Summary Chronic or repeated stressor exposure can induce a number of maladaptive behavioral and physiological consequences and among limbic structures, the bed nucleus of the stria terminalis (BNST) has been implicated in the integration and interpretation of stress responses. Previous work has demonstrated that chronic variate stress (CVS) exposure in rodents increases BNST pituitary adenylate cyclase activating polypeptide (PACAP, Adcyap1) and PAC1 receptor (Adcyap1r1) transcript expression, and that acute BNST PACAP injections can stimulate anxiety-like behavior. Here we show that chronic stress increases PACAP expression selectively in the oval nucleus of the dorsolateral BNST in patterns distinct from those for corticotropin releasing hormone (CRH). Among receptor subtypes, BNST PACAP signaling through PAC1 receptors not only heightened anxiety responses as measured by different behavioral parameters but also induced anorexic-like behavior to mimic the consequences of stress. Conversely, chronic inhibition of BNST PACAP signaling by continuous infusion with the PAC1 receptor antagonist PACAP(6-38) during the week of CVS attenuated these stress-induced behavioral responses and changes in weight gain. BNST PACAP signaling stimulated the hypothalamic-pituitary-adrenal (HPA) axis and heightened corticosterone release; further, BNST PACAP(6-38) administration blocked corticosterone release in a sensitized stress model. In aggregate with recent associations of PACAP/PAC1 receptor dysregulation with altered stress responses including post-traumatic stress disorder, these data suggest that BNST PACAP/PAC1 receptor signaling mechanisms may coordinate the behavioral and endocrine consequences of stress.

Retinal ischemia-reperfusion (I/R) is a pathophysiological process contributing to cellular damage in multiple ocular conditions, including glaucoma, diabetic retinopathy, and retinal vascular occlusions. Rodent models of I/R injury are providing significant insights into mechanisms and treatment strategies for human I/R injury, especially with regard to neurodegenerative damage in the retinal neurovascular unit. Presented here is a protocol for inducing retinal I/R injury in mice through elevation of intraocular pressure (IOP). In this protocol, the ocular anterior chamber is cannulated with a needle, through which flows the drip of an elevated saline reservoir. Using this drip to raise IOP above systolic arterial blood pressure, a practitioner temporarily halts inner retinal blood flow (ischemia). When circulation is reinstated (reperfusion) by removal of the cannula, severe cellular damage ensues, resulting ultimately in retinal neurodegeneration. Recent studies demonstrate inflammation, vascular permeability, and capillary degeneration as additional elements of this model. Compared to alternative retinal I/R methodologies, such as retinal arterial ligation, retinal I/R injury by elevated IOP offers advantages in its anatomical specificity, experimental tractability, and technical accessibility, presenting itself as a valuable tool for examining neuronal pathogenesis and therapy in the retinal neurovascular unit.

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BackgroundRetinal ischemia results in neuronal degeneration and contributes to the pathogenesis of multiple blinding diseases. Recently, the fumaric acid ester dimethyl fumarate (DMF) has been FDA-approved for the treatment of multiple sclerosis, based on its neuroprotective and anti-inflammatory effects. Its potential role as a neuroprotective agent for retinal diseases has received little attention. In addition, DMF’s mode of action remains elusive, although studies have suggested nuclear factor erythroid 2-related factor 2 (Nrf2) activation as an important mechanism. Here we investigated the neuroprotective role of monomethyl fumarate (MMF), the biologically active metabolite of DMF, in retinal ischemia-reperfusion (I/R) injury, and examined the role of Nrf2 in mediating MMF action.MethodsWild-type C57BL/6J and Nrf2 knockout (KO) mice were subjected to 90 min of retinal ischemia followed by reperfusion. Mice received daily intraperitoneal injection of MMF. Inflammatory gene expression was measured using quantitative reverse transcription PCR (qRT-PCR) at 48 h after I/R injury. Seven days after I/R, qRT-PCR for Nrf2 target gene expression, immunostaining for Müller cell gliosis and cell loss in the ganglion cell layer (GCL), and electroretinography for retinal function were performed.ResultsThe results of this study confirmed that MMF reduces retinal neurodegeneration in an Nrf2-dependent manner. MMF treatment significantly increased the expression of Nrf2-regulated antioxidative genes, suppressed inflammatory gene expression, reduced Müller cell gliosis, decreased neuronal cell loss in the GCL, and improved retinal function measured by electroretinogram (ERG) after retinal I/R injury in wild-type mice. Importantly, these MMF-mediated beneficial effects were not observed in Nrf2 KO mice.ConclusionsThese results indicate that fumaric acid esters (FAEs) exert a neuronal protective function in the retinal I/R model and further validate Nrf2 modulation as a major mode of action of FAEs. This suggests that DMF and FAEs could be a potential therapeutic agent for activation of the Nrf2 pathway in retinal and possibly systemic diseases.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-015-0452-z) contains supplementary material, which is available to authorized users.