Two novel variants of the ABCG5 gene cause xanthelasmas and macrothrombocytopenia: a brief review of hematologic abnormalities of sitosterolemia.

Essentials Diagnosis of sitosterolemia, a rare recessive or syndromic disorder, is usually delayed. Peripheral blood smear is extremely useful for establishing the suspicion of sitosterolemia. High-throughput sequencing technology enables the molecular diagnosis of inherited thrombocytopenias. Accurate characterization of sitosterolemia helps us determine appropriate management. SUMMARY: Background Sitosterolemia (STSL) is a recessive inherited disorder caused by pathogenic variants in the ABCG5 and ABCG8 genes. Increased levels of plasma plant sterols (PSs) usually result in xanthomas and premature coronary atherosclerosis, although hematologic abnormalities may occasionally be present. This clinical picture is unfamiliar to many physicians, and patients may be at high risk of misdiagnosis. Objectives To report two novel ABCG5 variants causing STSL in a Spanish patient, and review the clinical and mutational landscape of STSL. Patient/Methods A 46-year-old female was referred to us with lifelong macrothrombocytopenia. She showed familial hypercholesterolemia-related xanthomas. Molecular analysis was performed with high-throughput sequencing. Plasma PS levels were evaluated with gas-liquid chromatography. The STSL landscape was reviewed with respect to specific online databases and all reports published since 1974. Results A blood smear revealed giant platelets and stomatocytes. Novel compound heterozygous variants were detected in exons 7 (c.914C>G) and 13 (c.1890delT) of ABCG5. The patient showed an increased plasma level of sitosterol. These findings support the diagnosis of STSL. In our review, we identified only 25 unrelated STLS patients who presented with hematologic abnormalities including macrothrombocytopenia. It remains unknown why only some patients develop hematologic abnormalities. Conclusions This is the first Spanish STSL patient to be reported and molecularly characterized. The early diagnosis of STLS is strongly supported by the presence of stomatocytes in blood smears. The definitive diagnosis of STSL by measurement of serum PS levels and molecular analyses prompted the use of ezetimibe therapy.

SCO-spondin from embryonic cerebrospinal fluid is required for neurogenesis during early brain development.

The central nervous system (CNS) develops from the neural tube, a hollow structure filled with embryonic cerebrospinal fluid (eCSF) and surrounded by neuroepithelial cells. Several lines of evidence suggest that the eCSF contains diffusible factors regulating the survival, proliferation, and differentiation of the neuroepithelium, although these factors are only beginning to be uncovered. One possible candidate as eCSF morphogenetic molecule is SCO-spondin, a large glycoprotein whose secretion by the diencephalic roof plate starts at early developmental stages. In vitro, SCO-spondin promotes neuronal survival and differentiation, but its in vivo function still remains to be elucidated. Here we performed in vivo loss of function experiments for SCO-spondin during early brain development by injecting and electroporating a specific shRNA expression vector into the neural tube of chick embryos. We show that SCO-spondin knock down induces an increase in neuroepithelial cells proliferation concomitantly with a decrease in cellular differentiation toward neuronal lineages, leading to hyperplasia in both the diencephalon and the mesencephalon. In addition, SCO-spondin is required for the correct morphogenesis of the posterior commissure and pineal gland. Because SCO-spondin is secreted by the diencephalon, we sought to corroborate the long-range function of this protein in vitro by performing gain and loss of function experiments on mesencephalic explants. We find that culture medium enriched in SCO-spondin causes an increased neurodifferentiation of explanted mesencephalic region. Conversely, inhibitory antibodies against SCO-spondin cause a reduction in neurodifferentiation and an increase of mitosis when such explants are cultured in eCSF. Our results suggest that SCO-spondin is a crucial eCSF diffusible factor regulating the balance between proliferation and differentiation of the brain neuroepithelial cells.

Lymphocyte apoptosis, caspase activation and inflammatory response in septic shock.

