Nucleoside analogues and neuropathy in the era of HAART

Amphiphilic anti-SARS-CoV-2 drug remdesivir incorporates into the lipid bilayer and nerve terminal membranes influencing excitatory and inhibitory neurotransmission

Remdesivir is a novel antiviral drug, which is active against the SARS-CoV-2 virus. Remdesivir is known to accumulate in the brain but it is not clear whether it influences the neurotransmission. Here we report diverse and pronounced effects of remdesivir on transportation and release of excitatory and inhibitory neurotransmitters in rat cortex nerve terminals (synaptosomes) in vitro. Direct incorporation of remdesivir molecules into the cellular membranes was shown by FTIR spectroscopy, planar phospholipid bilayer membranes and computational techniques. Remdesivir decreases depolarization-induced exocytotic release of L-[¹⁴C] glutamate and [³H] GABA, and also [³H] GABA uptake and extracellular level in synaptosomes in a dose-dependent manner. Fluorimetric studies confirmed remdesivir-induced impairment of exocytosis in nerve terminals and revealed a decrease in synaptic vesicle acidification. Our data suggest that remdesivir dosing during antiviral therapy should be precisely controlled to prevent possible neuromodulatory action at the presynaptic level. Further studies of neurotropic and membranotropic effects of remdesivir are necessary.

Evidence for a novel subcortical mechanism for posterior cingulate cortex atrophy in HIV peripheral neuropathy

We previously reported that neuropathic pain was associated with smaller posterior cingulate cortical (PCC) volumes, suggesting that a smaller/dysfunctional PCC may contribute to development of pain via impaired mind wandering. A gap in our previous report was lack of evidence for a mechanism for the genesis of PCC atrophy in HIV peripheral neuropathy. Here we investigate if volumetric differences in the subcortex for those with neuropathic paresthesia may contribute to smaller PCC volumes, potentially through deafferentation of ascending white matter tracts resulting from peripheral nerve damage in HIV neuropathy. Since neuropathic pain and paresthesia are highly correlated, statistical decomposition was used to separate pain and paresthesia symptoms to determine which regions of brain atrophy are associated with both pain and paresthesia and which are associated separately with pain or paresthesia. HIV+ individuals (N = 233) with and without paresthesia in a multisite study underwent structural brain magnetic resonance imaging. Voxel-based morphometry and a segmentation/registration tool were used to investigate regional brain volume changes associated with paresthesia. Analysis of decomposed variables found that smaller midbrain and thalamus volumes were associated with paresthesia rather than pain. However, atrophy in the PCC was related to both pain and paresthesia. Peak thalamic atrophy (p = 0.004; MNI x = - 14, y = - 24, z = - 2) for more severe paresthesia was in a region with reciprocal connections with the PCC. This provides initial evidence that smaller PCC volumes in HIV peripheral neuropathy are related to ascending white matter deafferentation caused by small fiber damage observed in HIV peripheral neuropathy.

Dissociable Contributions of Precuneus and Cerebellum to Subjective and Objective Neuropathy in HIV

Neuropathy, typically diagnosed by the presence of either symptoms or signs of peripheral nerve dysfunction, remains a frequently reported complication in the antiretroviral (ART)-treated HIV population. This study was conducted in 109 healthy controls and 57 HIV-infected individuals to investigate CNS regions associated with neuropathy. An index of objective neuropathy was computed based on 4 measures: deep tendon ankle reflex, vibration sense (great toes), position sense (great toes), and 2-point discrimination (feet). Subjective neuropathy (self-report of pain, aching, or burning; pins and needles; or numbness in legs or feet) was also evaluated. Structural MRI data were available for 126/166 cases. The HIV relative to the healthy control group was impaired on all 4 signs of neuropathy. Within the HIV group, an objective neuropathy index of 1 (bilateral impairment on 1 measure) or 2 (bilateral impairment on at least 2/4 measures) was associated with older age and a smaller volume of the cerebellar vermis. Moderate to severe symptoms of neuropathy were associated with more depressive symptoms, reduced quality of life, and a smaller volume of the parietal precuneus. This study is consistent with the recent contention that ART-treated HIV-related neuropathy has a CNS component. Distinguishing subjective symptoms from objective signs of neuropathy allowed for a dissociation between the precuneus, a brain region involved in conscious information processing and the vermis, involved in fine tuning of limb movements. Graphical Abstract In HIV patients, objective signs of neuropathy correlated with smaller cerebellar vermis (red) volumes whereas subjective symptoms of neuropathy were associated with smaller precuneus (blue) volumes.

Reduced intraepidermal nerve fibre density, glial activation, and sensory changes in HIV type-1 Tat-expressing female mice: involvement of Tat during early stages of HIV-associated painful sensory neuropathy

INTRODUCTION

HIV infection is associated with chronic pain states, including sensory neuropathy, which affects greater than 40% of patients.

OBJECTIVES AND METHODS

To determine the impact of HIV-Tat induction on nociceptive behaviour in female mice conditionally expressing HIV Tat1-86 protein through a doxycycline (DOX)-driven glial fibrillary acidic protein promoter, intraepidermal nerve fibre density and immune cell activation in the dorsal root ganglion (DRG) and spinal cord were assessed by immunohistochemistry. Mice were assessed for mechanical and thermal sensitivity for 9 weeks using von-Frey and Hargreaves tests.

RESULTS

Intraepidermal nerve fibre density was significantly reduced after 6 weeks of Tat induction, similar to sensory neuropathy seen in clinical HIV infection. Tat induction through DOX caused a significant reduction in paw withdrawal thresholds in a time-dependent manner starting the 4th week after Tat induction. No changes in paw withdrawal latencies were seen in Tat(-) control mice lacking the tat transgene. Although reductions in paw withdrawal thresholds increased throughout the study, no significant change in spontaneous motor activity was observed. Spinal cord (cervical and lumbar), DRG, and hind paw skin were collected at 8 days and 6 weeks after Tat induction. HIV-Tat mRNA expression was significantly increased in lumbar DRG and skin samples 8 days after DOX treatment. Tat induced a significant increase in the number of Iba-1 positive cells at 6 weeks, but not after 8 days, of exposure. No differences in glial fibrillary acidic protein immunoreactivity were observed.

CONCLUSION

These results suggest that Tat protein contributes to painful HIV-related sensory neuropathy during the initial stages of the pathogenesis.

HIV Distal Neuropathic Pain Is Associated with Smaller Ventral Posterior Cingulate Cortex

Objective

. Despite modern antiretroviral therapy, HIV-associated neuropathy is one of the most prevalent, disabling and treatment-resistant complications of HIV disease. The presence and intensity of distal neuropathic pain is not fully explained by the degree of peripheral nerve damage. A better understanding of brain structure in HIV distal neuropathic pain may help explain why some patients with HIV neuropathy report pain while the majority does not. Previously, we reported that more intense distal neuropathic pain was associated with smaller total cerebral cortical gray matter volumes. The objective of this study was to determine which parts of the cortex are smaller.

Methods

. HIV positive individuals with and without distal neuropathic pain enrolled in the multisite (N = 233) CNS HIV Antiretroviral Treatment Effects (CHARTER) study underwent structural brain magnetic resonance imaging. Voxel-based morphometry was used to investigate regional brain volumes in these structural brain images.

Results

. Left ventral posterior cingulate cortex was smaller for HIV positive individuals with versus without distal neuropathic pain (peak P  = 0.017; peak t = 5.15; MNI coordinates x = -6, y = -54, z = 20). Regional brain volumes within cortical gray matter structures typically associated with pain processing were also smaller for HIV positive individuals having higher intensity ratings of distal neuropathic pain.

