Could Perinatal Asphyxia Induce a Synaptopathy? New Highlights from an Experimental Model

Pathophysiology of Perinatal Asphyxia in Humans and Animal Models

Perinatal asphyxia is caused by lack of oxygen delivery (hypoxia) to end organs due to an hypoxemic or ischemic insult occurring in temporal proximity to labor (peripartum) or delivery (intrapartum). Hypoxic-ischemic encephalopathy is the clinical manifestation of hypoxic injury to the brain and is usually graded as mild, moderate, or severe. The search for useful biomarkers to precisely predict the severity of lesions in perinatal asphyxia and hypoxic-ischemic encephalopathy (HIE) is a field of increasing interest. As pathophysiology is not fully comprehended, the gold standard for treatment remains an active area of research. Hypothermia has proven to be an effective neuroprotective strategy and has been implemented in clinical routine. Current studies are exploring various add-on therapies, including erythropoietin, xenon, topiramate, melatonin, and stem cells. This review aims to perform an updated integration of the pathophysiological processes after perinatal asphyxia in humans and animal models to allow us to answer some questions and provide an interim update on progress in this field.

Deep hypothermia prevents striatal alterations produced by perinatal asphyxia: Implications for the prevention of dyskinesia and psychosis

GABAergic medium spiny neurons are the main neuronal population in the striatum. Calbindin is preferentially expressed in medium spiny neurons involved in the indirect pathway. The aim of the present work is to analyze the effect of perinatal asphyxia on different subpopulations of GABAergic neurons in the striatum and to assess the outcome of deep therapeutic hypothermia. The uterus of pregnant rats was removed by cesarean section and the fetuses were exposed to hypoxia by immersion in water (19 min) at 37°C (perinatal asphyxia). The hypothermic group was exposed to 10°C during 30 min after perinatal asphyxia. The rats were euthanized at the age of one month (adolescent/adult rats), their brains were dissected out and coronal sections were immunolabeled for calbindin, calretinin, NeuN, and reelin. Reelin+ cells showed no staining in the striatum besides subventricular zone. The perinatal asphyxia (PA) group showed a significant decrease in calbindin neurons and a paradoxical increase in neurons estimated by NeuN staining. Moreover, calretinin+ cells, a specific subpopulation of GABAergic neurons, showed an increase caused by PA. Deep hypothermia reversed most of these alterations probably by protecting calbindin neurons. Similarly, there was a reduction of the diameter of the anterior commissure produced by the asphyxia that was prevented by hypothermic treatment.

Synaptoprotection in Perinatal Asphyxia: An Experimental Approach

Perinatal asphyxia (PA) is an obstetric complication occurring when the oxygen supply to the newborn is temporally interrupted. This health problem is associated with high morbimortality in term and preterm neonates. It severely affects the brain structure and function, involving cortical, hippocampal, and striatal loss of neurons. Nearly 25% of PA survivor newborns develop several neurodevelopmental disabilities. Behavioral alterations, as well as the morphological and biochemical pathways involved in PA pathophysiology, have been studied using an animal model that resembles intrauterine asphyxia. Experimental evidence shows that PA induces synaptic derangement. Then, synaptic dysfunction embodies a putative target for neuroprotective strategies. Over the last years, therapeutic hypothermia (TH), the only treatment available, has shown positive results in the clinic. Several pharmacological agents are being tested in experimental or clinical trial studies to prevent synaptopathy. Preservation of the synaptic structure and function, i.e., “synaptoprotection,” makes up a promising challenge for reducing incidental neurodevelopmental disorders associated with PA. Accordingly, here, we summarize and review the findings obtained from the referred experimental model and propose a renewed overview in the field.

Risk Factors of Perinatal Asphyxia Among Newborns Delivered at Public Hospitals in Addis Ababa, Ethiopia: Case-Control Study

Background

Perinatal asphyxia determines the newborn’s future health status and viability with risk factors yet to be completely understood. It measures the status of the healthcare delivery of an organization including antenatal, intranatal, and postnatal care. In Ethiopia, 31.6% of neonatal mortality was attributed to perinatal asphyxia. This study aimed to assess the risk factors of perinatal asphyxia.

Methods

An unmatched case–control study was conducted on 213 (71 cases selected using lottery method and 142 controls systematically) subjects in Addis Ababa from November 1, 2018 to June 30, 2019. Data were collected using a structured questionnaire through face-to-face interviews, entered to Epi data version 4.4, and exported to SPSS version 25 for analysis. Logistic regression was used for analysis. Variables with p< 0.25 in bivariate analysis were taken to multivariable analysis. Statistical significance was declared at P<0.05 and findings were presented using texts and tables.

