Nerve Blood Flow Research Articles

Secreted Factors from Dental Pulp Stem Cells Ameliorated Diabetic Polyneuropathy in Streptozotocin-Induced Diabetic Mice

We previously reported that stem cell transplantation into limb skeletal muscle improved diabetic polyneuropathy (DPN) in diabetic animal models without the differentiation of transplanted cells into neuron, suggesting that the improvement was due to a paracrine effect. The aim of our study is to examine whether the secreted factors from dental pulp stem cells from human exfoliated deciduous teeth (SHED) has a beneficial effect on DPN. Conditioned medium from SHED (SHED-CM) was collected 48 hours after culturing in serum-free DMEM. Incubation of dorsal root ganglion (DRG) neurons excised from C57BL/6J mice with SHED-CM significantly promoted neurite outgrowth compared that with DMEM. (SHED-CM: 3793.2±907.9 um/neuron, DMEM: 370.9±321.7 um/neuron) Among 4 fractions of SHED-CM according to molecular weight (less than 6kDa, 6-20kDa, 20-100kDa, and more than 100kDa), only fraction of less than 6kDa significantly increased neurite outgrowth. Incubation of DRG neurons with exosome isolated from SHED-CM didn’t have any effect on neurite outgrowth, indicating that only soluble factors from SHED-CM contributed to neurite outgrowth of DRG neurons. In in vivo study, 12 weeks after streptozotosin (STZ) administration, 100ul of SHED-CM or DMEM was injected into unilateral lower limb muscle of STZ-induced diabetic mice twice a week over a 4 weeks period. SHED-CM or DMEM injections didn’t change serum glucose levels and body weight in diabetic mice. SHED-CM significantly prevented decline in sensory nerve conduction velocity (SNCV), compared with DMEM. In diabetic mice, capillary number-to-muscle fiber ratio (CNMFR) and intraepidermal nerve fiber densities (IENFDs) decreased less than those in nondiabetic mice. SHED-CM significantly improved the decline of CNMFR, but not IENFDs, suggesting that SHED-CM in in vivo alleviated SNCV by improving of nerve blood flow. These data suggested that SHED-CM might have potential as a novel strategy for treatment of DPN. Disclosure E. Miura-Yura: None. S. Tsunekawa: None. T. Himeno: None. K. Naruse: None. M. Motegi: None. H. Shimoda: None. M. Kato: None. Y. Yamada: None. M. Kondo: None. Y. Kato: Speaker's Bureau; Self; Merck Sharp & Dohme Corp., Sanofi, Takeda Pharmaceutical Company, Eli Lilly Japan. H. Kamiya: Other Relationship; Self; MSD K.K., Ono Pharmaceutical Co., Ltd., Sanofi K.K., AstraZeneca, Astellas Pharma KK, Eli Lilly and Company, Novartis Pharma K.K., Dainippon Sumitomo Pharma Co., Ltd, Boehringer Ingelheim Pharmaceuticals, Inc., Takeda Pharmaceutical Co., Ltd, Ono Pharmaceutical Co., Ltd. J. Nakamura: Other Relationship; Self; Astellas Pharma US, Inc., AstraZeneca, Ono Pharmaceutical Co., Ltd., MSD K.K., Kyowa Hakko Kirin Co., Ltd., Kowa Pharmaceuticals America, Inc., Sanofi K.K., Taisho Pharmaceutical Co., Ltd., Takeda Development Center Asia, Pte. Ltd., Mitsubishi Tanabe Pharma Corporation, Eli Lilly and Company, Novartis Pharma K.K., Pfizer Inc..

Beneficial Effects of Xanthine Oxidase Inhibitor, Topiloxostat, on Experimental Diabetic Neuropathy in Mice