BACKGROUND: We examined lymphocyte apoptosis, activity of caspases-1, -3, -8 and -9 and the relationship between those two events and inflammation response in septic shock. MATERIALS AND METHODS: Blood samples were obtained within 24 h after diagnosis of septic shock from 16 patients to measure apoptosis, caspases-3, -8, -9 expression, changes in mitochondrial transmembrane potential and expression of Fas/FasL system of peripheral blood mononuclear cells (PBMCs). Moreover, serum levels of caspase-1 and blood concentrations of IL-6, IL-12, IL-15 and IL-18 were assessed. RESULTS: PBMCs from patients with septic shock compared to control individuals exhibited a greatly increased frequency of apoptosis (39.10 +/- 7.33% vs 4.19 +/- 1.13%; p < 0.001), an over expression of caspases-3, -8, and -9 (p < 0.01, p < 0.05, p < 0.001 for caspases-3, -8 and -9, respectively) as well as of Fas/FasL system (p < 0.05) and significant changes in mitochondrial transmembrane potential. Blood levels of caspase-1 (101.5 +/- 18.2 pg/ml vs 9.09 +/- 2.7 pg/ml, p < 0.001) and of IL-6, IL-12, IL-15 and IL-18 were significantly higher in septic patients vs control (p < 0.0001, p < 0.05, p < 0.05 and p < 0.0001, respectively). Furthermore, a correlation linking IL-6 blood level with both the apoptotic rate (r(2) = 0.75; p = 0.001) and caspase-9 expression (r(2) = 0.92; p = 0.0001) of PBMCs was observed.

The origin and evolution of stereotyped patterns of macrochaetes on the nota of cyclorraphous Diptera.

A long-standing problem in evolutionary biology is how genetic variation arises within populations and evolves to make species anatomically different. Many of the morphological differences in body plans between animal groups are thought to result from changes in gene expression during development. The rules governing the structure and evolution of cis-regulatory gene sequences are unknown, however, and the evolution of traits between closely related species remains relatively unexplored at a molecular level. To study the evolution of gene regulation, it is necessary to find a tractable trait that varies between species and for which the genetic regulation is well known in at least one of the species. The stereotyped, two-dimensional pattern of bristles on the thorax of Drosophila has been intensively investigated and is due to a precise spatial expression of proneural genes. Other species of flies have different bristle patterns and so comparisons between them provide a good paradigm for the study of changes in gene regulation. Here, we review the current state of understanding of these changes.

Pancuronium bromide, a non-depolarizing muscle relaxant which promotes apoptosis of blood lymphocytes in vitro.

BACKGROUND: Several compounds used in anesthesia practice have demonstrated to impair immune function and to influence the process of apoptotic death in T cell population following surgical trauma. We designed this study to test in vitro the impact of neuromuscular blocker, such as pancuronium, at clinically relevant concentration on lymphocyte apoptosis, death factor expression and mitochondrial function. METHODS: Following isolation, lymphocytes were incubated with pancuronium bromide at a clinically relevant concentration (0.136 micro mol l-1) for 3 h at 37 C in a 5% carbon-dioxide-humidified atmosphere and the frequency of apoptotic lymphocytes was then measured. We also investigated crucial steps in the apoptotic process, including Fas/Fas ligand (FasL) phenotype, intracellular expression of the interleukin-1beta-converting enzyme (ICE) p20, mitochondrial membrane potential (DeltaPsim), generation of mitochondrial reactive oxygen species, and glutathione (GSH) levels. Control experiments were performed incubating cells in the complete culture medium added with the dilution medium of the drug without addition of the drug. RESULTS: Expression of Fas, FasL and ICEp20 was six-fold, four-fold, and five-fold increased, respectively, among pancuronium-treated lymphocytes with respect to control cultures (P = 0.0001). The percentage of cells exhibiting either dissipation of mitochondrial membrane potential or increased production of reactive oxygen species was seven-fold increased following exposure to pancuronium compared with untreated lymphocytes (P = 0.0001). These findings were associated with a decrease in GSH level. In addition, the frequency of apoptotic cells was 10-fold greater among lymphocytes cultured in the presence of the drug with respect to control cultures. (P = 0.0001). CONCLUSION: Our data suggest an apoptogenic effect of pancuronium in vitro at clinically relevant concentration on peripheral blood lymphocytes. This could be implicated in the transient immune suppression following a surgical operation.

