Apoptotic cell death in mouse models of GM2 gangliosidosis and observations on human Tay-Sachs and Sandhoff diseases

Tay-Sachs and Sandhoff diseases are autosomal recessive neurodegenerative diseases resulting from the inability to catabolize GM2 ganglioside by beta-hexosaminidase A (Hex A) due to mutations of the alpha subunit (Tay-Sachs disease) or beta subunit (Sandhoff disease) of Hex A. Hex B (beta beta homodimer) is also defective in Sandhoff disease. We previously developed mouse models of both diseases and showed that Hexa-/- (Tay-Sachs) mice remain asymptomatic to at least 1 year of age while Hexb-/- (Sandhoff) mice succumb to a profound neurodegenerative disease by 4-6 months of age. Here we find that neuron death in Hexb-/- mice is associated with apoptosis occurring throughout the CNS, while Hexa-/- mice were minimally involved at the same age. Studies of autopsy samples of brain and spinal cord from human Tay-Sachs and Sandhoff diseases revealed apoptosis in both instances, in keeping with the severe expression of both diseases. We suggest that neuron death is caused by unscheduled apoptosis, implicating accumulated GM2 ganglioside or a derivative in triggering of the apoptotic cascade.      

Functional consequences of ROMK mutants linked to antenatal Bartter's syndrome and implications for treatment

The antenatal variant of Bartter's syndrome is an autosomal recessive kidney disease characterized by polyhydramnios, premature delivery, hypokalemic alkalosis and hypercalciuria. It is genetically heterogeneous, having been linked recently to mutations in an ATP- sensitive, renal outer medullary K+channel, ROMK, and earlier to mutations in the Na-K-2Cl co-transporter, NKCC2. We characterized four of the mutations reported in three heterozygous ROMK variants of antenatal Bartter's and found that each expressed a distinct phenotype in Sf9 cells. One mutation expressed normal function and appears to be an allelic polymorphism. The other three mutations produced channels with significantly reduced K+fluxes. However, the mechanisms in each case were different and reflected abnormalities in phosphorylation, proteolytic processing or protein trafficking. The different mechanisms may be important in the design of appropriate therapy for patients with this disease.      

The effect of etodolac on type II collagen-induced arthritis in mice

Type II collagen-induced arthritis (CIA) and mice was used as a model to evaluate the effect of etodolac on the arthritic and immunological parameters of the experimental disease. In a preventative protocol, a significant reduction was observed in the number of joints progressing to ankylosis. At high doses (16 mg/kg/day) a significant delay in the onset of arthritis was also observed. No significant effect was seen on the progression of the disease when etodolac was administered in established CIA. No consistent variations were observed in the anti-type II collagen response or other immunological parameters of the experimental arthritis.     

A prospective trial of colchicine for primary biliary cirrhosis

We entered 60 patients with primary biliary cirrhosis in a double-blind randomized controlled trial to determine whether colchicine is therapeutically effective. Thirty patients had early disease (Stages 1 and 2), and 30 had advanced disease (Stages 3 and 4). Fifteen patients with early disease and 15 with advanced disease received colchicine (0.6 mg twice daily), and the remainder received placebo. Patients were studied about every two months; those remaining in the blind phase at two years underwent repeat liver biopsy and were then placed on open-label colchicine (0.6 mg twice daily). With a few exceptions, the results in patients with early disease were similar to those in patients with advanced disease; hence, data on patients in all stages were combined in the main analysis. During the two-year study period the colchicine-treated patients, as compared with the placebo-treated patients, had improvement in levels of serum albumin, serum bilirubin, alkaline phosphatase, cholesterol, and aminotransferases. However, there was no such improvement in the severity of symptoms or physical findings; moreover, there was no significant difference in the histologic changes noted at liver biopsy in the two treatment groups. At four years after entry, the cumulative mortality from liver disease was 21 percent in patients given colchicine and 47 percent in those given placebo (P = 0.05). The only side effect of colchicine was diarrhea, noted in three patients. The consistent and significant improvement in a number of markers of liver disease and the apparent decreased mortality from liver disease suggest that colchicine may provide some long-term clinical benefit in patients with primary biliary cirrhosis. However, the failure of colchicine to reduce hepatic inflammation and fibrosis leaves uncertain the effect of the drug on the longterm outcome of this disease.