Xanthine oxidoreductase (XOR) catalyzes the final step of purine metabolism from xanthine to urate. XOR is then converted into xanthine oxidase (XO), incurring tissue damage when XO after XOR is activated such as in diabetes. The aim of this study is to evaluate the pathogenic role of XOR/XO in the development of diabetic polyneuropahty (DPN), and to clarify whether suppression of XO is beneficial for DPN. C57BL6 (C57) and db/db mice (db) 5-week of age were treated daily with a new potent XO-inhibitor, topiloxostat (To), 1mg/kg (dbT1) and 2mg/kg (dbT2) ad libitum with conventional laboratory chow for 8 weeks. During experimental period, glycemic levels, nerve conduction velocity (NCVs) and tail flick response were regularly monitored. At end, following the measurement of sciatic nerve blood flow (SNBF) by laser doppler, mice were killed for the evaluation of XO activity of the sciatic nerve (SN), intra-epidermal nerve fiber density (IENFD) and Iba-I positive macrophage infiltration (MI) intoSN. Glycemic levels were comparable among all diabetic groups. There was a significant delay of NCVs and elevated perception threshold of tail flick in db compared to C57. To-treatment improved these measures in a dose dependent manner (p<0.dbT2 vs. C57 for NCVs, and p<0.db vs. dbT1 and p<0.01 db vs. dbT2 for tail flick). XO activity in SN was dose-dependently suppressed compared to db (p<0.vs. dbT1, p<0.01 vs. dbT2). To-treatment at a high dose also corrected reduced SNBF and IENFD in db (p<0.01 dbT2 vs. db for both). There was a significant increase in Iba-I positive macrophages in SN of db compared to C57 after 4 week-treatment (p<0.01). MI was significantly suppressed in dbT1 and dbT2 (p<0.01). In contrast, there was no significant difference in MI at 8 week-treatment among all the groups. These results indicated the possible implication of XOR/XO metabolism in the pathophysiology of DPN and To may be a promising compound for the treatment of DPN. Disclosure H. Mizukami: Research Support; Self; Sanwa Kagaku Kenkyusho Co., Ltd., Mitsubishi Tanabe Pharma Corporation. R. Koyama: None. K. Takahashi: None. S. Osonoi: None. S. Ogasawara: None. S. Yagihashi: None.

Local blood flow in peripheral nerves and their ganglia: Resurrecting key ideas around its measurement and significance.

Over 3 decades ago, seminal work by Phillip Low and colleagues established exquisite physiology around the measurement of nerve blood flow (NBF). Although not widely explored recently, its connection to the clinic has awaited human methodology. While human studies have not achieved a convincing level of rigour, newer imaging technologies are offering early information. The peripheral nerve trunk has parallel blood flow compartments that include epineurial flow dominated by arteriovenous shunts and downstream endoneurial blood flow (EBF). NBF and EBF have lower values than central nervous system blood flow, lack autoregulation yet have sympathetic and peptidergic neurovascular control. Contrary to expectation, injury to nerves is often associated with rises in NBF rather than ischemia, a finding of biological interest corroborated by human studies. Despite its potential importance, quantitative human measurements of EBF and NBF are not yet available. However, with development, careful NBF analysis may present new insights into nerve disorders. Muscle Nerve 57: 884-895, 2018.

Effect of bupivacaine and adjuvant drugs for regional anesthesia on nerve tissue oximetry and nerve blood flow.

BackgroundNerve blood flow has a critical role in acute and chronic pathologies in peripheral nerves. Influences of local anesthetics and adjuvants on tissue perfusion and oxygenation are deemed as relevant factors for nerve damage after peripheral regional anesthesia. The link between low tissue perfusion due to local anesthetics and resulting tissue oxygenation is unclear.MethodsCombined tissue spectrophotometry and laser-Doppler flowmetry were used to assess nerve blood flow in 40 surgically exposed median nerves in pigs, as well as nerve tissue oximetry for 60 min. After baseline measurements, test solutions saline (S), bupivacaine (Bupi), bupivacaine with epinephrine (BupiEpi), and bupivacaine with clonidine (BupiCloni) were applied topically.ResultsBupivacaine resulted in significant decrease in nerve blood flow, as well as tissue oximetry values, compared with saline control. Addition of epinephrine resulted in a rapid, but nonsignificant, reduction of nerve blood flow and extensive lowering of tissue oximetry levels. The use of clonidine resulted in a reduction of nerve blood flow, comparable to bupivacaine alone (relative blood flow at T60 min compared with baseline, S: 0.86 (0.67–1.18), median (25th–75th percentile); Bupi: 0.33 (0.25–0.60); BupiCloni: 0.43 (0.38–0.63); and BupiEpi: 0.41(0.30–0.54). The use of adjuvants did not result in any relevant impairment of tissue oximetry values (saturation values in percent at T60, S: 91.5 [84–95]; Bupi: 76 [61–86]; BupiCloni: 84.5 [76–91]; and BupiEpi: 91 [56–92]).ConclusionThe application of bupivacaine results in lower nerve blood flow, but does not induce relevant ischemia. Despite significant reductions in nerve blood flow, the addition of clonidine or epinephrine to bupivacaine had no significant impact on nerve tissue oximetry compared with bupivacaine alone. Nerve ischemia due to local anesthetics is not enhanced by the adjuvants clonidine or epinephrine.