Conclusions

. The posterior cingulate is thought to be involved in inhibiting the perception of painful stimuli. Mechanistically a smaller posterior cingulate cortex structure may be related to reduced anti-nociception contributing to increased distal neuropathic pain.

Tracking Epidermal Nerve Fiber Changes in Asian Macaques: Tools and Techniques for Quantitative Assessment

Quantitative assessment of epidermal nerve fibers (ENFs) has become a widely used clinical tool for the diagnosis of small fiber neuropathies such as diabetic neuropathy and human immunodeficiency virus-associated sensory neuropathy (HIV-SN). To model and investigate the pathogenesis of HIV-SN using simian immunodeficiency virus (SIV)-infected Asian macaques, we adapted the skin biopsy and immunostaining techniques currently employed in human patients and then developed two unbiased image analysis techniques for quantifying ENF in macaque footpad skin. This report provides detailed descriptions of these tools and techniques for ENF assessment in macaques and outlines important experimental considerations that we have identified in the course of our long-term studies. Although initially developed for studies of HIV-SN in the SIV-infected macaque model, these methods could be readily translated to a range of studies involving peripheral nerve degeneration and neurotoxicity in nonhuman primates as well as preclinical investigations of agents aimed at neuroprotection and regeneration.

Adverse Effects Associated With Antiretroviral Therapy and Potential Management Strategies

A variety of adverse drug reactions (ADRs) affecting many organ systems may be observed with antiretroviral therapy (ARV), and they can be differentiated into short- and long- term effects, class effects, or individual drug effects. Commonly seen ADRs include dermatological reactions, associated with nonnucleoside reverse transcriptase inhibitors (NNRTIs) and some protease inhibitors (PIs), and gastrointestinal problems, a major side effect of PIs and of some nucleoside reverse transcriptase inhibitors (NRTIs). Metabolic complications are frequently reported in HIV-infected patients on ARV and often coexist. Lipodystrophy, hyperinsulinemia/hyperglycemia, and bone disorders (osteoporosis, osteonecrosis) are mainly associated with PIs, while lactic acidemia/acidosis are primarily a problem of NRTIs. Hyperlipidemia may be caused by almost all PIs, few NRTIs, and NNRTIs. All antiretroviral drug classes may cause both asymptomatic and symptomatic hepatotoxicity, although nevirapine is the agent most implicated in hepatic events. More drug-specific ADRs include nephrotoxicity (indinavir and tenofovir), central nervous system problems (efavirenz), hematological disturbances (zidovudine), and hypersensitivity reactions (abacavir). Anticipation of ADRs may influence a patient’s decision to delay ARV or to choose specific and potentially less active agents. Occurrence of ADRs may significantly impact a patient’s quality of life and drug adherence. Pharmacists counseling HIV-infected patients should be aware of common ADRs with ARV and potential management strategies.

Persistent Peripheral Nervous System Damage in Simian Immunodeficiency Virus-Infected Macaques Receiving Antiretroviral Therapy

Human immunodeficiency virus (HIV)-induced peripheral neuropathy is the most common neurologic complication associated with HIV infection. In addition to virus-mediated injury of the peripheral nervous system (PNS), treatment of HIV infection with combination antiretroviral therapy (cART) may induce toxic neuropathy as a side effect. Antiretroviral toxic neuropathy is clinically indistinguishable from the sensory neuropathy induced by HIV; in some patients, these 2 processes are likely superimposed. To study these intercurrent PNS disease processes, we first established a simian immunodeficiency virus (SIV)/pigtailed macaque model in which more than 90% of animals developed PNS changes closely resembling those seen in HIV-infected individuals with distal sensory neuropathy. To determine whether cART alters the progression of SIV-induced PNS damage, dorsal root ganglia and epidermal nerve fibers were evaluated in SIV-infected macaques after long-term suppressive cART. Although cART effectively suppressed SIV replication and reduced macrophage activation in the dorsal root ganglia, PGP 9.5 immunostaining and measurements of epidermal nerve fibers in the plantar surface of the feet of treated SIV-infected macaques clearly showed that cART did not normalize epidermal nerve fiber density. These findings illustrate that significant PNS damage persists in SIV-infected macaques on suppressive cART.

Predictors of new-onset distal neuropathic pain in HIV-infected individuals in the era of combination antiretroviral therapy

Despite modern combination antiretroviral therapy, distal neuropathic pain (DNP) continues to affect many individuals with HIV infection. We evaluated risk factors for new-onset DNP in the CNS Antiretroviral Therapy Effects Research (CHARTER) study, an observational cohort. Standardized, semiannual clinical evaluations were administered at 6 US sites. Distal neuropathic pain was defined by using a clinician-administered instrument standardized across sites. All participants analyzed were free of DNP at study entry. New-onset DNP was recorded at the first follow-up visit at which it was reported. Mixed-effects logistic regression was used to evaluate potential predictors including HIV disease and treatment factors, demographics, medical comorbidities, and neuropsychiatric factors. Among 493 participants, 131 (27%) reported new DNP over 2306 visits during a median follow-up of 24 months (interquartile range 12-42). In multivariable regression, after adjusting for other covariates, significant entry predictors of new DNP were older age, female sex, current and past antiretroviral treatment, lack of virologic suppression, and lifetime history of opioid use disorder. During follow-up, more severe depression symptoms conferred a significantly elevated risk. The associations with opioid use disorders and depression reinforce the view that the clinical expression of neuropathic pain with peripheral nerve disease is strongly influenced by neuropsychiatric factors. Delineating such risk factors might help target emerging preventive strategies, for example, to individuals with a history of opioid use disorder, or might lead to new treatment approaches such as the use of tools to ameliorate depressed mood.

A potential event-competition bias in safety signal detection: results from a spontaneous reporting research database in France

BACKGROUND

In spontaneous reporting databases, reports of well-established drug-event associations may mask alerts that arise from other drugs (drug competition bias). However, a symmetrical event-competition bias has not yet been explored whereby known events may mask an association with new events for a given drug or drug class.

OBJECTIVE

The objective of this study was to explore the effects of event-competition bias on safety signals generated from spontaneous reporting databases.

METHODS

The drug classes tested included statins, oral anticoagulants, antipsychotics and HIV antiretrovirals. For each, a type A reaction was selected, and its potential competitive effect on the generation of other safety signals for the drug was explored. These were rhabdomyolysis/myopathy for statins, haemorrhage for oral anticoagulants, extrapyramidal syndrome for antipsychotics and lipodystrophy for HIV antiretrovirals. Signals of disproportionate reporting (SDRs) were detected using the case/non-case approach in the French research spontaneous reporting database (which contains reports from 1 January 1986 to 31 December 2001), before and after removing all reports concerning these competitor events. SDRs were considered as potential signals if not reported in the literature before 1 January 2002 but confirmed since.

RESULTS

The whole database included 207,236 reports, 4,355 of which included statins as one of the suspected drugs. The removal of reports of rhabdomyolysis/myopathy concerned 8,425 reports among which 867 involved statins. After this removal, 11 new SDRs appeared for statins that had not been detected initially. Similarly, 15 SDRs were unmasked for oral anticoagulants, six for antipsychotics and nine for HIV antiretrovirals. After literature-based assessment, five of the 41 unmasked SDRs appeared related to potential safety signals confirmed after 2002.

CONCLUSION

This study demonstrated that a masking phenomenon resulting from an event-competition effect could occur when performing signal detection using disproportionality analyses of spontaneous reporting databases. This should be taken into account when routine signal detection is performed.

