Lecture 16: IBD pathophysiology and pharmacology Flashcards
What is the Epidemiology of CD?
Even F:M ratio
15-30 and another peak at 50-60
BIMODAL
Epidemiology of UC?
Even F:M ratio
Age of onset is similar to CD
What are the three factors that lead to pathophysiology of IBD?
- genetic predisposition
- microbiome
- immune system
What is the gene that leads to CD?
NOD2
Also CARD15
3 allele variants that lead to higher association
What does NOD2 do?
They are in paneth cells
Mutation leads to decrease in defensins
Defective in sensing bacteria, defective autophagy
What cytokines are involved in both CD and UC?
IL-23 and IL-12
What genes associated with autophagy lead to CD or UC?
Autophagy = CD and NOT UC
How does microbiome lead to IBD?
You need to have bacteria in order for IBD to occur, so it seems that bacteria definitely play a role
What methods can disturb balance of gut bacteria and immune system?
- pathogenic bacteria
- abnormal microbial composition
- defective host containment of commensal bacteria
- defective host immunoregulation (Treg is activated inappropriately)
What are 4 ways that immune system can be compromised in IBD?
- defect in innate community
- decrease in barrier function
- over activation of adaptive immunity
- leukocyte trafficking
What can TH17 (treg) is activated by?
IL-6, TGF-B, IL-21, 23
Produce cytokines that lead to inflammation and fibroblasts
What environmental factors lead to IBD?
Stress
Smoking
Dietary factors
What is the pathology and clinical presentation of CD?
Affect any level of GI tract
Focal, chronic inflammation
Most common in terminal ileum
Crypt inflammation with ABSCESS formation
Non-caseating granulomas!!
Grossly, it has skip lesions and cobblestoning
Cobblestoning = coalescence of ulceration with deep, serpiginous ulceration and heaped edematous mucosa adjacent
Crohn’s can have FISTULAS so transmural presentations
What are the penetrating and fibrotic complicatons of CD?
Stricturing from fibrosis Chronic inflammation = attempt to heal driven by TGF-Beta Subsequent type 3 deposition Resultant fibrosis Stricture formation
What are the pathologic features of UC?
Confined to mucosa Hyperemia, edema and granular appearance Starts in rectum and goes proximal No skip lesions Crypt abscesses and cryptitis
What is the clinical presentation of IBD?
- abdominal pain
- RLQ tenderness
- diarrhea
- hematochezia (blood from below)
- fever, night sweights
- weight loss, malabsorption (in CD)
- anemia
- elevated WBC
- hypoalbuminemia
What are extraintestinal manifestations of IBD?
Systemic inflammation that can affect other parts of body
- Joints (arthralgia)
- Bones (osteopenia)
- Dermatologic disorders (erythema nodosum)
- Opthalmologic complications (conjunctivitis)
- hepatobiliary (gall stones)
- Renal (nephrolithiasis, stones, due to fat malabsorption)
- HemeOnC, colorectal cancer
What is nephrolithiasis?
Calculi in kidney
What is calculi?
(a stone)
What is primary sclerosing cholangitis?
PSC results in chronic inflammation of intra/extrahepatic ducts of biliary tree
Beading irregularity and structuring of bile ducts
Confers high risk of colorectal cancer (CRC) and cholangiocarcinoma
What is MRCP?
Magnetic resonance cholangiopancreatography
Is smoking protective in UC?
Yes, but it worsens Crohn’s
What are goals of therapy for IBD?
- improvement of quality of life
- induction of remission
- avoidance of surgery
NO CURE for Crohn’s
Cure for UC = colectomy
What are indications for more aggressive therapy?
- tobacco use
- perianal or penetrating disease
- anemia
What is the treatment for mild IBD?
Short course glucocorticoids used for induction of remission
5-aminosalicylates (5-ASAs) for UC
Budesonide for CD
Topical steroid for distal disease
What is the treatment for mild UC?
5 aminosalicylates (5-ASAs) immunosuppresant
What is the treatment for mild CD?
Budesonide
A short course glucocorticoid
What is the treatment for moderate to severe IBD?
Immunosuppression to promote healing
- Immunomodulates like
i. Thiopurine antimetabolites (Aziathioprine)
ii. Methotrexate - Anti-TNF agents = Biologics
- Anti-alpha4 inhibitors
What are the key characteristics of aminosalicylates?
