Lipid Peroxidation in Atherosclerotic Cardiovascular Diseases

Significance: Atherosclerotic cardiovascular diseases (ACVDs) continue to be a primary cause of mortality worldwide in adults aged 35-70 years, occurring more often in countries with lower economic development, and they constitute an ever-growing global burden that has a considerable socioeconomic impact on society. The ACVDs encompass diverse pathologies such as coronary artery disease and heart failure (HF), among others. Recent Advances: It is known that oxidative stress plays a relevant role in ACVDs and some of its effects are mediated by lipid oxidation. In particular, lipid peroxidation (LPO) is a process under which oxidants such as reactive oxygen species attack unsaturated lipids, generating a wide array of oxidation products. These molecules can interact with circulating lipoproteins, to diffuse inside the cell and even to cross biological membranes, modifying target nucleophilic sites within biomolecules such as DNA, lipids, and proteins, and resulting in a plethora of biological effects. Critical Issues: This review summarizes the evidence of the effect of LPO in the development and progression of atherosclerosis-based diseases, HF, and other cardiovascular diseases, highlighting the role of protein adduct formation. Moreover, potential therapeutic strategies targeted at lipoxidation in ACVDs are also discussed. Future Directions: The identification of valid biomarkers for the detection of lipoxidation products and adducts may provide insights into the improvement of the cardiovascular risk stratification of patients and the development of therapeutic strategies against the oxidative effects that can then be applied within a clinical setting.

S-Thiolation Targets Albumin in Heart Failure

Human serum albumin (HSA) is associated with several physiological functions, such as maintaining oncotic pressure and microvascular integrity, among others. It also represents the major and predominant antioxidant in plasma due to the presence of the Cys34 sulfhydryl group. In this study, we assessed qualitative and quantitative changes in HSA in patients with heart failure (HF) and their relationship with the severity of the disease. We detected by means of mass spectrometry a global decrease of the HSA content in the plasma of HF patients in respect to control subjects, a significant increase of thio-HSA with a concomitant decrease in the reduced form of albumin. Cysteine and, at a lesser extent, homocysteine represent the most abundant thiol bound to HSA. A strong inverse correlation was also observed between cysteine-HSA and peak VO₂/kg, an index of oxygen consumption associated with HF severity. Moreover, in HL-1 cardiomyocytes incubated with H₂O₂, we showed a significant decrease of cell viability in cells treated with thio-HSA in respect to restored native-HSA. In conclusion, we found for the first time that S-thiolation of albumin is increased in the plasma of HF patients and induced changes in the structure and antioxidant function of HSA, likely contributing to HF progression.

Pro-oxidant and pro-inflammatory effects of glycated albumin on cardiomyocytes

Human serum albumin (HSA) is the most abundant circulating protein in the body and presents an extensive range of biological functions. As such, it is prone to undergo post-translational modifications (PTMs). The non-enzymatic early glycation of HSA, one of the several PTMs undergone by HSA, arises from the addition of reducing sugars to amine group residues, thus modifying the structure of HSA. These changes may affect HSA functions impairing its biological activity, finally leading to cell damage. The aim of this study was to quantitate glycated-HSA (GA) levels in the plasma of heart failure (HF) patients and to evaluate the biological effects of GA on HL-1 cardiomyocytes. Plasma GA content from HF patients and healthy subjects was measured by direct infusion electrospray ionization mass spectrometry (ESI-MS). Results pointed out a significant increase of GA in HF patients with respect to the control group (p < 0.05). Additionally, after stimulation with GA, proteomic analysis of HL-1 secreted proteins showed the modulation of several proteins involved, among other processes, in the response to stress. Further, stimulated cells showed a rapid increase in ROS generation, higher mRNA levels of the inflammatory cytokine interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α), and higher levels of the oxidative 4-HNE-protein adducts and carbonylated proteins. Our findings show that plasma GA is increased in HF patients. Further, GA exerts pro-inflammatory and pro-oxidant effects on cardiomyocytes, which suggest a causal role in the etiopathogenesis of HF.

Cell-specific expression of insulin/insulin-like growth factor-I receptor hybrids in the mouse brain

Insulin (IR) and insulin-like growth factor I (IGF-IR) receptors share structural homology and can form hybrid heterodimers. While different observations suggest that hybrid receptors are important in physiology and pathology, little is known about their function in the brain. To gain further insight into the role of IR/IGF-IR hybrids in this organ, we analyzed their cellular distribution in the mouse brain. We combined proximity ligation assays (PLA) for IR and IGF-IR, a technique that detects close protein-protein interactions, with immunocytochemistry for brain cell markers to identify IR/IGF-IR hybrids in the major types of brain cells. Intriguingly, while all the types of brain cells analyzed co-express both receptors, only neurons, astroglia, and microglia show readily detectable IR/IGF-IR hybrids. Hybrid PLA signal was negligible in brain endothelial cells and was absent in oligodendrocytes. Hybrids were comparatively more abundant in neurons and peaked after brain development was completed. Cell-specific expression and greater abundance in the adult brain suggests specialized actions of IR/IGF-IR hybrids in this organ, particularly in neurons.

Natural organic matter contained in clay rock pore water: Direct quantification at the molecular level using electrospray ionization mass spectrometry

RATIONALE

Natural organic matter (NOM) is present in the environment and could influence the migration of heavy metals/radionuclides. The dissolved fraction of NOM (DOM) is usually quantified using total organic carbon analysis or UV-visible spectrometry. Nonetheless, analysis using pattern recognition cannot provide the full spectrum of organic molecules contained in waters, especially low-molecular-weight compounds. In the context of nuclear performance assessment studies, ground waters may contain DOM and a key aspect is to quantify different categories of NOM types in order to further evaluate the transport and fate of radionuclides in the environment.

METHODS

Thus, a method for the quantification of DOM at the molecular level was developed, based on electrospray ionization mass spectrometry (ESI-MS). This method simultaneously gives structural information on DOM and the individual concentrations of these low-molecular-weight compounds without pretreatment and/or preconcentration of the samples.

RESULTS

Several methods of quantification (internal calibration, calibrated addition of external standard, sequential tandem mass spectrometry) have been optimized and successfully applied to real natural samples. They are discussed in this paper with a focus on acidic compounds, which are the compounds that most probably could influence the migration of heavy metals and radionuclides in the clay rock pore water from the French Callovo-Oxfordian (COx) nuclear repository site.

CONCLUSIONS

Quantification of in situ dissolved NOM from the COx has been performed using ESI-MS. For the first time to our knowledge, it was possible to give a quite exhaustive and quantitative inventory of the small organic compounds present without proceeding to any chemical treatment or sample crushing and for naturally occurring concentrations.

