Chronic granulomatous disease, the McLeod phenotype and the contiguous gene deletion syndrome-a review

Chronic Granulomatous Disease (CGD), a disorder of the NADPH oxidase system, results in phagocyte functional defects and subsequent infections with bacterial and fungal pathogens (such as Aspergillus species and Candida albicans). Deletions and missense, frameshift, or nonsense mutations in the gp91^phox gene (also termed CYBB), located in the Xp21.1 region of the X chromosome, are associated with the most common form of CGD. When larger X-chromosomal deletions occur, including the XK gene deletion, a so-called "Contiguous Gene Deletion Syndrome" may result. The contiguous gene deletion syndrome is known to associate the Kell phenotype/McLeod syndrome with diseases such as X-linked chronic granulomatous disease, Duchenne muscular dystrophy, and X-linked retinitis pigmentosa. These patients are often complicated and management requires special attention to the various facets of the syndrome.     

Increased K-ras protein and activity in mouse and human lung epithelial cells at confluence.

Although K-ras is frequently mutated in lung adenocarcinomas, the normal function of K-ras p21 in lung is not known. In two mouse (E10 and C10) and one human (HPL1D) immortalized lung cell lines from peripheral epithelium, we have measured total K-ras p21 and active K-ras p21-GTP during cell proliferation and at growth arrest caused by confluence. In all three cell types, total K-ras p21 increased 2- to 4-fold at confluence, and active K-ras p21-GTP increased 10- to 200-fold. It was estimated that 0.03% of total K-ras p21 was in the active GTP-bound state at 50% confluence, compared with 1.4% at postconfluence. By contrast, stimulation of proliferation by serum-containing medium did not involve K-ras p21 activation, even though a rapid, marked activation of both Erk1/2 and Akt occurred. At confluence, large increases, up to 14-fold, were seen in Grb2/Sos1 complexes, which may activate K-ras p21. In sum, increased protein expression and activity of K-ras p21 are associated with growth arrest, not with proliferation, in mouse and human lung cell lines.     

Pharmacokinetic profile of a 24-hour controlled-release OROS<Superscript>®</Superscript> formulation of hydromorphone in the presence and absence of food

Background

The objective of this study was to compare the pharmacokinetic profile of a novel, once-daily, controlled-release formulation of hydromorphone (OROS^® hydromorphone) under fasting conditions with that immediately after a high-fat breakfast in healthy volunteers. The effect of the opioid antagonist naltrexone on fasting hydromorphone pharmacokinetics also was evaluated.

Methods

In an open-label, three-way, crossover study, 30 healthy volunteers were randomized to receive a single dose of 16 mg OROS^® hydromorphone under fasting conditions, 16 mg OROS^® hydromorphone under fed conditions, or 16 mg OROS^® hydromorphone under fasting conditions with a naltrexone 50-mg block. Plasma samples taken pre-dose and at regular intervals up to 48 hours post-dose were assayed for hydromorphone concentrations. Analysis of variance was performed on log-transformed data; for mean ratios of 0.8 to 1.2 (20%), differences were considered minimal. Bioequivalence was reached if 90% confidence intervals (CI) of treatment mean ratios were between 80% and 125%.

Results

The mean geometric ratios of the fed and fasting treatment groups for maximum plasma concentration (C_max) and area under the concentration-time curve (AUC_0-t; AUC_0-∞) were within 20%. Confidence intervals were within 80% to 125% for AUC_0-t and AUC_0-∞ but were slightly higher for C_max (105.9% and 133.3%, respectively). With naltrexone block, the hydromorphone C_max increased by 39% and the terminal half-life decreased by 4.5 hours. There was no significant change in T_max, AUC_0-t or AUC_0-∞.

Conclusion

Standard bioavailability measures show minimal effect of food on the bioavailability of hydromorphone from OROS^® hydromorphone. Naltrexone co-administration results in a slight increase in the rate of absorption but not the extent of absorption.

Trial Registration

Clinical Trials.gov NCT00399295

     

Pharmacokinetic investigation of dose proportionality with a 24-hour controlled-release formulation of hydromorphone

Background

The purpose of this study was investigate the dose proportionality of a novel, once-daily, controlled-release formulation of hydromorphone that utilizes the OROS^® Push-Pull? osmotic pump technology.

