Hypothermia: novel approaches for premature infants

Pretreatment with oleuropein protects the neonatal brain from hypoxia-ischemia by inhibiting apoptosis and neuroinflammation

Hypoxic-ischemic (HI) encephalopathy is a cerebrovascular injury caused by oxygen deprivation to the brain and remains a major cause of neonatal mortality and morbidity worldwide. Therapeutic hypothermia is the current standard of care but it does not provide complete neuroprotection. Our aim was to investigate the neuroprotective effect of oleuropein (Ole) in a neonatal (seven-day-old) mouse model of HI. Ole, a secoiridoid found in olive leaves, has previously shown to reduce damage against cerebral and other ischemia/reperfusion injuries. Here, we administered Ole as a pretreatment prior to HI induction at 20 or 100 mg/kg. A week after HI, Ole significantly reduced the infarct area and the histological damage as well as white matter injury, by preserving myelination, microglial activation and the astroglial reactive response. Twenty-four hours after HI, Ole reduced the overexpression of caspase-3 and the proinflammatory cytokines IL-6 and TNF-α. Moreover, using UPLC-MS/MS we found that maternal supplementation with Ole during pregnancy and/or lactation led to the accumulation of its metabolite hydroxytyrosol in the brains of the offspring. Overall, our results indicate that pretreatment with Ole confers neuroprotection and can prevent HI-induced brain damage by modulating apoptosis and neuroinflammation.

Therapeutic hypothermia in preterm infants under 36 weeks: Case series on outcomes and brain MRI findings

PURPOSE

Perinatal hypoxic-ischemic encephalopathy (HIE) is a significant cause of neonatal brain injury. Therapeutic hypothermia (TH) is the standard treatment for term neonates, but its safety and efficacy in neonates < 36 weeks gestational age (GA) remains unclear. This case series aimed to evaluate the outcomes of preterm infants with HIE treated with TH.

METHODS

Retrospective analysis of preterm infants (< 36w GA) treated with TH (01/2019-06/2024). Data on demographics, clinical complications, coagulation profiles, brain magnetic resonance imaging (MRI), and neurodevelopment outcomes were analyzed.

RESULTS

Seventeen patients were included (range 32.5-35.5w, median 34.4; birthweight range 1556-2493 g, median 2300 g), 58.8% were male. Placental abruption was identified in 7 cases (41.2%), and 8 (47.1%) required advanced resuscitation. Thirteen patients (76.5%) presented anemia, 12 (70.6%) coagulopathy, 9 (52.9%) thrombocytopenia, and 9 (52.9%) acute liver failure. Hypofibrinogenemia (< 1 g/L) was significantly associated with severe intracranial hemorrhage (ICH), defined as extracerebral, intraventricular or parenchymal hemorrhage causing mass effect. MRI findings were classified based on the predominant lesion: I- hypoxic-ischemic injury, II- severe ICH, or III- normal/mild findings. Severe ICH was the predominant lesion in 4 cases (23.5%). White matter injury was seen in 12 (76%). Death occurred in 8 cases (47.1%). Of the 9 surviving patients, at 2 years, 6 (66.7%) had normal neurodevelopment, while 1 (11.1%) had severe disability.

CONCLUSION

Coagulation abnormalities, particularly hypofibrinogenemia, significantly increase the risk of severe ICH in < 36w infants treated with TH. The safety and efficacy of TH in this population require further investigation.

Long-chain omega-3 polyunsaturated fatty acids are reduced in neonates with substantial brain injury undergoing therapeutic hypothermia after hypoxic-ischemic encephalopathy

Hypoxic-ischemic encephalopathy (HIE) is a major cause of neonatal morbidity and mortality. Although therapeutic hypothermia is an effective treatment, substantial chronic neurological impairment often persists. The long-chain omega-3 polyunsaturated fatty acids (PUFAs), docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids, offer therapeutic potential in the post-acute phase. To understand how PUFAs are affected by HIE and therapeutic hypothermia we quantified for the first time the effects of HIE and therapeutic hypothermia on blood PUFA levels and lipid peroxidation. In a cross-sectional approach, blood samples from newborns with moderate to severe HIE, who underwent therapeutic hypothermia (sHIE group) were compared to samples from newborns with mild HIE, who did not receive therapeutic hypothermia, and controls. The sHIE group was stratified into cerebral MRI predictive of good (n = 10), or poor outcomes (n = 10; nine developed cerebral palsy). Cell pellets were analyzed for fatty acid content, and plasma for lipid peroxidation products, thiobarbituric acid reactive substances and 4-hydroxy-2-nonenal. Omega-3 Index (% DHA + EPA) was similar between control and HIE groups; however, with therapeutic hypothermia there were significantly lower levels in poor vs. good prognosis sHIE groups. Estimated Δ-6 desaturase activity was significantly lower in sHIE compared to mild HIE and control groups, and linoleic acid significantly increased in the sHIE group with good prognosis. Reduced long-chain omega-3 PUFAs was associated with poor outcome after HIE and therapeutic hypothermia, potentially due to decreased biosynthesis and tissue incorporation. We speculate a potential role for long-chain omega-3 PUFA interventions in addition to existing treatments to improve neurologic outcomes in sHIE.

