Publications by authors named "Jonathan J Hirst"

Preterm birth exposes the neonate to hypoxic-ischaemic and excitotoxic insults that impair neurodevelopment and are magnified by the premature loss of placentally supplied, inhibitory neurosteroids. The cerebellum is a neuronally dense brain region, which undergoes critical periods of development during late gestation, when preterm births frequently occur. We propose that neurosteroid replacement therapy using tiagabine and zuranolone will protect the cerebellum against preterm-associated insults.

View Article and Find Full Text PDF
Article Synopsis
  • High levels of the neurosteroid allopregnanolone during pregnancy are crucial for fetal brain development, but maternal stress can lower these levels, leading to myelination issues and increased behavioral disorders in childhood.
  • Supplementing neurosteroid action with allopregnanolone analogues or using mitochondrial translocator protein (TSPO) ligands can help reverse developmental deficits that arise from low allopregnanolone levels.
  • Preterm birth significantly decreases neurosteroid support, causing severe myelination deficits; however, postnatal treatments like ganaxolone can enhance myelination and reduce hyperactivity, suggesting potential therapeutic benefits of allopregnanolone after pregnancy issues.
View Article and Find Full Text PDF

Background: Research in the developmental origins of health and disease provides compelling evidence that adverse events during the first 1000 days of life from conception can impact life course health. Despite many decades of research, we still lack a complete understanding of the mechanisms underlying some of these associations. The Newcastle 1000 Study (NEW1000) is a comprehensive, prospective population-based pregnancy cohort study based in Newcastle, New South Wales, Australia, that will recruit pregnant women and their partners at 11-14 weeks' gestation, with assessments at 20, 28, and 36 weeks; birth; 6 weeks; and 6 months, in order to provide detailed data about the first 1000 days of life to investigate the developmental origins of noncommunicable diseases.

View Article and Find Full Text PDF

The postnatal environment is challenging for the preterm neonate with exposure to hypoxic and excitotoxic events, amplified by premature loss of placentally derived neurosteroids. Between preterm birth and term equivalent age (TEA), cerebellar development continues despite these challenges. We hypothesize that neurosteroid replacement therapy during this time will support optimal cerebellar development.

View Article and Find Full Text PDF
Article Synopsis
  • Preterm birth can lead to brain injuries and long-term behavioral issues due to the loss of neurosteroid support from the placenta, increasing the risk of excitotoxic damage.
  • The study used guinea pigs to test zuranolone, an analogue of allopregnanolone, by administering it to preterm pups and analyzing behavior and brain structure.
  • Zuranolone treatment improved behavioral outcomes, prevented hyperactivity in male pups, and restored myelination and neurotransmitter pathways in preterm offspring, suggesting its potential as a neuroprotective therapy for preventing long-term impairments after preterm birth.
View Article and Find Full Text PDF

Introduction: Multiple cohort studies have been established to investigate the impact of early life factors on development and health outcomes. In Australia the majority of these studies were established more than 20 years ago and, although longitudinal in nature, are inherently susceptible to socioeconomic, environmental and cultural influences which change over time. Additionally, rapid leaps in technology have increased our understanding of the complex role of gene-environment interactions in life course health, highlighting the need for new cohort studies with repeated biological sampling and in-depth phenotype data across the first 1000 days of life from conception.

View Article and Find Full Text PDF

Disruptions to neurodevelopment are known to be linked to behavioral disorders in childhood and into adulthood. The fetal brain is extremely vulnerable to stimuli that alter inhibitory GABAergic pathways and critical myelination processes, programing long-term neurobehavioral disruption. The maturation of the GABAergic system into the major inhibitory pathway in the brain and the development of oligodendrocytes into mature cells capable of producing myelin are integral components of optimal neurodevelopment.

View Article and Find Full Text PDF

The decidua undergoes proinflammatory activation in late pregnancy, promoting labor. Bromodomain and Extra-Terminal (BET) family proteins interact with acetylated histones and may control gene expression in inflammation. Here, we assessed whether BETs are involved in inflammatory gene regulation in human decidual cells.