Neuromuscular manifestations of HIV/AIDS

The human immunodeficiency virus (HIV) epidemic, now entering its fourth decade, affects approximately 33 million people living in both developed and resource-limited countries. Neurological complications of the peripheral nervous system are common in HIV-infected patients, and neuromuscular pathology is associated with significant morbidity. Peripheral neuropathy is the most common neuromuscular manifestation observed in HIV/AIDS, and in the antiretroviral era, its prevalence has increased. The purpose of this review was to describe the clinical spectrum of neuromuscular disorders in the setting of HIV infection and to provide an approach to diagnosis and management.

Painful HIV-associated sensory neuropathy

SUMMARY Painful HIV-associated sensory neuropathy (HIV-SN) is an early recognized neurological complication of HIV. The introduction of effective HIV treatments saw increased rates of HIV-SN, with some antiretrovirals (notably stavudine) being neurotoxic. Although neurotoxic antiretrovirals are being phased out, the available data suggest that incident HIV-SN will remain common, impairing quality of life, mobility and ability to work. Despite its major clinical importance, the pathogenesis and determinants of pain in HIV-SN are poorly understood, and effective prevention and analgesic strategies are lacking. Here, we review what is known about the rates and risk factors for painful HIV-SN, the laboratory models informing our understanding of neuropathic pain in HIV, and the future clinical and laboratory work needed to fully understand this debilitating condition and provide effective management strategies for those affected.

HIV-associated sensory neuropathy: risk factors and genetics

HIV-associated sensory neuropathy (HIV-SN) remains a common neurological complication of HIV infection despite the introduction of effective antiretroviral therapies. Exposure to neurotoxic antiretroviral drugs and increasing age have consistently been identified as risk factors for HIV-SN, while comorbid conditions with underlying predisposition to cause peripheral neuropathy (eg, diabetes mellitus, malnutrition, isoniazid exposure), ethnicity, and increasing height also have been implicated. Genetic association studies have identified genes affecting mitochondrial function and genes involved in the inflammatory response that modify the risk for HIV-SN among patients exposed to neurotoxic antiretrovirals. However, there is a lack of data on clinical, demographic, and genetic risk factors for HIV-SN in the modern era, with the rate of HIV-SN remaining unacceptably high despite the introduction of safer medications. Thus, more work is required to identify the principal factors that increase an individual's risk for HIV-SN so that effective preventative or therapeutic strategies can be implemented.

Polyneuropathy induced by HIV disease and antiretroviral therapy

OBJECTIVE

To investigate the underlying mechanisms of polyneuropathy induced by HIV infection or antiretroviral drugs.

METHODS

We tested 100 HIV patients (59 with AIDS). Ninety-three patients received antiretroviral drugs. Forty-four were treated with neurotoxic compounds (ddI, ddC, d4T). Nerve conduction velocities and the sympathetic skin response (SSR) in palms and soles were measured in all patients. In skin biopsies (ankle and thigh), the intraepidermal nerve fiber density (IENFD) and the number of epidermal fibers without contact to the basal membrane (fragments) were quantified using PGP9.5 staining.

RESULTS

Severity of the disease (CD4 +count) correlated to conduction velocities of peroneal (p < 0.01, Spearmans rank correlation), sural (p < 0.01) and median nerves (p < 0.05/p < 0.001, sensory/motor). In contrast, the duration of neurotoxic treatment did not impair conduction velocities (p > 0.3) but correlated to reduced IENFD in the ankle (r = -0.24, p < 0.05). Despite their reduced IENFD, patients with long neurotoxic treatment had a high number of fragments irrespective of their CD4 +count.

CONCLUSIONS

Neurotoxic treatment appears to primarily impair thin fiber conduction, whereas HIV neuropathy is linked to large fiber impairment and reduction of fragments of nerve fibers.

SIGNIFICANCE

These findings emphasize the differential pattern of polyneuropathy in HIV patients caused by the infection or induced by antiretroviral treatment.

Influence of Age and Neurotoxic HAART Use on Frequency of HIV Sensory Neuropathy

Background. Sensory neuropathy (SN) is one of the most common AIDS-associated neurologic disorders especially in the era of highly active antiretroviral therapy (HAART). The aim of this study was to determine the prevalence of SN among highly-active-antiretroviral-therapy- (HAART-) experienced and HAART-naïve HIV-positive individuals and to investigate the relationship to demographic, clinical, and laboratory factors. Methods. 323 patients with HIV infection (142 on HAART and 181 HAART naïve) were enrolled in a cross-sectional neuropathy screening program. Data was collected using structured questionnaires which contained the brief peripheral neuropathy screening tool of AIDS Clinical Trial Group protocol. Neuropathy was defined by the presence of at least 1 clinical sign in a distal, symmetrical pattern. Patients were classified as symptomatic if they described aching, stabbing, or burning pain, paresthesia, or numbness in a similar distribution. Demographic, clinical, and laboratory details were documented as risk factors. Result. The prevalence of sensory neuropathy was 39.0% (126/323), (of which 29/126 (23%)) were symptomatic. Amongst those on HAART, 60/142 (42.3%) had SN compared to 66/181 (36.5%) HAART-naïve individuals (P = 0.29). On multivariate analyses, the independent associations with SN were increasing age (P = 0.03) and current exposure to stavudine (P = 0.00). Gender (P = 0.99) height (P = 0.07) use of HAART (P = 0.50), duration of HAART treatment (P = 0.10), and lower CD4 count (P = 0.12) were not associated with an increased SN risk. Conclusion. HIV SN remains common despite improved immunologic function associated with HAART and decreased neurotoxic HAART use. In this cross-sectional analysis, age and stavudine-based therapies were the independent risk factors.

Lateral rectus muscle paralysis induced by ribavirin and pegylated interferon-α2a in a patient with HIV/HCV co-infection

We report a lateral rectus muscle paralysis occurring 2 weeks after initiation of an interferon-α and ribavirin treatment in a patient with human immunodeficiency virus (HIV) and hepatitis C virus (HCV) virus co-infection. This patient presented with horizontal diplopia that appeared rapidly and without any other neurological symptoms. Symptoms fully resolved with treatment interruption without any ophthalmological sequelae. This side effect is rare and has never been reported in a HIV-HCV co-infected patient.

Iatrogenic mitochondriopathies: a recent lesson from nucleoside/nucleotide reverse transcriptase inhibitors

The use of nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs) has revolutionized the treatment of infection by human immunodeficiency virus (HIV) and hepatitis-B virus. NRTIs can suppress viral replication in the long-term, but possess significant toxicity that can seriously compromise treatment effectiveness. The major toxicity of NRTIs is mitochondrial toxicity. This manifests as serious side effects such as myopathy, peripheral neuropathy and lactic acidosis. In general, it is believed that the mitochondrial pathogenesis is closely related to the effect of NRTIs on mitochondrial DNA polymerase-γ. Depletion and mutation of mitochondrial DNA during chronic NRTI therapy may lead to cellular respiratory dysfunction and release of reactive oxidative species, resulting in cellular damage. It is now apparent that the etiology is far more complex than originally thought. It appears to involve multiple mechanisms as well as host factors such as HIV per se, inborn mitochondrial mutation, and sex. Management of mitochondrial toxicity during NRTI therapy remains a challenge. Interruption of NRTI therapy and substitution of the causative agents with alternative better-tolerated NRTIs represents the mainstay of management for mitochondrial toxicity and its clinical manifestations. A range of pharmacological approaches has been proposed as treatments and prophylaxes.

