PAIN HYPERSENSITIVITY IN SLURP1 AND SLURP2 KNOCKOUT MOUSE MODELS OF HEREDITARY PALMOPLANTAR KERATODERMA.

SLURP1 and SLURP2 are both small secreted members of the Ly6/u-PAR family of proteins and are highly expressed in keratinocytes. Loss of function mutations in SLURP1 lead to a rare autosomal recessive Palmoplantar Keratoderma (PPK), Mal de Meleda (MdM), which is characterized by diffuse, yellowish palmoplantar hyperkeratosis. Some individuals with MdM experience pain in conjunction with the hyperkeratosis that has been attributed to fissures or microbial superinfection within the affected skin. By comparison, other hereditary PPKs such as Pachyonychia congenita (PC) and Olmsted syndrome (OS) show prevalent pain in PPK lesions. Two mouse models of MdM, Slurp1 knockout and Slurp2X knockout, exhibit robust PPK in all four paws. However, whether the sensory experience of these animals including augmented pain sensitivity remains unexplored. In this study, we demonstrate that both models exhibit hypersensitivity to mechanical and thermal stimuli as well as spontaneous pain behaviors in males and females. Anatomical analysis revealed increased paw pad skin epidermal innervation and substantial alterations in palmoplantar skin immune composition in Slurp2X knockout mice. Primary sensory neurons innervating hind paw glabrous skin from Slurp2X knockout mice exhibit increased incidence of spontaneous activity and mechanical hypersensitivity both in vitro and in vivo. Thus, Slurp knockout mice exhibit polymodal PPK-associated pain that is associated with both immune alterations and neuronal hyperexcitability, and might therefore be useful for the identification of therapeutic targets to treat PPK-associated pain.Significance Statement Palmoplantar keratodermas (PPKs) are rare human skin disorders associated with thickening of the skin on the palms and soles. Pain is a common feature of some PPKs, yet the causes of PPK-associated pain are not understood. Here we show that two mouse models of one PPK, SLURP1 knockout mice and SLURP2 knockout mice, exhibit enhanced pain sensitivity and increased activity of pain-associated sensory neurons. These mouse lines will therefore be of value in defining causes of pain in PPKs and possibly developing improved therapies for that pain.

Monocarboxylate transporter 1 in Schwann cells contributes to maintenance of sensory nerve myelination during aging.

Schwann cell (SC)-specific monocarboxylate transporter 1 (MCT1) knockout mice were generated by mating MCT1 f/f mice with myelin protein zero (P0)-Cre mice. P0-Cre+/- , MCT1 f/f mice have no detectable early developmental defects, but develop hypomyelination and reduced conduction velocity in sensory, but not motor, peripheral nerves during maturation and aging. Furthermore, reduced mechanical sensitivity is evident in aged P0-Cre+/- , MCT1 f/f mice. MCT1 deletion in SCs impairs both their glycolytic and mitochondrial functions, leading to altered lipid metabolism of triacylglycerides, diacylglycerides, and sphingomyelin, decreased expression of myelin-associated glycoprotein, and increased expression of c-Jun and p75-neurotrophin receptor, suggesting a regression of SCs to a less mature developmental state. Taken together, our results define the contribution of SC MCT1 to both SC metabolism and peripheral nerve maturation and aging.

Neuropathy symptom and change: Inotersen treatment of hereditary transthyretin amyloidosis.