[Proapoptotic effect of propofol on T cells]. / Effetto proapoptotico del propofol sulle cellule T.

BACKGROUND: Surgery and general anesthesia induce excessive apoptosis on peripheral lymphocytes and this phenomenon significantly contributes to the postoperative lymphocytopenia. However, the role played by anesthetic agents on this event remains to be elucidated. In this study we examined whether an anesthetic compound such as propofol is able to exert, in vitro, a proapoptotic effect on T cells. METHODS: Lymphocytes were isolated from heparinized venous blood in healthy volunteers and were incubated with propofol at clinically relevant concentration (5 mg/ml) and at 10 times this concentration (50 mg/ml). The counts of cells either bearing the Fas/FasL phenotype or expressing the intracellular Bcl2 protein were determined by means of flow cytometry. Assessment of lymphocytes undergoing apoptosis was made both by staining of apoptotic nuclei with propidium iodide (PI) and by phenotypic analysis of apoptotic cells with 7-amino-actinomycin D (7-AAD). RESULTS: Treated lymphocytes exhibit a significantly enhanced expression of Fas/FssL system associated with a decrease of Bcl2 expression at both 5 and 50 mg/ml propofol concentrations (p<0.05). On the other hand, the rate of apoptotic cells was not significantly different as compared to control in the absence of propofol. CONCLUSIONS: Propofol impairs, in vitro, both Fas/FasL and Bcl2 expressions on lymphocytes at clinically relevant concentrations but fails to induce apoptotic cell death. It is suggested that the antioxidative properties of the drug could inhibit some way the mechanisms by which mitochondrial free-radicals mediating apoptosis ultimately lead to cell death execution.

Mitochondrial perturbations and oxidant stress in lymphocytes from patients undergoing surgery and general anesthesia.

BACKGROUND: Previous studies have shown that a profound suppression of immune function transiently occurs in patients who undergo surgery under general anesthesia. The decline in the absolute counts of peripheral blood lymphocytes constitutes a major factor accounting for this immune defect, and recent evidence indicates that apoptosis plays a crucial role in determining postsurgical lymphocytopenia. HYPOTHESIS: An altered oxidation-reduction status of mitochondria may contribute through apoptosis to the loss of lymphocytes following surgical trauma and general anesthesia. DESIGN: We studied 16 patients with American Society of Anesthesiologists' physical status I or II who underwent elective surgery under general anesthesia. The data were collected prospectively. SETTING: University hospital. MAIN OUTCOME MEASURES: Samples of peripheral blood were drawn on the day before surgery and at 24 and 96 hours after the operation. Following lymphocyte isolation, the mitochondrial transmembrane potential was assessed by flow cytometry using 3,3'-dihexylocarbo-cyanine iodide, and stains with hydroethidine and 2'-7'-dichlorofluorescein diacetate were used to determine the generation of reactive oxygen species. The labeling of lymphocytes with monobromobimane was used to assess the presence of reduced glutathione. RESULTS: At 24 hours after surgery, we detected a significantly elevated frequency of peripheral blood lymphocytes (P =.002), which incorporated low levels of 3,3'-dihexylocarbo-cyanine iodide, compared with the preoperative period. At this same time point, the frequency of lymphocytes with the hydroethidine- and 2'-7'-dichlorofluorescein diacetate-positive phenotype was elevated compared with baseline levels. Conversely, at 24 hours after surgery, the frequency of cells that stained positive for glutathione was strongly decreased compared with preoperative values. Overall measurements returned to the baseline levels at 96 hours after surgery. CONCLUSION: The strict association we observed between the overproduction of reactive oxygen species and the disruption of the mitochondrial transmembrane potential supports the view that alterations in mitochondrial energy metabolism, paralleled by the presence of a pro-oxidant oxidation-reduction status, could be involved in the accelerated apoptotic loss of lymphocytes following surgical trauma and general anesthesia.