Ibudilast, a pharmacologic phosphodiesterase inhibitor, prevents human immunodeficiency virus-1 Tat-mediated activation of microglial cells

Human Immunodeficiency Virus-1 (HIV-1)-associated neurocognitive disorders (HAND) occur, in part, due to the inflammatory response to viral proteins, such as the HIV-1 transactivator of transcription (Tat), in the central nervous system (CNS). Given the need for novel adjunctive therapies for HAND, we hypothesized that ibudilast would inhibit Tat-induced excess production of pro-inflammatory cytokines, such as tumor necrosis factor-alpha (TNFα) in microglial cells. Ibudilast is a non-selective cyclic AMP phosphodiesterase inhibitor that has recently shown promise as a treatment for neuropathic pain via its ability to attenuate glial cell activation. Accordingly, here we demonstrate that pre-treatment of both human and mouse microglial cells with increasing doses of ibudilast inhibited Tat-induced synthesis of TNFα by microglial cells in a manner dependent on serine/threonine protein phosphatase activity. Ibudilast had no effect on Tat-induced p38 MAP kinase activation, and blockade of adenosine A_2A receptor activation did not reverse ibudilast's inhibition of Tat-induced TNFα production. Interestingly, ibudilast reduced Tat-mediated transcription of TNFα, via modulation of nuclear factor-kappa B (NF-κB) signaling, as shown by transcriptional activity of NF-κB and analysis of inhibitor of kappa B alpha (IκBα) stability. Together, our findings shed light on the mechanism of ibudilast's inhibition of Tat-induced TNFα production in microglial cells and may implicate ibudilast as a potential novel adjunctive therapy for the management of HAND.

Nano-NRTIs: efficient inhibitors of HIV type-1 in macrophages with a reduced mitochondrial toxicity

BACKGROUND

Macrophages serve as a depot for HIV type-1 (HIV-1) in the central nervous system. To efficiently target macrophages, we developed nanocarriers for potential brain delivery of activated nucleoside reverse transcriptase inhibitors (NRTIs) called nano-NRTIs.

METHODS

Nanogel carriers consisting of poly(ethylene glycol) (PEG)- or Pluronic-polyethylenimine (PEI) biodegradable networks, star PEG-PEI or poly(amidoamine) dendrimer-PEI-PEG dendritic networks, as well as nanogels decorated with brain-targeting peptide molecules, specifically binding to the apolipoprotein E receptor, were synthesized and evaluated. Nano-NRTIs were obtained by mixing aqueous solutions of zidovudine 5'-triphosphate or didanosine 5'-triphosphate and nanocarriers, followed by freeze-drying. Intracellular accumulation, cytotoxicity and antiviral activity of nano-NRTIs were monitored in monocyte-derived macrophages (MDMs). HIV-1 viral activity in infected MDMs was measured by a reverse transcriptase activity assay following treatment with nano-NRTIs. Mitochondrial DNA depletion in MDMs and human HepG2 cells was assessed by quantitative PCR.

RESULTS

Nanogels were efficiently captured by MDMs and demonstrated low cytotoxicity, and no antiviral activity without drugs. All nano-NRTIs demonstrated high efficacy of HIV-1 inhibition at drug levels as low as 1 μmol/l, representing a 4.9- to 14-fold decrease in 90% effective drug concentrations as compared with NRTIs, whereas 50% cytotoxicity effects started at 200× higher concentrations. Nano-NRTIs with a core-shell structure and decorated with brain-targeting peptides displayed the highest antiviral efficacy. Mitochondrial DNA depletion, a major cause of NRTI neurotoxicity, was reduced threefold compared with NRTIs at application of selected nano-NRTIs.

CONCLUSIONS

Nano-NRTIs demonstrated a promising antiviral efficacy against HIV-1 in MDMs and showed strong potential as nanocarriers for delivery of antiviral drugs to macrophages harbouring in the brain.

NeuroAIDS in the Asia Pacific Region

Over 8.3 million people living in the Asia Pacific region are human immunodeficiency virus (HIV) positive and up to 40% of these individuals have had prior acquired immunodeficiency syndrome (AIDS) illnesses. Recently endeavors have been made to better characterize the burden of HIV-related neurological disease within the Asia Pacific region and, with this in mind, the NeuroAIDS in Asia and the Pacific Rim workshop was held in Sydney, Australia, as an affiliated event of the 4th IAS Conference on HIV Pathogenesis, Treatment and Prevention. The workshop was supported by the National Institute of Neurological Disorders and Stroke (NINDS) and the National Institute of Mental Health (NIMH) of the United States National Institutes of Health and the Australian Government overseas AID program, AusAID. HIV neurologists, infectious disease physicians, pediatricians, psychiatrists, immunologists, virologists,and researchers from 12 countries of the Asia Pacific region (including Australia), the United States, and the United Kingdom attended the meeting. A broad range of topics were addressed, including common HIV neurological disorders, the lack of diagnostic, management, and research infrastructure, central nervous system (CNS) immune restoration disease, pediatric neuroAIDS, and current clinical and laboratory research projects being undertaken within the Asia Pacific region.

Incident neuropathy in HIV-infected patients on HAART

We determined the incidence of and risk factors for distal sensory polyneuropathy (DSP) in individuals on HAART. Sixty-one HIV-positive subjects on HAART for at least 6 months and neuropathy free were retrospectively selected. The study included subjects who had previously tolerated d-drugs without developing DSP. Neuropathy incidence over 4 years was calculated. Cox proportional hazards models were used to determine risk factors associated with incident DSP. Nineteen subjects developed DSP over a mean follow-up of 2.4 years. Subjects never treated with a d-drug developed DSP at a rate of 21 cases per 100 person-years (95% CI, 8.9-33.7). Subjects with a history of d-drug treatment but not on a d-drug at enrollment developed DSP at a rate of 17 cases per 100 person-years (95% CI, 2.1-31.8). Those on d-drug treatment developed DSP at a rate of 25 cases per 100 person-years (95% CI, 8.7-41.6). Multivariable analysis identified age [hazard ratio (HR) = 1.09; p < 0.01] and low CD4(+) nadir [hazard ratio (HR) = 0.79; p = 0.03] as significant risk factors. Current or prior history of treatment with d-drug was not a significant risk factor for incident DSP in subjects who had previously tolerated d-drug treatment without developing a toxic DSP. Age and low CD4(+) are risk factors for incident DSP. However, current or prior history of d-drug treatment is not a significant risk factor for incident DSP in subjects who had previously tolerated d-drug treatment without developing a toxic DSP.

Hepatitis C seropositivity is not a risk factor for sensory neuropathy among patients with HIV

BACKGROUND

Sensory neuropathy (SN) is common in patients with HIV. Hepatitis C (HCV) coinfection is often cited as an HIV-SN risk factor, but data to support this are lacking. This collaboration aimed to examine the association between HCV serostatus and SN risk among ambulatory HIV-positive patients.

METHODS

Patients with HIV were assessed in cross-sectional studies in Baltimore, Jakarta, Johannesburg, Kuala Lumpur, Melbourne, and Sydney for SN (defined by both supportive symptoms and signs). HCV seropositivity was assessed as an SN risk using a chi(2) test, followed by logistic regression modeling to correct for treatment exposures and demographics.

RESULTS

A total of 837 patients of African, Asian, and Caucasian descent were studied. HCV seroprevalence varied by site (Baltimore n = 104, 61% HCV+; Jakarta 96, 51%; Johannesburg 300, 1%; Kuala Lumpur 97, 10%; Melbourne 206, 16%; Sydney 34, 18%). HCV seropositivity was not associated with increased SN risk at any site, but was associated with reduced SN risk in Melbourne (p = 0.003). On multivariate analyses, the independent associations with SN were increasing age, height, and stavudine exposure. HCV seropositivity was not independently associated with an increased SN risk at any site, but associated independently with reduced SN risk in Baltimore (p = 0.04) and Melbourne (p = 0.06).