Gentiopicroside Ameliorates Diabetic Peripheral Neuropathy by Modulating PPAR- Γ/AMPK/ACC Signaling Pathway

Background/Aims: Gentiopicroside is promising as an important secoiridoid compound against pain. The present study aimed to investigate the analgesic effect and the probable mechanism of Gentiopicroside on Diabetic Peripheral Neuropathy (DPN), and to figure out the association among Gentiopicroside, dyslipidemia and PPAR- γ/AMPK/ACC signaling pathway. Methods: DPN rat models were established by streptozotocin and RSC96 cells were cultured. Hot, cold and mechanical tactile allodynia were conducted. Blood lipids, nerve blood flow, Motor Nerve Conduction Velocity (MNCV) and Sensory Nerve Conduction Velocity (SNCV) were detected. Gene and protein expression of PPAR- γ/AMPK/ACC pathway was analyzed by reverse transcription-quan titative polymerase chain reaction (RT-qPCR) and Westernblot. Besides, PPAR-γ antagonist GW9662 and agonist rosiglitazone, AMPK antagonist compound C and activator AICAR as well as ACC inhibitor TOFA were used to further confirm the relationship between PPAR-γ and AMPK. Results: The results demonstrated that Gentiopicroside markedly ameliorated hyperalgesia with prolonged paw withdrawal latency to heat and cold stimuli and fewer responses to mechanical allodynia compared with DPN model group. Gentiopicroside regulated dyslipidemia, enhanced nerve blood flow and improved MNCV as well as SNCV. Gentiopicroside suppressed ACC expression through the activation of AMPK and PPAR-γ mediated the activation of AMPK and subsequent inhibition of ACC expression. Conclusion: In conclusion, the present study demon strated that Gentiopicroside exerted nerve-protective effect and attenuated experimental DPN by restoring dyslipidmia and improved nerve blood flow through regulating PPAR-γ/AMPK/ACC signal pathway. These results provided a promising potential treatment of DPN.

Treatment with NADPH oxidase inhibitor apocynin alleviates diabetic neuropathic pain in rats.

Increased reactive oxygen species by the activation of NADPH oxidase (NOX) contributes to the development of diabetic complications. Apocynin, a NOX inhibitor, increases sciatic nerve conductance and blood flow in diabetic rats. We investigated potential protective effect of apocynin in rat diabetic neuropathy and its precise mechanism of action at molecular level. Rat models of streptozotocin-induced diabetes were treated with apocynin (30 and 100 mg/kg per day, intragastrically) for 4 weeks. Mechanical hyperalgesia and allodynia were determined weekly using analgesimeter and dynamic plantar aesthesiometer. Western blot analysis and histochemistry/immunohistochemistry were performed in the lumbar spinal cord and sciatic nerve respectively. Streptozotocin injection reduced pain threshold in analgesimeter, but not in aesthesiometer. Apocynin treatment increased pain threshold dose-dependently. Western blot analysis showed an increase in catalase and NOX-p47phox protein expression in the spinal cord. However, protein expressions of neuronal and inducible nitric oxide synthase (nNOS, iNOS), superoxide dismutase, glutathion peroxidase, nitrotyrosine, tumor necrosis factor-α, interleukin-6, interleukin-1β, aldose reductase, cyclooxygenase-2 or MAC-1 (marker for increased microgliosis) in the spinal cord remained unchanged. Western blot analysis results also demonstrated that apocynin decreased NOX-p47phox expression at both doses and catalase expression at 100 mg/kg per day. Histochemistry of diabetic sciatic nerve revealed marked degeneration. nNOS and iNOS immunoreactivities were increased, while S-100 immunoreactivity (Schwann cell marker) was decreased in sciatic nerve. Apocynin treatment reversed these changes dose-dependently. In conclusion, decreased pain threshold of diabetic rats was accompanied by increased NOX and catalase expression in the spinal cord and increased degeneration in the sciatic nerve characterized by increased NOS expression and Schwann cell loss. Apocynin treatment attenuates neuropathic pain by decelerating the increased oxidative stress-mediated pathogenesis in diabetic rats.

Potential utility of aldose reductase-deficient Schwann cells IKARS1 for the study of axonal degeneration and regeneration.

Potential utility of aldose reductase-deficient Schwann cells IKARS1 for the study of axonal degeneration and regeneration.

Neural Mobilization Attenuates Mechanical Allodynia and Decreases Proinflammatory Cytokine Concentrations in Rats With Painful Diabetic Neuropathy.