Results

A total of 210 newborns (70 cases and 140 controls) and their mothers were included with an overall response rate of 98.5%. Antepartum hemorrhage [AOR=7.17; 95% CI 1.73–29.72], low birth weight [AOR=2.87; 95% CI 1.01–8.13], preterm birth [AOR=3.4; 95% CI 1.04–11.16], caesarean section delivery [AOR=2.75; 95% CI 1.01–7.42], instrumental delivery [AOR=4.88; 95% CI 1.35–17.61], fetal distress [AOR=4.77; 95% CI 1.52–14.92] and meconium-stained amniotic fluid [AOR=9.02; 95% CI 2.96–30.24] were significantly associated with perinatal asphyxia. Hence, efforts ought to go to improve the quality of antenatal and intra-natal services.

Partial Reversal of Striatal Damage by Palmitoylethanolamide Administration Following Perinatal Asphyxia

Perinatal asphyxia (PA) is a clinical condition brought by a birth temporary oxygen deprivation associated with long-term damage in the corpus striatum, one of the most compromised brain areas. Palmitoylethanolamide (PEA) is a neuromodulator well known for its protective effects in brain injury models, including PA, albeit not deeply studied regarding its particular effects in the corpus striatum following PA. Using Bjelke et al. (1991) PA model, full-term pregnant rats were decapitated, and uterus horns were placed in a water bath at 37°C for 19 min. One hour later, the pups were injected with PEA 10 mg/kg s.c., and placed with surrogate mothers. After 30 days, the animals were perfused, and coronal striatal sections were collected to analyze protein-level expression by Western blot and the reactive area by immunohistochemistry for neuron markers: phosphorylated neurofilament-heavy/medium-chain (pNF-H/M) and microtubule-associated protein-2 (MAP-2), and the astrocyte marker, glial fibrillary acidic protein (GFAP). Results indicated that PA produced neuronal damage and morphological changes. Asphyctic rats showed a decrease in pNF-H/M and MAP-2 reactive areas, GFAP⁺ cells number, and MAP-2 as well as pNF-H/M protein expression in the striatum. Treatment with PEA largely restored the number of GFAP⁺ cells. Most important, it ameliorated the decrease in pNF-H/M and MAP-2 reactive areas in asphyctic rats. Noticeably, PEA treatment reversed the decrease in MAP-2 protein expression and largely prevented PA-induced decrease in pNF-H/M protein expression. PA did not affect the GFAP protein level. Treatment with PEA attenuated striatal damage induced by PA, suggesting its therapeutic potential for the prevention of neurodevelopmental disorders.

Neuroprotective Role of Hypothermia in Hypoxic-ischemic Brain Injury: Combined Therapies using Estrogen

Hypoxic-ischemic brain injury is a complex network of factors, which is mainly characterized by a decrease in levels of oxygen concentration and blood flow, which lead to an inefficient supply of nutrients to the brain. Hypoxic-ischemic brain injury can be found in perinatal asphyxia and ischemic-stroke, which represent one of the main causes of mortality and morbidity in children and adults worldwide. Therefore, knowledge of underlying mechanisms triggering these insults may help establish neuroprotective treatments. Selective Estrogen Receptor Modulators and Selective Tissue Estrogenic Activity Regulators exert several neuroprotective effects, including a decrease of reactive oxygen species, maintenance of cell viability, mitochondrial survival, among others. However, these strategies represent a traditional approach of targeting a single factor of pathology without satisfactory results. Hence, combined therapies, such as the administration of therapeutic hypothermia with a complementary neuroprotective agent, constitute a promising alternative. In this sense, the present review summarizes the underlying mechanisms of hypoxic-ischemic brain injury and compiles several neuroprotective strategies, including Selective Estrogen Receptor Modulators and Selective Tissue Estrogenic Activity Regulators, which represent putative agents for combined therapies with therapeutic hypothermia.

Determinants of birth asphyxia among live birth newborns in University of Gondar referral hospital, northwest Ethiopia: A case-control study

Background

Birth asphyxia, which accounts for 31.6% of all neonatal deaths, is one of the leading causes of such mortality in Ethiopia. Early recognition and management of its contributing factors would modify the problem. Thus, this study aimed to identify the determinants of birth asphyxia among live births at the University of Gondar Referral Hospital, northwest Ethiopia.