View Article and Find Full Text PDF

Objective: Seizures are more common in the neonatal period than at any other stage of life. Phenobarbital is the first-line treatment for neonatal seizures and is at best effective in approximately 50% of babies, but may contribute to neuronal injury. Here, we assessed the efficacy of phenobarbital versus the synthetic neurosteroid, ganaxolone, to moderate seizure activity and neuropathology in neonatal lambs exposed to perinatal asphyxia.

View Article and Find Full Text PDF

Preterm birth can lead to brain injury and currently there are no targeted therapies to promote postnatal brain development and protect these vulnerable neonates. We have previously shown that the neurosteroid-analogue ganaxolone promotes white matter development and improves behavioural outcomes in male juvenile guinea pigs born preterm. Adverse side effects in this previous study necessitated this current follow-up dosing study, where a focus was placed upon physical wellbeing during the treatment administration and markers of neurodevelopment at the completion of the treatment period.

View Article and Find Full Text PDF
Article Synopsis
  • The study investigates the impact of prenatal stress on the balance between inhibitory (GABA) and excitatory (glutamate) systems in guinea pig offspring, which can lead to neurological issues.
  • Pregnant guinea pigs were exposed to strobe lights to induce stress, and their pups received treatments like allopregnanolone or vehicle after birth to assess if neurosteroid supplementation could mitigate negative effects.
  • Findings revealed that stress resulted in immature GABA receptor expression and reduced inhibition in pups, though ganaxolone treatment provided some neuroprotective benefits against excitotoxicity.
View Article and Find Full Text PDF

Background: Prenatal stress is associated with long-term disturbances in white matter development and behaviour in children, such as attention deficit hyperactivity disorder (ADHD) and anxiety. Oligodendrocyte maturation and myelin formation is a tightly orchestrated process beginning during gestation, and therefore is very vulnerable to the effects of maternal prenatal stresses in mid-late pregnancy. The current study aimed to examine the effects of prenatal stress on components of the oligodendrocyte lineage to identify the key processes that are disrupted and to determine if postnatal therapies directed at ameliorating white matter deficits also improve behavioural outcomes.

View Article and Find Full Text PDF

Dehydroepiandrosterone (DHEA) and its sulfated metabolite (DHEAS) are dynamically regulated before birth and the onset of puberty. Yet, the origins and purpose of increasing DHEA[S] in postnatal development remain elusive. Here, we draw attention to this pre-pubertal surge from the adrenal gland-the adrenarche-and discuss whether this is the result of intra-adrenal gene expression specifically affecting the zona reticularis (ZR), if the ZR is influenced by the hypothalamic-pituitary axis, and the possible role of spino-sympathetic innervation in prompting increased ZR activity.

View Article and Find Full Text PDF

Preterm birth is associated with poor long-term neurodevelopmental and behavioral outcomes, even in the absence of obvious brain injury at the time of birth. In particular, behavioral disorders characterized by inattention, social difficulties and anxiety are common among children and adolescents who were born moderately to late preterm (32-37 weeks' gestation). Diffuse deficits in white matter microstructure are thought to play a role in these poor outcomes with evidence suggesting that a failure of oligodendrocytes to mature and myelinate axons is responsible.

View Article and Find Full Text PDF
Article Synopsis
  • Chronic stress during and after pregnancy can elevate cortisol levels, which is linked to developmental behavioral disorders in children.
  • The study aimed to investigate if prenatal (before birth) and postnatal (after birth) stress leads to deficits in the hippocampus related to behavior, myelination, and neurotransmitter pathways, specifically in guinea pigs.
  • Results showed that male guinea pig offspring exposed to prenatal stress displayed behavioral changes and alterations in brain markers associated with myelination and GABA/glutamate pathways.
View Article and Find Full Text PDF

Extensive evidence now shows that adversity during the perinatal period is a significant risk factor for the development of neurodevelopmental disorders long after the causative event. Despite stemming from a variety of causes, perinatal compromise appears to have similar effects on the developing brain, thereby resulting in behavioural disorders of a similar nature. These behavioural disorders occur in a sex-dependent manner, with males affected more by externalising behaviours such as attention deficit hyperactivity disorder (ADHD) and females by internalising behaviours such as anxiety.

