Lower Peripheral Blood Mononuclear Cells Research Articles

Peripheral blood mononuclear cell respiratory function is associated with progressive glaucomatous vision loss

Intraocular pressure (IOP) is currently the only modifiable risk factor for glaucoma and all licensed treatments lower IOP. However, many patients continue to lose vision despite IOP-lowering treatment. Identifying biomarkers for progressive vision loss would have considerable clinical utility. We demonstrate that lower peripheral blood mononuclear cell (PBMC) oxygen consumption rate (OCR) is strongly associated with faster visual field (VF) progression in patients treated by lowering IOP (P < 0.001, 229 eyes of 139 participants), explaining 13% of variance in the rate of progression. In a separate reference cohort of untreated patients with glaucoma (213 eyes of 213 participants), IOP explained 16% of VF progression variance. OCR is lower in patients with glaucoma (n = 168) than in controls (n = 50; P < 0.001) and is lower in patients with low baseline IOP (n = 99) than those with high baseline IOP (n = 69; P < 0.01). PBMC nicotinamide adenine dinucleotide (NAD) levels are lower in patients with glaucoma (n = 29) compared to controls (n = 25; P < 0.001) and strongly associated with OCR (P < 0.001). Our results support PBMC OCR and NAD levels as new biomarkers for progressive glaucoma.

Association Between Clonal Hematopoiesis Driver Mutations, Immune Cell Function, and the Vasculometabolic Complications of Obesity.

Obesity is accompanied by dysregulated inflammation, which can contribute to vasculometabolic complications including metabolic syndrome and atherosclerosis. Recently, clonal hematopoiesis of indeterminate potential (CHIP) has emerged as a risk factor for cardiovascular diseases. We aimed to determine how CHIP is related to immune cell function, systemic inflammation, and vasculometabolic complications in obese individuals. Two hundred ninety-seven individuals with overweight and obesity, between the ages of 54 and 81 years, were recruited in a cross-sectional study. Clonal hematopoiesis driver mutations (CHDMs) were identified with an ultrasensitive targeted assay. Assessment of carotid artery atherosclerosis was performed with ultrasound. Detailed immunological parameters, including cytokine production capacity of peripheral blood mononuclear cells, and targeted plasma proteomics analysis, were studied. Adipose tissue inflammation was determined in subcutaneous fat biopsies. Individuals with CHIP had higher concentrations of circulating IL (interleukin)-6. Total number of leukocytes and neutrophils were higher in individuals with CHIP. In contrast, exvivo cytokine production capacity of peripheral blood mononuclear cells was significantly lower in individuals with CHIP. Sex-stratified analysis showed that men with CHDMs had significantly higher leukocyte and neutrophil counts, and exvivo cytokine production capacity was lower in women with CHDMs. Surprisingly, the presence of atherosclerotic plaques was significantly lower in individuals with CHDMs. There was no relation between CHIP and metabolic syndrome. In individuals with overweight or obesity, CHDMs are not associated with vasculometabolic complications, but rather with a lower presence of carotid plaques. CHDMs associate with increased circulating inflammatory markers and leukocyte numbers, but a lower peripheral blood mononuclear cell cytokine production capacity.

Decreased Intestinal Microbiome Diversity in Pediatric Sepsis: A Conceptual Framework for Intestinal Dysbiosis to Influence Immunometabolic Function.

The intestinal microbiome can modulate immune function through production of microbial-derived short-chain fatty acids. We explored whether intestinal dysbiosis in children with sepsis leads to changes in microbial-derived short-chain fatty acids in plasma and stool that are associated with immunometabolic dysfunction in peripheral blood mononuclear cells. Prospective observational pilot study. Single academic PICU. Forty-three children with sepsis/septic shock and 44 healthy controls. Stool and plasma samples were serially collected for sepsis patients; stool was collected once for controls. The intestinal microbiome was assessed using 16S ribosomal RNA sequencing and alpha- and beta-diversity were determined. We measured short-chain fatty acids using liquid chromatography, peripheral blood mononuclear cell mitochondrial respiration using high-resolution respirometry, and immune function using ex vivo lipopolysaccharide-stimulated whole blood tumor necrosis factor-α. Sepsis patients exhibited reduced microbial diversity compared with healthy controls, with lower alpha- and beta-diversity. Reduced microbial diversity among sepsis patients (mainly from lower abundance of commensal obligate anaerobes) was associated with increased acetic and propionic acid and decreased butyric, isobutyric, and caproic acid. Decreased levels of plasma butyric acid were further associated with lower peripheral blood mononuclear cell mitochondrial respiration, which in turn, was associated with lower lipopolysaccharide-stimulated tumor necrosis factor-α. However, neither intestinal dysbiosis nor specific patterns of short-chain fatty acids were associated with lipopolysaccharide-stimulated tumor necrosis factor-α. Intestinal dysbiosis was associated with altered short-chain fatty acid metabolites in children with sepsis, but these findings were not linked directly to mitochondrial or immunologic changes. More detailed mechanistic studies are needed to test the role of microbial-derived short-chain fatty acids in the progression of sepsis.