INTRODUCTION: Hereditary transthyretin-mediated amyloidosis (hATTR) manifests as multisystem dysfunction, including progressive polyneuropathy. Inotersen, an antisense oligonucleotide, improved the course of neuropathic impairment in patients with hATTR in the pivotal NEURO-TTR study (NCT01737398). To determine inotersen's impact on symptoms and patients' neuropathy experience, we performed a post hoc analysis of the Neuropathy Symptoms and Change (NSC) score. METHODS: Stage 1 or 2 hATTR patients were randomized to receive weekly subcutaneous inotersen or placebo for 65 weeks. NSC score was assessed at baseline and 35 and 66 weeks. RESULTS: At 66 weeks, inotersen-treated patients had symptom stabilization as compared with worsening in patients receiving placebo, based on total NSC score. There were also improvements in the subdomains of muscle weakness, sensory, pain, and autonomic symptoms, and for various individual items. DISCUSSION: Inotersen treatment stabilized neuropathy symptoms, including autonomic symptoms, in patients with hATTR according to NSC score. Thus, the NSC may be an effective measure to assess neuropathy progression and patients' neuropathy experience in clinical practice.

An oral form of methylglyoxal-bis-guanylhydrazone reduces monocyte activation and traffic to the dorsal root ganglia in a primate model of HIV-peripheral neuropathy.

Peripheral neuropathy (PN) is a major comorbidity of HIV infection that is caused in part by chronic immune activation. HIV-PN is associated with infiltration of monocytes/macrophages to the dorsal root ganglia (DRG) causing neuronal loss and formation of Nageotte nodules. Here, we used an oral form of methylglyoxal-bis-guanylhydrazone (MGBG), a polyamine biosynthesis inhibitor, to specifically reduce activation of myeloid cells. MGBG is selectively taken up by monocyte/macrophages in vitro and inhibits HIV p24 expression and DNA viral integration in macrophages. Here, MGBG was administered to nine SIV-infected, CD8-depleted rhesus macaques at 21 days post-infection (dpi). An additional nine SIV-infected, CD8-depleted rhesus macaques were used as untreated controls. Cell traffic to tissues was measured by in vivo BrdU pulse labeling. MGBG treatment significantly diminished DRG histopathology and reduced the number of CD68+ and CD163+ macrophages in DRG tissue. The number of recently trafficked BrdU+ cells in the DRG was significantly reduced with MGBG treatment. Despite diminished DRG pathology, intraepidermal nerve fiber density (IENFD) did not recover after treatment with MGBG. These data suggest that MGBG alleviated DRG pathology and inflammation.

Monocyte Traffic, Dorsal Root Ganglion Histopathology, and Loss of Intraepidermal Nerve Fiber Density in SIV Peripheral Neuropathy.

HIV-associated sensory neuropathy remains the most common neurological complication of HIV infection and is characterized by dorsal root ganglion (DRG) inflammation and intraepidermal nerve fiber density (IENFD) loss. Chronic peripheral immune cell activation and accumulation may cause damage to the DRG, but has not been fully investigated yet. By using an SIV-infected, CD8-lymphocyte-depleted rhesus macaque model, we defined immune cells surrounding DRG neurons and their role in DRG pathology, measured cell traffic from the bone marrow to the DRGs using 5-bromo-2-deoxyuridine (BrdU) pulse, and serially measured IENFD. We found an increase in CD68(+) and CD163(+) macrophages in DRGs of SIV-infected animals. MAC387(+) recently recruited monocytes/macrophages were increased, along with BrdU(+) cells, in the DRGs of SIV-infected macaques. We demonstrated that 78.1% of all BrdU(+) cells in DRGs were also MAC387(+). The number of BrdU(+) monocytes correlated with severe DRG histopathology, which included neuronophagia, neuronal loss, and Nageotte nodules. These data demonstrate that newly recruited MAC387(+)BrdU(+) macrophages may play a significant role in DRG pathogenesis. IENFD decreased early (day 21), consistent with the development of sensory neuropathy in SIV-infected macaques. Decreased IENFD was associated with elevated BrdU(+) cells in the DRG. These data suggest that increased recruitment of macrophages to DRG is associated with severe DRG histopathology and IENFD loss.

Loss of intraepidermal nerve fiber density during SIV peripheral neuropathy is mediated by monocyte activation and elevated monocyte chemotactic proteins.

