¶ gastritis
¶ Definition
Inflammation of the gastric mucosa characterized by immune cell infiltration (neutrophils in acute phase, lymphocytes and plasma cells in chronic phase) in response to infection (primarily Helicobacter pylori in 80-90% of cases), autoimmune attack (parietal cell antibodies targeting H+/K+ ATPase and intrinsic factor), or chronic irritation (NSAIDs, alcohol, chronic stress). Represents the critical transition stage between acute mucosal injury and irreversible gastric atrophy, with progression determined by Th1/Th17 polarization, NOX2-mediated oxidative stress, and glandular destruction rates.
¶ Picture It
Think of the stomach lining as a factory floor with two types of workers: acid-producing parietal cells (the main workforce) and mucus-secreting cells (the protective maintenance crew). In acute gastritis, it's like a chemical spill—emergency responders (neutrophils) rush in to clean up the immediate damage from NSAIDs or alcohol. The factory can recover quickly if the spill stops. But in chronic gastritis—especially with H. pylori infection—it's more like termites in the walls. The bacteria burrow into the mucus layer and release toxins (CagA, VacA) that act like alarm bells, calling in a permanent construction crew (lymphocytes, macrophages). The problem: this "construction crew" doesn't just repair—it starts demolishing the walls (glandular tissue) to get at the infection. The factory responds by turning down acid production (via PGE2, the "safety shutdown signal"), which ironically makes the infection worse because acid normally kills invaders. The demolition continues year after year: acute gastritis (chemical spill) → chronic gastritis (termite infestation) → gastric atrophy (condemned building with no workers left). Meanwhile, the same stress response that activates emergency systems in your brain (insular cortex) simultaneously activates the same demolition enzymes (NOX2) in your stomach lining—social stress literally corrodes your stomach from the inside using the same molecular switches.
¶ Mechanism
¶ Acute Gastritis Cascade
Chemical/NSAID-induced:
NSAIDs → COX-1 inhibition → ↓PGE2 → loss of mucosal protection → epithelial damage → DAMPs release (HMGB1, ATP) → TLR4 activation on epithelial cells → NF-κB nuclear translocation → IL-8 secretion (primary neutrophil chemoattractant) → neutrophil infiltration → degranulation releasing myeloperoxidase and elastase → oxidative burst → epithelial necrosis → rapid-onset inflammation (hours to days)
H. pylori-induced acute phase:
H. pylori colonization in mucus layer → CagA toxin injection via Type IV secretion system → disruption of epithelial tight junctions (ZO-1, occludin) → VacA toxin → vacuole formation in epithelial cells → epithelial cell apoptosis → DAMP release → IL-8 and IL-1β secretion → neutrophil recruitment → active chronic gastritis
¶ Chronic Gastritis Cascade
Molecular detail:
- Th1 cells secrete IFN-γ → activates JAK-STAT pathway in macrophages → M1 polarization → TNF-α, IL-6, IL-1β secretion
- Th17 cells secrete IL-17A → binds IL-17R on epithelial cells → NF-κB and MAPK activation → IL-8, G-CSF, CXCL1 secretion → sustained neutrophil recruitment
- NOX2 (NADPH oxidase) in gastric epithelial cells: glutamate (from stress) → NMDA receptor activation → Ca²⁺ influx → protein kinase C activation → NOX2 assembly → superoxide (O₂⁻) production → hydrogen peroxide (H₂O₂) → hydroxyl radical (OH·) → lipid peroxidation and DNA damage
Autoimmune gastritis mechanism:
Antibodies against H+-K+ ATPase (proton pump on parietal cells) → antibody-dependent cell-mediated cytotoxicity (ADCC) → NK cell and macrophage-mediated parietal cell destruction → antibodies against intrinsic factor → B12-intrinsic factor complex cannot form → terminal ileum absorption blocked → vitamin B12 deficiency → pernicious anemia
Stress-gastritis neuroimmune link:
Social stress → insular cortex and striatum activation → glutamate release in brain and gastric mucosa simultaneously → NMDA receptor activation → NOX2 upregulation in both locations → parallel oxidative damage to neurons and gastric epithelial cells
¶ Progression Cascade
Normal mucosa → acute gastritis (neutrophil infiltration) → chronic active gastritis (lymphocytes + neutrophils) → chronic gastritis (lymphocytes, plasma cells) → multifocal atrophic gastritis → intestinal metaplasia → dysplasia → adenocarcinoma (Correa cascade)
¶ Clinical Significance
Gastritis is the pivotal intervention point in the stomach's progressive deterioration—catch it here or lose the battle downstream. In the cPNI framework, it exemplifies multiple metamodel failures simultaneously:
Metamodel 1 (Chronic inflammation): H. pylori infection creates sustained Th1/Th17 polarization with IL-6 >10 pg/mL, TNF-α elevation, and persistent neutrophil infiltration visible on histology—classic metaflammation that won't resolve without addressing the infection.