Reprint of: Proteomics in cardiovascular diseases: Unveiling sex and gender differences in the era of precision medicine

Cardiovascular diseases (CVDs) represent the most important cause of mortality in women and in men. Contrary to the long-standing notion that the effects of the major risk factors on CVD outcomes are the same in both sexes, recent evidence recognizes new, potentially independent, sex/gender-related risk factors for CVDs, and sex/gender-differences in the clinical presentation of CVDs have been demonstrated. Furthermore, some therapeutic options may not be equally effective and safe in men and women. In this context, proteomics offers an extremely useful and versatile analytical platform for biomedical researches that expand from the screening of early diagnostic and prognostic biomarkers to the investigation of the molecular mechanisms underlying CDVs. In this review, we summarized the current applications of proteomics in the cardiovascular field, with emphasis on sex and gender-related differences in CVDs.

SIGNIFICANCE

Increasing evidence supports the profound effect of sex and gender on cardiovascular physio-pathology and the response to drugs. A clear understanding of the mechanisms underlying sexual dimorphisms in CVDs would not only improve our knowledge of the etiology of these diseases, but could also inform health policy makers and guideline committees in tailoring specific interventions for the prevention, treatment and management of CVDs in both men and women.

Proteomics in cardiovascular diseases: Unveiling sex and gender differences in the era of precision medicine

Cardiovascular diseases (CVDs) represent the most important cause of mortality in women and in men. Contrary to the long-standing notion that the effects of the major risk factors on CVD outcomes are the same in both sexes, recent evidence recognizes new, potentially independent, sex/gender-related risk factors for CVDs, and sex/gender-differences in the clinical presentation of CVDs have been demonstrated. Furthermore, some therapeutic options may not be equally effective and safe in men and women. In this context, proteomics offers an extremely useful and versatile analytical platform for biomedical researches that expand from the screening of early diagnostic and prognostic biomarkers to the investigation of the molecular mechanisms underlying CDVs. In this review, we summarized the current applications of proteomics in the cardiovascular field, with emphasis on sex and gender-related differences in CVDs.

SIGNIFICANCE

Increasing evidence supports the profound effect of sex and gender on cardiovascular physio-pathology and the response to drugs. A clear understanding of the mechanisms underlying sexual dimorphisms in CVDs would not only improve our knowledge of the etiology of these diseases, but could also inform health policy makers and guideline committees in tailoring specific interventions for the prevention, treatment and management of CVDs in both men and women.

Exploring the biochemistry of the prenylome and its role in disease through proteomics: progress and potential

INTRODUCTION

Protein prenylation is a ubiquitous covalent post-translational modification characterized by the addition of farnesyl or geranylgeranyl isoprenoid groups to a cysteine residue located near the carboxyl terminal of a protein. It is essential for the proper localization and cellular activity of numerous proteins, including Ras family GTPases and G-proteins. In addition to its roles in cellular physiology, the prenylation process has important implications in human diseases and in the recent years, it has become attractive target of inhibitors with therapeutic potential. Areas covered: This review attempts to summarize the basic aspects of prenylation integrating them with biological functions in diseases and giving an account of the current status of prenylation inhibitors as potential therapeutics. We also summarize the methodologies for the characterization of this modification. Expert commentary: The growing body of evidence suggesting an important role of prenylation in diseases and the subsequent development of inhibitors of the enzymes responsible for this modification lead to the urgent need to identify the full spectrum of prenylated proteins that are altered in the disease or affected by drugs. Proteomic tools to analyze prenylated proteins are recently emerging, thanks to the advancement in the field of mass spectrometry coupled to enrichment strategies.

A role for astrocytes in cerebellar deficits in frataxin deficiency: Protection by insulin-like growth factor I

Inherited neurodegenerative diseases such as Friedreich's ataxia (FRDA), produced by deficiency of the mitochondrial chaperone frataxin (Fxn), shows specific neurological deficits involving different subset of neurons even though deficiency of Fxn is ubiquitous. Because astrocytes are involved in neurodegeneration, we analyzed whether they are also affected by frataxin deficiency and contribute to the disease. We also tested whether insulin-like growth factor I (IGF-I), that has proven effective in increasing frataxin levels both in neurons and in astrocytes, also exerts in vivo protective actions. Using the GFAP promoter expressed by multipotential stem cells during development and mostly by astrocytes in the adult, we ablated Fxn in a time-dependent manner in mice (FGKO mice) and found severe ataxia and early death when Fxn was eliminated during development, but not when deleted in the adult. Analysis of underlying mechanisms revealed that Fxn deficiency elicited growth and survival impairments in developing cerebellar astrocytes, whereas forebrain astrocytes grew normally. A similar time-dependent effect of frataxin deficiency in astrocytes was observed in a fly model. In addition, treatment of FGKO mice with IGF-I improved their motor performance, reduced cerebellar atrophy, and increased survival. These observations indicate that a greater vulnerability of developing cerebellar astrocytes to Fxn deficiency may contribute to cerebellar deficits in this inherited disease. Our data also confirm a therapeutic benefit of IGF-I in early FRDA deficiency.

Circulating Insulin-Like Growth Factor I Regulates Its Receptor in the Brain of Male Mice

The role of IGF-1 and its receptor (IGF-1R) in brain pathology is still unclear. Thus, either reduction of IGF-IR or treatment with IGF-1, two apparently opposite actions, has proven beneficial in brain diseases such as Alzheimer's dementia. A possible explanation of this discrepancy is that IGF-1 down-regulates brain IGF-1R levels, as previously seen in a mouse Alzheimer's dementia model. We now explored whether under normal conditions IGF-1 modulates its receptor. We first observed that in vitro, IGF-1 reduced IGF-1R mRNA levels in all types of brain cells including neurons, astrocytes, microglia, endothelial cells, and oligodendrocytes. IGF-1 also inhibited its own expression in neurons and brain endothelium. Next, we analyzed the in vivo actions of IGF-1. Because serum IGF-1 can enter the brain, we injected mice with IGF-1 ip. As soon as 1 hour after the injection, decreased hippocampal IGF-1 levels were observed, followed by increased IGF-1 and IGF-1R mRNAs 6 hours later. Because environmental enrichment (EE) stimulates the entrance of serum IGF-1 into the brain, we analyzed whether a physiological entrance of IGF-1 also produced changes in brain IGF-1R. Stimulation of IGF-1R by EE triggered a gradual decrease in hippocampal IGF-1 levels. After 6 hours of EE exposure, IGF-1 levels reached a significant decrease in parallel with increased IGF-1R expression. After longer times, IGF-1R mRNA levels returned to baseline. Thus, under nonpathological conditions, IGF-1 regulates brain IGF-1R. Because baseline IGF-1R levels are rapidly restored, a tight control of brain IGF-1R expression seems to operate under physiological conditions.