BACKGROUND: Peripheral neuropathy (PN) continues to be a major complication of human immunodeficiency virus (HIV) infection despite successful anti-retroviral therapy. Human HIV-PN can be recapitulated in a CD8-depleted, simian immunodeficiency virus (SIV)-infected rhesus macaque animal model, characterized by a loss of intraepidermal nerve fiber density (IENFD) and damage to the dorsal root ganglia (DRG). Increased monocyte traffic to the DRG has previously been associated with severe DRG pathology, as well as a loss in IENFD. Here, we sought to characterize the molecular signals associated with monocyte activation and trafficking to the DRGs. METHODS: Eleven SIV-infected CD8-depleted rhesus macaques were compared to four uninfected control animals. sCD14, sCD163, sCD137, regulated on activation normal T cell expressed and secreted (RANTES), and monocyte chemoattractant protein 1 (MCP-1) were measured in plasma and the latter three proteins were also quantified in DRG tissue lysates. All SIV-infected animals received serial skin biopsies to measure IENFD loss as well as BrdU inoculations to measure monocyte turnover during the course of infection. The number of BrdU+ and CD14+ CD16+ peripheral blood monocytes was determined by flow cytometry. The number of MAC387+, CCR2+, CCR5+, and CD137+ cells in DRG tissue was quantified by immunohistochemistry. RESULTS: sCD14, sCD163, MCP-1, and sCD137 increased significantly in plasma from pre-infection to necropsy. Plasma sCD163 and RANTES inversely correlated with IENFD. Additionally, sCD137 in DRG tissue lysate was elevated with severe DRG pathology and associated with the recruitment of MAC387+ cells to DRG. Elevated numbers of CCR5+ and CCR2+ satellite cells in the DRG were found, suggesting a chemotactic role of their ligands, RANTES, and MCP-1 in recruiting monocytes to the tissue. CONCLUSIONS: We characterized the role of systemic (plasma) and tissue-specific (DRG) monocyte activation and associated cytokines in the pathogenesis of SIV-PN. We identified sCD163 and RANTES as potential biomarkers for HIV-PN, as these were associated with a loss of IENFD. Additionally, we identified CD137 signaling to play a role in MAC387+ cell traffic to DRG and possibly contribute to severe pathology. These studies highlight the role of monocyte activation and traffic in the pathogenesis of SIV-PN, while identifying specific signaling proteins for future pharmacological blockade.

Long-term efficacy and safety of inotersen for hereditary transthyretin amyloidosis: NEURO-TTR open-label extension 3-year update.

BACKGROUND: Hereditary transthyretin amyloidosis (hATTR/ATTRv) results from the deposition of misfolded transthyretin (TTR) throughout the body, including peripheral nerves. Inotersen, an antisense oligonucleotide inhibitor of hepatic TTR production, demonstrated a favorable efficacy and safety profile in patients with the polyneuropathy associated with hATTR in the NEURO-TTR (NCT01737398) study. We report longer-term efficacy and safety data for inotersen, with a median treatment exposure of 3 years. METHODS: Patients who satisfactorily completed NEURO-TTR were enrolled in its open-label extension (OLE) study. Efficacy assessments included the modified Neuropathy Impairment Score + 7 (mNIS + 7), Norfolk Quality of Life-Diabetic Neuropathy (Norfolk QoL-DN) questionnaire total score, and the Short Form 36 (SF-36v2) Health Survey Physical Component Summary score. Safety and tolerability were also assessed. Efficacy is reported for patients living in Europe and North America (this cohort completed the study approximately 9 months before the remaining group of patients outside these regions); safety is reported for the full safety dataset, comprising patients living in Europe, North America, and Latin America/Australasia. This study is registered with ClinicalTrials.gov, identifier NCT02175004. RESULTS: In the Europe and North America cohort of the NEURO-TTR study, 113/141 patients (80.1%) completed the study, and 109 patients participated in the OLE study. A total of 70 patients continued to receive inotersen (inotersen-inotersen) and 39 switched from placebo to inotersen (placebo-inotersen). The placebo-inotersen group demonstrated sustained improvement in neurological disease progression as measured by mNIS + 7, compared with predicted worsening based on projection of the NEURO-TTR placebo data (estimated natural history). The inotersen-inotersen group demonstrated sustained benefit, as measured by mNIS + 7, Norfolk QoL-DN, and SF-36v2, compared with estimated natural history as well as compared with the placebo-inotersen group. With a maximum exposure of 6.2 years, inotersen was not associated with any additional safety concerns or increased toxicity in the OLE study. Platelet and renal monitoring were effective in reducing the risk of severe adverse events in the OLE study. CONCLUSION: Inotersen treatment for > 3 years slowed progression of the polyneuropathy associated with hATTR, and no new safety signals were observed.