Intravenous Statin Administration During Myocardial Infarction Compared With Oral Post-Infarct Administration

BackgroundBeyond lipid-lowering, statins exert cardioprotective effects. High-dose statin treatment seems to reduce cardiovascular complications in high-risk patients. The ideal timing and administration regime remain unknown. ObjectivesThis study compared the cardioprotective effects of intravenous statin administration during myocardial infarction (MI) with oral administration immediately post-MI. MethodsHypercholesterolemic pigs underwent MI induction (90 min of ischemia) and were kept for 42 days. Animals were distributed in 3 arms (A): A1 received an intravenous bolus of atorvastatin during MI; A2 received an intravenous bolus of vehicle during MI; and A3 received oral atorvastatin within 2 h post-MI. A1 and A3 remained on daily oral atorvastatin for the following 42 days. Cardiac magnetic resonance analysis (days 3 and 42 post-MI) and molecular/histological studies were performed. ResultsAt day 3, A1 showed a 10% reduction in infarct size compared with A3 and A2 and a 50% increase in myocardial salvage. At day 42, both A1 and A3 showed a significant decrease in scar size versus A2; however, A1 showed a further 24% reduction versus A3. Functional analyses revealed improved systolic performance in A1 compared with A2 and less wall motion abnormalities in the jeopardized myocardium versus both groups at day 42. A1 showed enhanced collagen content and AMP-activated protein kinase activation in the scar, increased vessel density in the penumbra, higher tumor necrosis factor α plasma levels and lower peripheral blood mononuclear cell activation versus both groups. ConclusionsIntravenous administration of atorvastatin during MI limits cardiac damage, improves cardiac function, and mitigates remodeling to a larger extent than when administered orally shortly after reperfusion. This therapeutic approach deserves to be investigated in ST-segment elevation MI patients.

The RFC1 80G&gt;A Relates to Survival Rate According to PBMCs DNA Global Methylation in Primary Liver Cancer

One-carbon metabolism regulates both nucleotide synthesis and biological methylation including that of DNA. DNA methylation is altered in cancer disease and variants of one-carbon metabolism genes have been associated to cancer risk. Aim of this study was to investigate a possible link among polymorphic variants, global DNA methylation in peripheral blood mononuclear cells (PBMCs) and cancer survival rate in human primary liver cancer. Forty-seven patients (31 hepatocellular carcinoma and 16 cholangiocarcinoma) were genotyped for 10 one-carbon genes polymorphisms. The methylcytosine (mCyt) content was measured by LC/MS/MS in PBMCs DNA. The homozygous AA variant of RFC1 80G>A was associated with a significantly reduced survival rate as compared to GG and GA (p=0.005). Moreover, when the mCyt levels were stratified as high (>5.34%) or low (蠄5.34%) according to the mCyt mean value, the combination of AA genotype with low mCyt led to a significantly worse survival as compared to G carriership (p<0.0001); no difference was found between G carriers and AA when associates to high mCyt (p=0.919). Moreover, a higher mortality risk was associated with the concomitant presence ofAA genotype and low mCyt, as compared to G carrier subjects (OR=8.35, p=0.001). In conclusion, in primary liver cancers RFC1 80G>A influences the survival rate, and the AA genotype combined with low PBMCs mCyt content is associated with poorer prognosis and higher mortality risk.