Metamodel 2 (Selfish systems): The selfish immune system prioritizes pathogen elimination over tissue preservation—chronic gastritis represents immune "scorched earth" tactics where the stomach lining becomes collateral damage. Simultaneously, the selfish brain activates NOX2 in gastric mucosa during social stress, stealing resources from gut barrier maintenance for threat processing.
Evolutionary mismatch: Modern dietary insults (NSAIDs, alcohol, processed foods) and chronic psychological stress (social defeat, isolation) were not selection pressures during evolution. H. pylori co-evolved with humans and was likely protective against childhood atopic disease via Treg induction—its elimination in developed nations correlates with rising asthma/eczema rates (hygiene hypothesis trade-off).
Patient phenotypes most affected:
- Chronic NSAID users (elderly with osteoarthritis)—COX-1 inhibition strips mucosal defenses
- H. pylori-positive with high CagA+ strains—accelerated progression to atrophy
- High-stress phenotypes (chronic stress, PTSD, social isolation)—NOX2-mediated damage
- Autoimmune predisposition (other autoimmune diseases, family history)—parietal cell antibodies
Clinical thresholds and biomarkers:
- Serum pepsinogen I/II ratio
.0 indicates corpus atrophy - Serum gastrin >150 pg/mL suggests hypochlorhydria from atrophy or PPI use
- IL-6 >10 pg/mL, CRP >3 mg/L indicate systemic inflammation spillover
- Fecal calprotectin can be elevated (>50 μg/g) if inflammation severe
- Anti-parietal cell antibodies present in 80-90% of autoimmune gastritis
- Anti-intrinsic factor antibodies (more specific, 50-70% sensitivity)
Intervention implications:
- H. pylori eradication: Triple therapy (PPI + amoxicillin + clarithromycin) or quadruple therapy—resolves inflammation in 90%+ if caught before severe atrophy
- NSAID cessation/alternatives: Switch to acetaminophen, topical NSAIDs, or add PPI if continuation necessary
- Stress axis intervention: HRV biofeedback, vagus nerve stimulation, social support restoration—directly reduces NOX2 activation
- Restore acid environment: Betaine HCl (if non-atrophic), bitter herbs, avoid PPIs unless absolutely necessary
- Antioxidant support: vitamin C 1000 mg/day, vitamin E, polyphenols (green tea EGCG) to counter NOX2 oxidative damage
- Monitor progression: Annual serum pepsinogen, gastrin, B12—intervene before irreversible atrophy
Critical clinical concept: PGE2 elevation during gastritis is a protective attempt to reduce acid and prevent perforation, but it creates a vicious cycle—hypochlorhydria → bacterial overgrowth → worse inflammation. This is why acid suppression with PPIs, while symptom-relieving, can worsen the underlying pathology long-term.
¶ Key Facts
- H. pylori infection causes 80-90% of chronic gastritis globally; CagA+ strains increase cancer risk 5-fold compared to CagA-negative strains
- Neutrophil infiltration (polymorphonuclear leukocytes) indicates acute or active chronic phase; lymphocytes and plasma cells indicate chronic phase
- Progression timeline: acute gastritis (days-weeks) → chronic active gastritis (months-years) → gastric atrophy (5-10 years) → intestinal metaplasia → dysplasia → adenocarcinoma (decades)
- Th1 polarization (IFN-γ dominant) drives macrophage activation and oxidative damage; Th17 (IL-17A dominant) drives neutrophil recruitment—both present in H. pylori gastritis
- PGE2 elevation during inflammation paradoxically suppresses H+-K+ ATPase activity (acid production) as protective brake, contributing to hypochlorhydria
- Social stress activates NOX2 in gastric mucosa simultaneously with insular cortex and striatum—same molecular pathway, parallel damage
- Autoimmune gastritis (10-15% of cases, more common in Northern European descent) targets parietal cells and intrinsic factor, causing B12 deficiency in 100% if untreated
- Serum pepsinogen I/II ratio .0 indicates corpus atrophy; gastrin >150 pg/mL indicates hypochlorhydria
- IL-8 is the primary neutrophil chemoattractant released during H. pylori infection (50-100 pg/mL in gastric juice vs. <10 pg/mL normal)
- Chronic atrophic gastritis increases gastric cancer risk 6-8 fold; intestinal metaplasia increases it 10-15 fold
¶ Connections
- Helicobacter pylori — primary infectious cause of chronic gastritis in 80-90% of cases; CagA and VacA toxins drive Th1/Th17 polarization and epithelial damage