View Article and Find Full Text PDF
Article Synopsis
  • Children born preterm face higher risks for cognitive issues and neuro-behavioral disorders like ADHD and anxiety, especially when compared to term-born peers.
  • Poor cognitive outcomes can arise from birth complications affecting newborns of any gestational age, but preterm infants are particularly vulnerable to learning difficulties and increased need for special education resources.
  • The loss of neuroprotective factors like allopregnanolone in preterm infants contributes to disrupted myelination and brain injury, leading to potential long-term neurodevelopmental challenges.
View Article and Find Full Text PDF

Inflammatory genes are expressed increasingly in the foetal membranes at late gestation triggering birth. Here we have examined whether epigenetic histone modifications contribute to the upregulation of proinflammatory genes in the amnion in late pregnancy and at labour. Amnion samples were collected from early pregnancy, at term in the absence of labour and after spontaneous birth.

View Article and Find Full Text PDF

The guinea pig (Cavia porcellus) displays many features of gestational physiology that makes it the most translationally relevant rodent species. Progesterone production undergoes a luteal to placental shift as in human pregnancy with levels rising during gestation and with labor and delivery occurring without a precipitous decline in maternal progesterone levels. In contrast to other laboratory rodents, labor in guinea pigs is triggered by a functional progesterone withdrawal, which involves the loss of uterine sensitivity to progesterone like in women.

View Article and Find Full Text PDF

DHEA and DHEAS are neuroactive neurosteroids that interact with several major receptor systems in the brain, including sigma (σ), glutamate, and GABA-A receptors. It has been recognized as early as 1952, that the loss of DHEA/DHEAS in adult life is associated with neuropsychiatric disorders (eg schizophrenia, depression). However, the mechanistic role for DHEA/DHEAS in any of these domains remains speculative, not the least because the presence of these androgens in the adrenal gland and brain is largely confined to humans and only some non-human primates.

View Article and Find Full Text PDF
Article Synopsis
  • Preterm-born children, especially boys, face higher risks of ADHD and learning challenges, and the study explores using ganaxolone (GNX) to potentially improve their neurodevelopment.
  • In an experiment with male preterm pups, those treated with GNX exhibited behavior similar to term-born pups, and improvements in myelin development were noted in key brain areas, indicating positive neurological effects.
  • However, the treatment was associated with poor weight gain and increased sedation, highlighting the need for further research to minimize adverse effects while reinforcing the benefits of ganaxolone for preterm infants.
View Article and Find Full Text PDF

Over 30 years ago Professor David Barker first proposed the theory that events in early life could explain an individual's risk of non-communicable disease in later life: the developmental origins of health and disease (DOHaD) hypothesis. During the 1990s the validity of the DOHaD hypothesis was extensively tested in a number of human populations and the mechanisms underpinning it characterised in a range of experimental animal models. Over the past decade, researchers have sought to use this mechanistic understanding of DOHaD to develop therapeutic interventions during pregnancy and early life to improve adult health.

View Article and Find Full Text PDF
Article Synopsis
  • Preterm birth increases the risk of cognitive and behavioral issues in children, particularly affecting cerebellum development and GABA pathways.
  • Researchers conducted a study on guinea pigs to analyze cerebellar markers and their differences between preterm (GA62) and term (GA69) deliveries.
  • Results showed altered GABAergic system components in the preterm cerebellum, with distinct changes in myelin and GAD67 expression based on sex, suggesting potential neurodevelopmental implications.
View Article and Find Full Text PDF
Article Synopsis
  • Prenatal stress may lead to behavioral issues in offspring due to its impact on cerebellar development and GABA signaling.
  • A study on guinea pigs exposed to prenatal stress showed significant changes in cerebellar cellular components, particularly a decrease in mature oligodendrocytes and reactive astrocytes, which improved by postnatal day 21.
  • While some markers related to GABA signaling remained unchanged, there was a notable increase in 5α-reductase type-1 mRNA, suggesting a potential neuroprotective adaptation in response to prenatal stress.
View Article and Find Full Text PDF

Neonatal seizures are amongst the most common neurologic conditions managed by a neonatal care service. Seizures can exacerbate existing brain injury, induce "de novo" injury, and are associated with neurodevelopmental disabilities in post-neonatal life. In this mini-review, we present evidence in support of the use of ganaxolone, a GABA agonist neurosteroid, as a novel neonatal therapy.

View Article and Find Full Text PDF