Painful diabetic neuropathy (PDN) is a common complication in patients with diabetes. It is related to ischemic nerve damage and the increase in the levels of proinflammatory mediators, such as tumor necrosis factor α (TNF-α) and interleukin 1β (IL-1β). Neural mobilization may have the potential to alleviate PDN, but it has not yet been tested. Also, the physiological mechanism of neural mobilization is unclear. The objective of this study was to investigate treatment effect and physiological mechanism of neural mobilization. This was an experimental study using rats with streptozocin (or streptozotocin)-induced type 1 diabetes. Three groups were used in the study, the control group (vehicle), the diabetes group (PDN group), and the neural mobilization treatment group (PDN-NM group) (n = 6). Rats in the vehicle group were healthy rats. Rats in the PDN and PDN-NM groups were rats with diabetes. Rats in the PDN-NM group received treatment in the right sciatic nerve, whereas rats in the PDN group did not. Mechanical pain sensitivity and the levels of IL-1β and TNF-α in the sciatic nerve branches and trunk, the L4 to L6 dorsal horn ganglion, and the spinal cord dorsal horn were measured. Techanical allodynia was alleviated after treatment, but the effect was limited to the treatment side. The concentrations of proinflammatory cytokines were decreased in the nerves that received treatment compared with those on the other side, indicating that neural mobilization may reduce mechanical sensitivity by decreasing the concentrations of local sensitizing agents. A limitation of this study was that no direct measurement of nerve blood flow was done. The results of this study showed that neural mobilization effectively alleviated mechanical allodynia in rats with PDN. The side that received treatment had lower concentrations of TNF-α and IL-1β in the sciatic nerve branches and sciatic nerve trunk; this result may have been related to the alleviation of mechanical allodynia.

Adenosine monophosphate-activated protein kinase modulation by berberine attenuates mitochondrial deficits and redox imbalance in experimental diabetic neuropathy

Adenosine monophosphate-activated protein kinase (AMPK) has been studied for its myriad metabolic and mitochondrial benefits in several chronic diseases. Recent studies have uncovered its therapeutic potential against mitochondrial dysfunction in cultured dorsal root ganglion (DRG) neurons isolated from streptozotocin (STZ) induced diabetic rats. The present study is aimed at evaluating the pharmacological efficacy of berberine (BRB), a natural AMPK activator against experimental diabetic neuropathy (DN) phenotype developed in STZ (55 mg/kg, i.p.) induced diabetic rats and neurotoxicity in high-glucose (30 mM) stimulated neuro 2a (N2A) cells. Diabetic-rats have shown reduced expression of p-AMPK (Thr 172) in sciatic nerves with a consequent reduction in mitochondrial biogenesis and autophagy. BRB (50 & 100 mg/kg, po) administration to diabetic rats for 2-weeks rescued mitochondrial functional deficits and autophagy impairment by increasing the p-AMPK expression. BRB administration also augmented the NEF-2 related factor 2 (Nrf2) mediated endogenous antioxidant defence systems to restrain neuronal damage and neuroinflammation. These effects after BRB administration resulted in enhanced conduction velocity, improved nerve blood flow and attenuated hyperalgesia. Similarly, BRB exposure (5 & 10 μM) to N2A cells attenuated high glucose induced ROS generation, mitochondrial membrane depolarization through the promotion of Nrf2 mediated antioxidant defence systems. BRB exposure augmented peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) mediated mitochondrial biogenesis in neuronal cells. Results from this study signify the importance of mitoprotection conferred by BRB in DN and can be used as a preliminary basis for further molecular exploration.

Morin exerts neuroprotection via attenuation of ROS induced oxidative damage and neuroinflammation in experimental diabetic neuropathy.

