Nerve growth factor acts through the TrkA receptor to protect sensory neurons from the damaging effects of the HIV-1 viral protein, Vpr.

Distal sensory polyneuropathy (DSP) with associated neuropathic pain is the most common neurological disorder affecting patients with human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS). Viral protein R (Vpr) is a neurotoxic protein encoded by HIV-1 and secreted by infected macrophages. Vpr reduces neuronal viability, increases cytosolic calcium and membrane excitability of cultured dorsal root ganglion (DRG) sensory neurons, and is associated with mechanical allodynia in vivo. A clinical trial with HIV/AIDS patients demonstrated that nerve growth factor (NGF) reduced the severity of DSP-associated neuropathic pain, a problem linked to damage to small diameter, potentially NGF-responsive fibers. Herein, the actions of NGF were investigated in our Vpr model of DSP and we demonstrated that NGF significantly protected sensory neurons from the effects of Vpr. Footpads of immunodeficient Vpr transgenic (vpr/RAG1(-/-)) mice displayed allodynia (p<0.05), diminished epidermalinnervation (p<0.01) and reduced NGF mRNA expression (p<0.001) compared to immunodeficient (wildtype/RAG1(-/-)) littermate control mice. Compartmented cultures confirmed recombinant Vpr exposure to the DRG neuronal perikarya decreased distal neurite extension (p<0.01), whereas NGF exposure at these distal axons protected the DRG neurons from the Vpr-induced effect on their cell bodies. NGF prevented Vpr-induced attenuation of the phosphorylated glycogen synthase-3 axon extension pathway and tropomyosin-related kinase A (TrkA) receptor expression in DRG neurons (p<0.05) and it directly counteracted the cytosolic calcium burst caused by Vpr exposure to DRG neurons (p<0.01). TrkA receptor agonist indicated that NGFacted through the TrkA receptor to block the Vpr-mediated decrease in axon outgrowth in neonatal and adult rat and fetal human DRG neurons (p<0.05). Similarly, inhibiting the lower affinity NGF receptor, p75, blocked Vpr's effect on DRG neurons. Overall, NGF/TrkA signaling or p75 receptor inhibition protects somatic sensory neurons exposed to Vpr, thus laying the groundwork for potential therapeutic options for HIV/AIDS patients suffering from DSP.

Gamma-glutamyl transpeptidase level is a novel adverse prognostic indicator in human metastatic colorectal cancer.

AIM: Biomarkers have been utilized for prognosis in colorectal cancer; however, relatively few have been identified. We compared the prognostic value of serum alkaline phosphatase (ALP), lactate dehydrogenase (LDH) and gamma-glutamyl transpeptidase (GGT) with carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9) in patients with metastatic colorectal cancer (mCRC). METHOD: Blood samples were collected from 239 patients with mCRC presenting between 2005 and 2010 in the Sun Yat-sen University Cancer Center. RESULTS: CEA (P < 0.001), CA19-9 (P < 0.001), GGT (P < 0.001), ALP (P < 0.001) and LDH (P = 0.001) were statistically significant prognostic factors of overall survival (OS). CEA (P = 0.002) and GGT (P = 0.021) were validated as independent predictors. On univariate analysis, CEA (P = 0.003), CA19-9 (P = 0.006), GGT (P < 0.001) and ALP (P = 0.001) were statistically significant predictive factors of progression-free survival (PFS) in patients having first-line chemotherapy. CEA (P = 0.011) and GGT (P = 0.027) were independent predictors. GGT (P = 0.001), ALP (P = 0.016) and LDH (P = 0.039) levels were correlated with the tumour response rate assessed by CT, whilst CEA (P = 0.724) and CA19-9 (P = 0.822) were not. There was a statistically significant difference in OS (P < 0.001) and PFS (P < 0.001) among patients who had elevations of both CEA and GGT compared with those in whom only one or neither was elevated. CONCLUSION: Among GGT, LDH and ALP, only GGT plays an independent role with CEA in predicting OS and PFS in mCRC. When coupled with CEA, GGT may lead to improved prognostic predictors.

