Give brief account of chemical mediators of inflammation md pathology

Give brief account of chemical mediators of inflammation md pathology exam question give robbins based answer

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"Inflammation Mediators"[MeSH Terms]

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Robbins pathology chemical mediators of inflammation complement histamine cytokines

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Chemical mediators of inflammation

Chemical mediators are substances that initiate, amplify, regulate, and terminate inflammatory reactions. They are produced by inflammatory cells or derived from plasma proteins.

General properties

May be cell-derived or plasma-derived.
Cell mediators may be stored preformed in granules, or synthesized de novo after stimulation.
Most act by binding to specific receptors on target cells.
Their effects are usually short-lived and are tightly regulated.
One mediator may stimulate release of other mediators, producing amplification of inflammation.

1. Vasoactive amines

Histamine

Principal source: mast cells; also basophils and platelets.
Released by physical injury, immune reactions, complement fragments C3a and C5a, and cytokines.
Causes arteriolar vasodilatation and increased venular permeability by endothelial contraction.
Important in the immediate phase of acute inflammation.

Serotonin

Mainly present in platelet granules.
Released during platelet aggregation.
Has vasoactive effects, especially altering vascular tone and permeability.

2. Arachidonic acid metabolites

Arachidonic acid is released from membrane phospholipids by phospholipase A2 and metabolized through cyclooxygenase and lipoxygenase pathways.

Mediator	Important actions
PGI2, PGE2, PGD2	Vasodilatation; PGE2 causes pain and fever
TXA2	Vasoconstriction and platelet aggregation
LTB4	Potent chemotaxis, leukocyte activation, adhesion, and generation of reactive oxygen species
LTC4, LTD4, LTE4	Increased vascular permeability, bronchospasm, vasoconstriction
Lipoxins	Inhibit neutrophil recruitment and promote resolution of inflammation

3. Platelet-activating factor (PAF)

Produced by platelets, mast cells, neutrophils, monocytes, and endothelial cells.

Actions:

Vasodilatation and increased vascular permeability
Leukocyte adhesion and chemotaxis
Leukocyte degranulation and oxidative burst
Platelet aggregation

4. Cytokines and chemokines

Tumor necrosis factor (TNF) and interleukin-1 (IL-1)

Produced mainly by activated macrophages, dendritic cells, and other leukocytes.
Cause endothelial activation with increased expression of adhesion molecules.
Promote leukocyte recruitment.
Produce systemic effects: fever, acute-phase protein synthesis, leukocytosis, and, in severe infection, shock and disseminated intravascular coagulation.

Chemokines

Small cytokines that direct migration of leukocytes.
Example: IL-8 (CXCL8) recruits neutrophils.
Important in chemotaxis and activation of specific leukocyte populations.

5. Complement system

Plasma proteins activated by classical, alternative, or lectin pathways.

C3a and C5a: anaphylatoxins. Cause mast-cell degranulation, histamine release, vasodilatation, and increased vascular permeability.
C5a: powerful chemotactic factor and activator of neutrophils and monocytes.
C3b: opsonin that enhances phagocytosis.
C5b-9: membrane attack complex causing lysis of microbes and cells.

6. Kinin system

The main mediator is bradykinin, formed from high-molecular-weight kininogen by kallikrein.

Actions:

Increased vascular permeability
Vasodilatation
Pain
Bronchoconstriction

7. Coagulation and fibrinolytic system

Thrombin promotes endothelial activation and leukocyte adhesion.
Plasmin activates complement and can generate inflammatory products.
Factor XII activation links coagulation, kinin formation, complement activation, and fibrinolysis.

8. Nitric oxide (NO)

Produced by endothelial cells and macrophages.

Actions:

Vasodilatation
Inhibition of platelet aggregation and leukocyte adhesion
Microbicidal activity when produced by activated macrophages

9. Reactive oxygen species and lysosomal enzymes

Released from activated neutrophils and macrophages.