The diagnostic challenges of cardiac amyloidosis: A practical approach to the two main types.

Systemic amyloidosis of the immunoglobulin light-chain (AL) or transthyretin type (ATTR) is a multisystem protein deposition disease that often involves the heart. Delays in diagnosis are very common and can have detrimental consequences on patient outcomes. Because both major types can now be distinguished quickly and treated effectively, clear approaches are required. There have been advances in radioisotope scintigraphy, monoclonal protein testing and mass spectrometry for typing that need coordinated application. We have entered an era in which rapid diagnosis and ready therapy will save lives, therefore we must develop coherent approaches to this multisystem disease. The prognosis for AL has improved significantly with the incorporation of novel agents such as proteasome inhibitors, immunomodulators and monoclonal antibodies against plasma cells. Multiple independent studies have demonstrated the efficacy of these agents in AL, though tolerability can become an issue with dose reductions required in many cases. Median overall survival for patients achieving complete responses after stem cell transplant and consolidation exceeds a decade. The prognosis for ATTR, both age-related wild-type (ATTRwt) and hereditary due to variants of transthyretin (ATTRv), has improved as well due to the availability of the stabilizer tafamidis and the RNA-interference agents patisiran and inotersen. In both AL and ATTR, with elimination or suppression of the pathologic amyloid-forming protein, symptomatic involvement of the heart, kidneys and peripheral nervous system can improve as well. In this review, we present the current state of diagnosing and treating the two major types of systemic amyloidosis, emphasizing the coherent clinical application of the new tools and treatments. Implementation of the approaches we provide will enable rapid identification of amyloid type and rational selection of therapy.

Research design considerations for chronic pain prevention clinical trials: IMMPACT recommendations.

Although certain risk factors can identify individuals who are most likely to develop chronic pain, few interventions to prevent chronic pain have been identified. To facilitate the identification of preventive interventions, an IMMPACT meeting was convened to discuss research design considerations for clinical trials investigating the prevention of chronic pain. We present general design considerations for prevention trials in populations that are at relatively high risk for developing chronic pain. Specific design considerations included subject identification, timing and duration of treatment, outcomes, timing of assessment, and adjusting for risk factors in the analyses. We provide a detailed examination of 4 models of chronic pain prevention (ie, chronic postsurgical pain, postherpetic neuralgia, chronic low back pain, and painful chemotherapy-induced peripheral neuropathy). The issues discussed can, in many instances, be extrapolated to other chronic pain conditions. These examples were selected because they are representative models of primary and secondary prevention, reflect persistent pain resulting from multiple insults (ie, surgery, viral infection, injury, and toxic or noxious element exposure), and are chronically painful conditions that are treated with a range of interventions. Improvements in the design of chronic pain prevention trials could improve assay sensitivity and thus accelerate the identification of efficacious interventions. Such interventions would have the potential to reduce the prevalence of chronic pain in the population. Additionally, standardization of outcomes in prevention clinical trials will facilitate meta-analyses and systematic reviews and improve detection of preventive strategies emerging from clinical trials.

