Neuroprotective effect of ACTH on collagenase-induced peri-intraventricular hemorrhage in newborn male rats

Intraventricular hemorrhage induces inflammatory brain damage with blood-brain barrier dysfunction in immature rats

BACKGROUND

We aimed to characterize a preclinical model of intraventricular hemorrhage-induced brain damage (IVH-BD) in extremely low birth weight newborns (ELBWN), to identify potential therapeutic targets based on its pathophysiology.

METHODS

IVH was induced in 1-day-old (P1) Wistar rats by left periventricular injection of clostridium collagenase (PVCC). At P6, P14, and P45 IVH-BD (area of damage, motor and cognitive deficits, Lactate/N-acetylaspartate ratio), white matter injury (WMI: ipsilateral hemisphere and corpus callosum atrophy, oligodendroglial population and myelin basic protein signal reduction), blood-brain barrier (BBB) dysfunction (occludin and Mfsd2a expression, Gadolinium leakage) and inflammation (TNFα, TLR4, NFkB, and MMP9 expression; immune cell infiltration), excitotoxicity (Glutamate/N-acetylaspartate), and oxidative stress (protein nitrosylation) were assessed. Sham animals were similarly studied.

RESULTS

IVH-BD leads to long-term WMI, resulting in motor and cognitive impairment, thus reproducing IVH-BD features in ELBWN. BBB dysfunction with increased permeability was observed at P6 and P14, coincident with an increased inflammatory response with TLR4 overexpression, increased TNFα production, and increased immune cell infiltration, as well as increased excitotoxicity and oxidative stress.

CONCLUSIONS

This model reproduced some key hallmarks of IVH-BD in ELBWN. Inflammation associated with BBB dysfunction appears as relevant therapeutic target to prevent IVH-BD-induced WMI.

IMPACT

Paraventricular injection of clostridium collagenase (PVCC) to 1-day-old Wistar rats uniquely reproduced the neuroimaging, histologic and functional characteristics of intraventricular hemorrhage-induced brain damage (IVH-BD) in extremely low birth weight newborns (ELBWN). PVCC-induced IVH triggered a prolonged inflammatory response associated with blood-brain barrier increased permeability, which in turn facilitates the infiltration of inflammatory cells. Thus, PVCC led to white matter injury (WMI) resulting in long-term motor and cognitive impairment. This model offers a valuable tool to obtain further insight into the mechanisms of IVH-BD in ELBWN and proposes some key therapeutic targets.

Neuroprotective Effects of Betulinic Acid Hydroxamate in Intraventricular Hemorrhage-Induced Brain Damage in Immature Rats

Intraventricular hemorrhage (IVH) is an important cause of long-term disability in extremely preterm infants, with no current treatment. We aimed to study in an IVH model in immature rats the neuroprotective effect of betulinic acid hydroxamate (BAH), a B55α/PP2A activator that inhibits the activity of the hypoxia-inducing factor prolyl-hydroxylase type 2. IVH was induced in 1-day-old (P1) Wistar rats by the left periventricular injection of Clostridial collagenase. Then, pups received i.p. vehicle or BAH 3 mg/kg single dose. At P6, P14 and P45, brain damage (area of damage, neurobehavioral deficits, Lactate/N-acetylaspartate ratio), white matter injury (WMI: corpus callosum atrophy and myelin basic protein signal reduction) and inflammation (TLR4, NF-κB and TNFα expression), excitotoxicity (Glutamate/N-acetylspartate) and oxidative stress (protein nitrosylation) were evaluated. BAH treatment did not reduce the volume of brain damage, but it did reduce perilesional tissue damage, preventing an IVH-induced increase in Lac/NAA. BAH restored neurobehavioral performance at P45 preventing WMI. BAH prevented an IVH-induced increase in inflammation, excitotoxicity and oxidative stress. In conclusion, in immature rats, BAH reduced IVH-induced brain damage and prevented its long-term functional consequences, preserving normal myelination in a manner related to the modulation of inflammation, excitotoxicity and oxidative stress.

Non-Canonical Effects of ACTH: Insights Into Adrenal Insufficiency

Introduction

Adrenocorticotropic hormone (ACTH) is produced from proopiomelanocortin, which is predominantly synthetized in the corticotroph and melanotroph cells of the anterior and intermediate lobes of the pituitary gland and the arcuate nucleus of the hypothalamus. Although ACTH clearly has an effect on adrenal homeostasis and maintenance of steroid hormone production, it also has extra-adrenal effects that require further elucidation.

Methods

We comprehensively reviewed English language articles, regardless of whether they reported the presence or absence of adrenal and extra-adrenal ACTH effects.

Results

In the present review, we provide an overview on the current knowledge on adrenal and extra-adrenal effects of ACTH. In the section on adrenal ACTH effects, we focused on corticosteroid rhythmicity and effects on steroidogenesis, mineralocorticoids and adrenal growth. In the section on extra-adrenal effects, we have analyzed the effects of ACTH on the osteoarticular and reproductive systems, adipocytes, immune system, brain and skin. Finally, we focused on adrenal insufficiency.

Conclusions

The role of ACTH in maintaining the function of the hypothalamic-pituitary-adrenal axis is well known. Conversely, if we broaden our vision and analyze its role as a potential treatment strategy in other conditions, it will be evident in the literature that researchers seem to have abandoned this aspect in studies conducted several years ago. We believe it is worth re-evaluating the role of ACTH considering its noncanonical effects on the adrenal gland itself and on extra-adrenal organs and tissues; however, this would not have been possible without the recent advances in the pertinent technologies.

Hyperoxia Leads to Transient Endocrine Alterations in the Neonatal Rat During Postnatal Development

Introduction: High oxygen concentrations have been identified as one factor contributing to the pathogenesis of the retinopathia of prematurity, chronic lung disease of the preterm infant and preterm brain injury. Preterm infants also show short- and long-term alterations of the endocrine system. If hyperoxia is one pathogenetic factor has not been investigated yet. With regard to the high prevalence of neurodevelopmental impairments in preterm infants, the hypothalamus-pituitary-thyroid (HPT) axis, the hypothalamus-pituitary-adrenal (HPA) axis and the hypothalamus-pituitary-somatotropic (HPS) axis are of special interest due to their important role in neurodevelopment. Objective: The aim of this study was to investigate the effect of hyperoxia on the endocrine system in the neonatal rat by analyzing the activities of the HPT, HPA and HPS axes, respectively. Methods: Three-days old Wistar rats were exposed to hyperoxia (oxygen 80%, 48 h). On postnatal day 5 (P5) and P11, transcript levels of thyroid-stimulating hormone (TSH), proopiomelanocortin and growth hormone (GH) were analyzed in pituitary sections by in situ hybridization. Serologic quantification of TSH and thyroxine (T4), adrenocorticotropic hormone and GH were performed by Multiplex analysis and Enzyme-linked Immunosorbent Assay. Results: At P5, significantly lower GH levels were observed in pituitaries (mRNA) and in sera of rats exposed to hyperoxia. Serum TSH was significantly elevated without changes in T4. Conclusion: This is the first study demonstrating transient endocrine alterations following hyperoxia in the neonatal rat making oxygen a possible contributor to the pathogenesis of endocrine alterations seen in preterm infants. Considering the detrimental multi-organ effects of hyperoxia on the immature organism, a rational use of therapeutic oxygen in the treatrnent of preterm infants is of utmost importance.