Morin, a bioflavonoid with diverse pharmacological effects against various diseases; in most cases morin protective effects were attributed to its detoxifying effect against reactive oxygen species (ROS). Diabetic neuropathy (DN) is a chronic, debilitating neuronal pain associated with intense generation of free radicals and proinflammatory cytokine accumulation in peripheral neurons. We investigated the pharmacological effect of morin against metabolic excess mediated mitochondrial ROS generation and corresponding effect on Nrf2, NF-κB pathways in Streptozotocin (STZ)-induced diabetic rats and in high glucose insulted Mouse neuroblastoma cell line, Neuro 2A (N2A). Animals were evaluated for nerve function parameters, motor and sensory nerve conduction velocities (MNCV and SNCV) and nerve blood flow (NBF) followed by TUNEL and immunoblot analysis. Mitochondrial function was evaluated by performing JC-1 and MitoSOX assays in high glucose (30 mM) incubated N2A cells. Diabetic animals showed significant impairment in MNCV, SNCV, and NBF as well as increased pain hypersensitivity. However, oral administration of morin at 50 and 100 mg/kg improved SNCV, MNCV, and NBF and reduced sensorimotor alterations (hyperalgesia and allodynia) in diabetic animals. Studies in N2A cells have revealed that morin ameliorated the high glucose-induced mitochondrial superoxide production, membrane depolarization, and total ROS generation. Morin effectively counteracted NF-κB-mediated neuroinflammation by reducing ROS mediated IKK activation and increased Nrf2-mediated antioxidant defenses in high glucose-induced N2A cells. The results of our study suggest that morin has exquisite role in offering neuroprotection in experimental DN and further clinical investigation may reward in finding better alternative for the management of DN. © 2017 BioFactors, 44(2):109-122, 2018.

Effects of olfactory stimulation with scents of grapefruit and lavender essential oils on the skeletal muscle sympathetic nerve and muscle blood flow in rats

AbstractWe have previously observed that olfactory stimulation with scents of grapefruit and lavender oils have opposing effects on autonomic neurotransmission and physiological phenomena in rats. Since the suppression and facilitation of activity of the sympathetic nerves innervating the skeletal muscles decreases and increases the skeletal muscle blood flow (skeletal muscle‐BF), respectively, the effects of olfactory stimulation with scent of a grapefruit essential oil (SGFO) and scent of a lavender essential oil (SLVO) on skeletal muscle sympathetic nerve activity (skeletal muscle‐SNA) and skeletal muscle‐BF were examined. SGFO reduced, and SLVO elevated skeletal muscle‐SNA and skeletal muscle‐BF, respectively. Furthermore, 1) anosmic treatment with ZnSO4 eliminated the changes in skeletal muscle‐SNA due to SGFO and SLVO, 2) diphenhydramine, a histamine H1‐antagonist, eliminated the SGFO‐induced suppression of skeletal muscle‐SNA, and thioperamide, a histamine H3‐antagonist, abolished the SLVO‐induced enhancement of skeletal muscle‐SNA, and 3) butoxamine, an adrenergic β2‐antagonist, blocked the SLVO‐induced increase in skeletal muscle‐BF. These findings suggest that olfactory stimulation with SGFO reduces, and SLVO enhances, skeletal muscle‐BF via these autonomic changes. In addition, the histamine H1‐receptor was found to be involved in the SGFO‐induced suppression of skeletal muscle‐SNA, the H3‐receptor was shown to be concerned to the SLVO‐induced enhancement of skeletal muscle‐SNA, and the adrenergic β2‐receptor was indicated to be implicated in the SLVO‐induced increase in skeletal muscle‐BF via an increase in skeletal muscle‐SNA. These findings suggest that SGFO may suppress, and SLVO may enhance, the muscle recovery from muscle fatigue and the growth of muscles, via changes in autonomic neurotransmission.

Optical coherence tomography angiography in glaucoma: a mini-review.

The advent of optical coherence tomography angiography (OCT-A) provides a new opportunity to visualize the retinal vasculature in a non-invasive and dye-free manner which may help identify vascular abnormalities in glaucoma. While a reduction in retinal and optic nerve head vessel densities and blood flow indexes measured by OCT-A has been demonstrated in patients with glaucoma in many studies, it is unclear whether OCT-A provides additional information for the detection and monitoring of glaucoma compared with OCT measurements such as retinal nerve fiber layer thickness, neuroretinal rim width, and ganglion cell inner plexiform layer thickness. Longitudinal studies are needed to elucidate whether vascular abnormalities detected by OCT-A are a cause or a consequence of optic nerve damage in glaucoma.

Isoliquiritigenin reduces oxidative damage and alleviates mitochondrial impairment by SIRT1 activation in experimental diabetic neuropathy

