Lesson 17

Question 1

What is inflammation and what are its symptoms?

Answer 1

Inflammation represents a complex response characterized by a set of signs known as rubor(redness), calor (warmth), tumor(swelling), dolor (pain), and functio laesa. The last addition, functio laesa, underscores the impairment of function of a tissue or organ associated with pain and other symptoms during inflammation. Various causes, including different pathogens, can trigger this response accompanied by the migration of white blood cells. The interconnected nature of inflammation and the immune system is evident in these responses.
A typical inflammatory response is a beneficial acute process designed to heal the body following an injury. Activation of the immune system initiates the inflammatory response, facilitating tissue healing and restoring homeostasis. However, in certain cases, inflammation becomes chronic, indicating an inadequate response to a stimulus, such as in allergies or chronic conditions.

Question 2

what are the two main strategies to manage inflammation? what are the main cathegories of anti inflammatory drugs? What type of NSAIDs do you know and what is their mechansim of action?

Answer 2

here are two main pharmacological strategies for managing inflammation:

1. Modifying Signalling Mediators or Suppressing Immune Components: This approach focuses on alleviating symptom providing relief from chronic inflammatory processes.
2. Modifying the Underlying Pathophysiological Stimulus: This strategy aims to eliminate the cause of inflammation, addressing the root of the issue. These drugs are more targeted and defined in their action.

Also, anti-inflammatory drugs can be divided in these major categories:

1. NSAIDs (Non-Steroidal Anti-Inflammatory Drugs): widely used and accessible to the general public without a prescription. They target the enzymes involved in prostanoid production, providing relief from inflammation.
2. DMARDs (Disease-Modifying Anti-Rheumatic Drugs): These drugs, categorized as antirheumatoid, can modify the progression of chronic inflammatory diseases. The exact mechanisms of action are not fully understood.
3. Glucocorticoids: Steroidal drugs, including the newer genetically engineered compounds. They play a role in modulating immune responses and inflammation.
4. Antihistamines: Used in the treatment of allergic inflammation, antihistamines provide relief by modulating allergic responses.
5. Gout-Specific Drugs: Certain drugs are specifically designed to control gout, a form of inflammatory arthritis.

With around 50 different drugs in this category, NSAIDs represent a thriving market, addressing the needs of many individuals. NSAIDs are categorized into two classes based on their target enzymes, known as cyclooxygenases (COX). There are two types of COX enzymes, COX-1 and COX-2.

• Nonselective NSAIDs: Inhibit both COX-1 and COX-2.
• COX-2 Selective NSAIDs: Developed later, targeting COX-2 specifically.

Understanding the distinction between COX-1 and COX-2 is crucial to comprehend the side effects associated with chronic NSAID use. These enzymes, with 61% homology in their genes, serve different roles: COX-1, constitutively expressed by most cells, is involved in protective functions crucial for tissue homeostasis. Functions include blood flow autoregulation in the kidneys, hemostasis in vessels and platelets, and a cytoprotective role in the gastric mucosa. It is also involved in prostaglandin formation during inflammation. COX-2 is Inducible and gets activated during inflammatory processes, it is expressed by inflammatory and immune cells and endothelial cells. Both isoforms exist as dimers inserted into the endoplasmic reticular membrane. Also, COX-1 and COX-2 exhibit similar structures and their action on arachidonic acid (AA), the precursor of prostanoids, involves the formation of heterodimers. A monomer of COX catalyses AA, while the other acts as an allosteric subunit. Structural differences, like the presence of valine instead of lysine in position 434 of COX-2, contribute to a bulge-structure not found in COX-1. The larger channel in COX-2 allows for potential selective drug development, although complete selectivity is not guaranteed.

The primary therapeutic effects of NSAIDs stem from their capacity to inhibit the production of prostaglandins (PGs) by blocking COX. How are prostaglandins formed? Arachidonic acid (AA) is released from cellular phospholipids by phospholipase A2. COX converts AA to unstable intermediates (PGG2 and PGH2), PGH2 serves as a precursor for various prostanoids, including prostaglandins, thromboxanes, and prostacyclins.

Question 3

What are the 3 main effects of NSAIDs? what are the 3 classes of NSAIDs? what is paracetamol? what are coxibs?

Answer 3

Except for aspirin, NSAIDs act as reversible, competitive inhibitors of cyclooxygenase. The class of NSAIDs comprises over 50 compounds, classified into various subclasses based on their structure or their effect on cyclooxygenase (COX). Due to chronic misuse, some now require a prescription.
Blocking COX results in three main effects:

• Anti-Inflammatory Action: Decreases prostaglandin and prostacyclin levels, reducing vasodilation.
• Analgesic Effect: Mild to moderate pain relief but less effective for severe pain.
• Antipyretic Effect: Reduces temperature in inflammatory conditions.

While NSAIDs provide positive effects on symptoms, they do not resolve the underlying inflammatory process. For chronic inflammatory diseases, they manage symptoms without halting the disease progression.