Methods

A hospital-based unmatched case-control study was conducted from April to July 2017.Cases were newborn babies with an APGAR score of < 7at 5 minutes of birth; controls were newborn babies with an APGAR score of ≥7 at 5 minutes of birth. Every other asphyxiated baby was selected as a case and every 6^th non-asphyxiated baby as a control. A pretested structured questionnaire was used to collect data on maternal sociodemographic characteristics. A pretested structured checklist was used to retrieve data on ante-partum, intra-partum, and neonatal factors of both cases and controls. Data were entered using Epi Info 7 and analyzed using SPSS 20. The bivariate logistic regression analysis was used to identify the relation of each independent variable to the outcome variable. Variables with p values of up to 0.2 in the bivariate analysis were considered for the multiple logistic regression analysis. An adjusted odds ratio (AOR) with a 95% CI and p-value of <0.05 was used to identify significant variables associated with birth asphyxia.

Results

In this study, prolonged labor (AOR = 2.75, 95% CI: 1.18, 6.94), cesarean section delivery (AOR = 3.58, 95% CI: 1.13, 11.31), meconium stained amniotic fluid (AOR = 7.69, 95% CI: 2.99, 17.70), fetal distress (AOR = 5.74, 95% CI: 1.53, 21.55), and low birth weight (AOR = 7.72, 95% CI: 1.88, 31.68) were factors which significantly increased the odds of birth asphyxia.

Conclusion

Prolonged labor, cesarean section (CS) delivery, meconium stained amniotic fluid (AF), fetal distress, and low birth weight were the determinants of birth asphyxia. Thus, efforts should be made to improve the quality of intra-partum care services in order to prevent prolonged labor and fetal complications, and to identify and make a strict follow up on mothers with meconium stained amniotic fluid.

Neuroprotection Targeting Protein Misfolding on Chronic Cerebral Hypoperfusion in the Context of Metabolic Syndrome

Metabolic syndrome (MetS) is a cluster of risk factors that lead to microvascular dysfunction and chronic cerebral hypoperfusion (CCH). Long-standing reduction in oxygen and energy supply leads to brain hypoxia and protein misfolding, thereby linking CCH to Alzheimer's disease. Protein misfolding results in neurodegeneration as revealed by studying different experimental models of CCH. Regulating proteostasis network through pathways like the unfolded protein response (UPR), the ubiquitin-proteasome system (UPS), chaperone-mediated autophagy (CMA), and macroautophagy emerges as a novel target for neuroprotection. Lipoxin A4 methyl ester, baclofen, URB597, N-stearoyl-L-tyrosine, and melatonin may pose potential neuroprotective agents for rebalancing the proteostasis network under CCH. Autophagy is one of the most studied pathways of proteostatic cell response against the decrease in blood supply to the brain though the role of the UPR-specific chaperones and the UPS system in CCH deserves further research. Pharmacotherapy targeting misfolded proteins at different stages in the proteostatic pathway might be promising in treating cognitive impairment following CCH.

Palmitoylethanolamide Ameliorates Hippocampal Damage and Behavioral Dysfunction After Perinatal Asphyxia in the Immature Rat Brain

Perinatal asphyxia (PA) is an obstetric complication associated with an impaired gas exchange. This health problem continues to be a determinant of neonatal mortality and neurodevelopmental disorders. Palmitoylethanolamide (PEA) has exerted neuroprotection in several models of brain injury and neurodegeneration. We aimed at evaluating the potential neuroprotective role of PEA in an experimental model, which induces PA in the immature rat brain. PA was induced by placing Sprague Dawley newborn rats in a water bath at 37°C for 19 min. Once their physiological conditions improved, they were given to surrogate mothers that had delivered normally within the last 24 h. The control group was represented by non-fostered vaginally delivered pups, mimicking the clinical situation. Treatment with PEA (10 mg/kg) was administered within the first hour of life. Modifications in the hippocampus were analyzed with conventional electron microscopy, immunohistochemistry (for NeuN, pNF-H/M, MAP-2, and GFAP) and western blot (for pNF H/M, MAP-2, and GFAP). Behavior was also studied throughout Open Field (OF) Test, Passive Avoidance (PA) Task and Elevated Plus Maze (EPM) Test. After 1 month of the PA insult, we observed neuronal nucleus degeneration in CA1 using electron microscopy. Immunohistochemistry revealed a significant increase in pNF-H/M and decrease in MAP-2 in CA1 reactive area. These changes were also observed when analyzing the level of expression of these markers by western blot. Vertical exploration impairments and anxiety-related behaviors were encountered in the OF and EPM tests. PEA treatment attenuated PA-induced hippocampal damage and its corresponding behavioral alterations. These results contribute to the elucidation of PEA neuroprotective role after PA and the future establishment of therapeutic strategies for the developing brain.