Sirtuin (SIRT1) inactivation underlies the pathogenesis of insulin resistance and hyperglycaemia-associated vascular complications, but its role in diabetic neuropathy (DN) has not been yet explored. We have evaluated hyperglycaemia-induced alteration of SIRT1 signalling and the effect of isoliquiritigenin (ILQ) on SIRT1-directed AMP kinase (AMPK) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) signalling in peripheral nerves of streptozotocin (STZ) (55 mg/kg, ip)-induced diabetic rats and in high glucose (30 mM)-exposed neuro2a (N2A) cells. Diabetic rats and high glucose-exposed N2A cells showed reduction in SIRT1 expression with consequent decline in mitochondrial biogenesis and autophagy. ILQ (10 & 20 mg/kg, po) administration to diabetic rats for 2 weeks and exposure to glucose-insulted N2A cells resulted in significant SIRT1 activation with concurrent increase in mitochondrial biogenesis and autophagy. ILQ administration also enhanced NAD+/NADH ratio in peripheral sciatic nerves which explains its possible SIRT1 modulatory effect. Functional and behavioural studies show beneficial effect of ILQ as it alleviated nerve conduction and nerve blood flow deficits in diabetic rats along with improvement in behavioural parameters (hyperalgesia and allodynia). ILQ treatment to N2A cells reduced high glucose-driven ROS production and mitochondrial membrane depolarization. Further, ILQ-mediated SIRT1 activation facilitated the Nrf2-directed antioxidant signalling. Overall, results from this study suggest that SIRT1 activation by ILQ mimic effects of calorie restriction, that is, PGC-1α-mediated mitochondrial biogenesis, FOXO3a mediated stress resistance and AMPK mediated autophagy effects to counteract the multiple manifestations in experimental DN.

The protective effect of the active components of ERPC on diabetic peripheral neuropathy in rats

Ethnopharmacological relevanceEuonymus alatus, Radix trichosanthis, Panax notoginseng and Coptis chinensis are popular plants used in traditional Chinese medicine to treat diabetes. Aim of the studyThe aim of the study is to investigate the therapeutic effect of the active components of Euonymus alatus, Radix trichosanthis, Panax notoginseng and Coptis chinensis (cERPC) on diabetic peripheral neuropathy in the rats and explore the underlying mechanism involved. MethodsAfter diabetes was induced in rats for 20 weeks, cERPC or water was administered for 12 weeks. After a hot plate test, motor nerve conduction velocity and sciatic nerve blood flow were determined; the sciatic nerves were isolated for toluidine blue staining; and the fibre area, fibre diameter, axon area, axon diameter and myelin thickness were evaluated. The levels of the myelin basic protein, myelin protein zero, Oct6 and Krox20 were measured by western blot or immunofluorescence. ResultscERPC was efficient in reducing the response latency, increasing motor nerve conduction velocity, enhancing sciatic nerve blood flow and ameliorating the pathological changes in diabetic rats. cERPC also had a role in increasing the levels of myelin basic protein and myelin protein zero and improving the expression of Oct6 and Krox20 in sciatic nerves of diabetic rats. ConclusionscERPC ameliorates diabetic peripheral neuropathy by attenuating electrophysiological, circulatory and morphological alterations, which is mediated by the Oct6-Krox20 pathway.

Microvascular Compromise Develops Following Nerve Fiber Layer Damage in Normal-Tension Glaucoma Without Choroidal Vasculature Involvement.

To investigate capillary densities in patients with unilateral normal-tension glaucoma (NTG) and normal controls using optical coherence tomography-angiography. We recruited 13 patients with unilateral NTG and 13 healthy controls. Optical coherence tomography-angiography was performed and pure peripapillary retinal capillary density was calculated after manually excluding large vessels and the optic disc. Paired comparison of capillary densities was performed among 3 categories of eye: NTG eye, fellow eye, and normal eye. Through vascular layer stratification we investigated differences in the retinal and choroidal circulation. In total, 33 eyes of 11 unilateral NTG patients and 11 controls were analyzed. Capillary densities of NTG eyes were significantly lower than those of fellow eyes or control eyes (both P=0.013). No significant differences were found between fellow eyes and control eyes (P=0.328). Area of capillary compromise was identical to the area of retinal nerve fiber layer (RNFL) defect in all 11 eyes. In layer analysis, a decrease in capillary plexus was demonstrated only in the inner retina and no definite changes were found in the outer retina and choroid. Optic nerve head microvasculature did not show areas of capillary dropout. In patients with unilateral NTG, we could observe significant retinal capillary compromise in the area of RNFL defect. No changes were demonstrated in the choroid and optic disc area. We speculated on a possibility of secondary microvascular changes in the retina to nerve damage from the wedge-shaped but not geographic shaped capillary compromise corresponding to RNFL defect area. Further studies on the optic nerve head microvasculature and blood flow are warranted to assess their relationship to glaucoma pathogenesis.