Evaluation of Specific Immune Responses to BoNT/A and Tetanus Toxoid in Patients Undergoing Treatment for Neurologic Disorders

Botulinum neurotoxins (BoNTs) are used in the treatment of many neurological disorders. The primary structure of BoNTs shows a high degree of homology with the tetanus neurotoxin, the toxoid of which is used as a vaccine. Because of the potential cross-reactivity between these toxins, we investigated the effects of Botulinum neurotoxin A (BoNT/A) and tetanus toxoid on peripheral blood mononuclear cells (PBMC) and the corresponding serum antibody levels, in twenty patients who had been treated with BoNT/A. We observed very low PBMC immunostimulation by BoNT/A at the tested dose (15 units/ml), as demonstrated by the low lymphocyte proliferation, and the absence of detectable antibodies cross-reacting with tetanus. However, exposure of PBMC from tetanus-sensitized patients to both neurotoxins showed that BoNT/A exerted a co stimulatory effect on tetanus-stimulated cells. Interestingly, in flow cytometry analysis, BoNT/A seemed to also alter the ratio of naïve (CD45RA) : memory/effector (CD45RO) T lymphocyte subsets, in favour of CD45RO. These preliminary data give a new insight on the potential immune crossreactivity between the two antigens. In view of the wide use of both neurotoxins, these immunotoxic effects merit a more detailed investigation.

Downregulation of the Longevity-Associated Protein Sirtuin 1 in Insulin Resistance and Metabolic Syndrome: Potential Biochemical Mechanisms

OBJECTIVESirtuins (SIRTs) are NAD+-dependent deacetylases that regulate metabolism and life span. We used peripheral blood mononuclear cells (PBMCs) to determine ex vivo whether insulin resistance/metabolic syndrome influences SIRTs. We also assessed the potential mechanisms linking metabolic alterations to SIRTs in human monocytes (THP-1) in vitro.RESEARCH DESIGN AND METHODSSIRT1-SIRT7 gene and protein expression was determined in PBMCs of 54 subjects (41 with normal glucose tolerance and 13 with metabolic syndrome). Insulin sensitivity was assessed by the minimal model analysis. Subclinical atherosclerosis was assessed by carotid intima-media thickness (IMT). In THP-1 cells exposed to high glucose or fatty acids in vitro, we explored SIRT1 expression, p53 acetylation, Jun NH2-terminal kinase (JNK) activation, NAD+ levels, and nicotinamide phosphoribosyltransferase (NAMPT) expression. The effects of SIRT1 induction by resveratrol and of SIRT1 gene silencing were also assessed.RESULTSIn vivo, insulin resistance and metabolic syndrome were associated with low PBMC SIRT1 gene and protein expression. SIRT1 gene expression was negatively correlated with carotid IMT. In THP-1 cells, high glucose and palmitate reduced SIRT1 and NAMPT expression and reduced the levels of intracellular NAD+ through oxidative stress. No effect was observed in cells exposed to linoleate or insulin. High glucose and palmitate increased p53 acetylation and JNK phosphorylation; these effects were abolished in siRNA SIRT1–treated cells. Glucose- and palmitate-mediated effects on NAMPT and SIRT1 were prevented by resveratrol in vitro.CONCLUSIONSInsulin resistance and subclinical atherosclerosis are associated with SIRT1 downregulation in monocytes. Glucotoxicity and lypotoxicity play a relevant role in quenching SIRT1 expression.

Clinical Significance of the Cellular Pharmacodynamics of Tacrolimus in Living-Donor Liver Transplantation

Successful immunosuppressive therapy is critical for liver transplantation; however, a considerable number of patients experience fatal rejection or alternatively exhibit serious infection resulting from excessive immunosuppression. The in vitro tacrolimus response of peripheral blood mononuclear cells (PBMCs) before transplantation was compared to the clinical outcome up to 4 weeks after operation in 28 living-donor liver transplant recipients treated with tacrolimus. The tacrolimus IC(50) values against concanavalin A-induced PBMC blastogenesis in vitro were calculated. These recipients were classified into two groups with the mean tacrolimus IC(50) (0.18 ng/ml) as the cutoff point, after which the clinical outcome between the patient groups was compared. The allograft rejection incidence in the low-sensitivity group (IC(50) < 0.18 ng/ml; n = 16) was 6/12 (50.0%), which was significantly higher than the incidence of 2/16 (12.5%) in the high-sensitivity group (IC(50) > 0.18 ng/ml; n = 12) (p = 0.0297). In contrast, the infection incidence in the high-sensitivity group was 6/16 (37.5%), which was significantly higher than that of the low-sensitivity group (1/12; 8.3%) (p = 0.0401). These data suggest that patients exhibiting a low PBMC sensitivity to tacrolimus have a risk of rejection, whereas highly sensitive patients have a risk of infection in living-donor liver transplantations under tacrolimus therapy.