Unanswered questions regarding therapeutic hypothermia for neonates with neonatal encephalopathy

Therapeutic hypothermia (TH) is now well established to improve intact survival after neonatal encephalopathy (NE). However, many questions could not be addressed by the randomized controlled trials. Should late preterm newborns with NE be cooled? Is cooling beneficial for mild NE? Is the current therapeutic time window optimal, or could it be shortened or prolonged? Will either milder or deeper hypothermia be effective? Does infection/inflammation exposure in the perinatal period in combination with NE offer potentially beneficial preconditioning or might it obviate hypothermic neuroprotection? In the present review, we dissect the evidence, for whom, when and how can TH best be delivered, and highlight areas that need further research.

Nutraceuticals in the Prevention of Neonatal Hypoxia-Ischemia: A Comprehensive Review of their Neuroprotective Properties, Mechanisms of Action and Future Directions

Neonatal hypoxia-ischemia (HI) is a brain injury caused by oxygen deprivation to the brain due to birth asphyxia or reduced cerebral blood perfusion, and it often leads to lifelong limiting sequelae such as cerebral palsy, seizures, or mental retardation. HI remains one of the leading causes of neonatal mortality and morbidity worldwide, and current therapies are limited. Hypothermia has been successful in reducing mortality and some disabilities, but it is only applied to a subset of newborns that meet strict inclusion criteria. Given the unpredictable nature of the obstetric complications that contribute to neonatal HI, prophylactic treatments that prevent, rather than rescue, HI brain injury are emerging as a therapeutic alternative. Nutraceuticals are natural compounds present in the diet or used as dietary supplements that have antioxidant, anti-inflammatory, or antiapoptotic properties. This review summarizes the preclinical in vivo studies, mostly conducted on rodent models, that have investigated the neuroprotective properties of nutraceuticals in preventing and reducing HI-induced brain damage and cognitive impairments. The natural products reviewed include polyphenols, omega-3 fatty acids, vitamins, plant-derived compounds (tanshinones, sulforaphane, and capsaicin), and endogenous compounds (melatonin, carnitine, creatine, and lactate). These nutraceuticals were administered before the damage occurred, either to the mothers as a dietary supplement during pregnancy and/or lactation or to the pups prior to HI induction. To date, very few of these nutritional interventions have been investigated in humans, but we refer to those that have been successful in reducing ischemic stroke in adults. Overall, there is a robust body of preclinical evidence that supports the neuroprotective properties of nutraceuticals, and these may represent a safe and inexpensive nutritional strategy for the prevention of neonatal HI encephalopathy.

Inter-rater reliability of the modified Sarnat examination in preterm infants at 32-36 weeks' gestation

OBJECTIVE

To test the inter-rater reliability of the modified Sarnat neurologic examination in preterm neonates and to correlate abnormalities with the presence of perinatal acidosis.

METHODS

Prospective study of 32-36 weeks' gestational age infants admitted to the neonatal intensive care unit. Each infant had two Sarnat examinations performed at <6 h, one by a gold standard (GS) study investigator, and the second either by (a) another GS examiner or (b) an attending physician (28 examiners), all blinded to clinical variables. Agreement was calculated using kappa (k) statistics.

RESULTS

One hundred and two (9, fetal acidosis) infants underwent a modified Sarnat examination. Among GS examiners, agreement was excellent (k > 0.8) except for Moro, while among all examiners agreement was very good (k > 0.7) except for both Moro and tone. Subgroup analysis at 32-34 weeks' showed fair/poor Moro compared to excellent agreement at ≥35 weeks. Increasing abnormalities correlated with acidosis (r = -0.6, P < 0.01).

CONCLUSIONS

Strong inter-rater reliability for the modified Sarnat was observed except for tone and Moro in preterm infants. Experience of the examiners resulted in improved reliability in tone, while for the Moro agreement improved only beyond 35 weeks. Findings suggest the need of adjustment of the examination form specific for preterm infants.

Behavioral and neuroanatomical outcomes in a rat model of preterm hypoxic-ischemic brain Injury: Effects of caffeine and hypothermia