Kill microbes within phagolysosomes.
If released extracellularly, cause endothelial and tissue injury.
Their harmful effects are limited by antioxidants and antiprotease mechanisms.

10. Neuropeptides

For example, substance P.

Transmit pain.
Cause vasodilatation and increased vascular permeability.
May contribute to neurogenic inflammation.

Key mediator-action correlation

Vasodilatation: histamine, prostaglandins, nitric oxide.
Increased vascular permeability: histamine, bradykinin, leukotrienes C4/D4/E4, PAF, C3a/C5a.
Chemotaxis and leukocyte activation: C5a, LTB4, chemokines, TNF, IL-1.
Pain: bradykinin and PGE2.
Fever: IL-1, TNF, and PGE2.
Opsonization: C3b.
Microbial lysis: C5b-9 membrane attack complex.

Robbins & Kumar Basic Pathology, “Mediators of Inflammation,” pp. 33-39.

Make one page revision pdf

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mkdir -p "/tmp/workspace/chemical-mediators-revision/src" "/tmp/workspace/chemical-mediators-revision/output"

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"Inflammation Mediators"[MeSH Terms]

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Robbins pathology mediators of inflammation histamine complement prostaglandins cytokines

Writing File

~/chemical-mediators-revision/src/create_revision_pdf.py

from reportlab.lib.pagesizes import A4
from reportlab.lib import colors
from reportlab.lib.styles import getSampleStyleSheet, ParagraphStyle
from reportlab.lib.enums import TA_CENTER
from reportlab.lib.units import mm
from reportlab.platypus import SimpleDocTemplate, Paragraph, Spacer, Table, TableStyle, KeepTogether
from reportlab.pdfbase.ttfonts import TTFont
from reportlab.pdfbase import pdfmetrics
from reportlab.lib.colors import HexColor
from reportlab.pdfbase.pdfmetrics import stringWidth

OUT = '/tmp/workspace/chemical-mediators-revision/output/Chemical_Mediators_of_Inflammation_Robbins_Revision.pdf'

# A4 one-page examination revision sheet
page_w, page_h = A4
M = 11*mm

doc = SimpleDocTemplate(OUT, pagesize=A4, leftMargin=M, rightMargin=M, topMargin=9*mm, bottomMargin=8*mm)

navy = HexColor('#17365D')
blue = HexColor('#D9EAF7')
light = HexColor('#F5F8FB')
line = HexColor('#8BA9C4')
red = HexColor('#9C1C1C')
green = HexColor('#1F6B46')

styles = getSampleStyleSheet()
title = ParagraphStyle('title', parent=styles['Title'], fontName='Helvetica-Bold', fontSize=15.3, leading=17, alignment=TA_CENTER, textColor=navy, spaceAfter=2)
sub = ParagraphStyle('sub', parent=styles['Normal'], fontName='Helvetica', fontSize=7.5, leading=8.7, alignment=TA_CENTER, textColor=HexColor('#44546A'), spaceAfter=5)
sec = ParagraphStyle('sec', parent=styles['Normal'], fontName='Helvetica-Bold', fontSize=8.2, leading=9.5, textColor=colors.white, spaceAfter=0)
body = ParagraphStyle('body', parent=styles['Normal'], fontName='Helvetica', fontSize=7.15, leading=8.6, textColor=HexColor('#17212B'), spaceAfter=0)
small = ParagraphStyle('small', parent=body, fontSize=6.6, leading=7.7)
mini = ParagraphStyle('mini', parent=body, fontSize=6.35, leading=7.25)
key = ParagraphStyle('key', parent=body, fontName='Helvetica-Bold', textColor=navy)
foot = ParagraphStyle('foot', parent=styles['Normal'], fontName='Helvetica-Oblique', fontSize=6.25, leading=7.2, alignment=TA_CENTER, textColor=HexColor('#52616B'))