Circulating neutrophils exhibit enhanced apoptosis associated with mitochondrial dysfunctions after surgery under general anaesthesia.

BACKGROUND: Evidence suggests that apoptosis plays a main role in the postoperative changes detected in the polymorphonuclear neutrophil (PMN) population. Furthermore, recent studies have demonstrated that mitochondrial alterations constitute critical events of the apoptotic cascade. In this study we investigated whether apoptosis among neutrophils taken from patients undergoing surgical trauma could be associated with perturbation of mitochondrial transmembrane potential (deltapsim) and/or exaggerated production of mitochondrial reactive oxygen species (ROS). METHODS: Twenty-seven patients undergoing elective surgery under general anaesthesia were enrolled in the study. Peripheral blood samples were drawn one day before the operation and at 12 and 24 h after surgery. Apoptosis rate was assessed by staining neutrophils with 7-amino-actinomycin D (7-AAD) and by analysis by a FACScan flow cytometer. In order to evaluate deltapsim, cells were exposed to 3,3-dihexyloxacarbocyanine iodide [DiOC6(3)]; intracellular ROS was measured by means of hydroethidine (HE) and 2,7-diclorofluorescein diacetate (DCFH-DA), followed by analysis on a cytofluorometer. RESULTS: At 12 h following surgery we observed a significantly (P<0.05) increased frequency of apoptotic PMNs compared to that preoperatively (30.79+/-3.68% vs 7.40+/-0.69%). At this same time-point, the rate of neutrophils stained with HE, DCFH-DA and [DiOC6(3)] were significantly (P<0.05) higher compared to baseline (51.05+/-5.44%, 50.58+/-5.84% and 55.31+/-4.33% vs 20.17+/-2.38%, 19.59+/-2.03 and 25.43+/-2.71% respectively). Overall measurements returned to the preoperative values 24 h after surgery. CONCLUSION: These data suggest that surgery under general anaesthesia triggers in the immediate postoperative period pathways of PMN accelerated apoptosis associated with significant alterations in mitochondrial function.

Apoptosis and apoptosis-associated perturbations of peripheral blood lymphocytes during HIV infection: comparison between AIDS patients and asymptomatic long-term non-progressors.

This study was designed to compare the degree of lymphocyte apoptosis and Fas-Fas ligand (FasL) expression in AIDS patients and long-term non-progressors (LTNPs) and correlate these parameters with apoptosis-associated perturbations in lymphocyte function. LTNPs had a lower frequency of apoptotic CD4+ and CD8+ T cells compared with subjects with AIDS. This correlated with a lower frequency of cells expressing Fas and FasL. The frequency of selected lymphocyte populations exhibiting a disrupted mitochondrial transmembrane potential (DeltaPsim) and increased superoxide generation was lower in LTNPs than in patients with AIDS; these abnormalities were associated with lower levels of caspase-1 activation in LTNPs. The results indicate a significantly reduced level of apoptosis and apoptosis-associated parameters in LTNPs than in patients developing AIDS. Based on these findings, a crucial role for mitochondria can be predicted in the process of lymphocyte apoptosis during the evolution of AIDS.

Apoptosis and surgical trauma: dysregulated expression of death and survival factors on peripheral lymphocytes.

