The influence of the prolactin/vasoinhibin axis on post-stroke lesion volume, astrogliosis, and survival.

Ischemic stroke is a significant global health issue, ranking fifth among all causes of death and a leading cause of serious long-term disability. Ischemic stroke leads to severe outcomes, including permanent brain damage and neuronal dysfunction. Therefore, decreasing and preventing neuronal injuries caused by stroke has been the focus of therapeutic research. In recent years, many studies have shown that fluctuations in hormonal levels influence the prognosis of ischemic stroke. Thus, it is relevant to understand the role of hormones in the pathophysiological mechanisms of ischemic stroke for preventing and treating this health issue. Here, we investigate the contribution of the prolactin/vasoinhibin axis, an endocrine system regulating blood vessel growth, immune processes, and neuronal survival, to the pathophysiology of ischemic stroke. Male mice with brain overexpression of prolactin or vasoinhibin by adeno-associated virus (AAV) intracerebroventricular injection or lacking the prolactin receptor (Prlr-/-) were exposed to transient middle cerebral artery occlusion (tMCAO) for 45 min followed by 48 h of reperfusion. Overexpression of vasoinhibin or the absence of the prolactin receptor led to an increased lesion volume and decreased survival rates in mice following tMCAO, whereas overexpression of prolactin had no effect. In addition, astrocytic distribution in the penumbra was altered, glial fibrillary acidic protein and S100b mRNA expressions were reduced, and interleukin-6 mRNA expression increased in the ischemic hemisphere of mice overexpressing vasoinhibin. Of note, prolactin receptor-null mice (Prlr-/-) showed a marked increase in serum vasoinhibin levels. Furthermore, vasoinhibin decreased astrocyte numbers in mixed hippocampal neuron-glia cultures. These observations suggest that increased vasoinhibin levels may hinder astrocytes' protective reactivity. Overall, this study suggests the involvement of the prolactin/vasoinhibin axis in the pathophysiology of ischemic stroke-induced brain injury and provides insights into the impact of its dysregulation on astrocyte reactivity and lesion size. Understanding these mechanisms could help develop therapeutic interventions in ischemic stroke and other related neurological disorders.

Improved Recovery of Complete Spinal Cord Transection by a Plasma-Modified Fibrillar Scaffold.

Complete spinal cord injury causes an irreversible disruption in the central nervous system, leading to motor, sensory, and autonomic function loss, and a secondary injury that constitutes a physical barrier preventing tissue repair. Tissue engineering scaffolds are presented as a permissive platform for cell migration and the reconnection of spared tissue. Iodine-doped plasma pyrrole polymer (pPPy-I), a neuroprotective material, was applied to polylactic acid (PLA) fibers and implanted in a rat complete spinal cord transection injury model to evaluate whether the resulting composite implants provided structural and functional recovery, using magnetic resonance (MR) imaging, diffusion tensor imaging and tractography, magnetic resonance spectroscopy, locomotion analysis, histology, and immunofluorescence. In vivo, MR studies evidenced a tissue response to the implant, demonstrating that the fibrillar composite scaffold moderated the structural effects of secondary damage by providing mechanical stability to the lesion core, tissue reconstruction, and significant motor recovery. Histologic analyses demonstrated that the composite scaffold provided a permissive environment for cell attachment and neural tissue guidance over the fibers, reducing cyst formation. These results supply evidence that pPPy-I enhanced the properties of PLA fibrillar scaffolds as a promising treatment for spinal cord injury recovery.

The RhoA-ROCK1/ROCK2 Pathway Exacerbates Inflammatory Signaling in Immortalized and Primary Microglia.

Neuroinflammation is a unifying factor among all acute central nervous system (CNS) injuries and chronic neurodegenerative disorders. Here, we used immortalized microglial (IMG) cells and primary microglia (PMg) to understand the roles of the GTPase Ras homolog gene family member A (RhoA) and its downstream targets Rho-associated coiled-coil-containing protein kinases 1 and 2 (ROCK1 and ROCK2) in neuroinflammation. We used a pan-kinase inhibitor (Y27632) and a ROCK1- and ROCK2-specific inhibitor (RKI1447) to mitigate a lipopolysaccharide (LPS) challenge. In both the IMG cells and PMg, each drug significantly inhibited pro-inflammatory protein production detected in media (TNF-α, IL-6, KC/GRO, and IL-12p70). In the IMG cells, this resulted from the inhibition of NF-κB nuclear translocation and the blocking of neuroinflammatory gene transcription (iNOS, TNF-α, and IL-6). Additionally, we demonstrated the ability of both compounds to block the dephosphorylation and activation of cofilin. In the IMG cells, RhoA activation with Nogo-P4 or narciclasine (Narc) exacerbated the inflammatory response to the LPS challenge. We utilized a siRNA approach to differentiate ROCK1 and ROCK2 activity during the LPS challenges and showed that the blockade of both proteins may mediate the anti-inflammatory effects of Y27632 and RKI1447. Using previously published data, we show that genes in the RhoA/ROCK signaling cascade are highly upregulated in the neurodegenerative microglia (MGnD) from APP/PS-1 transgenic Alzheimer's disease (AD) mice. In addition to illuminating the specific roles of RhoA/ROCK signaling in neuroinflammation, we demonstrate the utility of using IMG cells as a model for primary microglia in cellular studies.