CONCLUSIONS

Hepatitis C (HCV) seropositivity was not associated with increased sensory neuropathy risk among HIV-positive patients at any site. While we were unable to assess HCV RNA or liver damage, the data suggest that HCV coinfection is not a major contributor to HIV-SN. HCV = hepatitis C; SN = sensory neuropathy.

Continued high prevalence and adverse clinical impact of human immunodeficiency virus-associated sensory neuropathy in the era of combination antiretroviral therapy: the CHARTER Study

OBJECTIVE

To provide updated estimates of the prevalence and clinical impact of human immunodeficiency virus-associated sensory neuropathy (HIV-SN) and neuropathic pain due to HIV-SN in the combination antiretroviral therapy (CART) era.

DESIGN

Prospective, cross-sectional analysis. Clinical correlates for HIV-SN and neuropathic pain, including age, exposure to CART, CD4 levels, plasma viral load, hepatitis C virus infection, and alcohol use disorders, were evaluated in univariate and multivariate models.

SETTING

Six US academic medical centers.

PATIENTS

One thousand five hundred thirty-nine HIV-infected individuals enrolled in the CNS (Central Nervous System) HIV Anti-Retroviral Therapy Effects Research study.

MAIN OUTCOME MEASURES

The presence of HIV-SN, defined by 1 or more clinical signs (diminished vibration or sharp sensation in the legs and feet; reduced ankle reflexes) in a distal, symmetrical pattern. Neuropathic pain was defined as aching, stabbing, or burning in a similar distribution. The effect on quality of life was assessed with the Medical Outcomes Study HIV Health Survey.

RESULTS

We found HIV-SN in 881 participants. Of these, 38.0% reported neuropathic pain. Neuropathic pain was significantly associated with disability in daily activities, unemployment, and reduced quality of life. Risk factors for HIV-SN after adjustment were advancing age (odds ratio, 2.1 [95% confidence interval, 1.8-2.5] per 10 years), lower CD4 nadir (1.2 [1.1-1.2] per 100-cell decrease), current CART use (1.6 [1.3-2.8]), and past "D-drug" use (specific dideoxynucleoside analogue antiretrovirals) (2.0 [1.3-2.6]). Risk factors for neuropathic pain were past D-drug use and higher CD4 nadir.

CONCLUSIONS

Neuropathic pain and HIV-SN remain prevalent, causing substantial disability and reduced quality of life even with successful CART. The clinical correlates of HIV-SN have changed with the evolution of treatment. These findings argue for redoubled efforts to determine HIV-SN pathogenesis and the development of symptomatic and neuroregenerative therapies.

Targeting neuroprotection as an alternative approach to preventing and treating neuropathic pain

Neuropathic pain syndromes arise from dysfunction of the nerve itself, through traumatic or nontraumatic injury. Unlike acute pain syndromes, the pain is long-lasting and does not respond to common analgesic therapies. Drugs that disrupt nerve conduction and transmission or central sensitization, currently the only effective treatments, are only modestly effective for a portion of the patients suffering from neuropathic pain and come with the cost of serious adverse effects. Neurodegeneration, as a reaction to nerve trauma or chronic metabolic or chemical intoxication, appears to be an underlying cause of neuropathic pain. Identifying mechanisms of neurodegeneration and designing neuroprotective therapies is an ambitious goal toward treating or even preventing the development of these disabling disorders.

Pharmacogenetics of nucleoside reverse-transcriptase inhibitor-associated peripheral neuropathy

Peripheral neuropathy is an important complication of antiretroviral therapy. Nucleoside reverse-transcriptase inhibitor (NRTI)-associated mitochondrial dysfunction, inflammation and nutritional factors are implicated in its pathogenesis. Pharmacogenetic and genomic studies investigating NRTI neurotoxicity have only recently become possible via the linkage of HIV clinical studies to large DNA repositories. Preliminary case-control studies using these resources suggest that host mitochondrial DNA haplogroup polymorphisms in the hemochromatosis gene and proinflammatory cytokine genes may influence the risk of peripheral neuropathy during antiretroviral therapy. These putative risk factors await confirmation in other HIV-infected populations but they have strong biological plausibility. Work to identify underlying mechanisms for these associations is ongoing. Large-scale studies incorporating clearly defined and validated methods of neuropathy assessment and the use of novel laboratory models of NRTI-associated neuropathy to clarify its pathophysiology are now needed. Such investigations may facilitate the development of more effective strategies to predict, prevent and ameliorate this debilitating treatment toxicity in diverse clinical settings.

Hyperalgesia induced by oral stavudine administration to rats does not depend on spinal neuronal cell death, or on spinal or systemic inflammatory cytokine secretion, or metabolic dysregulation

To investigate possible mechanisms of the hyperalgesia induced by the nucleoside reverse transcriptase inhibitor (NRTI) stavudine in rats, we examined neuronal death and inflammatory cytokine secretion in the spinal cord, and cytokine and lactate secretion in the plasma. Stavudine (50 mg kg(-1)) or placebo was administered orally to Sprague-Dawley rats once daily for three or six weeks. In one group, rats' responses to a blunt noxious mechanical stimulus applied to their tails were recorded before and at the end of the period of stavudine or placebo administration. Spinal cords excised from these rats after three and six weeks of stavudine or placebo administration were examined for neuronal necrosis and apoptosis. In a second group of rats, plasma and spinal cord samples collected after three and six weeks of placebo or stavudine administration were examined for changes in CINC-1, IL-6, adiponectin (plasma only) and lactate (plasma only) concentration. Daily stavudine administration induced mechanical hyperalgesia within three weeks, which was sustained until week six, but the hyperalgesia was not associated with neuronal apoptosis or necrosis, or elevated IL-6 concentrations in the spinal cord. The spinal cord concentration of CINC-1 increased, but only after six weeks of stavudine administration, when the hyperalgesia had been established for over three weeks. Stavudine administration did not affect the plasma concentration of IL-6, CINC-1, adiponectin or lactate. Thus, neither peripheral nor central inflammatory cytokine secretion, or neuronal death, or metabolic dysregulation contributed to the development of hyperalgesia in our model of stavudine-induced hyperalgesia in rats.

Measuring and monitoring apoptosis and drug toxicity in HIV patients by ligation-mediated polymerase chain reaction

Apoptosis has a critical role in normal physiology while its dysregulation has causal links with certain pathologies. A biochemical hallmark of apoptosis, internucleosomal genomic DNA fragmentation, is detectable by ligation-mediated polymerase chain reaction (LM-PCR). Here we converted LM-PCR into a new apoptosis quantifier by dividing trace quantities of 600 bp apoptotic amplicons into those of a single copy house-keeping gene, generating the LM-PCR 'value'. Dynamic range was approximately 17-fold correlating with a approximately 200-fold difference in degree of apoptotic fragmentation. Inter- and intra-gel reliability were both excellent, supporting LM-PCR's utility with large sample sets. Validation experiments comprising cell exposure to staurosporine over time revealed LM-PCR is as sensitive as caspase-3/ELISA and more sensitive than terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling/flourescence-activated cell sorting (TUNEL/FACS) for distinguishing low degrees of apoptosis (the spectrum most relevant in vivo). The LM-PCR profile mirrored that of caspase-3/ELISA but not TUNEL/FACS. We then applied this molecular tool to clinical investigation. Increased apoptosis is implicated in lipoatrophy (subcutaneous fat wasting), a serious, persistent toxicity of some nucleoside analogue reverse transcriptase inhibitors (NRTIs) used in anti-HIV highly active antiretroviral therapy (HAART). We demonstrated in 105 peripheral blood mononuclear cell samples that elevated LM-PCR values are seen during therapy with stavudine (d4T), a particularly toxic NRTI (P< 0.0001 versus no HAART, unpaired t-test). Elevated values were also independently associated with clinical evidence of lipoatrophy (P= 0.007, multiple logistic regression modelling) but not with patient age, CD4 T-cell count nor HIV viral load (P> 0.8 for each). Together these data demonstrate that LM-PCR is a robust and reliable quantifier of apoptosis with potential for basic science and clinical investigation.