BACKGROUND: Surgery and anesthesia cause depression of cell-mediated immunity in the postoperative period, including a reduction in the numbers of circulating lymphocytes. It has been claimed that this immunosuppression is associated with an increased incidence of postoperative infections. HYPOTHESIS: Lymphocytopenia following surgical trauma depends on a dysregulated expression of death/and survival factors associated with apoptosis that, in turn, interferes with the occurrence of postsurgical infections. DESIGN: Fifteen subjects undergoing elective surgery under general anesthesia entered the study. The data of the patients who had infections during the postoperative outcome were compared with the data of those who did not. The data were collected prospectively. MAIN OUTCOME MEASURES: Peripheral blood samples were drawn before the operation, and 24 hours and 96 hours after the operation. Lymphocytes were isolated and examined for quantification and phenotypic analysis of apoptosis using the 7-amino-actinomycin D method, as well as for Fas and Fas ligand, interleukin 1-converting enzyme p20/caspase-1, Bcl-2, and p35 expression. The rate of apoptotic cells was correlated with the incidence of postoperative infections. SETTING: University hospital. RESULTS: Twenty-four hours after surgery, CD4(+) and CD8(+) cells exhibited a significantly higher frequency of apoptosis as well as of Fas and Fas ligand and interleukin 1-converting enzyme p20/caspase-1 expressions than preoperatively. This increase was paralleled by a significant down-regulation of antiapoptotic factors such as Bcl-2. However, the expression of the proapoptotic factor p35 was reduced. In addition, we found a relationship between the rate of the apoptotic CD8(+) subset and the occurrence of infectious complications during the postoperative course. At 96 hours after surgery, the variables studied returned to the baseline levels. CONCLUSIONS: In the early postoperative period, surgical trauma under general anesthesia induces an intracellular perturbation on peripheral lymphocytes, resulting in both up-regulation of death-signaling factors and down-regulation of survival-signaling factors. The increased apoptosis of CD8(+) lymphocytes, but not of CD4(+) cells, seemed to be associated with a greater risk of postsurgical infections.

Combined antiviral therapy reduces HIV-1 plasma load and improves CD4 counts but does not interfere with ongoing lymphocyte apoptosis.

The progression of HIV-1 disease appears associated with an unregulated Fas-mediated apoptosis of lymphocytes that involves the activation of ICE protease and ceramide generation and antiviral therapy may not be fully effective in the absence of a relevant impact on apoptosis. Six drug-naive HIV-1-infected symptomless patients with advanced immunodeficiency were treated with combined AZT and ddl for 4 months; plasma HIV-1 RNA levels, the counts of CD4 cells, CD4 and CD8 apoptotic lymphocytes, Fas-positive cells and ICE-positive cells, and intracellular ceramide levels were measured at base-line and after 7, 45 and 120 days of treatment. There was a prompt reduction in plasma viremia and a secondary increase in CD4 counts, but the treatment had no impact on apoptotic CD4 and CD8 lymphocytes, Fas-positive cells and ICE-positive cells, and on the intracellular levels of ceramide. A discrepancy exists between the positive impact of combined AZT and ddl treatment on plasma viral load and CD4 counts and the lack of any effect on the process of lymphocyte apoptosis. We suggest to use the measurement of apoptotic lymphocytes as a surrogate marker to predict, in combination with viral load and CD4 counts, a large proportion of the clinical effect of antiviral therapy.

Fas/Fas ligand on the road: an apoptotic pathway common to AIDS, autoimmunity, lymphoproliferation and transplantation.

There is considerable interest in the role of Fas protein as it induces apoptotic cell death when ligated by its natural ligand (FasL). Interaction between Fas and FasL is a crucial mechanism for clonal deletion and immune tolerance and privilege, control of T cell expansion during immune responses and killing by cytotoxic T lymphocytes. Loss of function of the system can block lymphocyte apoptosis and cause lymphoproliferation and autoimmunity but, when the system overfunctions, it can end to tissue injury and destruction. Recent studies have demonstrated that the Fas/FasL system is implicated in the pathogenesis of several human diseases ranging from AIDS to autoimmunity and lymphoproliferation, hepatitis, multiple sclerosis and transplant rejection. It is conceivable that modulating the activity of the Fas/fasL pathway would have clinical applications for the treatment of these patients.