P = lambda text, style=body: Paragraph(text, style)

def section_header(text):
    t = Table([[P(text, sec)]], colWidths=[187*mm])
    t.setStyle(TableStyle([('BACKGROUND',(0,0),(-1,-1),navy),('LEFTPADDING',(0,0),(-1,-1),3*mm),('RIGHTPADDING',(0,0),(-1,-1),2*mm),('TOPPADDING',(0,0),(-1,-1),1.4*mm),('BOTTOMPADDING',(0,0),(-1,-1),1.4*mm)]))
    return t

def boxed(data, widths, font=body, header=False):
    rows=[]
    for row in data:
        rows.append([cell if hasattr(cell,'wrap') else P(cell,font) for cell in row])
    t=Table(rows,colWidths=widths, repeatRows=1 if header else 0)
    cmds=[('GRID',(0,0),(-1,-1),0.35,line),('VALIGN',(0,0),(-1,-1),'TOP'),('LEFTPADDING',(0,0),(-1,-1),2.0*mm),('RIGHTPADDING',(0,0),(-1,-1),1.5*mm),('TOPPADDING',(0,0),(-1,-1),1.05*mm),('BOTTOMPADDING',(0,0),(-1,-1),1.05*mm)]
    if header:
        cmds += [('BACKGROUND',(0,0),(-1,0),blue),('FONTNAME',(0,0),(-1,0),'Helvetica-Bold')]
    else:
        cmds += [('BACKGROUND',(0,0),(-1,-1),light)]
    t.setStyle(TableStyle(cmds))
    return t

story=[]
story += [P('CHEMICAL MEDIATORS OF INFLAMMATION',title), P('Robbins-based one-page revision | Acute inflammation | Write sources + principal actions in exams',sub)]
story.append(section_header('CORE CONCEPT'))
story.append(boxed([[P('<b>Definition:</b> endogenous substances that initiate, amplify, regulate, and terminate inflammatory reactions.',body),P('<b>Sources:</b> <font color="#17365D">cell-derived</font> or <font color="#17365D">plasma-derived</font>. Cell mediators are preformed (histamine) or newly synthesized (eicosanoids, cytokines). Plasma mediators circulate as inactive precursors and are activated by proteolysis.',body)]],[91.5*mm,95.5*mm]))
story.append(Spacer(1,2.4*mm))