Loss of serum IGF-I input to the brain as an early biomarker of disease onset in Alzheimer mice

Circulating insulin-like growth factor I (IGF-I) enters the brain and promotes clearance of amyloid peptides known to accumulate in Alzheimer's disease (AD) brains. Both patients and mouse models of AD show decreased level of circulating IGF-I enter the brain as evidenced by a lower ratio of cerebrospinal fluid/plasma IGF-I. Importantly, in presymptomatic AD mice this reduction is already manifested as a decreased brain input of serum IGF-I in response to environmental enrichment. To explore a potential diagnostic use of this early loss of IGF-I input, we monitored electrocorticogram (ECG) responses to systemic IGF-I in mice. Whereas control mice showed enhanced ECG activity after IGF-I, presymptomatic AD mice showed blunted ECG responses. Because nonhuman primates showed identically enhanced electroencephalogram (EEG) activity in response to systemic IGF-I, loss of the EEG signature of serum IGF-I may be exploited as a disease biomarker in AD patients.

Regulation of the phosphatase calcineurin by insulin-like growth factor I unveils a key role of astrocytes in Alzheimer's pathology

Whether insulin-like growth factor I (IGF-I) signaling in Alzheimer's disease (AD) is beneficial or detrimental remains controversial. We now show that a competitive regulation by IGF-I of the phosphatase calcineurin in reactive, but not in quiescent astrocytes drives Alzheimer's pathology. Calcineurin de-phosphorylates the transcription factor Foxo3 in response to tumor necrosis factor-α (TNFα), an inflammatory cytokine increased in AD, activating nuclear factor-κB (NFκB) inflammatory signaling in astrocytes. In turn, IGF-I inactivates and displaces Foxo3 from calcineurin in TNFα-stimulated astrocytes by recruiting the transcription factor peroxisome proliferator-activated receptor-γ, and NFκB signaling is inhibited. This antagonistic mechanism reversibly drives the course of the disease in AD mice, even at advanced stages. As hallmarks of this calcineurin/Foxo3/NFκB pathway are present in human AD brains, treatment with IGF-I may be beneficial by antagonizing it.

Early brain amyloidosis in APP/PS1 mice with serum insulin-like growth factor-I deficiency

The influence of insulin-like growth factor I (IGF-I) on the progression of Alzheimer's disease (AD) is discussed controversially. To help clarify the role of this circulating neurotrophic factor in brain amyloidosis, the major pathological trait in AD, we analyzed plaque formation in a mouse model of AD transgenic for human APP and PS1 mutations with reduced serum IGF-I levels (LIDAD mice). We found that brain amyloidosis in LIDAD mice appeared earlier than in AD mice, at 2 months of age, while attained comparable levels at 6 months. In parallel, early microgliosis was observed in LIDAD mice also at 2 months and remained exacerbated at 6 months. Collectively, these observations suggest a role of serum IGF-I in delaying early brain amyloidosis.

Central actions of liver-derived insulin-like growth factor I underlying its pro-cognitive effects

Increasing evidence indicates that circulating insulin-like growth factor I (IGF-I) acts as a peripheral neuroactive signal participating not only in protection against injury but also in normal brain function. Epidemiological studies in humans as well as recent evidence in experimental animals suggest that blood-borne IGF-I may be involved in cognitive performance. In agreement with observations in humans, we found that mice with low-serum IGF-I levels due to liver-specific targeted disruption of the IGF-I gene presented cognitive deficits, as evidenced by impaired performance in a hippocampal-dependent spatial-recognition task. Mice with serum IGF-I deficiency also have disrupted long-term potentiation (LTP) in the hippocampus, but not in cortex. Impaired hippocampal LTP was associated with a reduction in the density of glutamatergic boutons that led to an imbalance in the glutamatergic/GABAergic synapse ratio in this brain area. Behavioral and synaptic deficits were ameliorated in serum IGF-I-deficient mice by prolonged systemic administration of IGF-I that normalized the density of glutamatergic boutons in the hippocampus. Altogether these results indicate that liver-derived circulating IGF-I affects crucial aspects of mature brain function; that is, learning and synaptic plasticity, through its trophic effects on central glutamatergic synapses. Declining levels of serum IGF-I during aging may therefore contribute to age-associated cognitive loss.

Gastrointestinal complications in renal transplant recipients: MITOS study

INTRODUCTION AND METHODS

An epidemiologic multicenter study was performed to evaluate the prevalence and management of gastrointestinal (GI) complications in solid organ transplant patients. A total of 1788 recipients were included, 1132 of which corresponded to renal transplanted patients.

RESULTS

The mean age for the renal transplanted patients was 52 +/- 13.2 years. The mean time from the transplantation was 5.4 +/- 5.4 years. 17.7% showed some pretransplant GI disease, while 53% presented this type of complication in the posttransplant period. Diarrhea was the most prevalent GI complication (51.5%) and digestive perforation was the GI disorder that affected the patients daily living the most. From the patients with GI complications, 71% received pharmacological treatment, using gastric protectors in 91.3% of the cases. Regarding immunosuppressive drugs, in 30.9% of the cases the dose of the drug was reduced, in 9.3% discontinued temporarily and in 7.5% discontinued permanently. These changes mainly affected the MMF (89%, 83% and 74% for dose change, temporary and permanent discontinuation, respectively).

CONCLUSIONS

The prevalence of GI complications in renal transplant exceeded 50%, and affected patients' daily living. The management of these complications was based on treatment with gastric protectors, dose reduction and/or partial or definitive MMF discontinuation.

Emerging roles of insulin-like growth factor-I in the adult brain

All tissues in the body are under the influence of insulin-like growth factor-I (IGF-I). Together with insulin, IGF-I is a key regulator of cell metabolism and growth. IGF-I also acts in the central nervous system, where it affects many different cell populations. In this brief review, we discuss the many roles of IGF-I in the adult brain, and present the idea that diseases affecting the brain will perturb IGF-I activity, although more refined studies at the molecular and cellular level are needed before we can firmly established this possibility. We also suggest that under normal physiological conditions IGF-I may play a significant role in higher brain functions underlying cognition, and may serve a homeostatic role during brain aging. Among newly emerging issues, the effects of IGF-I on non-neuronal cells within the nervous system and their impact in brain physiology and pathology are becoming very important in understanding the biology of this peptide in the brain.

Insulin-like growth factor I treatment for cerebellar ataxia: Addressing a common pathway in the pathological cascade?

