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Circulating Agonist Autoantibody to 5-Hydroxytryptamine 2A Receptor in Lean and Diabetic Fatty Zucker Rat Strains
M B Zimering1,2, M Grinberg1, J Burton1
1Medical Service, Veterans Affairs New Jersey Healthcare System, East Orange, New Jersey, USA.
Aims:
Circulating neurotoxic autoantibodies to the 5-hydroxytryptamine 2A receptor were increased in older adult type 2 diabetes in association with certain neurodegenerative complications. The male Zucker diabetic fatty (ZDF) rat is a model system for studies of obese, type 2 diabetes mellitus. The aim of the current study was to test for (and compare) circulating neurotoxic autoantibodies to the 5-hydroxytryptamine 2A receptor in the Zucker diabetic fatty rat and age-matched lean Zucker rat strains.
Methods:
Plasma from lean and Zucker diabetic fatty rat (obtained at different developmental stages) was subjected to protein G affinity chromatography. The resulting immunoglobulin G fraction was tested for neurotoxicity (acute neurite retraction, accelerated neuron loss) in N2A mouse neuroblastoma cells and for binding to a linear synthetic peptide corresponding to the second extracellular loop of the 5-hydroxytryptamine 2A receptor.
Results:
The male Zucker diabetic fatty rat (fa/fa) and two Zucker lean strains (+/?) and (fa/+) harbored autoantibodies to the 5-hydroxytryptamine 2A receptor which appeared spontaneously around 7-8.5 weeks of age. The circulating autoantibodies persisted until at least 25 weeks of age in the Zucker diabetic fatty rat and in the Zucker heterozygote (fa/+), but were no longer detectable in 25-week-old lean (+/?) Zucker rats. Autoantibody-induced acute neurite retraction and accelerated loss in mouse neuroblastoma N2A cells was dose-dependently prevented by selective antagonists of the 5-hydroxytryptamine 2A receptor. It was also substantially prevented by co-incubation with antagonists of RhoA/Rho kinase-mediated signaling (Y27632) or Gq11/phospholipase C/inositol triphosphate receptor-coupled signaling.
Conclusions:
These data suggest that neurotoxic 5-hydroxytryptamine 2A receptor-targeting autoantibodies increase in the aging male Zucker diabetic fatty rat and in male Zucker lean rats harboring a heterozygous mutation, but not in age-matched, older Zucker lean rats lacking a known leptin receptor mutation. The Zucker genetic strain may be useful in studies of the role of humoral and/or innate immunity in late neurodegeneration.
Insights
Neurotoxic autoantibodies targeting the 5-hydroxytryptamine 2A receptor increase in aging male Zucker diabetic fatty rats. These autoantibodies are linked to neurodegeneration and are present in specific Zucker rat strains, suggesting a role for immunity in late-stage neurodegeneration.
Area of Science:
- Neuroscience
- Immunology
- Endocrinology
Background:
- Type 2 diabetes is associated with neurodegenerative complications in older adults.
- Neurotoxic autoantibodies targeting the 5-hydroxytryptamine 2A receptor (5-HT2AR) have been implicated in these complications.
- The male Zucker diabetic fatty (ZDF) rat serves as a model for obese type 2 diabetes.
Purpose of the Study:
- To investigate and compare circulating neurotoxic autoantibodies against 5-HT2AR in ZDF rats and age-matched lean Zucker rats.
- To determine the developmental profile and persistence of these autoantibodies.
Main Methods:
- Plasma from lean and ZDF rats at various developmental stages was used.
- Immunoglobulin G (IgG) fractions were isolated via protein G affinity chromatography.
- Neurotoxicity was assessed using N2A mouse neuroblastoma cells, measuring neurite retraction and neuron loss.
- Binding to a synthetic peptide of the 5-HT2AR second extracellular loop was evaluated.
Main Results:
- Autoantibodies to 5-HT2AR were spontaneously detected in male ZDF rats (fa/fa) and Zucker lean rats (fa/+) around 7-8.5 weeks of age, persisting until at least 25 weeks in ZDF and fa/+ rats.
- These autoantibodies were absent in 25-week-old lean Zucker rats (+/?).
- Autoantibody-induced neurotoxicity in N2A cells was dose-dependently inhibited by 5-HT2AR antagonists and signaling pathway inhibitors (RhoA/ROCK, Gq11/PLC/IP3R).
Conclusions:
- Neurotoxic 5-HT2AR autoantibodies increase in aging male ZDF rats and heterozygous Zucker lean rats, but not in age-matched lean rats without the leptin receptor mutation.
- The Zucker rat strain is a valuable model for studying the role of humoral and innate immunity in late-onset neurodegeneration.
