Rapamycin: Biological and therapeutic effects, binding by immunophilins and molecular targets of action

A new flavonoid derivative and a new 5-hydroxyanthranilic acid derivative from the sea urchin-derived Streptomyces sp. HDa1

One new flavonoid derivative flavoside A (1), one new 5-hydroxyanthranilic acid derivative crassilin (2), along with the known angucyclinone PD116740 (3) and oxachelin (4), was isolated from the EtOAc extract of the fermentation broth of the sea urchin (Anthocidaris crassispina)-derived actinobacterium, Streptomyces sp. HD01. The structures of these compounds were established on the basis of their HR-ESI-MS and NMR spectroscopic data. All of these compounds were assessed for their antibacterial activity.

Rapamycin induces glucose intolerance in mice by reducing islet mass, insulin content, and insulin sensitivity

Rapamycin, a specific inhibitor for mTOR complex 1, is an FDA-approved immunosuppressant for organ transplant. Recent developments have raised the prospect of using rapamycin to treat cancer or diabetes and to delay aging. It is therefore important to assess how rapamycin treatment affects glucose homeostasis. Here, we show that the same rapamycin treatment reported to extend mouse life span significantly impaired glucose homeostasis of aged mice. Moreover, rapamycin treatment of lean C57B/L6 mice reduced glucose-stimulated insulin secretion in vivo and ex vivo as well as the insulin content and beta cell mass of pancreatic islets. Confounding the diminished capacity for insulin release, rapamycin decreased insulin sensitivity. The multitude of rapamycin effects thus all lead to glucose intolerance. As our findings reveal that chronic rapamycin treatment could be diabetogenic, monitoring glucose homeostasis is crucial when using rapamycin as a therapeutic as well as experimental reagent.

Sirolimus upregulates aP2 expression in human monocytes and macrophages

Rapamycin (Sirolimus) is a potent immunosuppressive drug that reduces renal transplant rejection. Hyperlipidemia is a significant side effect of rapamycin treatment, and frequently leads to cardiovascular disease. Adipocyte fatty acid binding protein (aP2) is a member of the cytoplasmic fatty acid binding protein (FABP) family. aP2 has been shown to affect insulin sensitivity, lipid metabolism, lipolysis, and has recently been shown to play an important role in atherosclerosis. We found that aP2 messenger RNA (mRNA) was increased in human THP-1 cells after rapamycin treatment. Exposure of human differentiated THP-1 cells to rapamycin led to a time- and dose-dependent induction of aP2 mRNA expression. While aP2 expression was undetectable in undifferentiated THP-1 cells, aP2 was induced in these cells by rapamycin. These data suggest that rapamycin-induced aP2 may play a role in increased triglyceride accumulation.

Recent advances in immunosuppressants

In recent years, a large number of structurally diverse immunosuppressants have been discovered that are effective for the treatment of organ transplantation. Some of them are undergoing clinical trials and may soon enter into routine clinical practice. These compounds are either chemical entities obtained from natural sources/synthetic means or biomaterials such as monoclonal antibodies/gene products/proteins. They have been found to interfere at different stages of T cell activation and proliferation, and can be identified as inhibitors of nucleotide synthesis, growth factor signal transduction and differentiation. Newer strategies involving combination of new agents with traditional immunosuppressants, monoclonal antibodies and gene therapy offer enormous potential, not only for the investigation of mechanisms pertaining to graft rejection, but also for its therapeutic prevention.

The 1997 Annual Renal Transplantation in Children Report of the North American Pediatric Renal Transplant Cooperative Study (NAPRTCS)

This report of the North American Pediatric Renal Transplant Cooperative Study (NAPRTCS), covering the years 1987-96 (January 15, 1997), analyzed data on 4898 patients who received 5362 transplants. Over the 10 yr of the study, 21.3% of the patients were under the age of 6 yr. Of the disorders that lead to end-stage renal disease (ESRD), structural and developmental anomalies of aplasia, dysplasia, and obstructive uropathy accounted for over 1500 patients. Despite the potential therapies for focal segmental glomerulosclerosis (FSGS), there has been little change in its incidence and this lesion continues to be the most common cause of renal failure and transplantation among acquired diseases. Eighty-nine per cent of patients with a functioning graft continue to receive cyclosporin A (CsA) 5 yr post-transplantation, and 84% of patients continue to receive azathioprine (AZA), whereas 26% of patients receive alternate-day steroid therapy at 4 yr post-transplant. Thirty-seven per cent of the living donor (LD) recipients and 47% of cadaver donor (CD) recipients were treated with the polyclonal T-cell antibody ATG/ALG for induction, and the monoclonal T-cell antibody, OKT3, was utilized for induction in 12% of LD patients and in 19% of CD patients. Twenty-five per cent of the 5362 transplants (1333) have failed over the 10-yr period. Graft survival is 90% at 1 yr and 74% at 6 yr for LD kidneys, and is 80% at 1 yr and 58% at 6 yr for CD patients. The most common cause for graft failure (30%) is chronic rejection. For recipients of LD grafts, relative risk (RR) factors for graft survival are African-American race (RR = 2.1, p < 0.001) and greater than five prior transfusions (RR = 1.6, p < 0.001). Prophylactic anti-T-cell antibody reduces the risk of graft failure (RR = 0.76, p = 0.009). For recipients of cadaver kidneys, risk factors are: recipient age < 2 yr (RR = 2, p < 0.001), donor age < 6 yr (RR = 1.3, p = 0.005), and absence of induction T-cell antibody (RR = 1.31, p < 0.001).

Rapamune (RAPA, rapamycin, sirolimus): mechanism of action immunosuppressive effect results from blockade of signal transduction and inhibition of cell cycle progression

OBJECTIVE

Rapamune is a novel immunosuppressive agent in Phase III clinical trial in renal transplantation. Its unique mechanism of action has created great interest in its use as a biochemical probe of signal transduction pathways that has provided insight into its molecular mechanism of action. This article reviews the current state of our understanding of the mechanism of action of rapamune.

Mechanism of action of rapamycin: new insights into the regulation of G1-phase progression in eukaryotic cells

The immunosuppressant drug, rapamycin (RAP), is a potent inhibitor of IL-2-dependent T-cell proliferation. The antiproliferative effect of RAP is mediated through the formation of an active complex with its cytosolic receptor protein, FKBP12. The molecular target of the FKBP12.RAP complex is a putative lipid kinase termed the mammalian Target Of Rapamycin (mTOR). This review will discuss recent findings suggesting that mTOR is a novel regulator of G1- to S-phase progression in eukaryotic cells.