Impact of long-term treatment with neurotoxic dideoxynucleoside antiretrovirals: implications for clinical care in resource-limited settings

OBJECTIVES

A minority of HIV-infected patients taking an antiretroviral (ARV) regimen containing dideoxynucleosides (d-drugs) such as stavudine (d4T) and didanosine (DDI) experiences dose-limiting neuropathic pain and paraesthesias, usually within weeks of starting these drugs. Because d-drugs are among the few affordable options available in developing countries, continuing d-drug therapy would be a desirable strategy for many HIV-infected individuals. Therefore, we evaluated the safety of continuing d-drug therapy.

METHODS

In a US cohort, we compared the rates of worsening neuropathic symptoms and signs in HIV-infected individuals on stable ARV regimens that did (n=252) or did not (n=250) include d-drugs. Rates of worsening were compared using proportional hazards model and the log-rank test.

RESULTS

The risk ratios (RR) were not significantly larger for worsening neuropathy signs [0.94; 95% confidence interval (CI) 0.84-1.07] or symptoms (0.99; 95% CI 0.88-1.14) in patients taking d-drugs continuously compared to those not taking d-drugs.

CONCLUSIONS

Continued d-drug exposure among patients tolerating an initial trial did not increase the risk of worsening neuropathy compared to non-d-drug-containing regimens. If applicable in developing countries, these findings suggest that in most patients d-drugs can be continued safely in the long term without increasing the risk of worsening neuropathy.

Comparison of dorsal root ganglion gene expression in rat models of traumatic and HIV-associated neuropathic pain

To elucidate the mechanisms underlying peripheral neuropathic pain in the context of HIV infection and antiretroviral therapy, we measured gene expression in dorsal root ganglia (DRG) of rats subjected to systemic treatment with the anti-retroviral agent, ddC (Zalcitabine) and concomitant delivery of HIV-gp120 to the rat sciatic nerve. L4 and L5 DRGs were collected at day 14 (time of peak behavioural change) and changes in gene expression were measured using Affymetrix whole genome rat arrays. Conventional analysis of this data set and Gene Set Enrichment Analysis (GSEA) was performed to discover biological processes altered in this model. Transcripts associated with G protein coupled receptor signalling and cell adhesion were enriched in the treated animals, while ribosomal proteins and proteasome pathways were associated with gene down-regulation. To identify genes that are directly relevant to neuropathic mechanical hypersensitivity, as opposed to epiphenomena associated with other aspects of the response to a sciatic nerve lesion, we compared the gp120 + ddC-evoked gene expression with that observed in a model of traumatic neuropathic pain (L5 spinal nerve transection), where hypersensitivity to a static mechanical stimulus is also observed. We identified 39 genes/expressed sequence tags that are differentially expressed in the same direction in both models. Most of these have not previously been implicated in mechanical hypersensitivity and may represent novel targets for therapeutic intervention. As an external control, the RNA expression of three genes was examined by RT-PCR, while the protein levels of two were studied using western blot analysis.

Safety of stavudine in the treatment of HIV infection with a special focus on resource-limited settings

BACKGROUND

Western randomized trials and prospective cohorts in resource-limited settings have proven virological success with stavudine-based highly active antiretroviral therapy. However, stavudine is no longer recommended in first-line treatments in these two settings due to its intrinsic toxicities and side effects. Yet it remains a cornerstone of treatment in resource-limited settings, due to lack of alternatives and its availability in generic fixed-dose combinations.

OBJECTIVE

To review the toxic effects of stavudine and their prevention and management strategies, especially in resource-limited settings.

METHODS

Data from clinical and pharmacological trials in Western countries, as well as prospective cohorts in resource-limited settings, were reviewed.

CONCLUSION

Initiating or switching to less toxic nucleoside analogues whenever possible, or lowering stavudine doses to 30 mg b.i.d., is strongly recommended.

The Risk of Developing Peripheral Neuropathy Induced by Nucleoside Reverse Transcriptase Inhibitors Decreases over Time: Evidence from the Delta Trial

Background

Peripheral neuropathy (PN) in HIV-infected individuals is thought be due to a toxic effect on mitochondria induced by some nucleoside reverse transcriptase inhibitors (NRTI).

Methods

A time-to-event analysis was performed using data from the Delta trial to study the incidence of PN in HIV-infected individuals receiving zidovudine (AZT) alone or in combination with didanosine (ddI) or zalcitabine (ddC). In an on-treatment analysis, changes in the incidence of PN by duration of treatment were directly estimated using a flexible parametric survival model.

Results

A total of 3,195 patients (total follow-up 4,593 person-years) were included in the analysis. AZT+ddC was associated with a higher incidence of PN (6.2 cases/100 person-years) compared with AZT monotherapy (3.0 cases/100 person-years) and AZT+ddI (2.2 cases/100 person-years). The risk of PN peaked around day 90 following randomization (at 8.9 events/100 person-years in the AZT+ddC arm). PN was also associated with age at entry (hazard ratio (HR)=2.35 for those aged 35–44 years compared with <30) and current CD4+ T-cell count (HR=2.27 for CD4+ T-cell counts <150 cell/mm3 compared with >350).

Conclusion

Our findings challenge the common supposition that PN arises from cumulative exposure to NRTIs. We found that patients who developed PN tended to do so shortly after exposure to antiretroviral therapy. Therefore, our results support the hypothesis of a susceptibility in a subgroup of patients. These results will be of direct interest to those working in resource-limited countries where potentially neurotoxic dideoxynucleosides are still widely used.

Oral administration of stavudine induces hyperalgesia without affecting activity in rats

We have investigated whether long-term oral administration of the nucleoside reverse transcriptase inhibitor (NRTI) stavudine affects nociception in Sprague-Dawley rats, and whether any changes of nociception are accompanied by deterioration in activity and appetite. Stavudine (50 mg kg(-1)) was administered to rats orally once daily for six weeks in gelatine cubes. Mechanical hyperalgesia of the tail was assessed using a bar algometer, and thermal hyperalgesia by tail immersion in 49 degrees C water. Withdrawal latencies were compared to those of rats receiving placebo gelatine cubes. Withdrawal latencies to the noxious thermal challenge were not affected by stavudine, but those to the mechanical challenge were significantly decreased in rats receiving stavudine, compared to rats receiving placebo, from week three to week six of drug administration (P<0.05, ANCOVA with Newman Keuls post-hoc comparisons). The overall condition of the rats was assessed by recording daily voluntary wheel running distance and maximum running speed, food intake and body mass. Daily stavudine administration did not adversely affect voluntary running activity, appetite or growth. We have shown that long-term daily oral administration of the NRTI stavudine results in mechanical hyperalgesia in rats within three weeks without affecting appetite, growth and physical activity.

