Radioprotection by N-palmitoylated nonapeptide of human interleukin-1beta

Modulators for palmitoylation of proteins and small molecules

As an essential form of lipid modification for maintaining vital cellular functions, palmitoylation plays an important role in in the regulation of various physiological processes, serving as a promising therapeutic target for diseases like cancer and neurological disorders. Ongoing research has revealed that palmitoylation can be categorized into three distinct types: N-palmitoylation, O-palmitoylation and S-palmitoylation. Herein this paper provides an overview of the regulatory enzymes involved in palmitoylation, including palmitoyltransferases and depalmitoylases, and discusses the currently available broad-spectrum and selective inhibitors for these enzymes.

Xinghamide A, a New Cyclic Nonapeptide Found in Streptomyces xinghaiensis

Xinghamide A (1), a new nonapeptide, was discovered in Streptomyces xinghaiensis isolated from a halophyte, Suaeda maritima (L.) Dumort. Based on high-resolution mass and NMR spectroscopic data, the planar structure of 1 was established, and, in particular, the sequence of nine amino acids was determined with ROESY and HMBC NMR spectra. The absolute configurations of the α-carbon of each amino acid residue were determined with 1-fluoro-2,4-dinitrophenyl-l-and -d-leucine amide (Marfey's reagents) and 2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl isothiocyanate, followed by LC-MS analysis. The anti-inflammatory activity of xinghamide A (1) was evaluated by inhibitory abilities against the nitric oxide (NO) secretion and cyclooxygenase-2 (COX-2) expression in lipopolysaccharide (LPS)-stimulated RAW264.7 cells.

Radioprotective effect of Curcuma longa extract on γ-irradiation-induced oxidative stress in rats

This study was conducted to evaluate the modulatory effect of aqueous extract of Curcuma longa (L.) against γ-irradiation (GR), which induces biochemical disorders in male rats. The sublethal dose of GR was determined in primary hepatocytes. Also, the effect of C. longa extract was examined for its activity against GR. In rats, C. longa extract was administered daily (200 mg/kg body mass) for 21 days before, and 7 days after GR exposure (6.5 Gy). The lipid profile and antioxidant status, as well as levels of transaminases, interleukin-6 (IL-6), and tumour necrosis factor α (TNFα) were assessed. The results showed that in hepatocytes, the aqueous extract exhibited radioprotective activity against exposure to GR. Exposure of untreated rats to GR resulted in transaminase disorders, lipid abnormalities, elevation of lipid peroxidation, trace element alterations, release of IL-6 and TNF, and decrease in glutathione and protein level of superoxide dismutase-1 (SOD-1) and peroxiredoxin-1 (PRDX-1). However, treatment of rats with this extract before and after GR exposure improved antioxidant status and minimized the radiation-induced increase in inflammatory cytokines. Changes occurred in the tissue levels of trace elements, and the protein levels of SOD-1 and PRDX-1 were also modulated by C. longa extract. Overall, C. longa exerted a beneficial radioprotective effect against radiation-induced oxidative stress in male rats by alleviating pathological disorders and modulating antioxidant enzymes.

Determination of sample sizes for demonstrating efficacy of radiation countermeasures

In response to the ever increasing threat of radiological and nuclear terrorism, active development of nontoxic new drugs and other countermeasures to protect against and/or mitigate adverse health effects of radiation is ongoing. Although the classical LD(50) study used for many decades as a first step in preclinical toxicity testing of new drugs has been largely replaced by experiments that use fewer animals, the need to evaluate the radioprotective efficacy of new drugs necessitates the conduct of traditional LD(50) comparative studies (FDA, 2002, Federal Register 67, 37988-37998). There is, however, no readily available method to determine the number of animals needed for establishing efficacy in these comparative potency studies. This article presents a sample-size formula based on Student's t for comparative potency testing. It is motivated by the U.S. Food and Drug Administration's (FDA's) requirements for robust efficacy data in the testing of response modifiers in total body irradiation experiments where human studies are not ethical or feasible. Monte Carlo simulation demonstrated the formula's performance for Student's t, Wald, and likelihood ratio tests in both logistic and probit models. Importantly, the results showed clear potential for justifying the use of substantially fewer animals than are customarily used in these studies. The present article may thus initiate a dialogue among researchers who use animals for radioprotection survival studies, institutional animal care and use committees, and drug regulatory bodies to reach a consensus on the number of animals needed to achieve statistically robust results for demonstrating efficacy of radioprotective drugs.