Acetyl-L-carnitine administration increases insulin-like growth factor 1 levels in asymptomatic HIV-1-infected subjects: correlation with its suppressive effect on lymphocyte apoptosis and ceramide generation.

The aim of this study was to investigate the impact of long-term acetyl-L-carnitine administration on CD4 and CD8 absolute counts, apoptosis, and insulin-like growth factor-1 (IGF-1) serum levels in HIV-1-infected subjects. The generation of cell-associated ceramide and HIV-1 viremia were also investigated. Eleven asymptomatic, HIV-1-infected subjects were treated daily with acetyl-L-carnitine (3 g) for 5 months. Immunologic and virologic measures and safety were monitored at the start of the treatment and then on days 90 and 150. Altogether our findings suggest that acetyl-L-carnitine administration has a substantial impact on the main immunologic abnormality associated with HIV infection, the loss of CD4 cells, by reducing the rate of apoptotic lymphocyte death. The reduction of ceramide generation and the increase of the serum levels of IGF-1, a major survival factor able to protect cells from apoptosis by different stimuli and conditions, could represent two important mechanisms underlying the observed anti-apoptotic effects of acetyl-L-carnitine.

Effect of L-carnitine on human immunodeficiency virus-1 infection-associated apoptosis: a pilot study.

The Fas/Fas ligand system is involved in uncontrolled apoptosis, which ultimately leads to the loss of T lymphocytes in human immunodeficiency virus (HIV)-infected individuals. The signal transduced by Fas receptor involves the activation of an acidic sphingomyelinase, sphingomyelin breakdown, and ceramide production. Our recent reports have shown that L-carnitine inhibits Fas-induced apoptosis and ceramide production both in vitro and in vivo. The aim of this study was to study, in a preliminary fashion, the impact of long-term L-carnitine administration on CD4 and CD8 absolute counts, rate, and apoptosis in HIV-1-infected subjects. The generation of cell-associated ceramide and HIV-1 viremia was also investigated. Eleven, asymptomatic, HIV-1-infected subjects, who refused any antiretroviral treatment despite experiencing a progressive decline of CD4 counts, were treated with daily infusions of L-carnitine (6 g) for 4 months. Immunologic and virologic measures and safety were monitored at the start of the treatment and then on days 15, 30, 90, and 150. L-carnitine therapy resulted in an increase of absolute CD4 counts, which was statistically significant on day 90 and 150 (P = . 010 and P = .019, respectively). A positive, not significant trend was also observed even in the change in absolute counts of CD8 lymphocytes. L-carnitine therapy also led to a drop in the frequency of apoptotic CD4 and CD8 lymphocytes. This reduction occurred gradually, but changes in actual values between each time point and baseline were strongly significant (P = .001 at the end of the study compared with the baseline). A strong reduction (P = .001) in cell-associated ceramide levels was found at the end of the study. In general, HIV-1 viremia increased slightly. No toxicity related to L-carnitine therapy was observed and dose reductions were not necessary. In HIV-1-infected subjects, long-term infusions of L-carnitine produced substantial increases in the rate and absolute counts of CD4 and, to a lesser degree, of CD8 lymphocytes. This was paralleled by a reduced frequency of apoptotic cells of both subgroups and a decline in the levels of ceramide. No clinically relevant change of HIV-1 viremia was observed.

Apoptosis: mechanisms and relation to AIDS.