We said that most NSAIDs act as reversible competitive inhibitors of COX, but actually we are able to categorize them based on how they behave with COX:

1. Class I, Simple Competitive Inhibition: Includes drugs like ibuprofen and piroxicam.
2. Class II, Competitive and Time-Dependent Reversible Inhibition: includes indomethacin and flurbiprofen.
3. Class III, Time-Dependent Irreversible Inhibition: Solely represented by acetylsalicylic acid, commonly known as aspirin.

In this classification we did not name paracetamol since it stands as a distinct entity. It is widely used over-the-counter for mild to moderate pain. While effective as an analgesic and antipyretic, it lacks significant anti-inflammatory properties. Inflammatory processes render paracetamol less useful. Overuse, especially when exceeding recommended doses, poses a risk of toxicity, potentially leading to fatal liver damage. Paracetamol misuse is prevalent, particularly in the UK.

NSAIDs, extensively used for prolonged periods, especially among the elderly, carry a high burden of unwanted side effects. These affect various organs, including the gastrointestinal (GI) tract, liver, kidney, spleen, and blood. GI side effects include gastric bleeding and ulceration, primarily due to the inhibition of prostaglandins that normally protect the mucosa.
To address the side effects associated with non-selective COX inhibition, researchers tried to create molecules selectively blocking COX-2. This led to the development of COX-2 inhibitors, known as coxibs, around two-three decades ago. The idea was to retain efficacy while minimizing GI complications. Six coxibs were initially approved: celecoxib, rofecoxib, valdecoxib, parecoxib, etoricoxib, and lumiracoxib. These were considered promising for chronic disorders. However, many were either restricted or withdrawn from the market due to adverse cardiovascular risks, particularly in terms of QT interval prolongation. Two coxibs, Celecoxib and Etoricoxib, remain on the market for symptomatic relief in osteoarthritis and rheumatoid arthritis. As per the other COX inhibitors, while they alleviate symptoms, they do not cure the underlying diseases.

It is also interesting to notice that there are certain older NSAIDs, like diclofenac that exhibit higher COX-2 selectivity compared to COX-1, demonstrating effects similar to coxibs. However, the quest for an ideal balance between efficacy and safety in NSAID therapy remains ongoing.

Question 4

What are DMARDs? What DMARDs do you know?

Answer 4

Chronic inflammatory conditions, such as Rheumatoid Arthritis (RA), are prevalent in developed countries, contributing significantly to disability. RA involves autoimmune reactions, characterized by increased antibodies targeting joints, leading to erosion of cartilage and bones. Patients cannot use well their hands since sometimes the joint are deformed because of the chronic inflammatory process. It is estimated that 1 in 3 patients suffering from this disease will develop severe symptoms and become disabled on top of having an increased risk of mortality; that is why we need drugs. These problems are caused by an autoimmune reaction; key players in the disease include inflammatory cytokines, notably IL-1 and TNF-α.

While NSAIDs offer relief from stiffness and pain in RA, they fall short in moderating disease progression.

The underlying mechanism involves antigen presenting cells which activate macrophages. At this stage IL2 has an important role, then we have lymphocytes proliferation that cause the increase of macrophages which in turn release IL1 ad TNF alpha causing the production of osteoclasts and fibroblasts, able to damage collagen and bones. TNF alpha is able to release other inflammatory cytokines which cause an influx of inflammatory cells, all of this causes the erosion of bone and joint damage.

A specific class designed to halt or potentially reverse the inflammatory process in RA is Disease-Modifying Antirheumatic Drugs DMARDs. While NSAIDs manage symptoms, DMARDs, considered second-line drugs due to side effects and delayed onset, play a crucial role. Among DMARDs we have:

• Methotrexate: A widely used and successful DMARD, a folic acid antagonist with cytotoxic and immunosuppressant properties. It stands as a common first-choice drug in Italy. It acts rapidly, differing from the slower onset of other DMARDs, though it carries adverse effects, primarily on bone marrow, leading to liver cirrhosis. Its mechanism involves folate antagonism and adenosine signalling modulation.
• Sulfasalazine: It induces remission in active RA and is also utilized for inflammatory bowel disease. Commonly considered a first choice in the UK, it comprises sulfapyridine and salicylate, acting by inhibiting COX and lipoxygenase pathways. Additionally, it demonstrates immunosuppressive effects by reducing IL-8 release from myofibroblasts and scavenging toxic free radicals. The complex nature of sulfasalazine, combining multiple abilities, contributes to its effectiveness.
• Penicillamine: derived from the hydrolysis of penicillin, possesses unique characteristics, primarily utilized in the therapy of rheumatoid disease. The D-isomer of penicillamine, comprising about 75% of patients responding to penicillamine, showcases therapeutic effects within weeks, reaching a plateau after several months. The probable mechanisms of action involve the reduction of the immune response and IL-1 generation, pivotal in the pathway leading to joint damage. Additionally, penicillamine prevents the maturation of newly synthesized collagen, a factor contributing to joint damage and reorganization in rheumatoid illnesses. The drug’s highly reactive thiol group grants it metal-chelating properties, proving beneficial in diseases like Wilson’s disease, characterized by pathological copper deposition. Despite its efficacy, unwanted effects occur in 40% of patients, with rashes and stomatitis being the most common. Dosage reduction can alleviate these side effects. Less frequent side effects include anorexia, fever, nausea, vomiting, and disturbances of taste. Regular blood monitoring is imperative due to potential alterations.
• Gold: administered as an organic complex called sodium aurothiomalate, exhibits anti-inflammatory effects over a gradual 3–4 month period. This treatment proves successful, alleviating pain, joint swelling, and reducing the progression of bone and joint damage. The mechanism of action remains unclear, but deep intramuscular injections gradually accumulate gold complexes in synovial cells, acting as reservoirs even after treatment cessation. One-third of patients experience unwanted effects, with approximately 1 in 10 encountering serious toxic effects. Side effects include severe rashes, mouth ulcers, non-specific flu-like symptoms, and, rarely, severe complications such as proteinuria, thrombocytopenia, and blood dyscrasias. Anaphylactic reactions, though less common, necessitate discontinuation of the drug.
• Antimalarial Agents: when other treatments prove ineffective, antimalarial drugs, such as Hydroxychloroquine and Chloroquine, emerge as alternatives. Originally designed for malaria prevention and treatment, they also function as DMARDs. However, their efficacy varies, with approximately half of the patients responding. Hydroxychloroquine and Chloroquine likely reduce lymphocyte proliferation, though their broader effects contribute to their antirheumatic properties. Chloroquine finds application in lupus erythematosus but is avoided in case of skin rashes due to potential exacerbation. Antirheumatic effects may take a month or more to manifest, and ocular toxicity is a crucial consideration, especially with Chloroquine, necessitating careful monitoring during treatment.

While these DMARDs play a crucial role in managing RA, for most of them their clinical effects are gradual, taking months to manifest. Their utilization often involves a tailored approach, sometimes combining different drugs to enhance efficacy and mitigate side effects.

Question 5

Speak about immunosuppressants

Answer 5

mmunosuppressants, a vital class of drugs, find applications in treating autoimmune diseases and preventing/transcending transplant rejection. Despite their efficacy, they pose a significant challenge by impairing the immune response, leading to a heightened vulnerability to infections and potential malignant cell line formation due to a compromised immune sentinel function.

These drugs primarily act during the induction phase of the immune response, with distinct effects based on their mode of action: Drugs inhibiting IL-2 production or action (e.g., ciclosporin, tacrolimus), drugs inhibiting cytokine gene expression (corticosteroids), drugs inhibiting purine or pyrimidine synthesis (azathioprine, mycophenolate mofetil, leflunomide).

Normally we have the activation of antigen presenting cells which interact with CD4 and CD8 cell lines and their activation, mediated by IL2 release, leads to the activation of macrophages and also innate immunity cells so it kills virally infected cells, this happens for both CD4 and CD8. So blocking this signal we might block this cell mediated immunity.

Ciclosporin, is part of the first class mentioned, it is a naturally occurring cyclic peptide initially isolated from a fungus, exhibits potent immunosuppressive properties. Its actions in immunosuppression include: decreasing clonal proliferation of T cells by inhibiting IL-2 synthesis and possibly reducing IL-2 receptor expression, diminishing the induction and clonal proliferation of cytotoxic T cells derived from CD8+ precursor T cells. Suppressing the function of effector T cells responsible for cell-mediated responses, leading to decreased delayed-type hypersensitivity, reducing T cell-dependent B-cell responses. While nephrotoxicity stands out as a notable side effect, Ciclosporin doesn’t depress bone marrow function. The probable mechanism of action lies in its selective inhibitory effect on IL-2, IFN gamma, and IL-3. Interaction with cyclophilin inhibits calcineurin, preventing IL-2 production.

Tacrolimus, is also part of the first class, it is an antibiotic of fungal origin and it shares a similar mechanism with Ciclosporin but boasts higher potency. It utilizes FKBP (FK-binding protein) as its internal receptor, diverging from Ciclosporin’s interaction with cyclophilin. Tacrolimus finds application in organ transplantation and severe atopic eczema.

Other compounds in this category include:

• Pimecrolimus: Used topically for treating atopic eczema.
• Sirolimus (Rapamycin): Prevents organ rejection and is used in cardiac stents to prevent restenosis. It interacts with an immunophilin but blocks the mTOR pathway, functioning differently from other immunosuppressants.

In the third class we find antimetabolites, a class adept at hindering purine or pyrimidine synthesis, which plays an important role in impeding clonal proliferation during the immune response’s induction phase. The intricacies lie in disrupting the production of lymphocytes crucial for a robust immune response.