Role of spinal serotonin 5-HT2A receptor in 2',3'-dideoxycytidine-induced neuropathic pain in the rat and the mouse

Several lines of evidence suggest that descending serotoninergic facilitatory pathways are involved in neuropathic pain. These pathways may involve 5-HT2A receptors known to play a role in spinal and peripheral sensitization. The implication of this receptor in neuropathy was investigated in a model of peripheral neuropathy induced by 2',3'-dideoxycytidine, a nucleoside analogue with reverse transcriptase inhibitory properties used in HIV/AIDS therapy. Four days after a single 100mg/kg i.v. administration in the tail vein, mitochondrial alterations in nociceptive and non-nociceptive dorsal root ganglion cells were observed at the lumbar level. These alterations were not associated with TUNEL labelling or with modification of the total number of dorsal root ganglion cells. At the same time point, 5-HT2A receptor immunolabelling was increased throughout the dorsal horn (by 49.5% in layer II and 57.8% in layer III). The number of 5-HT2A receptor immunoreactive neurons in the dorsal root ganglion was also increased by 30.7%. Four days after 2',3'-dideoxycytidine administration, rats had developed thermal allodynia as well as mechanical hyperalgesia and allodynia, which dose-dependently decreased after epidural injection of MDL 11,939, a 5-HT2A receptor antagonist. Moreover, 5-HT2A receptor knock-out mice did not develop 2',3'-dideoxycytidine-induced neuropathy whereas their control littermates displayed a neuropathy comparable to that observed in rats. Our data show that 2',3'-dideoxycytidine-induced neuropathy is associated with alterations of nociceptive and non-nociceptive peripheral cells and that the 5-HT2A receptor is involved in the peripheral sensitization of nociceptors as well as in a wide central sensitization of dorsal horn neurons.

Neurologic consequences of hepatitis C and human immunodeficiency virus coinfection

Human immunodeficiency virus (HIV) and hepatitis C virus (HCV) share overlapping, large worldwide distribution. The implications of coinfection are being explored because of the importance of these viruses and demographic factors that favor coinfection. The nervous system is affected by HIV in a variety of ways resulting in significant disease of all levels of the nervous system. Emerging evidence that HCV can also impact the nervous system raises concerns that detrimental interactions might occur. Several reports addressing the manifestations of coinfection support independent contributions for both HIV and HCV on central nervous system performance, but not on distal sensory neuropathy. Neuropsychological testing reveals independent contributions resulting in poorer performance in coinfection in several drug-abusing cohorts. Motor physiologic testing substantiates performance deficits from HCV in coinfected subjects as does testing in treatment naive coinfected subjects. Although ongoing deficits attributed to HCV may be seen during HIV treatment, these deficits may be less apparent in advanced HIV disease. Current evidence supports independent contributions of HCV and HIV to neurological impairment. Preliminary evidence suggests that coinfection-related impairment does not appear to accelerate HIV-1-associated cognitive disease.

Hemochromatosis (HFE) gene mutations and peripheral neuropathy during antiretroviral therapy

OBJECTIVE

Peripheral neuropathy (PN) often complicates nucleoside reverse transcriptase inhibitor (NRTI) therapy of HIV infection and may involve mitochondrial dysfunction. Since iron deficiency is associated with some types of PN, and iron is essential for mitochondrial function, we tested the hypothesis that hemochromatosis (HFE) gene mutations influence susceptibility to NRTI-induced PN.

DESIGN

Case-control study involving multicenter, AIDS Clinical Trials Group (ACTG) protocol 384 and ACTG Human DNA Repository specimens.

METHODS

Study participants were randomized to receive three- or four-drug antiretroviral therapy with didanosine (ddI) plus stavudine (d4T) or zidovudine plus lamivudine, given with efavirenz, nelfinavir, or both, with up to three years of follow-up. PN was ascertained based on signs and symptoms. HFE C282Y and H63D genotypes were determined, and associations with PN were assessed using logistic regression.

RESULTS

: Of 509 participants, 147 (29%) developed PN, 73% of whom had been randomized to receive ddI plus d4T. Among ddI/d4T-ever-treated individuals, HFE C282Y heterozygotes developed PN on ddI/d4T significantly less often than C282Y non-carriers, adjusting for age, CD4 lymphocyte count and viral load at baseline, and concomitant antiretroviral drugs [6% vs. 35%, respectively, in whites; adjusted odds ratio (OR), 0.17; 95% confidence interval (CI) 0.03-0.83; P = 0.021]. Regardless of race/ethnicity, ddI/d4T-associated PN was uncommon in C282Y heterozygotes [race-adjusted OR, 0.30; 95% CI 0.09-0.96); P = 0.042].

CONCLUSIONS

Iron-loading HFE mutations such as C282Y are associated with a decreased risk of PN during antiretroviral therapy. This finding has potential implications for the prediction and prevention of NRTI-associated PN, particularly in populations at risk of iron deficiency.

HIV-1, chemokines and neurogenesis

HIV-1 infection of the brain results in a large number of behavioural defecits accompanied by diverse neuropathological signs. However,it is not clear how the virus produces these effects or exactly how the neuropathology and behavioural defecits are related. In this article we discuss the possibility that HIV-1 infection may negatively impact the process of neurogenesis in the adult brain and that this may contribute to HIV-1 related effects on the nervous system. We have previously demonstrated that the development of the dentate gyrus during embryogenesis requires signaling by the chemokine SDF-1 via its receptor CXCR4. We demonstrated that neural progenitor cells that give rise to dentate granule neurons express CXCR4 and other chemokine receptors and migrate into the nascent dentate gyrus along SDF-1 gradients. Animals deficient in CXCR4 receptors exhibit a malformed dentate gyrus in which the migration of neural progenitors is stalled. In the adult, neurogenesis continues in the dentate gyrus. Adult neural progenitor cells existing in the subgranlar zone, that produce granule neurons, express CXCR4 and other chemokine receptors, and granule neurons express SDF-1 suggesting that SDF-1/CXCR4 signaling is also important in adult neurogenesis. Because the cellular receptors for HIV-1 include chemokine receptors such as CXCR4 and CCR5 it is possible that the virus may interfere with SDF-1/CXCR4 signaling in the brain including disruption of the formation of new granule neurons in the adult brain.

Chemokines: integrators of pain and inflammation

Chronic (neuropathic) pain is one of the most widespread and intractable of human complaints, as well as being one of the most difficult syndromes to treat successfully with drugs or surgery. The development of new therapeutic approaches to the treatment of painful neuropathies requires a better understanding of the mechanisms that underlie the development of these chronic pain syndromes. It is clear that inflammatory responses often accompany the development of neuropathic pain, and here we discuss the idea that chemokines might be key to integrating the development of pain and inflammation and could furnish new leads in the search for effective analgesic agents for the treatment of painful neuropathies.

HIV-associated neuropathic pain: epidemiology, pathophysiology and management

Peripheral neuropathy is associated with numerous systemic illnesses including HIV infection. Neuropathic pain constitutes approximately 25-50% of all pain clinic visits. Distal symmetrical polyneuropathy (DSP) is the most common form of peripheral neuropathy in individuals with HIV infection. DSP is distinguished from other forms of neuropathy on the basis of history and neurological examination. The pain associated with DSP can be debilitating. Therefore, it is important to diagnose HIV-associated DSP properly and treat the neuropathic pain in order to improve quality of life. We review the clinical manifestations, epidemiology, pathophysiology and management strategies for HIV-associated DSP.

