A role for NPC1 and NPC2 in intestinal cholesterol absorption – the hypothesis gutted

Dietary and biliary cholesterol are taken up by intestinal epithelial cells and transported to the endoplasmic reticulum. At the endoplasmic reticulum, cholesterol is esterified, packaged into chylomicrons and secreted into the lymph for delivery to the bloodstream. NPC1L1 (Niemann–Pick C1-like 1) is a protein on the enterocyte brush-border membrane that facilitates cholesterol absorption. Cholesterol's itinerary as it moves to the endoplasmic reticulum is unknown, as is the identity of any cellular proteins that facilitate the movement. Two proteins that play an important role in intracellular cholesterol transport and could potentially influence NPC1L1-mediated cholesterol uptake are NPC1 and NPC2 (Niemann–Pick type C disease proteins 1 and 2). In this issue of the Biochemical Journal, Dixit and colleagues show that the absence or presence of NPC1 and NPC2 has no effect on intestinal cholesterol absorption in the mouse. Thus neither protein fills the gap in our knowledge of intra-enterocyte cholesterol transport. Furthermore, the NPC1/NPC2 pathway would not be a good target for limiting the uptake of dietary cholesterol

Peer Review Practices for Evaluating Biomedical Research Grants: A Scientific Statement From the American Heart Association

The biomedical research enterprise depends on the fair and objective peer review of research grants, leading to the distribution of resources through efficient and robust competitive methods. In the United States, federal funding agencies and foundations collectively distribute billions of dollars annually to support biomedical research. For the American Heart Association, a Peer Review Subcommittee is charged with establishing the highest standards for peer review. This scientific statement reviews the current literature on peer review practices, describes the current American Heart Association peer review process and those of other agencies, analyzes the strengths and weaknesses of American Heart Association peer review practices, and recommends best practices for the future

Evaluation of an anti-tumor necrosis factor therapeutic in a mouse model of Niemann-Pick C liver disease.

Niemann-Pick type C (NPC) disease is a lysosomal storage disease characterized by the accumulation of cholesterol and glycosphingolipids. The majority of NPC patients die in their teen years due to progressive neurodegeneration; however, half of NPC patients also suffer from cholestasis, prolonged jaundice, and hepatosplenomegaly. We previously showed that a key mediator of NPC liver disease is tumor necrosis factor (TNF) α, which is involved in both proinflammatory and apoptotic signaling cascades. In this study, we tested the hypothesis that blocking TNF action with an anti-TNF monoclonal antibody (CNTO5048) will slow the progression of NPC liver disease.Treatment of wild-type C57BL/6 mice with NPC1-specific antisense oligonucleotides led to knockdown of NPC1 protein expression in the liver. This caused classical symptoms of NPC liver disease, including hepatic cholesterol accumulation, hepatomegaly, elevated serum liver enzymes, and lipid laden macrophage accumulation. In addition, there was a significant increase in the number of apoptotic cells and a proliferation of stellate cells. Concurrent treatment of NPC1 knockdown mice with anti-TNF had no effect on the primary lipid storage or accumulation of lipid-laden macrophages. However, anti-TNF treatment slightly blunted the increase in hepatic apoptosis and stellate cell activation that was seen with NPC1 knockdown.Current therapeutic options for NPC disease are limited. Our results provide proof of principle that pharmacologically blocking the TNF-α inflammatory cascade can slightly reduce certain markers of NPC disease. Small molecule inhibitors of TNF that penetrate tissues and cross the blood-brain barrier may prove even more beneficial

Effect of NPC1 knockdown and anti-TNF treatment on the number of foamy macrophages and hepatocytes.

<p>Quantification of foamy macrophages (A) and hepatocytes (B) in H&E stained liver sections from mice injected for 9 weeks with mismatched (MM) and NPC1-specific ASOs and subjected to treatment (TX) with saline or anti-TNF. Each bar represents the mean ± SD number of cells per field from 3 animals in each treatment group. The lettering (a, b) shows statistically dissimilar groups.</p

Effect of NPC1 knockdown and anti-TNF treatment on hepatic apoptosis.

<p>Liver sections from mice injected for 9 weeks with mismatched (MM) and NPC1-specific ASOs and subjected to treatment (TX) with saline or anti-TNF were subjected to fluorometric TUNEL staining. Apoptotic nuclei were quantified. Each bar represents the mean ± SD number of cells per field from 5 animals in each treatment group. The lettering (a, b) shows statistically dissimilar groups. Samples with two letters represent values that are intermediate to the statistical groups and are thus not considered significantly different from either group.</p

Hepatic formation and clustering of foamy macrophages in NPC1 knockdown mice.

<p>Masson's trichrome stained liver sections from mice injected for 9 weeks with mismatched (MM) and NPC1-specific ASOs and subjected to treatment with saline or anti-TNF. Images were photographed at 200X magnification.</p