In the present work we review evidence supporting the use of insulin-like growth factor I (IGF-I) for treatment of cerebellar ataxia, a heterogeneous group of neurodegenerative diseases of low incidence but high societal impact. Most types of ataxia display not only motor discoordination, but also additional neurological problems including peripheral nerve dysfunctions. Therefore, a feasible therapy should combine different strategies aimed to correct the various disturbances specific for each type of ataxia. For cerebellar deficits, and most probably also for other types of brain deficits, the use of a wide-spectrum neuroprotective factor such as IGF-I may prove beneficial. Intriguingly, both ataxic animals as well as human patients show altered serum IGF-I levels. While the pathogenic significance of IGF-I, if any, in this varied group of diseases is difficult to envisage, disrupted IGF-I neuroprotective signaling may constitute a common stage in the pathological cascade associated to neuronal death. Indeed, treatment with IGF-I has proven effective in animal models of ataxia. Based on this pre-clinical evidence we propose that IGF-I should be tested in clinical trials of cerebellar ataxia in those cases where either serum IGF-I deficiency (as in primary cerebellar atrophy) or loss of sensitivity to IGF-I (as in ataxia telangiectasia) has been reported. Taking advantage of the widely protective and anabolic actions of IGF-I on peripheral tissues, this neurotrophic factor may provide additional therapeutic advantages for many of the disturbances commonly associated to ataxia such as cardiopathy, muscle wasting, or immune dysfunction.

N-Succinyl-(beta-alanyl-L-leucyl-L-alanyl-L-leucyl)doxorubicin: an extracellularly tumor-activated prodrug devoid of intravenous acute toxicity

Intravenous administration of N-(beta-alanyl-L-leucyl-L-alanyl-L-leucyl)doxorubicin (4) induces an acute toxic reaction, killing animals in a few minutes. This results from its positive charge at physiological pH combined with its propensity to form large aggregates in aqueous solutions. Negatively charged N-capped versions of 4 such as the succinyl derivative 5 can be administered by the iv route at more than 10 times the LD(50) of doxorubicin without inducing the acute toxic reaction, and they are active in vivo.

Treatment of early seropositive rheumatoid arthritis: a two-year, double-blind comparison of minocycline and hydroxychloroquine

OBJECTIVE

To compare the efficacy of minocycline with that of a conventional disease-modifying antirheumatic drug (DMARD), hydroxychloroquine, in patients with early seropositive rheumatoid arthritis (RA).

METHODS

Sixty patients with seropositive RA of <1 year's duration who had not been previously treated with DMARDs were randomized to receive minocycline, 100 mg twice per day, or hydroxychloroquine, 200 mg twice per day, in a 2-year, double-blind protocol. All patients also received low-dose prednisone. The primary end points of the study were 1) the percentage of patients with an American College of Rheumatology (ACR) 50% improvement (ACR50) response at 2 years, and 2) the dosage of prednisone at 2 years.

RESULTS

Minocycline-treated patients were more likely to achieve an ACR50 response at 2 years compared with hydroxychloroquine-treated patients (60% compared with 33%, respectively; P = 0.04). Minocycline-treated patients were also receiving less prednisone at 2 years compared with the hydroxychloroquine group (mean 0.81 mg/day compared with 3.21 mg/day, respectively; P < 0.01). In addition, patients treated with minocycline were more likely to have been completely tapered off prednisone (P = 0.03). Trends favoring the minocycline treatment group were seen when outcomes were assessed according to components of the ACR core criteria set, with the differences reaching statistical significance for patient's global assessment of disease activity (P = 0.004).

CONCLUSION

Minocycline is an effective DMARD in patients with early seropositive RA. Patients treated with minocycline were more likely to achieve an ACR50 response and did so while receiving less prednisone. In addition, minocycline-treated patients were more likely to have discontinued treatment with prednisone at 2 years.

Insulin-like growth factor 1 (IGF-1)-induced twist expression is involved in the anti-apoptotic effects of the IGF-1 receptor

In this study we investigated the molecular mechanisms whereby insulin-like growth factor 1 (IGF-1) induced Twist gene expression and the role of Twist in the anti-apoptotic actions of the IGF-1 receptor. In NIH-3T3 fibroblasts overexpressing the human IGF-1 receptor (NWTb3), treatment with IGF-1 (10(-8) m) for 1 and 4 h increased the level of Twist mRNA as well as protein by 3-fold. In contrast, insulin at physiological concentrations did not stimulate Twist expression in NIH-3T3 fibroblasts overexpressing the human insulin receptor. The IGF-1 effect was specific for the IGF-1 receptor since, in cells overexpressing a dominant negative IGF-1 receptor, IGF-1 failed to increase Twist expression. Pre-incubation with the ERK1/2 inhibitor U0126 or expression of a dominant negative MEK-1 abolished the effect of IGF-1 on Twist mRNA expression in NWTb3 cells, suggesting that Twist induction by IGF-1 occurs via the mitogen-activated protein kinase signaling pathway. In vivo, IGF-1 injection increased the mRNA level of Twist in mouse skeletal muscle, the major site of Twist expression. Finally, using an antisense strategy, we demonstrated that a reduction of 40% in Twist expression decreased significantly the ability of IGF-1 to rescue NWTb3 cells from etoposide-induced apoptosis. Taken together, these results define Twist as an important factor involved in the anti-apoptotic actions of the IGF-1 receptor.

Liver-specific igf-1 gene deletion leads to muscle insulin insensitivity

Insulin and insulin-like growth factors (IGFs) mediate a variety of signals involved in mammalian development and metabolism. To study the metabolic consequences of IGF-I deficiency, we used the liver IGF-I-deficient (LID) mouse model. The LID mice show a marked reduction (approximately 75%) in circulating IGF-I and elevated growth hormone (GH) levels. Interestingly, LID mice show a fourfold increase in serum insulin levels (2.2 vs. 0.6 ng/ml in control mice) and abnormal glucose clearance after insulin injection. Fasting blood glucose levels and those after a glucose tolerance test were similar between the LID mice and their control littermates. Thus, the high levels of circulating insulin enable the LID mice to maintain normoglycemia in the presence of apparent insulin insensitivity. Insulin-induced autophosphorylation of the insulin receptor and tyrosine phosphorylation of insulin receptor substrate (IRS)-1 were absent in muscle, but were normal in liver and white adipose tissue of the LID mice. In contrast, IGF-I-induced autophosphorylation of its cognate receptor and phosphorylation of IRS-1 were normal in muscle of LID mice. Thus, the insulin insensitivity seen in the LID mice is muscle specific. Recombinant human IGF-I treatment of the LID mice caused a reduction in insulin levels and an increase in insulin sensitivity. Treatment of the LID mice with GH-releasing hormone antagonist, which reduces GH levels, also increased insulin sensitivity. These data provide evidence of the role of circulating IGF-I as an important component of overall insulin action in peripheral tissues.