Alteration of radioprotective effects of heat-killed Lactobacillus casei in X-irradiated C3H/He mouse related to blood level of proinflammatory cytokines by corticoids

It is well known that a pre-administration of proinflammatory cytokines alters hematopoietic progenitor cells to promote an increase resistance against radiation and increases the survival rate in mice irradiated with lethal doses of radiation. Inflammation stimulators, such as some bacterial constituents, are also reported to have similar radioprotective action. We found that pre-administration of heat-killed Lactobacillus casei (HLC) to mice increases the level of interleukin (IL)-1 beta in circulation as well as the survival rate following lethal dose of radiation. Since HLC stimulates early immune responses, effects by drugs to modify inflammation were studied. The increase of both blood IL-1 beta levels and survival rates by HLC were simultaneously accelerated by coadministration of mineralocorticoid and inhibited by glucocorticoids or corticotropin. Neither parameter was modified by non-steroidal anti-inflammatory or anti-rheumatoid drugs. This suggests that both expected radioprotective action and unexpected systemic action, realized as an increase in plasma cytokines, by inflammation-related radioprotectors can be controlled by the coadministration of drugs at least in C3H/He mice, based on consideration of their pharmacological properties.

Induction of cytokines by radioprotective tocopherol analogs

Tocols are a family of eight isomers consisting of four tocopherols and four tocotrienols that exist in four isomeric forms: alpha (alpha), beta (beta), gamma (gamma), and delta (delta). Recently, tocols were found to have important and unique biological effects on nutrition and health other than antioxidant properties and are, therefore, now receiving increased attention. We have demonstrated the radioprotective efficacy of various tocol analogs and some of their esters. Three forms of tocols - alpha-tocopherol, alpha-tocopherol succinate, and gamma-tocotrienol - significantly protected mice against lethal gamma irradiation when administered subcutaneously 24 h before irradiation. The radioprotective effects of tocols on survival were associated with peripheral blood cell recovery after radiation induced cytopenia. Hematopoietic cytokines are known to promote the proliferation and differentiation of blood cell progenitors. Therefore, we hypothesized that peripheral blood cell recovery is preceded by hematopoietic cytokine induction. To test this hypothesis and compare the various radioprotective and non-radioprotective analogs, we measured serum cytokines using a sandwich ELISA, Luminex, and cytokine array in mice treated with various tocols (alpha-tocopherol succinate, alpha-tocopherol, delta-tocopherol, gamma- tocopherol, gamma-tocotrienol, and tocopherol acetate). Among the serum cytokines measured, ELISA and Luminex studies indicated that alpha-tocopherol, alpha-tocopherol succinate, and gamma-tocotrienol increased G-CSF levels in mice. Alpha-tocopherol succinate was most effective in stimulating G-CSF. IL-6 was detected by Luminex in sera samples from mice treated with the above three analogs. The results of the cytokine array suggest that other cytokines and chemokines in addition to G-CSF and IL-6 are induced. Since G-CSF, IL-6, and certain chemokines are important hematopoietic factors, these results support our hypothesis that the protection of mice from radiation-induced hematopoietic death is mediated by cytokines and chemokines. These studies may indicate that alpha-tocopherol succinate can be used as an adjunct in cancer chemotherapy, where neutropenia is a serious problem with threatening infectious complications.

Radiation protectants: current status and future prospects

In today's heightened nuclear/biological/chemical threat environment, there is an increased need to have safe and effective means to protect not only special high-risk service groups, but also the general population at large, from the health hazards of unintended ionizing radiation exposures. An unfulfilled dream has been to have a globally effective pharmacologic that could be easily taken orally without any undue side effects prior to a suspected or impending nuclear/radiological event; such an ideal radioprotective agent has yet to be identified, let alone fully developed and approved for human use. No one would argue against the fact that this is problematic and needs to be corrected, but where might the ultimate solution to this difficult problem be found? Without question, representative species of the aminothiol family [e.g., Amifostine (MedImmune, Gaithersburg, Maryland)] have proven to be potent cytoprotectants for normal tissues subjected to irradiation or to radiomimetic chemicals. Although Amifostine is currently used clinically, drug toxicity, limited times of protection, and unfavorable routes of administration, all serve to limit the drug's utility in nonclinical settings. A full range of research and development strategies is being employed currently in the hunt for new safe and effective radioprotectants. These include: (1) large scale screening of new chemical classes or natural products; (2) restructuring/reformulating older protectants with proven efficacies but unwanted toxicities; (3) using nutraceuticals that are only moderately protective but are essentially nontoxic; (4) using low dose combinations of potentially toxic but efficacious agents that protect through different routes to foster radioprotective synergy; and (5) accepting a lower level of drug efficacy in lieu of reduced toxicity, banking on the premise that the protection afforded can be leveraged by post-exposure therapies. Although it is difficult to predict which of these strategies will ultimately prove to be successful, it is certain that the probability of a useful protectant being fielded is increased significantly. This is due to the resurgence of interest in radiation protection, increased resources being expended by federal agencies, and by the Food and Drug Administration's willingness to innovate relative to new approval guidance.