Differences in proviral DNA load between HIV-1-infected and HIV-2-infected patients

Gueudin et al. [1] recently reported statistically significant lower levels of ‘proviral’ HIV-2 DNA in peripheral blood mononuclear cells (PBMC) of HIV-2-infected individuals compared with that found in HIV-1-infected individuals. They call into question numerous previous studies (including their own) that have found similar levels of HIV-1 and HIV-2 DNA in PBMC despite remarkably lower levels of plasma HIV-2 RNA than HIV-1 RNA in infected individuals [2-12]. They base their findings on a novel real-time PCR assay that uses a ‘coplasmid’standard that contains both long-terminal repeat (LTR) targets for HIV-1 and HIV-2 primers and probes. In a stratified analysis by CD4 cell counts in 40 HIV-1-infected and 42 HIV-2-infected antiretroviral naive patients, they reported significantly higher levels of HIV-1 DNA compared with HIV-2 DNA in patients with CD4 cell counts greater than 500 cells/μl, between 500 and 300 cells/μl, and a nonsignificant trend for those lower than 300 cells/μl. Similar to previous studies, they found a significant increase in DNA levels for both HIV-1 and HIV-2 as CD4 cell counts decreased. Unfortunately (and unlike some previous studies that found similar statistical differences in unadjusted, but not in adjusted analyses), they failed to adjust for CD4 cell count, and other potential factors (age, duration of infection, sex, etc.) affecting HIV PBMC DNA levels in multivariate analyses. Thus, it is possible that their observation is biased by different distributions of CD4 cell counts (or other confounders) between the HIV-1 and HIV-2 patients (with HIV-1 patients tending to have more rapid disease and lower CD4 cell counts in each strata). Also, despite differing levels of detection sensitivity for HIV-1 (10 copies/μg) and HIV-2 (20 copies/μg) in their new assay, and differing rates of detection of HIV-1 (37/40, 93%) and HIV-2 (31/42, 74%) in infected patients, they report that they set samples below the detection limit for both HIV-1 and HIV-2 at 10 copies/μg. It would have been reasonable to do a sensitivity analysis to determine how that ‘arbitrary’ cutoff might affect their results. In addition, their assay actually measures total cellular HIV DNA (integrated, unintegrated, one and two LTR circles) and is not specific for ‘proviral’ (integrated) HIV: different levels of one and two LTR circles between HIV-1 and HIV-2 could, for example, confound measurements. A recent study by MacNeil et al. [12] reported that the total amount and percentage of integrated proviral HIV-1 and HIV-2 DNA are quite similar and not statistically different, and that lower levels of HIV-2 mRNA, and not proviral load levels, may help explain the markedly lower plasma HIV-2 RNA viral loads that have been universally observed. Finally, Gueudin et al. [1] report that the HIV-2 plasma RNA viral loads were above the detection limit (100 copies/ml) in 12 of 42 (29%) patients. This percentage of patients with detectable HIV-2 plasma RNA viral loads is substantially lower than in other studies that have looked at HIV-2 plasma RNA levels in antiretroviral (ARV)-naive patients (range 45-85%) [2,7-9,11,13-18], suggesting that their study population may not be representative of HIV-2 infection in general, and that their findings of low HIV-2 PBMC DNA levels may be a consequence of having the majority of their patients with low-plasma viral loads. Using the same CD4 cell count cutoffs as reported by Gueudin et al. [1] we reanalyzed additional patients with HIV-1 (n = 392) and HIV-2 (n = 104) PBMC DNA levels that we previously reported from our Senegal Cohort using a modified Roche Amplicor DNA assay (Roche Amplicor Diagnostic systems Inc., Nutley, New Jersey, USA) with a limit of detection of 1 copy/μg [11]. In contrast, our data suggest that, at CD4 cellcounts greater than 500 cells/μl, and between 300 and 500 cells/μl, the DNA levels are quite similar and, at low CD4 cell counts (<300 cells/μl), HIV-2 DNA levels are actually significantly higher compared with HIV-1 (Table 1). Table 1 Median log10 peripheral blood mononuclear cell HIV DNA copies/μg. Overall, the preponderance of data suggests that levels of HIV-1 and HIV-2 DNA in PBMC are not the major reason for the markedly different levels of plasma virus and rates of disease progression found between these two types of HIV infection.

