The role of prostaglandins in the inflammation pathway and the mechanism of action of NSAIDs
Student ID: 51555517 Date: 11-11-2015
Inflammation is a defense reaction, whereby harmful factors are removed and tissue structure and function are restored. During the acute phase of inflammation, first neutrophils will arrive, followed by monocytes. The monocytes mature into inflammatory macrophages and will finally affect the function of the resident tissue macrophages [Figure 1]. These responses lead to swelling, redness, heat and often pain. Once the first stimulus is removed, the reaction will stop and the inflammatory cells will be returned to pre-inflammatory numbers. Prostaglandins play an important role in immune reactions and are therefore often targeted by anti-inflammatory drugs, such as non-steroid anti-inflammatory drugs (NSAIDs). The specific role of prostaglandins and the mechanism of action of NSAIDs will be discussed (Ricciotti; FitzGerald, 2011). Figure 1. Basic diagram of acute inflammation (Reilkoff; Bucala et al., 2011)
Prostaglandins in general
Prostaglandins are formed when arachidonic acid is released from the plasma membrane by phospholipases [Figure 2]. This acid is metabolized by PGG/H synthase or cyclooxygenase (COX).
The four main bioactive prostaglandins are generated in vivo: prostaglandin E2 (PGE2), prostacyclin (PGI2), prostaglandin D2 (PGD2) and prostaglandin F2 (PGF2).
Acetaminophen is an non-opioid analgesic while ibuprofen is a non-steroidal anti-inflammatory drug (NSAIDs). Acetaminophen is an equipotent inhibitor of cyclooxygenase 1 and 2, while ibuprofen is more selective for cyclooxygenase 1 than 2.
of prostaglandin E2, which lessen the hypothalamic target point to reduce fever, and creating active the descending inhibitory serotonergic pathways to produce analgesia. Even though acetaminophen have similarities with the analgesic and antipyretic properties of other COX inhibitors like the aspirin and the non-steroidal anti-inflammatory drugs (NSAIDs), still it does not possess considerable anti-inflammatory properties. Contrary to aspirin, acetaminophens do not hinder thromboxane and, as such, aggregation of platelet does not change.
NSAIDs are group of pharmaceutical drugs used in the treatment of fever, pain and swelling in mild to intermediate acute inflammatory
Table 2 shows some of the chemical mediators involved in Mr X’s inflammatory process, causing it to become more severe and uncontrolled, resulting in a further decline in his clinical presentation.
The anti-inflammatory test was evaluated adopting the carrageenan-induced rat hind paw edema test (Winter et al., 1962). This model uses carrageenan as an irritant to induce paw edema. Non-steroidal anti-inflammatory drugs such as indomethacin, reduce paw swelling in a dose-dependent manner to a maximum of 60 %. Test materials are assessed for acute anti-inflammatory activity by examining their ability to reduce or prevent the development of carrageenan-induced paw swelling. Forty eight adult male albino rats, divided into eight groups, each of six animals, each was orally treated with one of the following: 50 and 100 mg/kg b. wt. of the total ethanol extract, 100 mg/kg b. wt. of each successive extract, 20 mg/kg b. wt. indomethacin and saline
In vitro: Although cyclosomatostatin could fully block the effect of somatostatin, it only partially reversed the inhibitory effect of cortistatin, a new anti-inflammatory peptide. This observation was further supported by the fact that cyclosomatostatin reversed the antiinfl ammatory effect of somatostatin and octreotide in vitro completely, while only partially reversing the effect of cortistatin
Nonsteroidal anti-inflammatory drugs, both topical and oral, are another treatment consideration for OA (Alshami, 2014). More aggressive treatment includes the use of opioids or corticosteroid injections (Alshami, 2014). Acetaminophen has a maximum daily dose of 4g/day (Mazaleuskaya et al., 2015a). The mechanism of action in acetaminophen remains unclear (Mazaleuskaya et al., 2015a). However, what is known is that the primary mechanism of action is to inhibit the synthesis of prostaglandins (Mazaleuskaya et al., 2015a). Prostaglandins originate from the arachidonic acid pathway (Mazaleuskaya et al., 2015a). This pathway promotes inflammation, fever, and pain (Mazaleuskaya et al., 2015a). I would recommend the patient take the maximum dosage of 4g/day. This would allow the patient to take 1,000 mg every 6 hours. I would also recommend that the patient alternate with ibuprofen. Ibuprofen can be taken over-the-counter (OTC) with a dosage of 800-1200mg/day or as a prescription with a dosage of 1800-2400mg/day (Mazaleuskaya et al., 2015b). Prescription dosages are typically used for long term management of OA (Mazaleuskaya et al., 2015b). Adults on a prescription dosage are recommended to take 200-800 mg every six to eight hours (Mazaleuskaya et al., 2015b). Ibuprofen acts to inhibit two cyclooxygenase enzymes, COX-1 and COX-2 (Mazaleuskaya et al., 2015b). For Jonathon, I would prescribe 800 mg of ibuprofen to be taken alternatively with acetaminophen every 6 hours. In order to maximize therapy, I would suggest that if Jonathon takes acetaminophen at 9 am then at noon he should take ibuprofen. This way he is able to take medication every three hours and stay within safe dose
Naproxen (Naprosyn) is a nonsteroidal anti-inflammatory drug (NSAIDs) used to treat joint pain. M.H. was previously prescribed Naproxen to reduce the bilateral wrist pain and associated inflammation. Naproxen is mainly used to reduce inflammation, stiffness, and pain. NSAIDs block the formation of prostaglandins. Prostaglandins are involved in the body’s normal function and inflammatory response. Proteins, Cox-1 and Cox-2, control these prostaglandins. Cox-1 controls the formation of the prostaglandins involved in the normal function of the body’s organs. Cox-2 controls the formation of the prostaglandins involved in the body’s inflammatory response. By preventing the body from producing prostaglandins, NSAIDs reduce swelling and pain.