5-ASA moiety was therapeutic
If you have the whole thing, you have really bad side effects like agranulocytosis
Preparations of MESALAMINE have been developed to target bowel
What is mesalamine?
A type of aminosalicylates
What is the MoA of aminosalicylate/mesalamine?
Inhibition of T cell proliferation Inhibition of antigen presentation Decreased TNF production Inhibition of adhesion Used for UC
What are the side effects for Aminosalicylates?
Paradoxical diarrhea
Interstitial nephritis
What are the two main classes of glucocorticoids?
- Budesonide
- systemic corticosteroids like prednisone
Used more for CD
What is the MoA of glucocorticoids?
- inhibition of pro-inflammatory cytokines, adhesion molecules, leukotrienese
- inhibition of proteases such as elastase
- regulation of NF-kbeta in the nuclear
- decreased phagocytosis for neutrophils
- apoptosis of lymphocytes
What is the drawback for glucocorticoids?
They are not useful for MAINTENANCE of remission
Used instead to induce remission NOT to maintain it
What are the side effects of glucocorticoids
- Neuropsychiatric
2. Cushingoid response
What are the key characteristics of Budesonide?
- Novel steroid compound available in ileal release
- high degree of first pass metabolism in the liver
- Budesonide has been demonstrated to INDUCE remission in CD
Standard therapy for mild CD
What are the steroid-sparing agents?
- Immunomodulators
- Anti-TNFs
- Anti-alpha4 antibodies
What are the two types of immune modulaters?
- Thiopurines
2. Methotrexaate
What are the two types of thiopurines?
- Azithioprine
2. 6MP
What is MoA of Azathioprine and 6MP?
Act to INHIBIT DNA synthesis
AZA is converted to 6MP
6MP can then enter 3 pathways, one of hwhich converts it to 6-TIMP which inhibits DNA synthesis through apoptosis and inhibition of purine synthesis
What is contraindicated in the use of thiopurinols for moderate/severe IBD?
The presence of LOW TPMT activity
Some individuals possess a mutation with low TPMT activity
TPMT is an enzyme that converts 6-MP and 6-TIMP to shit that is hepatotoxic and inhibits purine synthesis
Low activity = bone marrow suppression and leukopenia
What is TPMT?
Thiopurine Methyltransferase
What are thiopurines used for?
Induction AND maintenance of remission of CD
Couple of months for effect
What are adverse effects of thiopurines?
- leukopenia, marrow suppression
- pancreatitis
- drug induced hepatitis
- infection (but lower risk than steroids)
- 3-5x increase risk of NHLymphoma
What is the MoA of methotrexate?
Folate antagonist
Inhibits multiple interleukins
Anti-inflmmatory properties
Effective for induction and maintenance of CD
What are the adverse effects of methotrexate?
- Nausea
- cirrhosis (lung issues)
- Teratogenic (induces abnormal prenatal development)
- pneumonitis
What is the characteristic of cyclosproin A?
Used for UC but discontinued for side effects
What are the types of anti-TNF therapies?
- Infliximab (IV)
- Adalimumab (subcutaneous)
- Certolizumab pegol
What is MoA of anti-TNF therapy?
Bind both soluble and cell-bound TNFalpha
Direct inhibition of TNF alpha
Induction of apoptosis of T cells and lymphocytes in lamina propria
Complement mediated apoptosis
Alters cytokine secretion in serum and lamina propria
Decrases IL, 1, 6, 18 and IFN gamma
What are infliximab, adalimumab and certolizumab used for?
CD
What are infliximab and adalimumab used for?
UC
What are the side effects of Anti-TNF therapy?
- transfusion reactions
- delayed hypersensitivity reactions
- drug induced lupus
- infection
- screened for Tb, hep b before initiating anti-TNF
- Hepatospelnic T cell lymphoma
What is the MoA of Anti-alpha4 Integrin inhibitors?
Directed against leukocyte adhesion molecules
What is an example of anti-alpha4 integrin inhibitor?
Natalizumab
What are the side effects of anti-alpha4 inhibitors?
PML (progressive multifocal leukoencephalopathy) if you have JC virus
Requires screening of JC virus
What are antibiotics used for in IBD?
Used for penetrating complications for IBD
What drug increases risk of PML?
Natalizumab (anti-alpha4 inhibitor)