Neuroprotective Effects and Treatment Potential of Incretin Mimetics in a Murine Model of Mild Traumatic Brain Injury.

Traumatic brain injury (TBI) is a commonly occurring injury in sports, victims of motor vehicle accidents, and falls. TBI has become a pressing public health concern with no specific therapeutic treatment. Mild TBI (mTBI), which accounts for approximately 90% of all TBI cases, may frequently lead to long-lasting cognitive, behavioral, and emotional impairments. The incretins glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are gastrointestinal hormones that induce glucose-dependent insulin secretion, promote ß-cell proliferation, and enhance resistance to apoptosis. GLP-1 mimetics are marketed as treatments for type 2 diabetes mellitus (T2DM) and are well tolerated. Both GLP-1 and GIP mimetics have shown neuroprotective properties in animal models of Parkinson's and Alzheimer's disease. The aim of this study is to evaluate the potential neuroprotective effects of liraglutide, a GLP-1 analog, and twincretin, a dual GLP-1R/GIPR agonist, in a murine mTBI model. First, we subjected mice to mTBI using a weight-drop device and, thereafter, administered liraglutide or twincretin as a 7-day regimen of subcutaneous (s.c.) injections. We then investigated the effects of these drugs on mTBI-induced cognitive impairments, neurodegeneration, and neuroinflammation. Finally, we assessed their effects on neuroprotective proteins expression that are downstream to GLP-1R/GIPR activation; specifically, PI3K and PKA phosphorylation. Both drugs ameliorated mTBI-induced cognitive impairments evaluated by the novel object recognition (NOR) and the Y-maze paradigms in which neither anxiety nor locomotor activity were confounds, as the latter were unaffected by either mTBI or drugs. Additionally, both drugs significantly mitigated mTBI-induced neurodegeneration and neuroinflammation, as quantified by immunohistochemical staining with Fluoro-Jade/anti-NeuN and anti-Iba-1 antibodies, respectively. mTBI challenge significantly decreased PKA phosphorylation levels in ipsilateral cortex, which was mitigated by both drugs. However, PI3K phosphorylation was not affected by mTBI. These findings offer a new potential therapeutic approach to treat mTBI, and support further investigation of the neuroprotective effects and mechanism of action of incretin-based therapies for neurological disorders.

Adenosine triphosphate released from HIV-infected macrophages regulates glutamatergic tone and dendritic spine density on neurons.

Despite wide spread use of combination antiretroviral therapy (cART) in developed countries, approximately half of HIV-infected patients will develop impairments in cognitive function. Accumulating evidence suggests that neuronal dysfunction can be precipitated by HIV-infection of macrophages by mechanisms that involve alterations in innate and adaptive immune responses. HIV-infection of macrophages is known to increase the release of soluble neurotoxins. However, the composition of products released from infected macrophages is complex and not fully known. In this study we provide evidence that ATP and other immuno-/neuromodulatory nucleotides are exported from HIV-infected macrophages and modify neuronal structure. Supernatants collected from HIV-infected macrophages (HIV/MDM) contained large amounts of ATP, ADP, AMP and small amounts of adenosine, in addition to glutamate. Dilutions of these supernatants that were sub-threshold for glutamate receptor activation evoked rapid calcium flux in neurons that were completely inhibited by the enzymatic degradation of ATP, or by blockade of calcium permeable purinergic receptors. Applications of these highly diluted HIV/MDM onto neuronal cultures increased the amount of extracellular glutamate by mechanisms dependent on purinergic receptor activation, and downregulated spine density on neurons by mechanisms dependent on purinergic and glutamate receptor activation. We conclude from these data that ATP released from HIV-infected macrophages downregulates dendritic spine density on neurons by a mechanism that involves purinergic receptor mediated modulation of glutamatergic tone. These data suggest that neuronal function may be depressed in HIV infected individuals by mechanisms that involve macrophage release of ATP that triggers secondary effects on glutamate handling.

