Browsing Pathways

Lumiracoxib (also named Prexige) is a nonsteroidal anti-inflammatory drug (NSAID). It can be used as the mediators of certain kinds of intraocular inflammation. Lumiracoxib can block prostaglandin synthesis by the action of inhibition of prostaglandin G/H synthase 1 and 2. Prostaglandin G/H synthase 1 and 2 catalyze the arachidonic acid to prostaglandin G2, and also catalyze prostaglandin G2 to prostaglandin H2 in the metabolism pathway.

Valdecoxib, a selective prostaglandin G/H synthase 2 (better known as cyclooxygenase-2 or COX-2) inhibitor, is classified as a nonsteroidal anti-inflammatory drug (NSAID). Valdecoxib was used for its anti-inflammatory, analgesic, and antipyretic effects in the management of osteoarthritis and for the treatment of dysmenorrhea or acute pain. Unlike celecoxib, valdecoxib lacks a sulfonamide chain and does not require CYP450 enzymes for metabolism. Both COX-1 and COX-2 catalyze the conversion of arachidonic acid to prostaglandin G2 (PGG2) and PGG2 to prostaglandin H2 (PGH2). PGH2 is the precursor of a number of prostaglandins, including prostaglandin E2 (PGE2), prostaglandin I2 (PGI2) and thomboxane A2 (TxA2). Valdecoxib selectively inhibits the cyclooxygenase-2 (COX-2) enzyme, a key enzyme in the production of PGE2. PGE2 is a potent mediator of pain, inflammation and fever. The first part of this figure depicts the anti-inflammatory, analgesic and antipyretic pathway of valdecoxib. The latter portion of this figure depicts valdecoxib’s potential involvement in platelet aggregation. Prostaglandin synthesis varies across different tissue types. Platelets, anuclear cells derived from fragmentation from megakaryocytes, contain COX-1, but not COX-2. COX-1 activity in platelets is required for thromboxane A2 (TxA2)-mediated platelet aggregation. Platelet activation and coagulation do not normally occur in intact blood vessels. After blood vessel injury, platelets adhere to the subendothelial collagen at the site of injury. Activation of collagen receptors initiates phospholipase C (PLC)-mediated signaling cascades resulting in the release of intracellular calcium from the dense tubula system. The increase in intracellular calcium activates kinases required for morphological change, transition to procoagulant surface, secretion of granular contents, activation of glycoproteins, and the activation of phospholipase A2 (PLA2). Activation of PLA2 results in the liberation of arachidonic acid, a precursor to prostaglandin synthesis, from membrane phospholipids. The accumulation of TxA2, ADP and thrombin mediates further platelet recruitment and signal amplification. TxA2 and ADP stimulate their respective G-protein coupled receptors, thomboxane A2 receptor and P2Y purinoreceptor 12, and inhibit the production of cAMP via adenylate cyclase inhibition. This counteracts the adenylate cyclase stimulatory effects of the platelet aggregation inhibitor, PGI2, produced by neighbouring endothelial cells. Platelet adhesion, cytoskeletal remodeling, granular secretion and signal amplification are independent processes that lead to the activation of the fibrinogen receptor. Fibrinogen receptor activation exposes fibrinogen binding sites and allows platelet cross-linking and aggregation to occur. Neighbouring endothelial cells found in blood vessels express both COX-1 and COX-2. COX-2 in endothelial cells mediates the synthesis of PGI2, an effective platelet aggregation inhibitor and vasodilator, while COX-1 mediates vasoconstriction and stimulates platelet aggregation. PGI2 produced by endothelial cells encounters platelets in the blood stream and binds to the G-protein coupled prostacyclin receptor. This causes G-protein mediated activation of adenylate cyclase, which catalyzes the conversion of adenosine triphosphate (ATP) to cyclic AMP (cAMP). Four cAMP molecules then bind to the regulatory subunits of the inactive cAMP-dependent protein kinase holoenzyme causing dissociation of the regulatory subunits and leaving two active catalytic subunit monomers. The active subunits of cAMP-dependent protein kinase catalyze the phosphorylation of a number of proteins. Phosphorylation of inositol 1,4,5-trisphosphate receptor type 1 on the endoplasmic reticulum (ER) inhibits the release of calcium from the ER. This in turn inhibits the calcium-dependent events, including PLA2 activation, involved in platelet activation and aggregation. Inhibition of PLA2 decreases intracellular TxA2 and inhibits the platelet aggregation pathway. cAMP-dependent kinase also phosphorylates the actin-associated protein, vasodilator-stimulated phosphoprotein. Phosphorylation inhibits protein activity, which includes cytoskeleton reorganization and platelet activation. Valdexocib preferentially inhibits COX-2 with little activity against COX-1. COX-2 inhibition in endothelial cells decreases the production of PGI2 and the ability of these cells to inhibit platelet aggregation and stimulate vasodilation. These effects are thought to be responsible for the rare, but severe, adverse cardiovascular effects observed with rofecoxib, a COX-2 inhibitor which was subsequently been withdrawn from the market. Valdexocib was withdrawn from the Canadian, U.S. and E.U. markets in 2005 due to concerns of possible increased risk of heart attack and stroke.

