Activity of the astrocyte-neuronal lactate shuttle (ANLS) in the anterior cingulate cortex (ACC) has been proposed to be necessary for chronic pain development in inflamm... More
Activity of the astrocyte-neuronal lactate shuttle (ANLS) in the anterior cingulate cortex (ACC) has been proposed to be necessary for chronic pain development in inflammatory pain models but is yet to be investigated in chronic neuropathic pain. A spared nerve injury (SNI) model of chronic neuropathic pain was utilized to examine the involvement of the ANLS in male and female mice. Knockdown of a key lactate transporter, monocarboxylate transporter 4 (MCT4), was performed in vitro and in vivo to assess the impact of lactate shuttling inhibition. L-lactate levels in the ACC were increased in SNI in males, but not females, which was accompanied by sex-specific increases in ANLS and neuroplasticity-related protein markers. MCT4 knockdown in vivo led to sex-specific changes in these markers. In contrast, MCT4 knockdown in vitro did not effectively reduce protein levels in varied experimental conditions, demonstrating the complex role of the ANLS in multiple cell types.
Keywords:
chronic pain, astrocytes, astrocyte-neuronal lactate shuttle, cnterior cingulate cortex, MCT4
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Traumatic brain injury (TBI) is a major cause of morbidity and mortality worldwide, affecting over 10 million people annually, with an estimated cost of $76.5 billion. Al... More
Traumatic brain injury (TBI) is a major cause of morbidity and mortality worldwide, affecting over 10 million people annually, with an estimated cost of $76.5 billion. Although apocynin freely transverses the blood–brain barrier (BBB), its application is limited due to its rapid elimination, low terminal half-life (t1/2 = 6.7 min), narrow dose–response relationship, and cytotoxicity, thereby requiring repeated dosages. With this study, we aimed to develop transferrin-functionalized nanoparticles encapsulating apocynin to treat neuroinflammation for targeted drug delivery to sites of brain injury. As a preliminary approach, we endeavored to optimize the formulation parameters of apocynin-loaded albumin nanoparticles prepared through the desolvation method. The nanoparticles were characterized for their size, polydispersity, surface charge, drug loading and in vitro drug release. In this study, we also investigated the anti-inflammatory and neuroprotective effects of free apocynin and nanoparticle-loaded apocynin in neuronal cells. We show that the developed formulation displayed monodispersed, nanosized particles with higher entrapment efficiency, loading, stability, and sustained release profiles. The permeability of the nanoparticles across HBMECs reached the maximum at 67%. The in vivo evaluation revealed the enhanced uptake of transferrin-anchored nanoparticles in the brain tissues when compared with unmodified nanoparticles after I.V. administration. In vivo nanoparticle localization studies using a blast TBI (bTBI) model and confocal fluorescence microscopy have shown that tf-apoANPs are successful in delivering relatively high amounts of nanoparticles to the brain parenchyma and glial cells compared to non-targeted nanoparticles. We also establish that targeted nanoparticles accumulate in the brain. In conclusion, tf-apoANPs are efficacious carriers for targeted delivery across the blood–brain barrier to potentially treat neuroinflammation in brain injury and other diseases.
Keywords:
apocynin; nanoparticle; albumin; HPLC; desolvation method; targeted delivery; biodistribution; neuroprotection Less
Exposure to traffic-generated pollution is associated with alterations in blood-brain barrier (BBB) integrity and exacerbation of cerebrovascular disorders. Angiotensin (... More
Exposure to traffic-generated pollution is associated with alterations in blood-brain barrier (BBB) integrity and exacerbation of cerebrovascular disorders. Angiotensin (Ang) II signaling through the Ang II type 1 (AT1) receptor is known to promote BBB disruption. We have previously reported that exposure to a mixture of gasoline and diesel vehicle engine emissions (MVE) mediates alterations in cerebral microvasculature of C57Bl/6 mice, which is exacerbated through consumption of a high-fat (HF) diet. Thus, we investigated the hypothesis that inhalation exposure to MVE results in altered central nervous system microvascular integrity mediated by Ang II-AT1 signaling. Three-month-old male C57Bl/6 mice were placed on an HF or low-fat diet and exposed via inhalation to either filtered air (FA) or MVE (100 μg/m3 PM) 6 h/d for 30 days. Exposure to HF+MVE resulted in a significant increase in plasma Ang II and expression of AT1 in the cerebral microvasculature. Results from a BBB coculture study showed that transendothelial electrical resistance was decreased, associated with reduced expression of claudin-5 and occludin when treated with plasma from MVE+HF animals. These effects were attenuated through pretreatment with the AT1 antagonist, Losartan. Our BBB coculture showed increased levels of astrocyte AT1 and decreased expression of aryl hydrocarbon receptor and glutathione peroxidase-1, associated with increased interleukin-6 and transforming growth factor-β in the astrocyte media, when treated with plasma from MVE-exposed groups. Our results indicate that inhalation exposure to traffic-generated pollutants results in altered BBB integrity, mediated through Ang II-AT1 signaling and inflammation, which is exacerbated by an HF diet. Less
Injury to the vertebrate central nervous system (CNS) induces astrocytes to change their morphology, to increase their rate of proliferation, and to display directional m... More
Injury to the vertebrate central nervous system (CNS) induces astrocytes to change their morphology, to increase their rate of proliferation, and to display directional migration to the injury site, all to facilitate repair. These astrocytic responses to injury occur in a clear temporal sequence and, by their intensity and duration, can have both beneficial and detrimental effects on the repair of damaged CNS tissue. Studies on highly regenerative tissues in non-mammalian vertebrates have demonstrated that the intensity of direct-current extracellular electric fields (EFs) at the injury site, which are 50–100 fold greater than in uninjured tissue, represent a potent signal to drive tissue repair. In contrast, a 10-fold EF increase has been measured in many injured mammalian tissues where limited regeneration occurs. As the astrocytic response to CNS injury is crucial to the reparative outcome, we exposed purified rat cortical astrocytes to EF intensities associated with intact and injured mammalian tissues, as well as to those EF intensities measured in regenerating non-mammalian vertebrate tissues, to determine whether EFs may contribute to the astrocytic injury response. Astrocytes exposed to EF intensities associated with uninjured tissue showed little change in their cellular behavior. However, astrocytes exposed to EF intensities associated with injured tissue showed a dramatic increase in migration and proliferation. At EF intensities associated with regenerating non-mammalian vertebrate tissues, these cellular responses were even more robust and included morphological changes consistent with a regenerative phenotype. These findings suggest that endogenous EFs may be a crucial signal for regulating the astrocytic response to injury and that their manipulation may be a novel target for facilitating CNS repair. Less