Reducing monocarboxylate transporter MCT1 worsens experimental diabetic peripheral neuropathy.

Diabetic peripheral neuropathy (DPN) is one of the most common complications in diabetic patients. Though the exact mechanism for DPN is unknown, it clearly involves metabolic dysfunction and energy failure in multiple cells within the peripheral nervous system. Lactate is an alternate source of metabolic energy that is increasingly recognized for its role in supporting neurons. The primary transporter for lactate in the nervous system, monocarboxylate transporter-1 (MCT1), has been shown to be critical for peripheral nerve regeneration and metabolic support to neurons/axons. In this study, MCT1 was reduced in both sciatic nerve and dorsal root ganglia in wild-type mice treated with streptozotocin (STZ), a common model of type-1 diabetes. Heterozygous MCT1 null mice that developed hyperglycemia following STZ treatment developed a more severe DPN compared to wild-type mice, as measured by greater axonal demyelination, decreased peripheral nerve function, and increased numbness to innocuous low-threshold mechanical stimulation. Given that MCT1 inhibitors are being developed as both immunosuppressive and chemotherapeutic medications, our results suggest that clinical development in patients with diabetes should proceed with caution. Collectively, our findings uncover an important role for MCT1 in DPN and provide a potential lead toward developing novel treatments for this currently untreatable disease.

Research design considerations for chronic pain prevention clinical trials: IMMPACT recommendations.

Although certain risk factors can identify individuals who are most likely to develop chronic pain, few interventions to prevent chronic pain have been identified. To facilitate the identification of preventive interventions, an IMMPACT meeting was convened to discuss research design considerations for clinical trials investigating the prevention of chronic pain. We present general design considerations for prevention trials in populations that are at relatively high risk for developing chronic pain. Specific design considerations included subject identification, timing and duration of treatment, outcomes, timing of assessment, and adjusting for risk factors in the analyses. We provide a detailed examination of 4 models of chronic pain prevention (ie, chronic postsurgical pain, postherpetic neuralgia, chronic low back pain, and painful chemotherapy-induced peripheral neuropathy). The issues discussed can, in many instances, be extrapolated to other chronic pain conditions. These examples were selected because they are representative models of primary and secondary prevention, reflect persistent pain resulting from multiple insults (ie, surgery, viral infection, injury, and toxic or noxious element exposure), and are chronically painful conditions that are treated with a range of interventions. Improvements in the design of chronic pain prevention trials could improve assay sensitivity and thus accelerate the identification of efficacious interventions. Such interventions would have the potential to reduce the prevalence of chronic pain in the population. Additionally, standardization of outcomes in prevention clinical trials will facilitate meta-analyses and systematic reviews and improve detection of preventive strategies emerging from clinical trials.

Peripheral nerve toxic effects of nitrofurantoin.

OBJECTIVE: To investigate the role of skin biopsy in nitrofurantoin peripheral neuropathy. DESIGN: We describe the clinical features and skin biopsies of 2 cases of non-length-dependent small-fiber neuropathy/ganglionopathy attributable to nitrofurantoin. SETTING: Clinical evaluation and skin biopsies were performed at a tertiary teaching hospital in Baltimore, Maryland. PATIENTS: A 59-year-old woman with disabling generalized dysesthesia and a 53-year-old woman with progressive burning pain in the perineum and extremities. MAIN OUTCOME MEASURES: Slow or incomplete recovery and possibly irreversible damage. RESULTS: The neuropathy was neither dose dependent nor associated with impaired renal function. Results from nerve conduction studies were normal. Skin biopsies revealed distinctive morphologic changes with clustered terminal nerve swellings without evidence of nerve fiber degeneration. CONCLUSIONS: These distinct morphologic changes associated with nitrofurantoin have not been previously reported to our knowledge. Skin biopsy appears to be helpful in confirming the diagnosis in these patients.

