Cell Injury

Presented

By

Ahmed El-Rashedy

Professor & Previous Head

of Pathology Department

Al-Azhar University

Cell Injury

Def.: A sequence of events occurring in the living cells or

tissues after their exposure to the stimulus.

Course: Usually reversible (i.e. returns to normal). When

the stimulus persists or being severe from the start, the

cell injury will be irreversible.

Causes:

1. Hypoxia: Lack in O2 pressure & supply occurring in:

Anemia.

Ischemia.

Carbon monoxide poisoning.

Cardio-respiratory failure (Shock).

Prof. Dr. Ahmed Elrashedy

2. Physical agents:

Mechanical trauma or crush injury.

Extremes of temperature (excess heat or severe coldness).

Irradiation whether ionizing (cobalt, gamma) or non-ionizing

(X-, ultraviolet) rays.

Electric shock.

3. Chemical agents:

Air pollutants & hydrocarbons.

Hypertonic solutions.

Poisons: Cyanide, Mercury, Arsenic.

Insecticides.

Fungicides.

Industrial vapors or fibers (Asbestos, silica).

Drugs: Narcotics.

Prof. D

r. Ahmed E

lrash

edy

4.Micro-organisms(viable agents):

Bacteria.

Viruses.

Fungi.

Parasites.

Rickettsia.

5. Immunologic disorders:

Hypersensitivity to a foreign protein (injectable,

ingestible, inhaler).

Hypersensitivity to a self- antigen as extrusion of

eye lens protein or sperm head protein in obstructed

epididymis.

Prof. Dr. Ahmed Elrashedy

6. Genetic diseases:

Sickle cell anemia: production of Hb-S instead

of Hb-A.

Down’s syndrome (Mongolism): aberration in

chromosome no; 21.

7. Nutritional disorders:

Hyper- or Hypo- vitaminosis A & D.

Protein-Calorie deficiency: Marasmic baby

(Kwashiorkor's disease).

Fat-rich diet intake: Obesity &

atherosclerosis.

Prof. Dr. Ahmed Elrashedy

Types of cell injury:

1.Cell adaptations: Hyperplasia, Hypertrophy,

Metaplasia, Dysplasia.

2.Reversible injury: Degenerations (Hydropic

degeneration, fatty change and hyaline change).

3.Irreversible injury: Cell death and necrosis.

Mechanisms of cell Injury:

1.Hypoxic injury.

2.O2 free radical-mediated injury.

3.Viral injury.

Prof. Dr. Ahmed Elrashedy

O2 free Radicals

Def.: They are chemicals characterized by the presence of a

single unpaired electron on the outer orbital layer of their

atom.

Significance:

They are unstable & liable to enter in oxidative reactions

with organic & inorganic chemicals found in the cell &

organeller membranes & nucleic acids.

Synthesis:

1. Absorption of radiant energy.

2.Oxidative reactions in the normal metabolism.

3.Enzymatic metabolism of the exogenous chemicals or

drugs.

Prof. Dr. Ahmed Elrashedy

Types:

1.Superoxide ion .

2.Hydrogen peroxide.

3.Hydroxyl group.

4.Organic free radicals formed by oxidative reactions.

Effects:

1.Lipid peroxidation & membrane damage.

2.Protein breakdown.

3.DNA damage.

Removal ( Inactivation): through

1.Antioxidants: as

Vitamins (E, C, folic acid),

Selenium,

Amino acids &

serum proteins (ceruloplasmin & transferrin).

Prof. Dr. Ahmed Elrashedy

2. Enzymes: as

Catalase: changes hydrogen peroxide into water.

Superoxide dismutase: converts superoxide into water.

Glutathione peroxidase: causes reduction of glutathione by

removal of H2 from its SH-group.

Examples of cell injury mediated by O2 free Radicals

1.Ageing process with production of O2 free radicals that cause

lipid peroxidation & membrane damage.

2.Exposure to high concentration of O2 & ozone.

3.Chemical injury: e.g. Carbon tetrachloride poisoning.

4.Irradiation with release of O2 free radicals due to tissue lysis.

5.Inflammation with tissue damage.

6.Microbial killing with production of O2 free radicals.

7.Atherosclerosis.

8.Carcinogenesis.

Prof. Dr. Ahmed Elrashedy

من نقص ومن خطإ فمني ومن الشيطان ما كان و ا كان من صواب فمن هللام

فأستغفر هللا إنه هو الغفور الرحيم والحمد هلل رب العالمينProf. Dr. Ahmed Elrashedy