Anti-inflammation + Steroids - Guo

• Molecular mechanism of steroids as anti-inflammation agents

• Biochemistry of steroids

• Glucocorticoids and mineralocorticoids

• SAR of glucocorticoids

4 Learning objectives

NF-kB, MAPK, and JAK-STAT

Three inflammation signaling pathways

NF-kB

This pathway is the main “inflammation switch” — it activates genes that make cytokines (like TNF-α, IL-1, IL-6) and other immune molecules that start and sustain inflammation.

MAPK

This pathway boosts inflammatory signals by increasing production of cytokines and enzymes (like COX-2) that amplify the inflammatory response.

JAK-STAT

This pathway responds to inflammatory cytokines (like interferons and interleukins) and helps immune cells communicate and keep inflammation going or regulate it.

Chromatin remodeling and gene expression

• Histones acetylated

• Coactivator molecules interact with transcription factors, and increase intrinsic HAT activity. 

• This results in opening/activation of chromatin structure and allow binding of RNA polymerase to chromatin = GENE TRANSCRIPTION!! 

A molecular mechanism of inflammation inhibition by steroids is ___

• corticosteroid binds to GR (receptor) and make a complex that can

  • Bind to NF-kB complex and decrease inflammation (by decreasing mediators and receptors/proteins)

  • Bind to GRE (glucocorticoid response element) and increase Anti-inflammatory effects

  • Bind to negative GRE and decrease keratin, osteocalcin, POMC, etc

Glucocorticoid receptors MOA

1. CS enters the cell because fat soluble

2. CS binds to Glucocorticoid receptor

3. Receptor complex (CS + GR) move to nucleus of cell and:

   1. GR binds to special DNA spots called GRE’s that TURN ON anti-inflammatory genes

   2. GR can BLOCK other proteins (like CBP, HATm and NF-kB or AP-1) which leads to gene repression and less inflammation

Easier explanation of how corticosteroids can reduce inflammation: 

1. Steroid binds to GR and makes complex

2. Complex enters nucleus and interferes with NF-kB and CBP/HAT, and stops them from opening the DNA

3. Gr also recruits HDAC2 which removes acetyl groups, and tightens DNA and turns off inflammatory gene transcription

How Corticosteroids stop the NF-kB path

• Their most important action is switching off multiple activated inflammatory genes through inhibition of HAT and recruitment of HDAC2 activity to the inflammatory gene transcriptional complex.

• HDAC2 may play an important role in deacetylating the acetylated GR after corticosteroid binding so that it can repress NF‐kB regulated inflammatory genes.

• In addition, corticosteroids may activate several anti‐inflammatory genes and increase the degradation of mRNA encoding certain inflammatory proteins.

Corticosteroids exert their anti‐inflammatory effects through influencing multiple signal transduction pathways

Structure of Cholestane

Structure of cholesterol

• Steroids + metabolites function as signaling molecules (most notable steroid hormones)

• Steroids and phospholipids are components of cell membranes

• Steroids such as cholesterol decrease membrane fluidity (not sources of energy though) 

• Steroids plat critical roles in number of disorders, including inflammation

Biological significance of steroids

Stimulate gluconeogenesis
Mobilization of amino acids
Inhibition of glucose uptake by tissues
Stimulation of lipid breakdown in adipose
Anti‐inflammation

Glucocorticoid Activities

Increase Na+/K+ reabsorption
Increase reabsorption of water

Mineralocorticoid Activities

Cortisone and Hydrocortisone

Different forms of cortisone and hydrocortisone, side effects

Having an extra Aldehyde group

mineralocorticoids differ in chemical structure from cortisol (glucocorticoids) by 

Anti-inflammatory activity increased by 10 times, while mineralocorticoid activity increased 300-800 times

when adding a OH group and Fluoride group to cortisol, the activity:

Similar increment for anti-inflammatory activity (4 times increased), with relatively lowered mineralocorticoid activities

A C1 to C2 double bond can do this effect for structure modifications (Prednisone and Prednisolone)

• As in hydrocortisone and cortisone

• Lower affinity to GR

• Faster metabolism on ring A

Ring A confirmation can change potencies of steroid drugs, including the half-chair conformation which: 

• As in prednisone and prednisolone

• Higher affinity to GR

• slower metabolism on ring A

Ring A confirmation can change potencies of steroid drugs, including the flattened-boat conformation which: 

• 11beta hydroxysteroid-dehydrogenase (from prednisolone to prednisone)

• CYP450 (into active metabolite)

• 20alpha/beta hydroxysteroid-dehydrogenase (into active metabolite)

Major metabolism routes of prednisolone and prednisone

• 6alpha-methyl analog of prednisolone

• Has similar glucocorticoid activity

• No significant mineralocorticoid activity

Methylprednisolone is the

• 9alpha-fluoro increases glucocorticoid potency as well as increases mineralocorticoid potency

• 16alpha-OH reduces mineralocorticoid potency while maintaining glucocorticoid activity

• The end result is similar glucocorticoid activity to prednisolone with no significant mineralocorticoid activity

Other combinations and structure changes that effect activity

Introduction of 16-methyl group

• Lipophilicity and metabolism slowdown

• Long acting and 20x more portent that cortisol as a gluco, with no activity

• DEXAMETHASONE!

Additional combinations and structure changes that effect activity

Fluocinolone

• two Fluorides

• Owl group (O connected to carbon and other O)

Beclomethasone

• Cl group and 16alpha methyl

Characteristics of Fluocinolone and Beclomethasone

Halcinonide and Fluticasone

Chloro group attached to carbon 21 (Top right) - “betasols”!!

The 21 chlorocorticoids have