hepatotoxicity
TRANSCRIPT
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HEPATOTOXICITY: TOXIC
EFFECTS ON THE LIVER
By Prandeep Borah
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FUNCTIONS
(1) Filtration
(2) carbohydrate storage and metabolism;
(3) metabolism of hormones, endogenous wastes, and
foreign chemicals;
(4) synthesis of blood proteins;
(5) urea formation;
(6) metabolism of fats; and
(7) bile formation
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TYPES OF TOXIN INDUCED LIVER INJURY:
Hepatocellular Degeneration and Death-
1. Mitochondria. These organelles are important for
energy metabolism and synthesis of ATP.
-> Release calcium/ maintain homeostasis
->lose the ability to regulate solute and water balance,
and undergo swelling.
-> chemicals- carbon tetrachloride, cocaine,
dichloroethylene etc.
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2. Plasma Membrane- Important in maintaining the ion
balance between the cytoplasm and the external
environment.
-> Loss of ionic control can cause a net movement of water
into the cell, resulting in cell swelling.
->chemicals- acetaminophen, ethanol etc.
3. Endoplasmic Reticulum- Responsible for synthesis of
proteins and phospholipids in the hepatocyte.
->Principal site of biotransformation of foreign
chemicals;maintain Ca homeostasis.
->chemicals- acetaminophen, bromobenzene, carbon
tetrachloride, and cocaine.
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4. Nucleus-
->Some chemicals or their metabolites can bind to DNA,
producing mutations > leading to cell death.
->Some chemicals appear to cause activation of
endonucleases, enzymes located in the nucleus that
digest chromatin material >leads to uncontrolled
digestion of the cell’s DNA.
->chemicals- aflatoxin B, beryllium, Ethionine etc.
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5. Lysosomes- These subcellular structures contain
digestive enzymes (e.g., proteases) and are important in
degrading damaged or aging cellular constituents
-> In hepatocytes injured by chemical toxicants, their
numbers and size are often increased.
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FIBROSIS & CIRRHOSIS
Hepatic fibrosis (scaring) occurs by the accumulation of
excessive amounts of fibrous tissue, specifically fibril
forming collagens type I and III.
> central veins, portal tracts, disse
>With continuing collagen deposition,
>fibrous scars.
> nodular regeneration of hepatocytes leads fibrosis to
progress to cirrhosis
* Blood flow through the liver becomes obstructed,
leading to portal hypertension, internal hemorrhage.
* Chemicals involves ethanol, carbon tetrachloride,
trinitrotoluene.
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LIVER TUMORS
Chemicals can induce neoplasia which leads
to tumors . Etiology :-
• Hepatitis B
• Hepatitis C
• Cirrhosis
- 70% of HCC arise on top of cirrhosis
• Toxins -Alcohol -Tobacco - Aflatoxins
• Autoimmune hepatitis
• States of insulin resistance- Overweight in males
Diabetes mellitus
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CLASSIFICATION
Malignant
>hepatocellular
carcinomas:-derived
from hepatocytes,
>cholangiocarcinomas:
-from bile duct cells,
>hemangiosarcoma:-
arising from liver cells.
Benign
>adenomas:-epithelial
origin with gland.
>fibromas-fibrotic cell
origin.
>cholangiofibromas:-
Arise from bile ducts
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TUMORS
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CHOLESTASIS
>Refers to decreased or arrested bile flow.
>elevated serum levels-bile salts and bilirubin.
>Impairment of yellowish bilirubin pigment reflects
jaundice.
>Structural changes I
>dilation of the bile canaliculus
>presence of bile plugs in bile ducts and canaliculi.
* Chemical involves- Chlorpromazine, cyclosporin A,
ethanol, ampicillin,estrogens etc.
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CHOLESTASIS
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SINUSOIDAL DAMAGE
Its a specialized capillary with numerous fenestrae for
high permeability.
>damages occurs two pathways-
1.Dilation of the sinusoid- whenever efflux of hepatic
blood is impeded. Known as peliosis hepatis.
*Chemials- anabolic steroids ,danazol.
2.blockade of its lumen- occurs due to enlargement
of fenestrae & red blood cells become caught.
*Chemicals- acetaminophen
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PELIOSIS HEPATIS
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Fatty liver :- Caused by chemicals produce an accumulation of lipids in the liver, called fatty liver or steatosis.
> hepatocellular necrosis occurs in specific acinarzones.
> zone 1 –lipid accumulation from white phosphorus.
>zone 3 -lipid accumulation with tetracycline and ethanol.
The lipid accumulates in vacuoles within the cytoplasm.
> macrovesicular steatosis
> microvesicular steatosis
> This vesicular steatosis has been associated with tetracycline, valproic acid, salicylates, aflatoxin etc.
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POTENTIAL CHEMICAL EFFECTS GIVE RISE TO
ACCUMULATION OF LIPID
1. Inhibition of Lipoprotein Synthesis.- Eg. carbon
tetrachloride, ethionine.
2. Decreased Conjugation of Triglycerides with
Lipoproteins . Eg.Carbon tetrachloride
3. Interference with Very-Low-Density Lipoprotein
(VLDL) Transfer: Eg. Tetracycline
4. Impaired Oxidation of Lipids by Mitochondria: Eg.
Carbon tetrachloride, ethionine.
5. Increased Synthesis of Fatty Acids: Eg. Ethanol.
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FATTY LIVER
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THANK YOU !