Overexpression of human HSP27 protects sensory neurons from diabetes.

OBJECTIVES: To evaluate whether augmenting neuronal protective mechanisms might slow or arrest experimental diabetic peripheral neuropathy (DPN). DPN is one of the most common neurodegenerative disorders and is rising in prevalence. How it targets sensory neurons is uncertain; the disorder is irreversible and untreatable. We explored the intrinsic protective properties of overexpressed human HSP27 on experimental DPN. HSP27 is a small pro-survival heat shock protein that also increases axonal regeneration. METHODS: Experimental diabetes was superimposed on mice overexpressing a human HSP27 transgene and its impact was evaluated on epidermal innervation, behavioral tests of sensation and electrophysiological indices of DPN. RESULTS: Mice that overexpress human HSP27 in their sensory and motor neurons and that were made diabetic for 6 months by streptozotocin treatment were protected from a range of neuropathic abnormalities, including loss of footpad thermal sensation, mechanical allodynia, loss of epidermal innervation, and slowing of sensory conduction velocity. The protection was selective for sensory neurons in comparison to motor neurons and at 6 months provided better protection in female than male mice. Markers of RAGE-NFκB activation were attenuated by the transgene. CONCLUSIONS: The findings support the idea that diabetic polyneuropathy involves a unique, sensory-centric neurodegenerative process which can be reduced by overexpressing a single gene, an important starting point for new disease-modifying therapeutic approaches.

Activated RHOA and peripheral axon regeneration.

The regeneration of adult peripheral neurons after transection is slow, incomplete and encumbered by severe barriers to proper regrowth. The role of RHOA GTPase has not been examined in this context. We examined the expression, activity and functional role of RHOA GTPase and its ROK effector, inhibitors of regeneration, during peripheral axon outgrowth. We used qRT-PCR, quantitative immunohistochemistry, and assays of RHOA activation to examine expression in sensory neurons of rats with sciatic transection injuries. In vitro, we exposed dissociated adult sensory neurons, not grown on inhibitory substrates, to a RHOA-ROK inhibitor HA-1077 and measured neurite initiation and outgrowth. In vivo, we exposed early regenerating axons and Schwann cells directly to HA-1077 in a conduit connecting the proximal and distal stumps of transected sciatic nerves. Intact adult dorsal root ganglia sensory neurons expressed RHOA and ROK 1 mRNAs and protein and there were rises in RHOA after injury. Activated GTP-bound RHOA, undetectable in intact ganglia, was dramatically upregulated in both neurons and axons after injury. Adult rat sensory neurons in vitro demonstrated a dose-related increase in the initiation of neurite outgrowth, and in the proportion with long neurites when they were exposed to a ROK antagonist. Regenerative bridges that were directly exposed to the ROK inhibitor had a dose-related rise in the extent and distance of in vivo axon and partnered Schwann cell regrowth within them. RHOA activation and signaling are features of adult peripheral axon regeneration within its own milieu, independent of myelin. Inhibition of its activation may benefit peripheral axon lesions.

Local erythropoietin signaling enhances regeneration in peripheral axons.

Erythropoietin (EPO) and its receptor (EPO-R), mediate neuroprotection from axonopathy and apoptosis in the peripheral nervous system (PNS). We examined the impact and potential mechanisms of local EPO signaling on regenerating PNS axons in vivo and in vitro. As a consequence of injury, peripheral nerve axons and DRG neurons have a marked increase in the expression of EPO and EPO-R. Local delivery of EPO via conduit over 2 weeks to rat sciatic nerve following crush injury increased the density and maturity of regenerating myelinated axons growing distally from the crush site. In addition, EPO also rescued retrograde degeneration and atrophy of axons. EPO substantially increased the density and intensity of calcitonin gene-related peptide (CGRP) expression within outgrowing axons. Behavioral improvements in sensorimotor function also occurred in rats exposed to near nerve EPO delivery. EPO delivery led to decreased nuclear factor kappaB (NFkB) activation but increased phosphorylation of Akt and STAT3 within nerve and dorsal root ganglia neurons indicating rescue from an injury phenotype. Spinal cord explant studies also demonstrated a similar dose-dependent effect of EPO upon motor axonal outgrowth. Local EPO signaling enhances regenerating peripheral nervous system axons in addition to its known neuroprotection. Exogenous EPO may have a therapeutic role in a large number of peripheral nerve diseases through its impact on regeneration.