Herpes zoster among persons living with HIV in the current antiretroviral therapy era.

BACKGROUND: Previously, herpes zoster (HZ) was found to occur at a higher rate in the HIV population than the general population. However, there are limited data about the incidence, risk factors, and clinical outcomes of HZ in the current antiretroviral therapy (ART) era. METHODS: We identified HZ episodes in an urban HIV clinic cohort between 2002 and 2009. Three controls were matched to each case, and conditional logistic regression was used to assess for risk factors associated with incident HZ cases. Logistic regression was used to assess for factors associated with complicated HZ. RESULTS: One hundred eighty-three new HZ cases were identified in 4353 patients with 19,752 person-years (PY) of follow-up--an incidence rate 9.3/1000 PY. Cases were majority men (62%) and African American (75%), with a mean age of 39 years (interquartile range, 32-44 years). Fifty patients (28%) had complicated HZ with 12% developing postherpetic neuralgia. In multivariate regression, factors associated with the increased risk of HZ were having started ART within 90 days of the episode [adjusted odds ratio (AOR), 4.02; 95% confidence interval (CI), 1.31 to 12.41], having a viral load of >400 copies per milliliter (AOR, 1.49; 95% CI, 1.00 to 2.24), and having a CD4 <350 cells per cubic millimeter (AOR, 2.46; 95% CI, 1.42 to 4.23) or 350 to 500 cells per cubic millimeter (AOR, 2.02; 95% CI, 1.14 to 3.57) as compared with CD4 >500 cells per cubic millimeter. CONCLUSIONS: The incidence of HZ is lower than previously reported in HIV cohorts but remains higher than the general population. Over one fourth of patients developed complicated HZ, which is remarkable given the young age of our population. Risk factors for HZ include markers of poor immune function, suggesting that appropriate ART may reduce the burden of HZ in this population.

The incidence of, risk factors for, and sequelae of herpes zoster among HIV patients in the highly active antiretroviral therapy era.

BACKGROUND: Whereas the incidence, risk factors, and clinical sequelae of herpes zoster have been studied in the general population and in HIV patients in the era before highly active antiretroviral therapy (HAART), they have yet to be fully understood in the current era of HAART. METHODS: We conducted a retrospective cohort study of patients enrolled in an urban HIV clinic between January 1, 1997 and December 31, 2001. Patients with an episode of herpes zoster during this period were identified, and their charts were reviewed. A nested case-control analysis was used to assess factors associated with an initial episode of herpes zoster. Multivariate conditional logistic regression analyses were used to assess risk factors for zoster. Logistic regression was performed to assess factors associated with complicated zoster. RESULTS: Two hundred eighty-two episodes of herpes zoster were identified in 239 patients. Of these episodes, 158 were new occurrences of zoster and 124 were recurrent zoster events. The incidence of zoster during the study period was 3.2 per 100 person-years of follow-up. The incident cases reflected the clinic population, with most patients being male (63%) and African American (77%) and having injection drug use as their HIV risk factor (49%). The mean age of the patients was 41 years. Sixty-seven percent of patients had single dermatomal involvement, and the thorax was involved in 41%. In multivariate regression, being on HAART (odds ratio [OR] = 2.39, 95% confidence interval [CI]: 1.65 to 3.49) and a CD4 count of 50 to 200 cells/mm (OR = 2.69, 95% CI: 1.44 to 5.01) compared with a CD4 count less than 50 cells/mm were associated with an increased risk of zoster. Twenty-eight patients (18%) developed post-herpetic neuralgia (PHN), and 29 patients (18%) had other complications. Male-to-male sex as an HIV risk factor (P = 0.02) and being on HAART at a zoster episode (P = 0.03) were protective against complicated zoster. CONCLUSIONS: Our results suggest that zoster infection rates have not changed in the current HAART era but that a significant percentage of patients develop complications, particularly PHN, which is quite remarkable considering the young age of our population.