Methods

In an open-label, four-way, crossover study, 32 healthy volunteers were randomized to receive a single dose of OROS^® hydromorphone 8, 16, 32, and 64 mg, with a 7-day washout period between treatments. Opioid antagonism was provided by three or four doses of naltrexone 50 mg, given at 12-hour intervals pre- and post-OROS^® hydromorphone dosing. Plasma samples for pharmacokinetic analysis were collected pre-dose and at regular intervals up to 48 hours post-dose (72 hours for the 64-mg dose), and were assayed for hydromorphone concentration to determine peak plasma concentration (C_max), time at which peak plasma concentration was observed (T_max), terminal half-life (t_1/2), and area under the concentration-time curve for zero to time t (AUC_0-t) and zero to infinity (AUC_0–∞). An analysis of variance (ANOVA) model on untransformed and dose-normalized data for AUC_0-t, AUC_0–∞, and C_max was used to establish dose linearity and proportionality.

Results

The study was completed by 31 of 32 subjects. Median T_max (12.0–16.0 hours) and mean t_1/2 (10.6–11.0 hours) were found to be independent of dose. Regression analyses of C_max, AUC_0–48, and AUC_0–∞ by dose indicated that the relationship was linear (slope, P ≤ 0.05) and that the intercept did not differ significantly from zero (P > 0.05). Similar analyses with dose-normalized parameters also indicated that the slope did not differ significantly from zero (P > 0.05).

Conclusion

The pharmacokinetics of OROS^® hydromorphone are linear and dose proportional for the 8, 16, 32, and 64 mg doses.

Trial Registration

Clinical Trials.gov NCT00398957

     

Lipid peroxidation associated cardiolipin loss and membrane depolarization in rat brain mitochondria

Oxidative stress induced by Fe2+ (50 microM) and ascorbate (2 mM) in isolated rat brain mitochondria incubated in vitro leads to an enhanced lipid peroxidation, cardiolipin loss and an increased formation of protein carbonyls. These changes are associated with a loss of mitochondrial membrane potential (depolarization) and an impaired activity of electron transport chain (ETC) as measured by MTT reduction assay. Butylated hydroxytoluene (0.2 mM), an inhibitor of lipid peroxidation, can prevent significantly the loss of cardiolipin, the increased protein carbonyl formation and the decrease in mitochondrial membrane potential induced by Fe2+ and ascorbate, implying that the changes are secondary to membrane lipid peroxidation. However, iron-ascorbate induced impairment of mitochondrial ETC activity is apparently independent of lipid peroxidation process. The structural and functional derangement of mitochondria induced by oxidative stress as reported here may have implications in neuronal damage associated with brain aging and neurodegenerative disorders.     

HLA-B44 polymorphisms at position 116 of the heavy chain influence TAP complex binding via an effect on peptide occupancy

A single residue polymorphism distinguishes HLA-B*4402(D116) from HLA-B*4405(Y116), which was suggested to allow HLA-B*4405 to acquire peptides without binding to tapasin-TAP complexes. We show that HLA-B*4405 is not inherently unable to associate with tapasin-TAP complexes. Under conditions of peptide deficiency, both allotypes bound efficiently to TAP and tapasin, and furthermore, random nonamer peptides conferred higher thermostability to HLA-B*4405 than to HLA-B*4402. Correspondingly, under conditions of peptide sufficiency, more rapid peptide-loading, dissociation from TAP complexes, and endoplasmic reticulum exit were observed for HLA-B*4405, whereas HLA-B*4402 showed greater endoplasmic reticulum retention and enhanced tapasin-TAP binding. Together, these studies suggest that position 116 HLA polymorphisms influence peptide occupancy, which in turn determines binding to tapasin and TAP. Relative to HLA-B*4405, inefficient peptide loading of HLA-B*4402 is likely to underlie its stronger tapasin dependence for cell surface expression and thermostability, and its enhanced susceptibility to pathogen interference strategies.