title: Sensory neurons derived from diabetic rats have diminished internal Ca2+ stores linked to impaired re-uptake by the endoplasmic reticulum.
abstract: Distal symmetrical sensory neuropathy in diabetes involves the dying back of axons, and the pathology equates with axonal dystrophy generated under conditions of aberrant Ca2+ signalling. Previous work has described abnormalities in Ca2+ homoeostasis in sensory and dorsal horn neurons acutely isolated from diabetic rodents. We extended this work by testing the hypothesis that sensory neurons exposed to long-term Type 1 diabetes in vivo would exhibit abnormal axonal Ca2+ homoeostasis and focused on the role of SERCA (sarcoplasmic/endoplasmic reticulum Ca2+-ATPase). DRG (dorsal root ganglia) sensory neurons from age-matched normal and 3-5-month-old STZ (streptozotocin)-diabetic rats (an experimental model of Type 1 diabetes) were cultured. At 1-2 days in vitro an array of parameters were measured to investigate Ca2+ homoeostasis including (i) axonal levels of intracellular Ca2+, (ii) Ca2+ uptake by the ER (endoplasmic reticulum), (iii) assessment of Ca2+ signalling following a long-term thapsigargin-induced blockade of SERCA and (iv) determination of expression of ER mass and stress markers using immunocytochemistry and Western blotting. KCl- and caffeine-induced Ca2+ transients in axons were 2-fold lower in cultures of diabetic neurons compared with normal neurons indicative of reduced ER calcium loading. The rate of uptake of Ca2+ into the ER was reduced by 2-fold (P<0.05) in diabetic neurons, while markers for ER mass and ER stress were unchanged. Abnormalities in Ca2+ homoeostasis in diabetic neurons could be mimicked via long-term inhibition of SERCA in normal neurons. In summary, axons of neurons from diabetic rats exhibited aberrant Ca2+ homoeostasis possibly triggered by sub-optimal SERCA activity that could contribute to the distal axonopathy observed in diabetes.
authors.affiliation: Division of Neurodegenerative Disorders, St. Boniface Hospital Research Centre, and Department of Pharmacology and Therapeutics, University of Manitoba, Winnipeg, MB, Canada, R2H 2A6.
authors.forename: Elena
authors.initials: E
authors.lastname: Zherebitskaya
authors.forename: Jason
authors.initials: J
authors.lastname: Schapansky
authors.forename: Eli
authors.initials: E
authors.lastname: Akude
authors.forename: Darrell R
authors.initials: DR
authors.lastname: Smith
authors.forename: Randy
authors.initials: R
authors.lastname: Van der Ploeg
authors.forename: Natasha
authors.initials: N
authors.lastname: Solovyova
authors.forename: Alexei
authors.initials: A
authors.lastname: Verkhratsky
authors.forename: Paul
authors.initials: P
authors.lastname: Fernyhough
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism; D011984:Sensory Receptor Cells / Q000378:metabolism*
chemical_list: D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D002118:Calcium