Extracellularly tumor-activated prodrugs for the selective chemotherapy of cancer: application to doxorubicin and preliminary in vitro and in vivo studies

Oligopeptidic derivatives of anthracyclines unable to penetrate cells were prepared and screened for their stability in human blood and their reactivation by peptidases secreted by cancer cells. N-beta-alanyl-L-leucyl-L-alanyl-L-leucyl-doxorubicin was selected as a new candidate prodrug. The NH2-terminal beta-alanine allows a very good blood stability. A two-step activation by peptidases found in conditioned media of cancer cells ultimately yields N-L-leucyl-doxorubicin. In vitro, when MCF-7/6 cancer cells are exposed to the prodrug, they accumulate about 14 times more doxorubicin than MRC-5 normal fibroblasts, whereas when exposed to doxorubicin the uptake is slightly higher in fibroblasts than in MCF-7/6 cells. This increased specificity of the prodrug over doxorubicin was confirmed in cytotoxicity assays using the same cell types. In vivo, the prodrug proved about nine times less toxic than doxorubicin in the normal mouse and also much more efficient in two different experimental chemotherapy models of human breast tumors.

Mice transgenically overexpressing sulfonylurea receptor 1 in forebrain resist seizure induction and excitotoxic neuron death

The ability of the sulfonylurea receptor (SUR) 1 to suppress seizures and excitotoxic neuron damage was assessed in mice transgenically overexpressing this receptor. Fertilized eggs from FVB mice were injected with a construct containing SUR cDNA and a calcium-calmodulin kinase IIalpha promoter. The resulting mice showed normal gross anatomy, brain morphology and histology, and locomotor and cognitive behavior. However, they overexpressed the SUR1 transgene, yielding a 9- to 12-fold increase in the density of [(3)H]glibenclamide binding to the cortex, hippocampus, and striatum. These mice resisted kainic acid-induced seizures, showing a 36% decrease in average maximum seizure intensity and a 75% survival rate at a dose that killed 53% of the wild-type mice. Kainic acid-treated transgenic mice showed no significant loss of hippocampal pyramidal neurons or expression of heat shock protein 70, whereas wild-type mice lost 68-79% of pyramidal neurons in the CA1-3 subfields and expressed high levels of heat shock protein 70 after kainate administration. These results indicate that the transgenic overexpression of SUR1 alone in forebrain structures significantly protects mice from seizures and neuronal damage without interfering with locomotor or cognitive function.

Modeling, mutagenesis, and structural studies on the fully conserved phosphate-binding loop (loop 8) of triosephosphate isomerase: toward a new substrate specificity

Loop 8 (residues 232-242) in triosephosphate isomerase (TIM) is a highly conserved loop that forms a tight binding pocket for the phosphate moiety of the substrate. Its sequence includes the fully conserved, solvent-exposed Leu238. The tight phosphate-binding pocket explains the high substrate specificity of TIM being limited to the in vivo substrates dihydroxyacetone-phosphate and D-glyceraldehyde-3-phosphate. Here we use the monomeric variant of trypanosomal TIM for exploring the structural consequences of shortening this loop. The mutagenesis, guided by extensive modeling calculations and followed up by crystallographic characterization, is aimed at widening the phosphate-binding pocket and, consequently, changing the substrate specificity. Two new variants were characterized. The crystal structures of these variants indicate that in monomeric forms of TIM, the Leu238 side-chain is nicely buried in a hydrophobic cluster. Monomeric forms of wild-type dimeric TIM are known to exist transiently as folding intermediates; our structural analysis suggests that in this monomeric form, Leu238 of loop 8 also adopts this completely buried conformation, which explains its full conservation across the evolution. The much wider phosphate-binding pocket of the new variant allows for the development of a new TIM variant with a different substrate specificity.

Neurodegeneration is associated to changes in serum insulin-like growth factors

Serum levels of insulin and insulin-like growth factors and their binding proteins (IGFs and IGFBPs, respectively) are changed in human neurodegenerative diseases of very different etiology, such as Alzheimer's disease, amyotrophic lateral sclerosis, or cerebellar ataxia. However, the significance of these endocrine disturbances is not clear. We now report that in two very different inherited neurodegenerative conditions, ataxia-telangiectasia (AT) and Charcot-Marie-Tooth 1A (CMT-1A) disease, serum levels of IGFs are also altered. Both types of patients have increased serum IGF-I and IGFBP-2 levels, and decreased serum IGFBP-1 levels, while only AT patients have high serum insulin levels. Furthermore, serum IGFs are also changed in three different animal models of neurodegeneration: neurotoxin-induced motor discoordination, diabetic neuropathy, and hereditary cerebellar ataxia. In these three models, serum insulin levels are significantly decreased, serum IGF-I and IGFBP-1, -2, and -3 are decreased in diabetic and neurotoxin-injected rats, while serum IGFBP-1 is increased in hereditary ataxic rats. Altogether, these observations indicate that a great variety of neurodegenerative diseases show endocrine perturbations, resulting in changes in serum IGFs levels. These perturbations are disease-specific and are probably due to metabolic and endocrine derangements, nerve cell death, and sickness-related disturbances associated to the neurodegenerative process. Our observations strongly support the need to evaluate serum IGFs in other neurodegenerative conditions.

Antenatal use of ambroxol for the prevention of infant respiratory distress syndrome

OBJECTIVE

Our purpose was to evaluate the efficacy and safety of ambroxol for the prenatal prophylaxis of infant respiratory distress syndrome (IRDS).

STUDY DESIGN

This was a prospective study with 2 groups of pregnant patients with premature labor or with premature rupture of membranes at an estimated gestation between 27 to 34 completed weeks. Ambroxol treatment group consisted of 39 subjects in whom 1,000 mg of ambroxol diluted in 500 ml of 5% glucose solution was given intravenously for 4 hours once a day for 3 days, while the control group consisted of 41 subjects in whom ambroxol was not administered. Main measures included Apgar scores, clinical signs of one or more of the following: respiratory rate of > 60/min, intercostal retraction, alar flaring, expiratory grunting, cyanosis on room air and radiological evidence of IRDS. Chi-square test was used to determine the statistical significance of the results.

RESULTS

Tolerable maternal side effects were noted. Profile of newborns delivered were similar in both groups. Incidence of IRDS was significantly less in the treatment group (p < 0.01).

CONCLUSIONS

Antenatal administration of ambroxol resulted in a significant decrease in the incidence of IRDS as well as perinatal morbidity and mortality. Due to the efficacy and safety of this drug, it might be useful for the prevention of IRDS.

Estrogen receptors and insulin-like growth factor-I receptors mediate estrogen-dependent synaptic plasticity

Previous studies have shown that estradiol induces a transient disconnection of axo-somatic inhibitory synapses in the hypothalamic arcuate nucleus of adult ovariectomized rats. The synaptic disconnection is accompanied by an increase in the levels of insulin-like growth factor-I (IGF-I) in the arcuate nucleus, suggesting that IGF-I signaling may be involved in the estrogen-induced synaptic plasticity. The role of estrogen receptors and IGF-I receptors in the synaptic changes has been studied by assessing the number of axo-somatic synapses in ovariectomized rats treated with intracerebroventricular administration of the estrogen receptor antagonist ICI 182,780 and the IGF-I receptor antagonist JBI to ovariectomized rats. Estradiol administration resulted in a significant decrease in the number of axo-somatic synapses on arcuate neurons in control ovariectomized rats. Both the estrogen receptor antagonist and the IGF-I receptor antagonist blocked the estrogen-induced synaptic decrease. This finding suggest that estrogen-induced synaptic plasticity in the arcuate nucleus is dependent on the activation of both estrogen receptors and IGF-I receptors.