Suprofen (also named Profenal and Maldocil) is a nonsteroidal anti-inflammatory drug (NSAID). It can be used to relieve pain (analgesic) and reduce fever (antipyretic). Suprofen is also a type of ophthalmic anti-inflammatory medicines which may be used to help prevent eye constrict for pupil during surgery. Suprofen can block prostaglandin synthesis by the action of inhibition of prostaglandin G/H synthase 1 and 2. Prostaglandin G/H synthase 1 and 2 catalyze the arachidonic acid to prostaglandin G2, and also catalyze prostaglandin G2 to prostaglandin H2 in the metabolism pathway. Since prostaglandin is the messenger molecules in the process of inflammation; hence, inhibition of prostaglandin synthesis can reduce the pain and inflammation (e.g. in the eyes).

Zellweger syndrome, also known as cerebrohepatorenal syndrome, is an autosomal recessive peroxisome biogenesis disorder that is part of the family of Zellweger spectrum disorders. It is caused by a defect in one of 12 or more of the PEX genes (PEX1, 2, 3, 5, 6, 10, 12, 13, 14, 16, 19 and 26) that produce proteins called peroxins. Peroxins are used in the formation of peroxisomes, and can be involved in recognition of proteins targeted for the peroxisome, as well as their transport into the peroxisome. Peroxisomes typically break down both very long chain and branched fatty acids, but if they aren't present, these fatty acids build up in the blood and body, harming organs such as the brain and liver. Additionally, due to the fact that some processes, such as plasmalogen biosynthesis, occur in or using peroxisomes, and can lead to deficiencies in plasmalogens. These are important in brain and lung function, leading to other symptoms. Zellweger syndrome is characterized by an increase in levels of very long chain fatty acids in the blood plasma, as well as more visible physical symptoms, such as an abnormally large or small head at birth, characteristic facial features and poor muscle tone, which can lead to an inability of infants to feed. Other symptoms include an enlarged liver, skeletal abnormalities and low CNS function. Infants very rarely live longer than one year, and the only treatment is for symptoms the patient is experiencing, not for the syndrome itself.

Familial lipoprotein lipase deficiency (LPLD), also known as familial chylomicronemia syndrome, chylomicronemia, chylomicronemia syndrome, and hyperlipoproteinemia type Ia, is an extremely rare inherited inborn error of metabolism (IEM) of lipid metabolism. LPLD affects about 1 out of 1 000 000 people. It is an autosomal recessive disorder that is caused by a defect or deficiency in the enzyme lipoprotein lipase. Lipoprotein lipase is a water-soluble enzyme that hydrolyzes triglycerides in lipoproteins, such as those found in chylomicrons and very-low-density lipoproteins (VLDL), into two free fatty acids and one monoacylglycerol molecule. Defects in lipoprotein lipase will lead to accumulations of triglycerides and massive accumulation of fatty droplets called chylomicrons in the blood. As a result, LPLD is characterized by abnormally elevated levels of triglycerides and chylomicrons in serum and plasma (chylomicronemia). Affected individuals often experience episodes of abdominal pain, acute recurrent inflammation of the pancreas (pancreatitis), abnormal enlargement of the liver and/or spleen, and the development of skin lesions known as eruptive xanthomas. Most cases of LPLD are identified before the age of 10. In roughly one-quarter of patients, the disorder is identified during the first year of life. Some affected individuals may not be identified until adulthood. Treatment of LPLD is mainly based on medical nutrition therapy to maintain plasma triglyceride concentration below 11.3 mmol/L. Lipid-lowering agents such as fibrates and omega-3-fatty acids can be used to lower triglyceride levels in LPLD.