Facilitated sprouting in a peripheral nerve injury.

During regeneration of injured peripheral nerves, local conditions may influence how regenerative axon sprouts emerge from parent axons. More extensive lesions might be expected to disrupt such growth. In this work, we discovered instead that long segmental crush injuries facilitate the growth and maturation of substantially more axon sprouts than do classical short crush injuries (20 mm length vs. 2 mm). At identical distances from the proximal site of axon interruption there was a 45% rise in the numbers of neurofilament labeled axons extending through a long segmental crush zone by 1 week. By 2 weeks, there was a 35% greater density of regenerating myelinated axons in long compared with short crush injuries just beyond (5 mm) the proximal injury site. Moreover, despite the larger numbers of axons, their maturity was identical and they were regular, parallel, associated with Schwann cells (SCs) and essentially indistinguishable between the injuries. Backlabeling with Fluorogold indicated that despite these differences, the axons arose from similar numbers of parent motor and sensory neurons. Neither injury was associated with ischemia. Both injuries were associated with rises in GFAP (glial acidic fibrillary protein) and p75 mRNAs, markers of SC plasticity but p75, GFAP and brain-derived neurotrophic factor mRNAs did not differ between the injuries. There was a higher local mRNA level of GAP43/B50 at 7 days following injury and a higher sonic hedgehog protein (Shh) mRNA at 24 h in long crush zones. GAP43/B50 protein and SHH protein both had prominent localization within regenerating axons. Long segmental nerve trunk crush injuries do not impair regeneration but instead generate greater axon plasticity that results in larger numbers of mature myelinated axons. The changes occur without apparent change in SC activation, overall nerve architecture or nerve blood flow. While the mechanism is uncertain, the findings indicate that manipulation of the nerve microenvironment can induce substantial changes in regenerative sprouting.

Building international partnerships.

Health is a global concern. Although nursing is a global profession, most schools of nursing concentrate on teaching health exclusively within the context of their own nation. Sister-school partnerships that cross national boundaries are one way of extending the learning opportunities of faculties and students. An example of a 5-year partnership is described and analysed.

Reversible infra-Hisian atrioventricular block in acute myocarditis.

Symptomatic second- or third-degree atrioventricular (AV) block at any anatomical level is a class I indication for permanent pacemaker implantation. We describe a 44-year-old male with acute viral myocarditis who suffered from syncope followed by a seizure attack associated with AV conduction disturbance. His initial electrocardiogram in our emergency room revealed sinus tachycardia with 2:1 AV conduction and a right bundle branch block QRS morphology with a ventricular rate of 60 beats/min. Because of episodic slowing of the heart rate below 40 beats/min, he received 1 mg atropine intravenously which increased the atrial rate but further worsened the AV conduction, resulting in ventricular asystole for more than 30 seconds associated with loss of consciousness and seizure-like activity. He was immediately paced transcutaneously and transferred to the catheterization laboratory to receive temporary transvenous cardiac pacing. The cardiac catheterization study showed a normal coronary angiogram and very mild diffuse hypokinesis. Electrophysiological studies revealed advanced infra-Hisian AV block. The infra-Hisian AV block, however, resolved rapidly in 2 days. The patient did not receive a permanent pacemaker and remained asymptomatic with normal electrocardiogram over 1 year of follow-up. We suggest that symptomatic infra-Hisian AV block due to viral myocarditis can be reversible, and implantation of a permanent pacemaker may not be necessary.