A new Hu-PBL model for the study of human islet alloreactivity based on NOD- scid mice bearing a targeted mutation in the IL-2 receptor gamma chain gene

Immunodeficient NOD-scid mice bearing a targeted mutation in the IL2 receptor common gamma chain (Il2rgamma(null)) readily engraft with human stem cells. Here we analyzed human peripheral blood mononuclear cells (PBMC) for their ability to engraft NOD-scid Il2rgamma(null) mice and established engraftment kinetics, optimal cell dose, and the influence of injection route. Even at low PBMC input, NOD-scid Il2rgamma(null) mice reproducibly support high human PBMC engraftment that plateaus within 3-4 weeks. In contrast to previous stocks of immunodeficient mice, we observed low intra- and inter-donor variability of engraftment. NOD-scid Il2rgamma(null) mice rendered hyperglycemic by streptozotocin treatment return to normoglycemia following transplantation with human islets. Interestingly, these human islet grafts are rejected following injection of HLA-mismatched human PBMC as evidenced by return to hyperglycemia and loss of human C-peptide. These data suggest that humanized NOD-scid Il2rgamma(null) mice may represent an important surrogate for investigating in vivo mechanisms of human islet allograft rejection.

Fas/Fas-L expression, apoptosis and low proliferative response are associated with heart failure in patients with chronic Chagas' disease

Chagas' disease affects 16–18 million patients in South America and heart involvement is the major cause of morbidity and mortality. Heart failure is the most severe clinical manifestation of the chronic phase of infection with Trypanosoma cruzi. The intensity and nature of the immune response is associated with the clinical outcome of the disease. In murine models, a low proliferative response and T-cell apoptosis have been observed during acute infection. In the present study the immune response of patients in the chronic phase of infection was analyzed. Patients were divided into: (a) asymptomatic, i.e., without involvement of the heart or digestive system; and (b) with heart failure. Patients with heart failure presented a significantly lower peripheral blood mononuclear cell (PBMC) proliferative response to T. cruzi antigens compared to asymptomatic patients. This low response was associated with antigen-induced apoptosis. Apoptosis of PBMC and a low proliferative response were also associated with double Fas/Fas-L expression and high production of TNF-α, a cytokine known to induce programmed cell death. These results suggest that apoptosis of PBMC, probably triggered by double expression of Fas/Fas-L and TNF-α, is implicated in the immune regulatory mechanism during the chronic phase of Chagas' disease.

Cytomodulation of interleukin-2 effect by L-2-oxothiazolidine-4-carboxylate on human malignant melanoma.

Glutathione (GSH), the most prevalent intracellular non-protein thiol, plays an important role in the interleukin-2 (IL-2)-induced proliferative activity of normal and tumour cells expressing IL-2 receptor (IL-2R). In the present study, we investigate the effect of IL-2 on proliferation of the human melanoma A375 cell line, and the possible selective cytomodulation effect of this cytokine by L-2-oxothiazolidine-4-carboxylate (OTZ) on these melanoma cells and on human peripheral blood mononuclear cells (PBMCs). We found that recombinant IL-2 (rIL-2) significantly increased the proliferation rate of A375 melanoma cells, which was associated with an increase in GSH levels, the enhancement of IL-2Ralpha expression and the endogenous production of IL-2 in these tumour cells. In contrast, OTZ decreased GSH content and the proliferation rate of A375 cells, and abrogated the growth-promoting effects of rIL-2. Thus, compared to cells treated with rIL-2, pre-treatment with OTZ reduced IL-2Ralpha expression, and also decreased the consumption of rIL-2 and the endogenous secretion of IL-2 by these tumour cells. With regard to PBMCs, the combination of OTZ plus rIL-2 resulted in a more rapid and greater increase of IL-2Ralpha expression than rIL-2 alone, with the proliferation rate being similar in the first 24 h, but with a lower PBMC' count found thereafter compared to rIL-2 treatment alone. These results suggest that OTZ plays a crucial role in obtaining a selective cytomodulation of rIL-2, enabling it to exert its growth-promoting effect on normal cells, but not on melanoma cells, thereby possibly improving biochemotherapy with rIL-2.

