Intranasal Methylprednisolone Ameliorates Neuroinflammation Induced by Chronic Toluene Exposure.

Inhalants are chemical substances that induce intoxication, and toluene is the main component of them. Increasing evidence indicates that a dependence on inhalants involves a state of chronic stress associated to the activation of immune cells in the central nervous system and release of proinflammatory mediators, especially in some brain areas such as the nucleus accumbens and frontal cortex, where the circuits of pleasure and reward are. In this study, anti-neuroinflammatory treatment based on a single dose of intranasal methylprednisolone was assessed in a murine model of chronic toluene exposure. The levels of proinflammatory mediators, expression levels of Iba-1 and GFAP, and histological changes in the frontal cortex and nucleus accumbens were evaluated after the treatment. The chronic exposure to toluene significantly increased the levels of TNF-α, IL-6, and NO, the expression of GFAP, and induced histological alterations in mouse brains. The treatment with intranasally administered MP significantly reduced the expression of TNF-α and NO and the expression of GFAP (p < 0.05); additionally, it reversed the central histological damage. These results indicate that intranasally administered methylprednisolone could be considered as a treatment to reverse neuroinflammation and histological damages associated with the use of inhalants.

Nose-to-Brain Delivery of Dexamethasone: Biodistribution Studies in Mice.

Neuroinflammation (NI) is an important physiologic process which promotes the tissue repair and homeostatic maintenance in the central nervous system after different types of insults. However, when it is exacerbated and sustained in time, NI plays a critical role in the pathogenesis of different neurologic diseases. The high systemic doses required for brain-specific targeting lead to severe undesirable effects. The intranasal (IN) route has been proposed as an alternative drug administration route for a better NI control. Herein, the brain biodistribution of intranasally administered dexamethasone versus intravenously administered one is reported. A higher amount of dexamethasone was found in every analyzed region of those brains of intranasally administered mice. HPLC analysis also revealed that IN administration allows Dex to arrive faster and in a greater concentration to the brain in comparison with intravenous administration, data confirmed by immunofluorescence and HPLC analysis. These data support the proposal of the IN administration of Dex as an alternative for a more efficient control of NI. SIGNIFICANCE STATEMENT: This work highlights the biodistribution of dexamethasone after its intranasal administration. Intranasal administration allows for a faster arrival, better distribution, and a higher concentration of the drug within the brain compared to its intravenous administration. These results explain some of the evidence shown in a previous work in which dexamethasone controls neuroinflammation in a murine stroke model and can be used to propose alternative treatments for neuroinflammatory diseases.

Intranasal Dexamethasone Reduces Mortality and Brain Damage in a Mouse Experimental Ischemic Stroke Model.

Neuroinflammation triggered by the expression of damaged-associated molecular patterns released from dying cells plays a critical role in the pathogenesis of ischemic stroke. However, the benefits from the control of neuroinflammation in the clinical outcome have not been established. In this study, the effectiveness of intranasal, a highly efficient route to reach the central nervous system, and intraperitoneal dexamethasone administration in the treatment of neuroinflammation was evaluated in a 60-min middle cerebral artery occlusion (MCAO) model in C57BL/6 male mice. We performed a side-by-side comparison using intranasal versus intraperitoneal dexamethasone, a timecourse including immediate (0 h) or 4 or 12 h poststroke intranasal administration, as well as 4 intranasal doses of dexamethasone beginning 12 h after the MCAO versus a single dose at 12 h to identify the most effective conditions to treat neuroinflammation in MCAO mice. The best results were obtained 12 h after MCAO and when mice received a single dose of dexamethasone (0.25 mg/kg) intranasally. This treatment significantly reduced mortality, neurological deficits, infarct volume size, blood-brain barrier permeability in the somatosensory cortex, inflammatory cell infiltration, and glial activation. Our results demonstrate that a single low dose of intranasal dexamethasone has neuroprotective therapeutic effects in the MCAO model, showing a better clinical outcome than the intraperitoneal administration. Based on these results, we propose a new therapeutic approach for the treatment of the damage process that accompanies ischemic stroke.

Intranasal Methylprednisolone Effectively Reduces Neuroinflammation in Mice With Experimental Autoimmune Encephalitis.

Relapsing-remitting multiple sclerosis, the most common form, is characterized by acute neuroinflammatory episodes. In addition to continuous disease-modifying therapy, these relapses require treatment to prevent lesion accumulation and progression of disability. Intravenous methylprednisolone (1-2 g for 3-5 days) is the standard treatment for relapses. However, this treatment is invasive, requires hospitalization, leads to substantial systemic exposure of glucocorticoids, and can only reach modest concentrations in the central nervous system (CNS). Intranasal delivery may represent an alternative to deliver relapse treatment directly to the CNS with higher concentrations and reducing side effects. Histopathological analysis revealed that intranasal administration of methylprednisolone to mice with experimental autoimmune encephalomyelitis (EAE) suppressed the neuroinflammatory peak, and reduced immune cell infiltration and demyelination in the CNS similarly to intravenous administration. Treatment also downregulated Iba1 and GFAP expression. A similar significant reduction of IL-1ß, IL-6, IL-17, IFN-γ, and TNF-α levels in the spinal cord was attained in both intranasal and intravenously treated mice. No damage in the nasal cavity was found after intranasal administration. This study demonstrates that intranasal delivery of methylprednisolone is as efficient as the intravenous route to treat neuroinflammation in EAE.

Sepsis: developing new alternatives to reduce neuroinflammation and attenuate brain injury.

Sepsis occurs when a systemic infection induces an uncontrolled inflammatory response that results in generalized organ dysfunction. The exacerbated peripheral inflammation can induce, in turn, neuroinflammation which may result in severe impairment of the central nervous system (CNS). Indeed, the ensuing blood-brain barrier disruption associated with sepsis promotes glial activation and starts a storm of proinflammatory cytokines in the CNS that leads to brain dysfunction in sepsis survivors. Endotoxic shock induced in mice by peripheral injection of lipopolysaccharides closely resembles the peripheral and central inflammation observed in sepsis. In this review, we provide an overview of the neuroinflammatory features in sepsis and of recent progress toward the development of new anti-neuroinflammatory therapies seeking to reduce mortality and morbidity in sepsis survivors.

Recovery from an acute systemic and central LPS-inflammation challenge is affected by mouse sex and genetic background.

Genetic and sexual factors influence the prevalence and the pathogenesis of many inflammatory disorders. In this study their relevance on the peripheral and central inflammatory status induced by a peripheral injection of lipopolysaccharide (LPS) was evaluated. BALB/c and CD-1 male and female mice were intraperitoneally injected with LPS. Spleens and brains were collected 2 and 72 hours later to study the levels of IL-6, TNF-α and IL-1ß. Percentage of microglia and astrocytes was determined in the cortex and hippocampus. Locomotor activity was registered before and during the 72 hours after LPS-treatment. Two hours after LPS-injection, a peripheral increase of the three cytokines was found. In brains, LPS increased TNF-α only in males with higher levels in CD-1 than BALB/c. IL-1ß increased only in CD-1 males. IL-6 increased in both strains with lower levels in BALB/c females. Peripheral and central levels of cytokines decline 72 hrs after LPS-treatment whilst a significantly increase of Iba-1 expression was detected. A dramatic drop of the locomotor activity was observed immediately after LPS injection. Our results show that acute systemic administration of LPS leads to peripheral and central increase of pro-inflammatory cytokines and microglia activation, in a strain and sex dependent manner.