- gastric ulcers — gastritis is the precursor inflammatory condition that erodes mucosal defenses, increasing ulcer risk 3-5 fold
- gastric atrophy — end result of chronic gastritis with irreversible glandular destruction, loss of parietal cells, and hypochlorhydria
- hypochlorhydria — both cause and consequence: low acid allows H. pylori colonization, inflammation-induced PGE2 suppresses acid production
- neutrophils — primary immune cells in acute and active chronic gastritis; degranulation releases myeloperoxidase and elastase causing tissue damage
- Th1 — T helper subset secreting IFN-γ, driving M1 macrophage activation and chronic H. pylori gastritis pathology
- Th17 — inflammatory T cell subset secreting IL-17A, recruiting neutrophils and amplifying mucosal damage in chronic gastritis
- PGE2 — elevated 5-10 fold during gastritis as protective brake on acid secretion; paradoxically worsens hypochlorhydria and bacterial overgrowth
- NSAIDs — cause chemical gastritis via COX-1 inhibition, stripping mucus/bicarbonate protection and causing acute epithelial injury within hours
- parietal cell — acid-producing cell targeted in autoimmune gastritis; destruction causes hypochlorhydria, hypergastrinemia, and B12 malabsorption
- NOX2 — NADPH oxidase activated by stress (glutamate-NMDA pathway) and infection, generating superoxide and oxidative DNA damage in gastric epithelium
- chronic stress — activates NOX2 in gastric mucosa via insular cortex-mediated glutamate release; social defeat increases gastritis severity 2-3 fold in animal models
- insular cortex — brain region linking social stress to gastric NOX2 activation; same glutamate-NMDA pathway operates in parallel in brain and stomach
- IL-6 — pro-inflammatory cytokine elevated in gastritis (>10 pg/mL serum); drives Th17 polarization and systemic inflammation spillover
- IL-8 — neutrophil chemoattractant released by H. pylori-infected epithelium (50-100 pg/mL gastric juice); primary driver of neutrophil infiltration
- TNF-α — pro-inflammatory cytokine amplified by M1 macrophages; contributes to epithelial apoptosis and barrier dysfunction in chronic gastritis
- intrinsic factor — glycoprotein secreted by parietal cells; target of antibodies in autoimmune gastritis, causing B12 deficiency and pernicious anemia
- vitamin B12 deficiency — inevitable consequence of chronic atrophic gastritis and intrinsic factor loss; manifests as megaloblastic anemia and neurological symptoms
- SIBO — consequence of gastritis-associated hypochlorhydria; loss of gastric acid barrier allows small intestinal bacterial overgrowth
- chronic inflammation — fundamental pathological process driving gastritis progression; metaflammation phenotype with sustained Th1/Th17 activation
- IL-1β — early inflammatory cytokine released by H. pylori-infected epithelium; polymorphisms (IL-1β-31T/T, IL-1β-511C/C) increase gastric cancer risk 3-fold
- NF-κB — transcription factor activated by TLR4, IL-1R, TNF-R; master regulator of inflammatory gene expression in gastritis
- TLR4 — pattern recognition receptor activated by H. pylori LPS; initiates inflammatory cascade via NF-κB and MAPK pathways
- IFN-γ — Th1 cytokine driving M1 macrophage polarization and oxidative damage; elevated 10-50 fold in H. pylori-infected gastric mucosa
- COX-2 — inducible cyclooxygenase upregulated in gastritis; generates PGE2 as protective brake but contributes to hypochlorhydria
- Treg cells — regulatory T cells that suppress inflammation; H. pylori strains with low virulence induce Tregs, potentially explaining hygiene hypothesis
- autoimmunity — autoimmune gastritis represents loss of tolerance to parietal cell antigens; associated with other autoimmune diseases (Hashimoto's, type 1 diabetes)
- oxidative stress — NOX2-generated ROS cause DNA damage, lipid peroxidation, and protein oxidation in gastric epithelium; antioxidant depletion accelerates atrophy
- gut barrier — gastritis represents barrier failure at gastric level; epithelial tight junction disruption allows bacterial antigen translocation
- GALT — gastric-associated lymphoid tissue activated during H. pylori infection; drives Th1/Th17 polarization and antibody production
¶ Module References
- Module 5 — Pain mechanisms, stress-pain interface, insular cortex activation in gastritis
- Module 6 — Organ pathology, gastric inflammation progression, gut barrier dysfunction