Response of peripheral blood mononuclear cells in hemodialyzed patients against endotoxin and muramyldipeptide

Microbial fragments of endotoxin (ET) and peptidoglycan (PG) are recognized as pyrogen in dialysate. The aim of this study was to evaluate the effect of contaminated dialysate on peripheral blood mononuclear cells (PBMC) in hemodialyzed patients by measuring production of interleukine 1-beta (IL-1beta) in vitro. Venous blood was withdrawn before dialysis session. The effects of a dialysis membrane, a magnitude of dialysate contamination and a duration of hemodialysis were studied. PBMC was stimulated by the addition of water containing either ET or muramyldipeptide (MDP), the minimum biological activated fragment of PG, or ET+MDP. IL-1beta production of PBMC stimulated by ET or ET+MDP in patients on hemodialysis using a polysulfon (PS) membrane was significantly lower than those using a cuprammonium-rayon (CU) membrane, ethylenevinylalcohol (EVAL) membrane, polymethylmetacrylate (PMMA) membrane, respectively. Among patients on the PS membranes, those who were exposed to dialysate with higher pyrogen contamination had lower PBMC cytokine production than those dialyzed with ultrapure dialysate. Response of PBMC in patients against ET+MDP stimulant decreased with duration of dialysis treatment. This suggested that chronic exposure to ET or MDP during hemodialysis treatment, might cause a tolerance against ET and ET+MDP in PBMC.

Administration of recombinant rhesus interleukin-12 during acute simian immunodeficiency virus (SIV) infection leads to decreased viral loads associated with prolonged survival in SIVmac251-infected rhesus macaques.

The ability of recombinant rhesus interleukin-12 (rMamu-IL-12) administration during acute simian immunodeficiency virus SIVmac251 infection to influence the quality of the antiviral immune responses was assessed in rhesus macaques. Group I (n = 4) was the virus-only control group. Group II and III received a conditioning regimen of rMamu-IL-12 (10 and 20 microg/kg, respectively, subcutaneously [s.c.]) on days -2 and 0. Thereafter, group II received 2 microg of IL-12 per kg and group III received 10 microg/kg s.c. twice a week for 8 weeks. On day 0 all animals were infected with SIVmac251 intravenously. While all four group I animals and three of four group II animals died by 8 and 10 months post infection (p.i.), all four group III animals remained alive for >20 months p.i. The higher IL-12 dose led to lower plasma viral loads and markedly lower peripheral blood mononuclear cell and lymph node proviral DNA loads. During the acute viremia phase, the high-IL-12-dose monkeys showed an increase in CD3(-) CD8 alpha/alpha(+) and CD3(+) CD8 alpha/alpha(+) cells and, unlike the control and low-IL-12-dose animals, did not demonstrate an increase in CD4(+) CD45RA(+) CD62L(+) naive cells. The high-IL-12-dose animals also demonstrated that both CD8 alpha/alpha(+) and CD8 alpha/beta(+) cells produced antiviral factors early p.i., whereas only CD8 alpha/beta(+) cells retained this function late p.i. Long-term survival correlated with sustained high levels of SIV gag/pol and SIV env cytotoxic T lymphocytes and retention of high memory responses against nominal antigens. This is the first study to demonstrate the capacity of IL-12 to significantly protect macaques from SIV-induced disease, and it provides a useful model to more precisely identify correlates of virus-specific disease-protective responses.

Clinical pharmacokinetics of 5-fluorouracil with consideration of chronopharmacokinetics