Neuroprotective actions of peripherally administered insulin-like growth factor I in the injured olivo-cerebellar pathway

Exogenous administration of insulin-like growth factor I (IGF-I) restores motor function in rats with neurotoxin-induced cerebellar deafferentation. We first determined that endogenous IGFs are directly involved in the recovery process because infusion of an IGF-I receptor antagonist into the lateral ventricle blocks gradual recovery of limb coordination that spontaneously occurs after partial deafferentation of the olivo-cerebellar circuitry. We then analysed mechanisms whereby exogenous IGF-I restores motor function in rats with complete damage of the olivo-cerebellar pathway. Treatment with IGF-I normalized several markers of cell function in the cerebellum, including calbindin, glutamate receptor 1 (GluR1), gamma-aminobutyric acid (GABA) and glutamate, which are all depressed after 3-acetylpyridine (3AP)-induced deafferentation. IGF-I also promoted functional reinnervation of the cerebellar cortex by inferior olive (IO) axons. In the IO, increased expression of bax in neurons and bcl-X in astrocytes after 3AP was significantly reduced by IGF-I treatment. On the contrary, IGF-I prevented the decrease in poly-sialic-acid neural cell adhesion molecule (PSA-NCAM) and GAP-43 expression induced by 3AP in IO cells. IGF-I also significantly increased the number of neurons expressing bcl-2 in brainstem areas surrounding the IO. Altogether, these results indicate that subcutaneous IGF-I therapy promotes functional recovery of the olivo-cerebellar pathway by acting at two sites within this circuitry: (i) by modulating death- and plasticity-related proteins in IO neurons; and (ii) by impinging on homeostatic mechanisms leading to normalization of cell function in the cerebellum. These results provide insight into the neuroprotective actions of IGF-I and may be of practical consequence in the design of new therapeutic approaches for neurodegenerative diseases.

Phospholipid interactions of a peptide from the fusion-related domain of the glycoprotein of VHSV, a fish rhabdovirus

Previous studies mapped a p2 domain (aa 82-109) which binds phosphatidylserine (PS) (Estepa and Coll, 1996a) and contains three contiguous hydrophobic amino acid heptad repeats followed by a positively charged stretch (Coll, 1995b) in the glycoprotein G of the viral hemorrhagic septicemia virus (VHSV), a fish rhabdovirus. Anti-p2 antibodies inhibited low-pH VHSV-induced fusion (Estepa and Coll, 1997) and low-pH PS binding to VHSV (Estepa and Coll, 1996a). We report here further studies on the interaction of the synthetic peptide p2 with phospholipid vesicles. The synthetic p2 peptide was able to mediate aggregation, lipid mixing, and leakage of contents only with negatively charged phospholipid vesicles and in a concentration-dependent manner. As shown by its effect on lipid phase transitions deduced from data with fluorescence polarization and differential scanning calorimetry, the p2 peptide becomes inserted into the hydrophobic negatively charged phospholipid vesicle bilayers. In addition, data based on circular dichroism showed that the p2 peptide folds as a structure with a high content of beta-sheets stabilized by interaction with anionic phospholipids. These studies are potentially relevant to viral fusion in VHSV.

Insulin-like growth factor I restores motor coordination in a rat model of cerebellar ataxia

We tested the potential of insulin-like growth factor I (IGF-I) to induce functional recovery in an animal model of cerebellar ataxia because this motor impairment is accompanied in humans and rodents by distinct changes in several components of the IGF-I trophic system. Rats rendered ataxic by deafferentation of the cerebellar cortex with 3-acetylpyridine recovered motor function after IGF-I was administered, as determined by behavioral and electrophysiological tests. When treated with IGF-I, inferior olive neurons, the targets of the neurotoxin, were rescued to various degrees (from 92 to 27% of surviving neurons), depending on the time that treatment with IGF-I was initiated. Furthermore, full recovery was obtained regardless of the route by which the trophic factor was administered (intraventricular or subcutaneous) even in rats with severe neuronal loss. These results suggest that human ataxia could be treated with IGF-I by a simple procedure.

Technology assessment in healthcare: a review and description of a "best practice" technology assessment process

BACKGROUND

Technology assessment has become a rapidly growing component of the healthcare system. It has assumed a functional role in operational settings and is rapidly impacting decisions involving purchasing, coverage, and reimbursement. This review is intended to assist the healthcare decision maker in considering the application of technology assessment in healthcare, so as to maximize the efficiency of future purchasing decisions.

METHODS

This "best practice" was synthesized after identifying key institutions performing technology assessment in healthcare and analyzing their working processes, including literature review, consensus panel discussions, and expert opinion.

RESULTS

We describe this best practice on a reiterative loop that consists of five processes: awareness, strategic appropriateness, analysis versus need, acquisition and implementation, and reassessment. Typical barriers to adoption of technology assessment are also identified and discussed.

CONCLUSIONS

This review suggests a common terminology for the core processes involved in technology assessment, thereby facilitating a more uniform understanding among the different components of the healthcare system (i.e., payer, provider, and society) while recognizing their different perspectives.

Insulin-like growth factor I modulates c-Fos induction and astrocytosis in response to neurotoxic insult

Insulin-like growth factor I participates in the cellular response to brain insult by increasing its messenger RNA expression and/or protein levels in the affected area. Although it has been suggested that insulin-like growth factor I is involved in a variety of cellular responses leading to homeostasis, mechanisms involved in its possible trophic effects are largely unknown. Since activation of c-Fos in postmitotic neurons takes place both in response to insulin-like growth factor I and after brain injury, we have investigated whether this early response gene may be involved in the actions of insulin-like growth factor I after brain insult. Partial deafferentation of the cerebellar cortex by 3-acetylpyridine injection elicited c-Fos protein expression on both Purkinje and granule cells of the cerebellar cortex. This neurotoxic insult also triggered gliosis, as determined by an increased number of glial fibrillary acidic protein-positive cells (reactive astrocytes) in the cerebellar cortex. When 3-acetylpyridine-injected animals received a continuous intracerebellar infusion of either a peptidic insulin-like growth factor I receptor antagonist or an insulin-like growth factor I antisense oligonucleotide for two weeks through an osmotic minipump, c-Fos expression was obliterated while reactive gliosis was greatly increased. On the contrary, continuous infusion of insulin-like growth factor I significantly decreased reactive gliosis without affecting the increase in c-Fos expression. These results indicate that insulin-like growth factor I is involved in both the neuronal (c-Fos) and the astrocytic (glial fibrillary acidic protein) activation in response to injury.