Tay-Sachs Disease (TSD; GM2-Gangliosidosis, type I; B-Variant GM2-Gangliosidosis; Hexosaminidase A Deficiency; HEXA Deficiency; Tay-Sachs Disease Variant B1), is an autosomal recessive lysosomal storage disease. TSD is caused by a mutation in the alpha subunit of the hexosaminidase A gene (HEXA), which codes for the enzyme hexosaminidase A. HEXA degrades GM2 gangliosides and other molecules with terminal N-acetyl hexosamines in the brain and other tissues. A defect in this enzyme causes accumulation of oligosaccharides in urine. The most lethal variant of this disease is the classical infantile Tay-Sachs disease, in which children exhibit developmental retardation, dementia and blindness, finally ending in death by the second or third years. Tay-Sachs disease also has debilitating juvenile and adult forms. The majority of cases of TSD are found among (but not limited to) the Ashkenazi Jews and French Canadians in Eastern Quebec. Symptoms include ataxia, visual impairment and loss, cherry-red spot on retinal macula, dystosis multiplex, mental retardation, myoclonus, encephalopathy and psychosis.

Argininemia is caused by a mutation in the gene ARG, encoding liver arginase, which hydrolyses arginine to urea and ornithine in the last step of the urea cycle. A defect in liver arginase causes accumulation of ammonia in blood; arginine, creatine, guanidinoacetate, and homoarginine in plasma; urea nitrogen in serum; arginine and homoarginine in spinal fluid; and arginiosuccinate orotic acid, and uracil in urine. Symptoms include ataxia, cerebral atrophy, chorea, jaundice, and seizures.

Mucopolysaccharidosis type VII (MPS VII), also called Sly syndrome, is a rare inborn error of metabolism (IEM) and autosomal recessive disorder caused by mutations in the GUSB gene. This gene encodes for the beta-glucuronidase enzyme, which normally breaks down glycosaminoglycans (GAGs). However, without beta-glucuronidase, accumulation of GAGs in cells specifically the lysosome increases. The increase in cell size causes tissues and organs to become enlarged as well. This disorder is characterized by macrocephaly, a buildup of fluid in the brain, characteristic facial features, and a large tongue. Other symptoms may include hepatosplenomegaly, heart valve abnormalities, and umbilical or inguinal hernias. MPS VII also causes various skeletal abnormalities, including joint issues and decreased growth. Treatments such as enzyme replacement therapy are still fairly new, however traditionally treatments for Mucopolysaccharidosis VII included symptom relief such as surgery. It is estimated that MPS VII affects 1 in 250,000 individuals.  

Increased lactic acid concentrations in urine or serum can be a result of many metabolic disorders but also of other origin (infections, etc.). Respiratory chain defects account for most of the metabolic causes of lactic acid accumulation. Often alanine is also high. A urine spectrum indicating an increased lactic acid and alanine concentration is shown.

4-Hydroxybutyric Aciduria/Succinic Semialdehyde Dehydrogenase Deficiency (SSADH; Gamma-hydroxybutyric acidemia) inhibits the formation of succinate from GABA. This deficiency results in urinary excretion of 4-hydroxybutyric acid. In vivo proton MR also indicates elevated GABA levels as compared with an age-matched control. Symptoms include ataxia, chorea or athetosis, motor retardation, seizures, macrocephaly and delayed or abnormal speech development.