Mechanism of action of colchicine

Allopurinol to Febuxostat: How far have we come?

For decades allopurinol has been used as a xanthine oxidase inhibitor for treatment of hyperuricemia and gout. Although effective in many patients, some experience sensitivity to the drug. In some cases, this sensitivity may lead to allopurinol hypersensitivity disorder, which if untreated can be fatal. Recently the Food and Drug Administration has approved the use of febuxostat as an alternative therapy for hyperuricemia and gout. Febuxostat is a new xanthine oxidase inhibitor, but is not purine based and therefore decreases adverse reactions due to patient sensitivity. This review is a comprehensive look at the background of hyperuricemia and gout treatment with allopurinol compared to recent clinical studies with febuxostat. Each clinical study is evaluated and summarized, identifying the advances in treatment that have been made as well as the concerns that still exist with either treatment.

Colchicine effects on the mouse liver

With histochemical methods an instantaneous and marked inhibitory effect of a single dose of colchicine on the activity of succinic-, lactic-, glucose-6-phosphate-, NADH- and NADPH-dehydrogenase in the mouse liver was observed. This effect was essentially the same as that previously described in the intestinal mucosa and not dependent on or a consequence of the inhibitory effect of colchicine on cell division. The enzymatic inhibitory effect of colchicine was qualitatively similar regardless of the dose of the drug given, although a single large dose (1.5 mg/kg body weight) produced alterations and depression of dehydrogenase activity more marked and not so rapidly repaired as those appearing after a small dose of colchicine (0.24 mg/kg body weight). Following repeated doses of colchicine the degree of histochemically demonstrable depression of dehydrogenase activity was not obviously different from that found after a single dose. After large repeated doses morphological alterations and prolonged depression of dehydrogenase activity of liver cells were found and many of the animals died. After repeated administration of the small dose (0.24 mg/kg body weight) no morphological alterations were found and the activity of dehydrogenases was normalized, although the injection of colchicine was continued.

Involvement of the cytoskeletal elements in articular cartilage homeostasis and pathology

The cytoskeleton of all cells is a three-dimensional network comprising actin microfilaments, tubulin microtubules and intermediate filaments. Studies in many cell types have indicated roles for these cytoskeletal proteins in many diverse cellular processes including alteration of cell shape, movement of organelles, migration, endocytosis, secretion, cell division and extracellular matrix assembly. The cytoskeletal networks are highly organized in structure enabling them to fulfil their biological functions. This review will primarily focus on the organization and function of the three major cytoskeletal networks in articular cartilage chondrocytes. Articular cartilage is a major load-bearing tissue of the synovial joint; it is well known that the cytoskeleton acts as a physical interface between the chondrocytes and the extracellular matrix in 'sensing' mechanical stimuli. The effect of mechanical load on cytoskeletal element expression and organization will also be reviewed. Abnormal mechanical load is widely believed to be a risk factor for the development of osteoarthritis. Several studies have intimated that the major cytoskeletal networks are disorganized or often absent in osteoarthritic cartilage chondrocytes. The implications and possible reasoning for this are more widely discussed and placed into context with their potential relevance to disease and therapeutic strategies.

The dissociation by colchicine of phagocytosis from increased oxygen consumption in human leukocytes

The effect of colchicine on the uptake of oxygen by human leukocytes during phagocytosis of live streptococci or of killed staphylococci was compared with the effect of colchicine on phagocytosis per se, measured in a sensitive bacterial system. The increase in oxygen consumption that normally accompanies phagocytosis was consistently diminished in leukocytes incubated with colchicine in concentrations as low as 2.5 x 10(-6) mole per L (1 mug per ml), and this inhibition was dosage dependent. Yet there was no evidence of decreased phagocytosis with concentrations of colchicine as high as 2.5 x 10(-4) mole per L (100 mug per ml). Furthermore, with measurements at 20, 40, and 60 minutes, the rate of phagocytosis was comparable with and without colchicine.A clue to the dissociation between oxygen consumption and phagocytosis was found in rapidly dried preparations of the incubated leukocytes. Ingested bacteria were present in both control and colchicine-treated granulocytes. In addition, control cells showed normal loss of granules (lysosomal particles) and prominent cytoplasmic vacuoles (digestive vacuoles). Colchicine-treated cells, however, showed less such degranulation and vacuolization. Measurements of granule-associated acid phosphatase activity after phagocytosis support the morphologic observations of less degranulation in colchicine-treated leukocytes. The muted metabolic and morpholgic response to phagocytosis in colchicine-treated cells may be important for the anti-inflammatory effect of colchicine in acute gouty arthritis. Colchicine may also find wider use in defining structure-function dependencies in metabolically stimulated cells.