Infection with the human immunodeficiency virus (HIV) is considered to lead to the acquired immunodeficiency syndrome (AIDS) via the progressive loss of immune competence in the infected host. Recent research has highlighted that HIV may indirectly trigger an active cell suicide process, referred to as programmed cell death or apoptosis, that contributes to the decline in lymphocyte counts throughout the course of HIV infection. We review here the main host- and HIV-related factors actively involved in inducing lymphocyte apoptosis. Among them, the relationships linking HIV, the oxidant/antioxidant balance in the cellular redox system, tumor necrosis factor (TNF) and lymphocyte-associated ceramide generated through the activation of sphingomyelin pathway are receiving growing consideration. Recognizing the importance of apoptosis in AIDS pathogenesis may have a great impact on the design of new strategies for the treatment of the disease. Available data indicate that antioxidant compounds exert antiapoptotic activity. These compounds, in our opinion, should be used in combination regimens with antiretroviral drugs in the treatment of HIV-infected subjects.

Influence of L-carnitine on CD95 cross-lining-induced apoptosis and ceramide generation in human cell lines: correlation with its effects on purified acidic and neutral sphingomyelinases in vitro.

Recently, we examined the effects of a short-term (5-days) intravenous L-carnitine (6 g/die) treatment on apoptosis of CD4 and CD8 cells from 10 AIDS patients. Without inducing side effects, L-carnitine administration has been shown to induce a potent reduction in the percentage of cells undergoing apoptosis, paralleled by a significant increase of CD4 an CD8 cells. Interestingly, L-carnitine treatment led to a significant reduction of peripheral blood mononuclear cell-associated ceramide (an intracellular messenger for apoptosis) that correlated with the decrease of apoptotic CD4- and CD8-positive cells. These results suggest that L-carnitine could be an effective antiapoptotic drug use with AIDS patients. In this article we report the results of in vitro studies performed to better characterize the effects of L-carnitine on cell apoptosis. Previously, a high expression of the Fas (CD95/APO-1)/Fas ligand system in peripheral blood mononuclear cells from HIV-positive individuals has been reported and could be responsible for the observed relevant apoptosis of both infected and uninfected cells. Thus, we investigated the in vitro effects of L-carnitine on CD95 cross-linking-induced apoptosis through an anti-CD95 mAb in Fas-sensitive cell lines (HuT78 and U937). The results strongly support the in vivo observations. Our data indicate that L-carnitine is able to inhibit CD95-induced apoptosis of these cells, most likely by preventing sphingomyelin breakdown and consequent ceramide synthesis. The effect of L-carnitine seems to be specific for acidic sphingomyelinase as shown by experiments performed in vitro and using purified neutral or acidic sphingomyelinases.

Acetyl-carnitine deficiency in AIDS patients with neurotoxicity on treatment with antiretroviral nucleoside analogues.

OBJECTIVE: A severe dose limiting axonal peripheral neuropathy may develop in subjects on treatment with the nucleoside analogues didanosine (ddl), zalcitabine (ddC), and stavudine (d4T). The impairment of mitrochondrial DNA synthesis is crucial to the pathogenesis of this disorder although other mechanisms have not been ruled out. The depletion of acetyl-carnitine, which regulates the metabolism and function of peripheral nerves could contribute to the neurotoxicity of these compounds. DESIGN: Non-randomized, cross-sectional study of selected patients. METHODS: We measured the serum levels of acetyl- and total carnitine in 12 subjects with axonal peripheral neuropathy developed on treatment with different regimens of neurotoxic nucleoside analogues (ddl, ddC, d4T). Subjects who did not develop peripheral neuropathy while staying on treatment with ddl (n = 10) or zidovudine (n = 11) served as the control groups. HIV-negative subjects with axonal on demyelinating autoimmune neuropathies (n = 10) and healthy individuals (n = 13) were additional control groups. RESULTS: Subjects experiencing axonal peripheral neuropathy on treatment with ddl, ddC and d4T had significantly reduced levels of acetyl-carnitine in comparison to the control groups. No difference was observed in the levels of total carnitine between study subjects and the control groups. CONCLUSIONS: Our results demonstrate that subjects who developed peripheral neuropathy while staying on treatment with ddl, ddC and d4T had acetyl-carnitine deficiency. The normal levels of total carnitine in the study group appear to indicate the specificity of the defect and rule out coexisting relevant nutritional problems. The critical role of acetyl-carnitine for the metabolism and function of the peripheral nerves supports the view that the acetyl-carnitine deficiency found in these subjects may contribute to the neurotoxicity of ddl, ddC and d4T, even though the interference with mitochondrial DNA synthesis is regarded as the main cause of their toxicity.

