégradent la membrane cellulaire par peroxydation lipidique, ce qui entraîne une génotoxicité par des dommages à l’ADN.

Question 25

vrai que plus les poissons sont gros moins ils sont sensibles aux metaux lourds ?

Answer 25

Generally, the larger fish is less susceptible to heavy metals than the smaller ones.

Question 26

Pourquoi certains metaux lourds sont important pour le corps ?

Answer 26

Some of the heavy metals and/or trace elements such as Cu, Zn, Fe, Cr are essential for animals including fish for maintaining the basic metabolic processes, particularly their role as component or co-factor of different enzymes

Question 27

que sont les effets sur les composantes du sang des métaux lourds ?

Answer 27

Hematological parameters such as red blood cell (RBC), hemoglobin (Hb), leucocytes, and lymphocytes decreased significantly irrespective of the heavy metals exposed to different fish species

Other hematological parameters such as neutrophil has increased significantly (Witeska, 2005) but in case of hematocrit, white blood cell (WBC)

Question 28

Dans les bramchies, que sont les premiers signes d’exposition aux metaux lourds

Answer 28

Generally, edema of lamellar epithelial cells is considered to be the first pathological sign in gill exposed to any heavy metal. This could be due to the lifting away of the epithelium, a covering layer of the secondary lamellae, from the pilaster cell system, which makes the diffusion distance/blood-water diffusion distance larger, thus separating the blood vessel in the lamellae from the external medium

Question 29

quel est l’effet des metaux lourds sur les pompes à calcium

Answer 29

Calcium channel along with enzyme act as a carrier for heavy metals such as Cd to transport to the chloride cells of the gill and in response to that, chloride cells try to eject the heavy metals which causes hypertrophy or hyperplasia of the cells

Question 30

quel est l’impact sur le foie des lésion des branchies

Answer 30

Degeneration of the gills and disruption of the blood vessels are responsible for the insufficient supply of oxygen to the liver, which may cause the damage of the hepatic cells in the liver (Hossain et al., 2016; Sharmin et al., 2015).

Question 31

Comment les cellules produisent des ROS

Answer 31

Intracellular ROS is primarily produced by the mitochondria, in which ROS are largely generated by the electron transport chain. Other sources of ROS include the transmembrane NADPH oxidases; xanthine oxidoreductase in peroxisomes; protein disulfide isomerase, which are involved in the unfolded protein response in the endoplasmic reticulum (ER); and diverse enzymatic reactions that, among others, include prostaglandin synthesis, auto-oxidation of adrenalin, and reduced riboflavin. Voir schéma schema_ros.pdf

Question 32

pourquoi le Fe ets toxique ? Quelle st la forme la plus toxique du fer

Answer 32

Iron is an essential micronutrient that is problematic for biological systems since it is toxic as it generates free radicals by interconverting between ferrous (Fe2 +) and ferric (Fe3 +) forms

Solubilité accrue :
Fe²⁺ est plus soluble que le fer ferrique (Fe³⁺) dans des conditions de faible pH (milieux acides) ou pauvres en oxygène (conditions anoxiques). Cela augmente sa disponibilité pour les organismes aquatiques.

Réactivité chimique :
Fe²⁺ peut participer à des réactions redox, notamment la formation de radicaux libres via la réaction de Fenton, ce qui peut causer un stress oxydatif et des dommages cellulaires chez les organismes.

Oxidative DNA damage is decreased by the presence of O2 during Fe(2+)-mediated Fenton reactions when H2O2 is in excess

he Fenton reaction involves the reaction of hydrogen peroxide with ferrous iron (Fe2+). This produces either ferric iron (Fe3+), hydroxide, and hydroxyl radical, or a ferryl oxoiron species ([Fe=O]2+) and water. Ferric iron can be reduced back to ferrous iron by superoxide, and the ferryl oxoiron species can be converted back to ferrous iron by hydrogen peroxide–