OCT angiography of acute non-arteritic anterior ischemic optic neuropathy

To describe changes of the retinal peripapillary microvasculature on optical coherence tomography angiography (OCT-A) in non-arteritic anterior ischemic optic (NAION) neuropathy. Observational study of 10 patients at the acute phase of NAION. OCT-A was performed using a 3mm×3mm square centered on the optic disc (Cirrus HD-OCT with Angioplex, Carl Zeiss Meditec, Dublin, CA). A qualitative comparison was made with the healthy fellow eye of each patient. All patients had a fluorescein angiography (HRA2, Heidelberg, Germany) and a visual field examination (Octopus 101®, Haag-Streit, USA). In the affected eyes, OCT-A showed clear modifications in the radial peripapillary network. In all these eyes, a focal disappearance of the superficial capillary radial pattern was present, twisted and irregular. In 8 eyes, there was also a lack of vascularization in some focal areas, appearing as dark areas. No correlation was found between the topography of the vascular alteration shown on OCT-A and visual field pattern defects. OCT-A is a new imaging technology able to demonstrate easily and safely the changes in the peripapillary capillary network during the acute phase of NAION. These changes are likely related to a decrease of the prelaminar optic nerve blood flow during the acute phase of NAION. Visual field defects are not correlated with OCT-A images, suggesting that they may be due mainly to disturbances in posterior ciliary artery blood flow.

Erratum to: Adenosine Monophosphate-Activated Protein Kinase Abates Hyperglycaemia-Induced Neuronal Injury in Experimental Models of Diabetic Neuropathy: Effects on Mitochondrial Biogenesis, Autophagy and Neuroinflammation.

Impaired adenosine monophosphate kinase (AMPK) signalling under hyperglycaemic conditions is known to cause mitochondrial dysfunction in diabetic sensory neurons. Facilitation of AMPK signalling is previously reported to ameliorate inflammation and induce autophagic response in various complications related to diabetes. The present study assesses the role of AMPK activation on mitochondrial biogenesis, autophagy and neuroinflammation in experimental diabetic neuropathy (DN) using an AMPK activator (A769662). A769662 (15 and 30 mg/kg, i.p) was administered to Sprague–Dawley rats (250–270 g) for 2 weeks after 6 weeks of streptozotocin (STZ) injection (55 mg/kg, i.p.). Behavioural parameters (mechanical/thermal hyperalgesia) and functional characteristics (motor/sensory nerve conduction velocities (MNCV and SNCV) and sciatic nerve blood flow (NBF)) were assessed. For in vitro studies, Neuro2a (N2A) cells were incubated with 25 mM glucose to simulate high glucose condition and then studied for mitochondrial dysfunction and protein expression changes. STZ administration resulted in significant hyperglycaemia (>250 mg/dl) in rats. A769662 treatment significantly improved mechanical/thermal hyperalgesia threshold and enhanced MNCV, SNCV and NBF in diabetic animals. A769662 exposure normalised the mitochondrial superoxide production, membrane depolarisation and markedly increased neurite outgrowth of N2A cells. Further, AMPK activation also abolished the NF-κB-mediated neuroinflammation. A769662 treatment increased Thr-172 phosphorylation of AMPK results in stimulated PGC-1α-directed mitochondrial biogenesis and autophagy induction. Our study supports that compromised AMPK signalling in hyperglycaemic conditions causes defective mitochondrial biogenesis ultimately leading to neuronal dysfunction and associated deficits in DN and activation of AMPK can be developed as an attractive therapeutic strategy for the management of DN.

Peripheral nerve conduction abnormalities precede morphological alterations in an experimental rat model of sepsis.

The pathological mechanisms of critical illness polyneuropathy (CIP), an acute neuromuscular disorder, remain unknown. In this study, we evaluated nerve and vascular properties that might account for electrophysiological abnormalities, including reduced nerve conduction amplitude, in the early phase of CIP. Rats were administered intravenous saline (C-group; n=31) or lipopolysaccharide (3mg/kg/day; L-group; n=30) for 48h. Subsequently, tracheotomy was performed and sciatic nerves exposed bilaterally. A catheter was inserted into the left internal carotid artery to measure the mean arterial pressure (MAP). Nerve conduction velocity (NCV), nerve blood flow (NBF), evoked amplitudes, chronaxie, rheobase, and the absolute refractory period (ARP) were measured from the sciatic nerves. Degeneration, myelination, and neutrophil infiltration were examined in the sciatic nerves using histology and electron microscopy. The NBF (C-group 25±3ml/100g/min, L-group 13±3ml/100g/min, p<0.001) was lower in the L-group, but the MAP was similar between groups (C-group 119±17mmHg, L-group 115±18mmHg, p=0.773). LPS also caused a severe reduction in amplitude (C-group 0.9±0.2mV, L-group 0.2±0.1mV, p<0.001), while latency and NCV were not affected. Of note, response amplitudes partially recovered with an increase in stimulus intensity. LPS treatment increased the rheobase and decreased the chronaxie (rheobase: C vs L-group; 0.35±0.07 vs 1.29±0.66mA, p<0.001; chronaxie 171±24 vs 42±20µs, p<0.001), while ARP was unchanged. No primary axonal degeneration or inflammatory infiltration was observed. Our findings suggest that primary electrophysiological deterioration is due to threshold alterations rather than morphological alterations after 48h of LPS treatment.