Delayed administration of VEGF rescues spinal motor neurons from death with a short effective time frame in excitotoxic experimental models in vivo.

VEGF (vascular endothelial growth factor) prevents neuronal death in different models of ALS (amyotrophic lateral sclerosis), but few studies have addressed the efficacy of VEGF to protect motor neurons after the onset of symptoms, a critical point when considering VEGF as a potential therapeutic target for ALS. We studied the capability of VEGF to protect motor neurons after an excitotoxic challenge in two models of spinal neurodegeneration in rats induced by AMPA (α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid) administered either chronically with osmotic minipumps or acutely by microdialysis. VEGF was administered through osmotic minipumps in the chronic model or injected intracerebroventricularly in the acute model, and its effects were assessed by immunohistochemical and histological analyses and motor performance tests. In the chronic model, VEGF stopped the progression of the paralysis and protected motor neurons when administered after AMPA before the onset of the motor symptoms, whereas no protection was observed when administered after the onset. VEGF was also protective in the acute model, but with a short time window, since the protection was effective when administered 1 h but not 2 h after AMPA. Our results indicate that while VEGF has an indubitable neuroprotective effect, its therapeutic potential for halting or delaying the progression of motor neuron loss in ALS would likely have a short effective time frame.

Roles for biological membranes in regulating human immunodeficiency virus replication and progress in the development of HIV therapeutics that target lipid metabolism.

Infection by the human immunodeficiency virus (HIV) involves a number of important interactions with lipid components in host membranes that regulate binding, fusion, internalization, and viral assembly. Available data suggests that HIV actively modifies the sphingolipid content of cellular membranes to create focal environments that are favorable for infection. In this review, we summarize the roles that membrane lipids play in HIV infection and discuss the current status of therapeutics that attempt to modify biological membranes to inhibit HIV.

VEGF protects spinal motor neurons against chronic excitotoxic degeneration in vivo by activation of PI3-K pathway and inhibition of p38MAPK.

Vascular endothelial growth factor (VEGF) protects spinal motor neurons in models of familial amyotrophic lateral sclerosis. We previously demonstrated that VEGF also prevents motor neuron death and hindlimb paralysis in rats subjected to α-amino-3-hydroxy-5-isoxazolepropionate (AMPA)-induced chronic excitotoxic motor neuron degeneration. Here, we show that tyrosine kinase receptor-2 for VEGF (VEGFR2) is expressed in spinal motor neurons of the adult rat, and that its blockade impedes the VEGF-mediated protection against motor neuron death and paralysis. In addition, inhibition of phosphatidyl-inositol-3-kinase, which is activated by VEGFR2, completely prevented this protection, whereas blockade of mitogen-activated protein kinase kinases resulted only in a partial prevention. We show as well that AMPA induces an increased p38 mitogen-activated protein kinase (p38MAPK) phosphorylation and that VEGF blocks this effect. Furthermore, inhibition of p38MAPK prevents the paralysis induced by AMPA. These results shed light into the mechanisms of the protective effect of VEGF against excitotoxic motor neuron death in vivo and suggest that VEGFR2 and activation of phosphatidyl-inositol-3-kinase or inhibition of p38MAPK might be important therapeutic targets for amyotrophic lateral sclerosis.

Vascular endothelial growth factor prevents paralysis and motoneuron death in a rat model of excitotoxic spinal cord neurodegeneration.

Vascular endothelial growth factor (VEGF) delays disease onset and progression in transgenic rodent models of familial amyotrophic lateral sclerosis (ALS). Because most cases of ALS are sporadic, it is important to determine whether VEGF can protect motoneurons in a nontransgenic ALS paradigm. We tested this possibility in a new model of chronic excitotoxic spinal neurodegeneration in the rat. Using osmotic minipumps, we continuously infused the glutamate receptor agonist alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) directly in the lumbar spinal cord. The effect of this treatment on motor behavior was assessed with 3 motor performance tests, and neurodegeneration was evaluated by histologic and immunohistochemical analyses. AMPA infusion produced dose-dependent progressive hindlimb motor deficits, reaching complete bilateral paralysis in approximately 10 days, which was correlated with the loss of spinal motoneurons. VEGF administered together with AMPA completely prevented the motor deficits, and the motoneuron death was reduced by more than 75%. Thus, we have developed an in vivo model of progressive spinal motoneuron death due to overactivation of AMPA receptors. The finding that VEGF protected motoneurons from this AMPA receptor-mediated excitotoxic death suggests that it may be a therapeutic agent in sporadic ALS.