When patients are prescribed to a medicine for low amounts of pain, they are usually prescribed daily use of anti-inflammatory pills such as ibuprofen or tylenol. For more severe pain, patients are often prescribed these pills in higher dosages, or even prescribed opiates such as vicodin or oxycontin (Meisel & Perrone). Anti-inflammatory pills are not as powerful as drugs such as opioids, but they present the risk of cardiovascular problems
Inflammation is a normal immune reaction in response to tissue injury or invading exogenous molecules/ pathogens and can be either localized or systemic. The aim of acute inflammation is restoring the tissue homeostatic imbalance by promoting tissue repair and eliminating the causative stimuli through a complex but highly regulated cascade of events (Medzhitov 2008). Under physiological conditions, successful acute inflammation is followed by a resolution phase during which pro-inflammatory processes are suppressed and physiological homeostasis is achieved. However, an ongoing inflammatory event or an impaired resolution phase characterized by continuous pro-inflammatory processes results in chronic inflammation (Maskrey et al. 2011; Fullerton
Injured cells and nearby circulating cells release chemicals that initiate defensive actions and sound an alarm to other defense mechanisms. These chemicals include histamine (mostly secreted by basophils, white blood cells found in connective tissue), kinins, prostaglandins (PGs), and complement proteins.
The most feared pathophysiological effect of sepsis is the disturbance of the cardiovascular system through vasodilation and fluid loss from the vascular system into the tissue induced by elevated NO• concentrations. The successive drop in blood pressure and reduced supply of tissues leads to systemic circulatory failure and death of the patient. Inhibitor studies have shown that PARP-1 is not only involved in DNA repair, but also in septic shock. Hauschildt and coworkers have shown that the induction of pro-inflammatory cytokines by LPS treatment of macrophages could be prevented by inhibiting PARP (Hauschildt et al., 1997). An anti-inflammatory effect of PARP activity suppression either induced by Parp1 gene knockout or pharmacological inhibition was also reported (Szabó et al., 1997). Also, LPS treatment of rats led to weakened endothelial functions, which could be alleviated by administration of PARP inhibitor 3-aminobenzamide (3AB) (Szabó et al., 1996).
IL-1b and TNFα also activate the MAPK pathway (mitogen-activated protein kinase)2. In RA this is another implicated path in the pro-inflammatory pathway2, the MAPK pathway activates kinases which targets pro-inflammatory mRNA2 and acts to stabilise them (as a co-chaperone)2. The stabilisation is important for the production of the final protein and Corticosteroids can affect this as the co-chaperones (such as Src) interact with the cGCR (cytolic glucocorticoid receptor)1 and reduces the levels of mRNA1. Other possible methods of corticosteroid interference with MAPK is via MPK-1 induction, MPK-1 also destabilised the pro-inflammatory mRNA2.
These drugs are used as anti-inflammatory medication for various disorders such as psoriasis or eczema. Corticosteroids inhibit a variety of the processes associated with inflammation and immune response. The anti-inflammatory and immunosuppressive properties of corticosteroids are mainly caused by their inhibitory action on eicosanoid synthesis and cytokine production from lymphocytes. The inhibition of these compounds also has further effects for other mediators of inflammation and the immune responses53. Corticosteroids inhibit both bradykinin formation and the migration of white blood cells into the site of inflammation. They reduce granulation tissue formation by inhibiting the proliferation of fibroblasts and blood vessels. As for the immune system, steroids decrease the production of interleukin (IL) -2, which subsequently decrease the action of T-helper cells and the clonal proliferation of T
Figure 2 from Lasky (1992) shows the three major steps of inflammation. Step I is the initial low-affinity rolling interaction that is mediated by all three selectins. Step II involved activation of leukocytes that alter concentration gradients of various chemotactic factors. Step III is the high-affinity adhesion, change in shape of leukocyte, and finally extravasation. Figure 2 left out another important factor of selectin’s role in inflammation: PSGL-1. PSGL-1 on the plasma memebranes of neutrophils or monocytes binds to P-selectin translocated to the surfaces of inflamed endothelial cells (Zimmerman 2001). The binding of PSGL-1 by P-selectin is particularly important in the initial steps of inflammation. This intereaction is responsible for the recruitment of inflammatory leukocyte (Ley 2013).