Sensory neuron diseases

Sensory neuron diseases (SND) are a distinct subgroup of peripheral-nervous-system diseases, first acknowledged in 1948. Acquired SND have a subacute or chronic course and are associated with systemic immune-mediated diseases, vitamin intoxication or deficiency, neurotoxic drugs, and life-threatening diseases such as cancer. SND are commonly idiopathic but can be genetic diseases; the latter tend to involve subtypes of sensory neurons and are associated with certain clinical pictures. The loss of sensory neurons in dorsal root ganglia causes the degeneration of short and long peripheral axons and central sensory projections in the posterior columns. This pathological process leads to a pattern of sensory nerve degeneration that is not length dependent and explains distinct clinical and neurophysiological abnormalities. Here we propose a comprehensive approach to the diagnosis of acquired and hereditary SND and discuss clinical, genetic, neurophysiological, neuroradiological, and neuropathological assessments.

Mitochondrial Dna Levels of Peripheral Blood Mononuclear Cells and Subcutaneous Adipose Tissue from Thigh, Fat and Abdomen of HIV-1 Seropositive and Negative Individuals

Mitochondrial dysfunction has been demonstrated in subcutaneous adipose tissue from lipoatrophic HIV-1-infected patients treated with nucleoside reverse transcriptase inhibitors (NRTIs). To further assess mitochondrial toxicity, mitochondrial DNA (mtDNA) copies/cell were measured in subcutaneous fat from various sites. Peripheral adipose tissues were obtained from the abdominal wall near the umbilicus, anterior lateral thigh, and dorsal cervical region of the neck of individuals from four cohorts: 1) seven lipoatrophic HIV-1-infected patients receiving a regimen with nucleoside reverse transcriptase inhibitors (NRTIs) as part of highly active antiretroviral therapy (HAART) for >6 months; 2) seven non-lipoatrophic HIV-1-infected patients receiving NRTIs-containing HAART; 3) five HIV-1-infected patients on antiretroviral therapy <2 weeks (naive); 4) and five HIV-1-negative participants. Along with the adipose tissue samples, peripheral blood mononuclear cells (PBMC) were also obtained from each patient for mtDNA depletion examination. Total DNA was isolated and mtDNA copies/cell quantitated by competitive and realtime PCR. MtDNA copies/cell in abdomen, thigh, and neck fat were depleted in lipoatrophic HIV-1 seropositive compared to the seropositive naive and seronegative cohorts. MtDNA copies/cell in thigh and neck fat were also decreased in non-lipoatrophic subjects exposed to NRTIs compared with NRTI-naive and HIV seronegative controls. PBMC values did not differ among the cohorts and there was no correlation with lipoatrophy state or HIV-1 serostatus. Additionally, differences in mtDNA copies/cell were observed in the fat depots from seronegative subjects. Thigh fat mtDNA levels were 45–55% lower than abdomen and neck. These studies help demonstrate that mtDNA levels can vary in different subcutaneous adipose depots suggesting possible metabolic differences.

Controlling neuropathic pain in HIV

Neuropathic pain is associated with numerous systemic illnesses, including HIV infection. The diagnosis and management of peripheral neuropathy presents diagnostic and therapeutic challenges. Among various forms of HIV-associated peripheral neuropathies, distal symmetrical polyneuropathy (DSP) is the most common. DSP may be caused or exacerbated by neurotoxic antiretrovirals, particularly the dideoxynucleoside analogues (d-drugs). Selection of appropriate pharmacologic intervention for peripheral neuropathy should be based on efficacy, safety, ease of administration, and cost. We review treatment options for painful HIV neuropathy, including experimental agents studied in recent and ongoing clinical trials.

Mitochondrial effects of HIV infection on the peripheral blood mononuclear cells of HIV-infected patients who were never treated with antiretrovirals

To investigate the effects of HIV infection on mitochondrial DNA (mtDNA) content and other mitochondrial parameters, we used peripheral blood mononuclear cells (PBMCs) from 25 asymptomatic antiretroviral-naive human immunodeficiency virus (HIV)-infected patients and from 25 healthy control subjects. HIV-infected patients had significant decreases in mtDNA content (decrease, 23%; P<.05) and in the activities of mitochondrial respiratory chain (MRC) complex II (decrease, 41%; P<.001), MRC complex III (decrease, 38%; P<.001), MRC complex IV (decrease, 19%; P=.001), and glycerol-3-phosphate dehydrogenase (decrease, 22%; P<.001), along with increased lipid peroxidation of PBMC membranes (P=.007). Therefore, HIV infection is associated not only with mtDNA depletion, but also with extensive MRC disturbances and increased oxidative damage.

Activation of c-Jun N-terminal kinase mediates gp120IIIB- and nucleoside analogue-induced sensory neuron toxicity

Peripheral neuropathy is the most common neurological symptom in patients with acquired immunodeficiency syndrome (AIDS). Here, we examine possible mechanisms of gp120 and nucleoside reverse transcriptase inhibitors (NRTIs) in the pathogenesis of AIDS peripheral neuropathy. Neonatal dorsal root ganglion (DRG) neurons were found to undergo apoptosis in response to chronic treatment with gp120IIIB, an effect enhanced by the co-application of hCD4, as well as upon exposure to the nucleoside reverse transcriptase inhibitor (NRTI), 2',3'-dideoxyinosine (ddI). DRG neurons were rescued from the neurotoxic effects of these agents by CEP-1347, an inhibitor of the mixed lineage kinases (MLKs), upstream activators of the c-Jun N-terminal kinase (JNK) signaling pathway. In addition, gp120- or ddI-mediated toxicity were also inhibited by neuronal expression of dominant negative versions of the MLKs. Our results suggest that both gp120 and the NRTIs cause sensory neuron apoptosis through the activation of the JNK pathway, and that CEP-1347-like compounds may serve as a therapeutic option in patients with AIDS-associated peripheral neuropathy.

Controlling Neuropathic Pain in HIV

Neuropathic pain is associated with numerous systemic illnesses, including HIV infection. The diagnosis and management of peripheral neuropathy presents diagnostic and therapeutic challenges. Among various forms of HIV-associated peripheral neuropathies, distal symmetrical polyneuropathy (DSP) is the most common. DSP may be caused or exacerbated by neurotoxic antiretrovirals, particularly the dideoxynucleoside analogues (d-drugs). Selection of appropriate pharmacologic intervention for peripheral neuropathy should be based on efficacy, safety, ease of administration, and cost. We review treatment options for painful HIV neuropathy, including experimental agents studied in recent and ongoing clinical trials.

The cellular pharmacology of nucleoside- and nucleotide-analogue reverse-transcriptase inhibitors and its relationship to clinical toxicities

Nucleoside- and nucleotide-analogue reverse-transcriptase inhibitors (NRTIs) require intracellular phosphorylation for anti-human immunodeficiency virus (HIV) activity and toxicity. Long-term toxicities associated with NRTIs may be related to overactivation of this process. In vitro experiments have shown increased rates of NRTI and endogenous nucleoside phosphorylation to be associated with cellular activation. Patients with advanced HIV disease often have overexpression of cytokines, which corresponds to an elevated cellular activation state. These patients also have higher rates of NRTI phosphorylation and NRTI toxicity, suggesting an interaction between a proinflammatory biological state, NRTI phosphorylation, and toxicity. Studies suggest that women may have higher rates of NRTI phosphorylation than do men, as well as increased risk for NRTI-induced toxicity. Future research is needed to understand the NRTI activation process and improve the long-term toxicity profile of NRTIs. Such research should include comparisons of NRTI phosphorylation according to sex and cellular activation state (i.e., elevated vs. low).