Activating transcription factor 3 modulates protein kinase C epsilon activation in diabetic peripheral neuropathy

Abstract

BackgroundSkin denervation that develops in patients with diabetes mellitus as a neuropathic manifestation is known as diabetic peripheral neuropathy (DPN). Skin denervation is parallel to neuronal injuries that alter intracellular signaling. To date, the correlation between nerve injury and the activation of intracellular responses to neuropathic manifestations has not been elucidated; specifically, whether activating transcription factor 3 (ATF3) is responsible for neuronal injury and a critical molecule that modulates the activation of intracellular protein kinase C epsilon (p-PKCε) and pain development in DPN is a crucial question.MethodsTo address, ATF3 knockout (atf3−/− group, C57/B6 genetic background) and wild-type mice (atf3+/+ group) received a single dose of streptozotocin (200 mg/kg) to generate a mouse model of DPN.ResultsBoth atf3+/+ and atf3−/− mice exhibited hyperglycemia and the same pathology of skin denervation at posttreatment month 2, but only atf3+/+ mice developed thermal hyperalgesia (P<0.001) and mechanical allodynia (P=0.002). The atf3+/+ group, but not the atf3−/− group, had preferential ATF3 upregulation on p-PKCε(+) neurons with a ratio of 37.7%±6.1% in p-PKCε(+):ATF3(+) neurons (P<0.001). In addition, B-cell lymphoma-extra large (Bcl-XL), an antiapoptotic Bcl2 family protein, exhibited parallel patterns to p-PKCε (ie, Bcl-XL upregulation was reversed in atf3−/− mice). These two molecules were colocalized and increased by approximately two-fold in the atf3+/+ group compared with the atf3−/− group (30.0%±3.4% vs 13.7% ± 6.2%, P=0.003). Furthermore, linear analysis results showed that the densities of p-PKCε and Bcl-XL had a reverse linear relationship with the degrees of thermal hyperalgesia and mechanical allodynia.ConclusionCollectively, this report suggested that ATF3 is a critical upstream molecule that modulates p-PKCε and Bcl-XL expression, which consequently mediated the development of neuropathic manifestation in DPN.

Genetic loss-of-function of activating transcription factor 3 but not C-type lectin member 5A prevents diabetic peripheral neuropathy

“…To confirm the genotypes of the atf3 −/− and clec5a −/− mice used in this study, genotyping was performed through polymerase chain reaction (PCR) of the genomic DNA extracted from the tail. The same method employed and primer sequences in another study were used for atf3 [ 10 ] and clec5a [ 20 ] genotyping.…”

“…The small nociceptors became sensitized after their terminal IENFs degeneration. Particularly, activating transcription factor 3 (ATF3), a potential neuronal marker under pathology, was activated on small nociceptors in concert with skin denervation [ 10 ], suggesting that ATF3 is a critical marker in addition to noxious transduction by IENF. ATF3 has also been suggested to be a marker of ER stress, and it negatively affects ER stress in obesity-related diabetes [ 11 , 12 ] and in renal tissue failure [ 13 ] due to obesity-lipotoxicity-induced ATF3 activation and ER stress.…”

Lysophosphatidic Acid Receptor 1- and 3-Mediated Hyperalgesia and Hypoalgesia in Diabetic Neuropathic Pain Models in Mice

“…The clinical pathogenesis underlying diabetic neuropathic pain remains elusive, although several mechanisms have been proposed, including the involvement of hemodynamic factors and thalamic neuronal dysfunction [ 44 , 45 , 46 ]. On the other hand, multiple mechanisms have been proposed in studies using diabetic rodent models, including aldose reductase/AR [ 47 , 48 ], high mobility group box 1/HMGB1- receptor for advanced glycation end-product/RAGE signaling [ 49 , 50 ], protein kinase C/PKC [ 51 , 52 ], poly(ADP-ribose) polymerase/PARP [ 53 , 54 ] and oxidative stress [ 55 , 56 , 57 ]. These are all presumed to play critical roles in the activation through primary sensory neurons and the DRG.…”

“…Several studies have used rodent models to evaluate hypoalgesia. Thermal hypoalgesia in rodents has been observed in the late stage of STZ-induced type I diabetic models [ 47 , 51 , 58 , 59 , 60 , 61 , 62 ] and in various type II diabetic models, including the HFD-induced diabetic model and db/db mice [ 63 , 64 , 65 ]. Here, we confirmed the paradoxical alteration of pain perception, such as hyperalgesia and hypoalgesia/hypoesthesia in the type II HFD- or db/db model and type I STZ-model.…”

“…Here, we confirmed the paradoxical alteration of pain perception, such as hyperalgesia and hypoalgesia/hypoesthesia in the type II HFD- or db/db model and type I STZ-model. Notably, many studies revealed that hyperalgesia occurs at the early stage after STZ-treatment(s), and hypoalgesia does several weeks later, though the timing showing the transition from hyperalgesia to hypoalgesia depends on the experimental models [ 47 , 51 , 58 , 61 , 62 ]. In the present study, we observed significant thermal hyperalgesia in HFD-, db/db- and STZ-models, but failed to detect the thermal hypoalgesia by the time of 10 weeks after the start of HFD-treatments, or 49 days (7 weeks) after STZ-treatment.…”