Loss of bone marrow adrenergic beta 1 and 2 receptors modifies transcriptional networks, reduces circulating inflammatory factors, and regulates blood pressure.

Hypertension (HTN) is a prevalent condition with complex etiology and pathophysiology. Evidence exists of significant communication between the nervous system and the immune system (IS), and there appears to be a direct role for inflammatory bone marrow (BM) cells in the pathophysiology of hypertension. However, the molecular and neural mechanisms underlying this interaction have not been characterized. Here, we transplanted whole BM cells from the beta 1 and 2 adrenergic receptor (AdrB1(tm1Bkk)AdrB2(tm1Bkk)/J) knockout (KO) mice into near lethally irradiated C57BL/6J mice to generate a BM AdrB1.B2 KO chimera. This allowed us to evaluate the role of the BM beta 1 and beta 2 adrenergic receptors in mediating BM IS homeostasis and regulating blood pressure (BP) in an otherwise intact physiological setting. Fluorescence-activated cell sorting demonstrated that a decrease in systolic and mean BP in the AdrB1.B2 KO chimera is associated with a decrease in circulating inflammatory T cells, macrophage/monocytes, and neutrophils. Transcriptomics in the BM identified 7,419 differentially expressed transcripts between the C57 and AdrB1.B2 KO chimera. Pathway analysis revealed differentially expressed transcripts related to several cell processes in the BM of C57 compared with AdrB1.B2 KO chimera, including processes related to immunity (e.g., T-cell activation, T-cell recruitment, cytokine production, leukocyte migration and function), the cardiovascular system (e.g., blood vessel development, peripheral nerve blood flow), and the brain (e.g., central nervous system development, neurite development) among others. This study generates new insight into the molecular events that underlie the interaction between the sympathetic drive and IS in modulation of BP.

Adenosine Monophosphate-Activated Protein Kinase Abates Hyperglycaemia-Induced Neuronal Injury in Experimental Models of Diabetic Neuropathy: Effects on Mitochondrial Biogenesis, Autophagy and Neuroinflammation.

Impaired adenosine monophosphate kinase (AMPK) signalling under hyperglycaemic conditions is known to cause mitochondrial dysfunction in diabetic sensory neurons. Facilitation of AMPK signalling is previously reported to ameliorate inflammation and induce autophagic response in various complications related to diabetes. The present study assesses the role of AMPK activation on mitochondrial biogenesis, autophagy and neuroinflammation in experimental diabetic neuropathy (DN) using an AMPK activator (A769662). A769662 (15 and 30mg/kg, i.p) was administered to Sprague-Dawley rats (250-270g) for 2weeks after 6weeks of streptozotocin (STZ) injection (55mg/kg, i.p.). Behavioural parameters (mechanical/thermal hyperalgesia) and functional characteristics (motor/sensory nerve conduction velocities (MNCV and SNCV) and sciatic nerve blood flow (NBF)) were assessed. For in vitro studies, Neuro2a (N2A) cells were incubated with 25mM glucose to simulate high glucose condition and then studied for mitochondrial dysfunction and protein expression changes. STZ administration resulted in significant hyperglycaemia (>250mg/dl) in rats. A769662 treatment significantly improved mechanical/thermal hyperalgesia threshold and enhanced MNCV, SNCV and NBF in diabetic animals. A769662 exposure normalised the mitochondrial superoxide production, membrane depolarisation and markedly increased neurite outgrowth of N2A cells. Further, AMPK activation also abolished the NF-κB-mediated neuroinflammation. A769662 treatment increased Thr-172 phosphorylation of AMPK results in stimulated PGC-1α-directed mitochondrial biogenesis and autophagy induction. Our study supports that compromised AMPK signalling in hyperglycaemic conditions causes defective mitochondrial biogenesis ultimately leading to neuronal dysfunction and associated deficits in DN and activation of AMPK can be developed as an attractive therapeutic strategy for the management of DN.