Synthesis of a photoaffinity labeling analogue of the inactivating peptide of the Shaker B potassium channel

A photoactivatable derivative of the inactivating peptide of the Shaker B potassium channel (ShB peptide) has been synthesized from ShB peptide containing an added cysteine residue at the peptide carboxy-terminus and 1-(p-azidosalicylamido)-4-(iodoacetamido)butane. The peptide derivative restores rapid inactivation in the deletion mutant Shaker Bdelta6-46 potassium channel in a manner indistinguishable from that of the wild-type ShB peptide. Also, both peptides display similar conformational behavior when challenged in vitro by an artificial model target that partly imitates the properties of the putative receptor site for the inactivating peptide in the Shaker B potassium channel. Therefore, we conclude that both functionally and conformationally the photoreactive peptide derivative is an adequate analogue of the wild-type ShB peptide, suitable for photoaffinity labeling of its binding site in the Shaker B potassium channel. Moreover, because the ShB peptide also serves as an efficient inactivating peptide for a large variety of other potassium channels, it appears that the photoreactive analogue may be useful to explore homologous sites in many different channel proteins.

Interaction between ion channel-inactivating peptides and anionic phospholipid vesicles as model targets

Studies of rapid (N-type) inactivation induced by different synthetic inactivating peptides in several voltage-dependent cation channels have concluded that the channel inactivation "entrance" (or "receptor" site for the inactivating peptide) consists of a hydrophobic vestibule within the internal mouth of the channel, separated from the cytoplasm by a region with a negative surface potential. These protein domains are conformed from alternative sequences in the different channels and thus are relatively unrestricted in terms of primary structure. We are reporting here on the interaction between the inactivating peptide of the Shaker B K+ channel (ShB peptide) or the noninactivating ShB-L7E mutant with anionic phospholipid vesicles, a model target that, as the channel's inactivation "entrance," contains a hydrophobic domain (the vesicle bilayer) separated from the aqueous media by a negatively charged vesicle surface. When challenged by the anionic phospholipid vesicles, the inactivating ShB peptide 1) binds to the vesicle surface with a relatively high affinity, 2) readily adopts a strongly hydrogen-bonded beta-structure, likely an intramolecular beta "hairpin," and 3) becomes inserted into the hydrophobic bilayer by its folded N-terminal portion, leaving its positively charged C-terminal end exposed to the extravesicular aqueous medium. Similar experiments carried out with the noninactivating, L7E-ShB mutant peptide show that this peptide 1) binds also to the anionic vesicles, although with a lower affinity than does the ShB peptide, 2) adopts only occasionally the characteristic beta-structure, and 3) has completely lost the ability to traverse the anionic interphase at the vesicle surface and to insert into the hydrophobic vesicle bilayer. Because the negatively charged surface and the hydrophobic domains in the model target may partly imitate those conformed at the inactivation "entrance" of the channel proteins, we propose that channel inactivation likely includes molecular events similar to those observed in the interaction of the ShB peptide with the phospholipid vesicles, i.e., binding of the peptide to the region of negative surface potential, folding of the bound peptide as a beta-structure, and its insertion into the channel's hydrophobic vestibule. Likewise, we relate the lack of channel inactivation seen with the mutant ShB-L7E peptide to the lack of ability shown by this peptide to cross through the anionic interphase and insert into the hydrophobic domains of the model vesicle target.

Chemical heterogeneity in adult rat cerebellar Purkinje cells as revealed by zebrin I and low-affinity nerve growth factor receptor immunocytochemical expression following injury

Cerebellar Purkinje cells in rat express low-affinity nerve growth factor receptor during development, but rarely in normal adult animals. However, after either mechanical injury or colchicine treatment during adulthood, these cells re-express low-affinity nerve growth factor receptor-immunoreactive protein. Two Purkinje cell subpopulations were defined in normal adult cerebellum by the presence or the absence of zebrin I antigen. Nevertheless, it remains an open question as to whether low-affinity nerve growth factor receptor-immunoreactive protein can be expressed by all damaged Purkinje cells, independent of their location and their staining with antibodies against intrinsic molecular markers that reveal Purkinje cell heterogeneity, such as zebrin I. In this study, a serial-section immunocytochemical mapping of the expression zebrin I and low-affinity nerve growth factor receptor, using specific monoclonal antibodies, we carried out in colchicine-treated rats. After mechanical damage of the cerebellar cortex, co-localization of these antigens at the cellular level was also analysed in thin adjacent sections, and by using a combined immunocytochemical staining method in individual sections. The findings revealed the existence of three sub-sets of Purkinje cells: (1) two complementary groups distinctly immunoreactive to one antibody, but not to the other and (2) a third group that contained double-labelled cells. In contrast, co-expression of both antigens was never observed following mechanical lesions. The seemingly independent response to mechanical injury of Purkinje cells located in different zebrin-defined compartments, indicates that particular subpopulations of Purkinje cells may respond differentially to traumatic injury.

Recurrent leukocytoclastic vasculitis as the initial manifestation of acute myelomonocytic leukemia

The association between cutaneous and systemic leukocytoclastic vasculitis and myeloproliferative and lymphoproliferative malignancies has been reported. We describe a patient who developed recurrent episodes of leukocytoclastic vasculitis 10 months before the diagnosis of acute myelomonocytic leukemia. To our knowledge, this is the first documented case of leukocytoclastic vasculitis presenting as the initial manifestation of acute myelomonocytic leukemia, a subtype of acute myelogenous leukemia.

Posterior interosseous nerve entrapment in rheumatoid arthritis

Posterior interosseous nerve (PIN) entrapment is a rare complication of rheumatoid arthritis (RA) which, together with extensor tendon rupture and metacarpophangeal joint dislocation, should be considered in the differential diagnosis of inability to extend the fingers. The inability to extend the thumb in PIN entrapment is a useful distinguishing clue on physical examination, and nerve conduction studies confirm the diagnosis. Elbow joint swelling and compression of the PIN at the arcade of Frohse are the main reasons for PIN entrapment in RA. Intraarticular steroid injections and surgical intervention resolve symptoms of PIN entrapment in RA. In our case, the addition of methotrexate, which induces a rapid antiinflammatory effect, resulted in resolution of weakness with complete recovery in the extensor muscles of the fingers.