Even though 5-fluorouracil (FU) is one of the oldest anticancer drugs, its use in cancer chemotherapy continues to increase. Fluorouracil is a pro-drug that requires intracellular activation to exert its effects. This makes it difficult to associate blood drug concentration with cell toxicity directly, although data from the literature show the existence of such a relationship. The relationship between FU pharmacokinetics and patient response has been explored extensively and reports attest a link between systemic drug exposure and response and survival. This has led to the concept of maximal tolerated exposure, and strategies to achieve this rely on pharmacokinetic follow-up and individual dose adjustment. More than 80% of the administered FU dose is eliminated by catabolism through dihydropyrimidine dehydrogenase (DPD), the rate-limiting enzyme. Dihydropyrimidine dehydrogenase activity is found in most tissues but is highest in the liver. Peripheral blood mononuclear cells (PBMC) are used to monitor clinically DPD activity. A significant, but weak correlation between PBMC and liver DPD activity has been observed. The relationship between PBMC–DPD activity and FU systemic clearance is weak (r2=0.10); thus, simply determining PBMC–DPD is not sufficient to predict accurately FU clearance. Population pharmacokinetic analysis identified patient co-variables that influence FU clearance; drug kinetics is significantly reduced by increased age, high serum alkaline phosphatase, length of drug infusion, and low PBMC–DPD. Autoregulation of FU metabolism also is suggested; inhibition of DPD activity was observed after FU administration in both colorectal cancer patients and an animal model. Circadian rhythmicity in DPD activity is suggested from both human and animal investigations. In patients receiving protracted low dose 5-FU infusion, the circadian rhythm in FU plasma concentration peaks at 11:00h and is lowest at 23:00h, on average. The inverse relationship observed between the circadian profile of FU plasma concentration and PBMC–DP activity in these same patients suggests a link between DPD activity and FU pharmacokinetics. The impact of the biological time of drug administration was also studied with short venous infusions; clearance was 70% greater at 13:00h than at 01:00h. Similarly, peak drug concentration occurred in the first half of the night in patients receiving constant rate 5-FU infusion for 2–5 d. Several studies describe wide interindividual variation in the timing of the peak and trough of the 24h rhythm in DPD activity. The rational for FU chronomodulated therapy has been the circadian rhythm in host drug tolerance, which is greatest during the night time when the proliferation of normal target tissue is least. A randomized study of chronomodulated FU therapy with maximal delivery rate at 04:00h was shown clearly to be significantly more effective and less toxic than control flat FU therapy. Future research must focus on easy-to-obtain markers of specific rhythms to individualize the chronomodulated FU delivery.

Zidovudine Treatment in Patients with Primary (Acute) Human Immunodeficiency Virus Type 1 Infection: A Randomized, Double-Blind, Placebo-Controlled Trial

A multicenter, double-blind, placebo-controlled trial randomized 28 patients with primary (acute) human immunodeficiency virus (HIV)-1 infection (PHI) to receive zidovudine, 1000 mg daily, or placebo for 24 weeks. At week 48, compared with placebo patients, zidovudine-treated patients had significantly higher CD4 cell counts (zidovudine, 666 cells/mm3; placebo, 362; P = .004) and lower peripheral blood mononuclear cell (PBMC) culture titers (zidovudine, 0.58 log infectious units per million cells; placebo, 1.68; P = .02) but no difference in plasma RNA (zidovudine, 3.93 log copies/mL; placebo, 4.00; P = .83). Serious adverse events and minor clinical events were infrequent and comparable in both arms. There were two deaths: 1 patient died of sepsis and renal disease (zidovudine arm), and 1 patient died of sepsis and tension pneumothorax (placebo arm). Six months of high-dose zidovudine initiated during PHI results in higher CD4 cell counts and lower PBMC culture titers but no difference in plasma HIV-1 RNA. Further studies with more potent antiretroviral combination therapies are warranted.

Prothymosin α enhances interleukin 2 receptor expression in normal human T-lymphocytes

We investigated whether the enhancement, by prothymosin alpha (Proα), of the phytohaemagglutinin-stimulated proliferation of human peripheral blood mononuclear cells (PBMC) is due to its affect on the number of cells expressing the interleukin 2 receptor (IL-2R) or the surface density of IL-2R on PBMC. Peripheral blood mononuclear cells were obtained from 21 donors. For both an optimal phytohaemagglutinin (PHA) concentration (H) and a 10-fold dilution (L), their responses fell in two classes, high (h) and low (l), making four dose - response situations. Proα significantly increased the number and IL-2R density of cells expressing IL-2R only when the response in its absence was about half maximal, i.e. for PBMC responding well to the low PHA stimulus (group Lh) or PBMC responding poorly to the optimal stimulus (group Hl). The enhancement of IL-2R expression in group Lh by Proα was dose-dependent and paralleled by increased proliferative response. It appears not to be mediated by IL-2, since it was unaffected when IL-2 production was suppressed by cycloporin A. The early interaction of Proα with lymphocytes did not require the presence of macrophages, but macrophages were necessary during lymphocyte activation for modulation of PHA-stimulated IL-2R expression to be affected. The immunoregulatory activity of Proα may prove useful for improving the decreased T-cell function associated with immunodeficiency, or for restoration of normal IL-2R expression by the lymphocytes of aged individuals.