CD8 lymphocytes in HIV infection: helpful and harmful.

The part played by CD8 lymphocytes in the pathogenesis of human immunodeficiency virus infection (HIV) is much disputed and the relevant issue of the controversy ranges as to whether the functional activity of these cells is beneficial or detrimental to the host. Even though CD8 cells could efficiently suppress HIV replication through both major histocompatibility complex (MHC)-restricted cytotoxic killing of infected cells, particularly during primary infection, and HIV-suppressing soluble factors, there is evidence that tissue-infiltrating CD8 lymphocytes mediate injury in several organs of HIV-infected subjects. Furthermore, CD8 lymphocytes could contribute to the destruction of CD4 cells in vivo. Of note, the virus has the capability to escape the recognition by cytotoxic CD8 cells and the cytotoxic activity of CD8 cells and their counts decline with evolving HIV infection. Several mechanisms are proposed to explain this latter finding, including the direct in vivo infection of CD8 cells by the virus. It is likely that early during the course of HIV infection when viral loads are generally low an efficient CD8 cell response can control HIV replication whereas in subjects with evolving disease, who have very high viral loads, CD8 lymphocytes remove essential components of the immune response and mediate tissue injury.

Cellular dysmetabolism: the dark side of HIV-1 infection.

The progression to disease in subjects infected with the human immunodeficiency virus type I (HIV-1) cannot be explained solely on the basis of the infecting HIV-1 species. There is recent evidence that abnormalities in the cellular metabolism are crucial to the progression of the infection through common pathways that involve the induction of apoptosis and oxidant stress. Conversely, the low propensity of lymphocytes to undergo apoptosis, a normal redox status, and a balanced ceramide metabolism appear to predict a slow progression, or the non-progression at all, of the infection. It is likely that the ability of the host to maintain over time a balanced cellular metabolism despite the chronic infection with the virus contributes to the especially favourable outcome of an otherwise fatal infection seen in a discrete subgroup of HIV-1-infected individuals (long-term non-progressors) who might never experience any of the adverse effects of HIV-1 infection and will never demonstrate disease progression. Furthermore, this background supports the hypothesis that adjunctive therapies directed at correcting certain abnormalities of cellular metabolism seen in the infected host should be given in combination with antiretroviral drugs in order to slow the progression of the infection.

Abnormalities of carnitine metabolism in chronic fatigue syndrome.

Carnitine may be involved in the pathogenesis of the chronic fatigue syndrome (CFS). However, no information about the cellular metabolism of carnitine in CFS patients is currently available. Therefore, we aimed to measure the levels of carnitine (total, free and short-chain) in both peripheral blood lymphocytes (PBLs) and sera from patients with CFS. The serum levels of total, free and short-chain were comparable in CFS patients, considered as the whole group, to those in healthy control subjects, even though a trend indicating slightly reduced serum concentrations of free carnitine was observed in male patients with CFS. In contrast, the concentrations of total, free and short-chain carnitine in PBLs from patients with CFS were significantly lower than in cells from healthy controls. Our study indicates that patients with CFS require exogenous carnitine supplementation. The low carnitine concentrations in PBLs from patients with CFS probably reflect the carnitine deficiency occurring in other tissues, including the skeletal muscles. The low cellular concentrations of carnitines may help to explain both the immunological abnormalities and the impaired energy metabolism in skeletal muscles.