A role for cholesterol as a structural effector of the nicotinic acetylcholine receptor

The effects of cholesterol on the protein structure and on the ionic channel activity of purified acetylcholine receptor (AcChR) reconstituted into lipid vesicles have been studied, respectively, by Fourier-transform infrared spectroscopy and by rapid kinetics of cation influx. Reconstitution of the AcChR in asolectin phospholipid vesicles in the absence of either cholesterol or the nonpolar lipids present in crude asolectin extracts results in a considerable loss of the ability of the AcChR to support cation channel function. This functional loss is accompanied by spectral changes in the conformationally-sensitive amide I band of the protein infrared spectrum which are indicative of alteration in the protein secondary structure. Quantitative estimation of such alteration by band-fitting analysis reveals a marked decrease in ordered protein structures such as the alpha-helix and beta-pleated sheet, concomitant with an increase in less ordered structures appearing at 1644 cm-1 in the infrared spectrum. Furthermore, the addition of increasing amounts of cholesterol to the reconstituted bilayer produces a progressive, complete recovery both in the control of cation channel function and in the infrared spectrum. This restoration of AcChR structure and function by cholesterol, however, does not occur when the AcChR is reconstituted in vesicles made from purified egg phosphatidylcholine, thus suggesting that the presence in the reconstituted bilayer of phospholipids other than phosphatidylcholine may be required for cholesterol to exert its modulatory effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term trends in blood lead levels among children in Chicago: relationship to air lead levels

OBJECTIVES

To evaluate trends in blood lead levels among children in Chicago from 1968 through 1988, and to determine the impact of the changes in the Centers for Disease Control and Prevention (CDC) blood lead level of concern.

METHODS

We reviewed a systematic sample of blood lead screening records of the Chicago Department of Health Laboratory for high-risk children aged 6 months to 5 years. Median blood lead levels for each quarter of the years 1974 through 1988 were determined and regressed against mean air lead levels recorded at air-monitoring stations in Chicago during the same period.

RESULTS

Median blood lead levels declined from 30 micrograms/dL in 1968 to 12 micrograms/dL in 1988, and were strongly associated with declining average air lead levels (r = .8, P < .001) from 1974 through 1988. A regression model using log-transformed data predicted a decline of 0.56 microgram/dL in the median blood lead level with each 0.1 microgram/m3 decline in the mean air lead level when the air lead level was near 1.0 microgram/m3; the predicted slope was steeper at lower air lead levels. Despite the nearly 20-fold reduction in air lead levels, the median blood lead level of 12 micrograms/dL in 1988 indicates substantial continuing lead exposure. The CDC blood lead level of concern was lowered twice from 1968 to 1988, but due to the decline in blood lead levels, fewer than 30% of the children were above the level of concern throughout most of the study.

CONCLUSION

Although substantial lead exposure persists in Chicago, reductions in airborne lead emissions seem to have contributed to a long-term decline in the median blood lead level of high-risk Chicago children.

Labeling of the nicotinic acetylcholine receptor by a photoactivatable steroid probe: effects of cholesterol and cholinergic ligands

A photoactivatable steroid, p-azidophenacyl 3 alpha-hydroxy-5 beta-cholan-24- ate (APL), has been synthesized and used instead of cholesterol to functionally reconstitute purified acetylcholine receptor (AcChR) into vesicles made of asolectin phospholipids. Upon irradiation, the extent of AcChR photolabeling by APL is directly proportional to the amount of APL incorporated into the reconstituted vesicles and the maximum stoichiometry observed corresponds to approx. 50 mol of APL bound per mol of AcChR. Furthermore, all four subunits of the AcChR become labeled by APL and the observed labeling pattern resembles the 2:1:1:1 stoichiometry characteristic of these subunits within the AcChR complex. The presence of either cholesterol or neutral lipids from asolectin in the reconstituted bilayer decreases both, the incorporation of APl into the vesicles and the covalent labeling of the AcChR upon irradiation, without altering the stoichiometry of labeling in AcChR subunits stated above. This suggests that the potential interaction sites for the photoactivatable probe in the reconstituted AcChR are mostly those normally occupied by the natural neutral lipids. Carbamylcholine, a cholinergic agonist, also reduces the extent of APL photolabeling of the AcChR in a dose-dependent manner but, in contrast to the effects of cholesterol, the presence of carbamylcholine alters the stoichiometry of labeling in the AcChR subunits. This, along with the observation that such a decrease in the extent of APL photolabeling caused by carbamylcholine can be blocked by preincubation with alpha-bungarotoxin, suggest that AcChR desensitization induced by prolonged exposure to cholinergic agonists encompasses a rearrangement of transmembrane portions of the AcChR protein, which can be sensed by the photoactivatable probe. Conversely, presence of (+)-tubocurarine, a competitive cholinergic antagonist, has no effects on altering either the extent of APL photolabeling of the AcChR or the distribution of the labeling among AcChR subunits.

Protein structural effects of agonist binding to the nicotinic acetylcholine receptor

The effects on the protein structure produced by binding of cholinergic agonists to purified acetylcholine receptor (AcChR) reconstituted into lipid vesicles, has been studied by Fourier-transform infrared spectroscopy and differential scanning calorimetry. Spectral changes in the conformationally sensitive amide I infrared band indicates that the exposure of the AcChR to the agonist carbamylcholine, under conditions which drive the AcChR into the desensitized state, produces alterations in the protein secondary structure. Quantitative estimation of these agonist-induced alterations by band-fitting analysis of the amide I spectral band reveals no appreciable changes in the percent of alpha-helix, but a decrease in beta-sheet structure, concomitant with an increase in less ordered structures. Additionally, agonist binding results in a concentration-dependent increase in the protein thermal stability, as indicated by the temperature dependence of the protein infrared spectrum and by calorimetric analysis, which further suggest that AcChR desensitization induced by the cholinergic agonist implies significant rearrangements in the protein structure.

Progressive cellular immune impairment leading to development of AIDS: two-year prospective study of HIV infection in drug addicts

We have studied immunological, serological and clinical abnormalities in 264 HIV-positive and HIV-negative drug abusers. Ninety percent of the 264 drug addicts (mean age 26 +/- 0.8 years) were found to have HIV antibodies and there was a significant increase (P less than 0.01) in the frequency of HIV antibody positivity with increasing duration of exposure to parenteral drug abuse. There was a very strong correlation between the progressive decline of the mean T4+ helper/inducer cells and T4+/T8+ ratio, the low response to pokeweed mitogen and the more severe clinical manifestations of HIV infection. Impairment of delayed-type hypersensitivity reaction to recall antigens was only seen in group IV as defined by the Center for Disease Control. Within group IV, anergy was found to be highly associated (83%) in patients with opportunistic infections. All other HIV-positive addicts from groups II and III, as well as HIV-negative addicts had normal in vivo responses to test antigens. We have also analysed in a prospective follow-up lasting 6-24 months, the evolution of HIV infection in a cohort of 50 HIV-antibody-positive drug addicts. Thirty-two percent showed clinical progression and most of the drug addicts that proceeded to full-blown AIDS developed anergy (82%) prior to clinical deterioration with development of opportunistic infections. We conclude, that in seropositive drug addicts a low absolute count of helper/inducer cells (mean +/- s.e. = 243 +/- 48 cells/mm3), a low response to pokeweed mitogen and anergy are predictive markers of progression to AIDS.