story.append(section_header('PRINCIPAL MEDIATORS: SOURCE AND ACTION'))
data=[
 [P('<b>MEDIATOR</b>',key),P('<b>MAIN SOURCE</b>',key),P('<b>HIGH-YIELD ACTIONS</b>',key)],
 [P('<b>Histamine</b>',body),P('Mast cells; basophils; platelets',small),P('<b>Vasodilatation</b>, ↑ vascular permeability (endothelial contraction), endothelial activation.',small)],
 [P('<b>Serotonin</b>',body),P('Platelets',small),P('Vasoactive effects, mainly vasoconstriction.',small)],
 [P('<b>Prostaglandins</b><br/><font size="6.2">PGE<sub>2</sub>, PGI<sub>2</sub>, PGD<sub>2</sub></font>',body),P('Mast cells, leukocytes, endothelium',small),P('<b>Vasodilatation</b>; PGE<sub>2</sub>: <b>pain + fever</b>. TXA<sub>2</sub>: vasoconstriction, platelet aggregation.',small)],
 [P('<b>Leukotrienes</b>',body),P('Leukocytes, mast cells',small),P('LTB<sub>4</sub>: <b>chemotaxis</b>, leukocyte activation. LTC<sub>4</sub>/LTD<sub>4</sub>/LTE<sub>4</sub>: ↑ permeability, bronchospasm, vasoconstriction.',small)],
 [P('<b>Lipoxins</b>',body),P('Leukocytes, platelets',small),P('Inhibit neutrophil recruitment and adhesion: <b>resolution</b>.',small)],
 [P('<b>PAF</b>',body),P('Platelets, mast cells, leukocytes, endothelium',small),P('↑ permeability, vasodilatation, leukocyte adhesion/chemotaxis/degranulation, platelet aggregation.',small)],
 [P('<b>TNF, IL-1</b>',body),P('Macrophages, dendritic cells, other leukocytes',small),P('Endothelial activation, leukocyte recruitment; systemic: <b>fever</b>, acute-phase response, leukocytosis; excess: shock/DIC.',small)],
 [P('<b>Chemokines</b><br/><font size="6.2">e.g., IL-8/CXCL8</font>',body),P('Leukocytes, endothelium, many cells',small),P('<b>Chemotaxis</b> and activation of leukocytes. IL-8 recruits neutrophils.',small)],
 [P('<b>Complement</b>',body),P('Plasma proteins',small),P('C3a/C5a: anaphylatoxins, histamine release. C5a: chemotaxis/activation. C3b: opsonization. C5b-9: microbial lysis.',small)],
 [P('<b>Bradykinin</b>',body),P('Plasma kinin system',small),P('↑ permeability, vasodilatation, <b>pain</b>, bronchoconstriction.',small)],
 [P('<b>Nitric oxide</b>',body),P('Endothelium, macrophages',small),P('Vasodilatation; inhibits platelet/leukocyte adhesion; macrophage NO is microbicidal.',small)],
 [P('<b>ROS, lysosomal enzymes</b>',body),P('Neutrophils, macrophages',small),P('Microbial killing; extracellular release causes tissue and endothelial injury.',small)],
 [P('<b>Neuropeptides</b><br/><font size="6.2">Substance P</font>',body),P('Sensory nerves',small),P('Pain, vasodilatation, ↑ permeability.',small)],
]
story.append(boxed(data,[34*mm,47*mm,106*mm],header=True))
story.append(Spacer(1,2.4*mm))

story.append(section_header('LAST-MINUTE ACTION MAP'))
map_data=[
 [P('<b>Vasodilatation</b><br/>Histamine, PGE<sub>2</sub>/PGI<sub>2</sub>, NO',small),P('<b>↑ Vascular permeability</b><br/>Histamine, bradykinin, LTC<sub>4</sub>/D<sub>4</sub>/E<sub>4</sub>, PAF, C3a/C5a',small),P('<b>Chemotaxis / activation</b><br/>C5a, LTB<sub>4</sub>, chemokines, TNF, IL-1',small)],
 [P('<b>Pain</b><br/>Bradykinin, PGE<sub>2</sub>',small),P('<b>Fever</b><br/>IL-1, TNF → PGE<sub>2</sub>',small),P('<b>Opsonization / lysis</b><br/>C3b / C5b-9 (MAC)',small)],
]
story.append(boxed(map_data,[62.3*mm,62.3*mm,62.4*mm],font=small))
story.append(Spacer(1,2.2*mm))
story.append(P('<b>Exam line:</b> “The major chemical mediators are vasoactive amines, arachidonic acid metabolites, cytokines and chemokines, PAF, complement, kinins, nitric oxide, lysosomal enzymes, reactive oxygen species, and neuropeptides.”',small))
story.append(Spacer(1,1.3*mm))
story.append(P('Source: Robbins & Kumar Basic Pathology, chapter “Inflammation and Repair”, Mediators of Inflammation, pp. 33-39. Content condensed for revision.',foot))

doc.build(story)
print(OUT)

Running Command

python "/tmp/workspace/chemical-mediators-revision/src/create_revision_pdf.py" && python -c "from pypdf import PdfReader; p='/tmp/workspace/chemical-mediators-revision/output/Chemical_Mediators_of_Inflammation_Robbins_Revision.pdf'; r=PdfReader(p); print('pages=',len(r.pages)); print('chars=',len(r.pages[0].extract_text()))"

One-page Robbins-based revision PDF:

Chemical Mediators of Inflammation Robbins Revision

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