The current study investigated behavioral and post mortem neuroanatomical outcomes in Wistar rats with a neonatal hypoxic-ischemic (HI) brain injury induced on postnatal day 6 (P6; Rice-Vannucci HI method; Rice et al., 1981). This preparation models brain injury seen in premature infants (gestational age (GA) 32-35 weeks) based on shared neurodevelopmental markers at time of insult, coupled with similar neuropathologic sequelae (Rice et al., 1981; Workman et al., 2013). Clinically, HI insult during this window is associated with poor outcomes that include attention deficit hyperactivity disorder (ADHD), motor coordination deficits, spatial memory deficits, and language/learning disabilities. To assess therapies that might offer translational potential for improved outcomes, we used a P6 HI rat model to measure the behavioral and neuroanatomical effects of two prospective preterm neuroprotective treatments - hypothermia and caffeine. Hypothermia (aka "cooling") is an approved and moderately efficacious intervention therapy for fullterm infants with perinatal hypoxic-ischemic (HI) injury, but is not currently approved for preterm use. Caffeine is a respiratory stimulant used during removal of infants from ventilation but has shown surprising long-term benefits, leading to consideration as a therapy for HI of prematurity. Current findings support caffeine as a preterm neuroprotectant; treatment significantly improved some behavioral outcomes in a P6 HI rat model and partially rescued neuropathology. Hypothermia treatment (involving core temperature reduction by 4 °C for 5 h), conversely, was found to be largely ineffective and even deleterious for some measures in both HI and sham rats. These results have important implications for therapeutic intervention in at-risk preterm populations, and promote caution in the application of hypothermia protocols to at-risk premature infants without further research.

Hypothermia in acute ischemic stroke therapy

Therapeutic hypothermia (TH) is a potent neuroprotective therapy in experimental cerebral ischemia, with multiple effects at several stages of the ischemic cascade. In animals, TH is so powerful that all preclinical stroke studies require strict temperature control. In humans, multiple clinical studies documented powerful protection with TH after accidental neonatal hypoxic-ischemic injury and global cerebral ischemia with return of spontaneous circulation after cardiac arrest. National and international guidelines recommend TH for selected survivors of global ischemia, with profound benefits seen. Recently, a study comparing target temperature 33-36°C failed to demonstrate significant effects in cardiac arrest patients. Additionally, clinical trials of TH for head trauma and stroke have so far failed to confirm benefit in humans despite a vast preclinical literature. Therefore, it is now critical to understand the fundamental explanation for the success of TH in some, but famously not all, clinical trials. TH in animals appears to work when used soon after ischemia onset; for a short duration; and at a deep target temperature.

Impact of transient period of metabolic adaptation on perinatal asphyxia in neonates with intrauterine growth retardation

INTRODUCTION

Temperature, glycemia and respiration make neonatal energy triangle (NET). In growth retardation (IUGR) neonates pathological metabolic adaptation exists in transient neonatal period.

AIM

The of this study was to examine the occurrence of pathological NET and check its impact on perinatal asphyxia during the transient period in IUGR neonates.

MATERIAL AND METHODS

One hundred and fifty-nine neonates with IUGR were classified into - early preterm, late preterm and term neonates. By the presence of hypothermia, hypoglycemia and hypoxia in the first hour after birth neonates were classified into: group of pathological NET, group of unstable NET and group of stable NET. We analyzed distribution per body mass, gestational age, type of IUGR, gender and the frequency of perinatal asphyxia between the groups.

RESULTS

The late preterm neonates were the most frequent in the group of pathological NET. Perinatal asphyxia was diagnosed in 52 (32.7%) neonates, with highest frequency in the group of pathological NET. Univariate binary logistic regression analysis showed that pathological NET in neonates with IUGR is significant predictor for perinatal asphyxia occurrence (OR = 8.57; CI = 4.05-18.12; p < 0.001 R² = 0.27).

CONCLUSION

Poor metabolic adaptation in neonates with IUGR in the first hour after birth is significant risk factor for the perinatal asphyxia.

Thioredoxin 1 and glutaredoxin 2 contribute to maintain the phenotype and integrity of neurons following perinatal asphyxia

BACKGROUND

Thioredoxin (Trx) family proteins are crucial mediators of cell functions via regulation of the thiol redox state of various key proteins and the levels of the intracellular second messenger hydrogen peroxide. Their expression, localization and functions are altered in various pathologies. Here, we have analyzed the impact of Trx family proteins in neuronal development and recovery, following hypoxia/ischemia and reperfusion.

METHODS

We have analyzed the regulation and potential functions of Trx family proteins during hypoxia/ischemia and reoxygenation of the developing brain in both an animal and a cellular model of perinatal asphyxia. We have analyzed the distribution of 14 Trx family and related proteins in the cerebellum, striatum, and hippocampus, three areas of the rat brain that are especially susceptible to hypoxia. Using SH-SY5Y cells subjected to hypoxia and reoxygenation, we have analyzed the functions of some redoxins suggested by the animal experiment.

RESULTS AND CONCLUSIONS

We have described/discovered a complex, cell-type and tissue-specific expression pattern following the hypoxia/ischemia and reoxygenation. Particularly, Grx2 and Trx1 showed distinct changes during tissue recovery following hypoxia/ischemia and reoxygenation. Silencing of these proteins in SH-SY5Y cells subjected to hypoxia-reoxygenation confirmed that these proteins are required to maintain the normal neuronal phenotype.

GENERAL SIGNIFICANCE

These findings demonstrate the significance of redox signaling in cellular pathways. Grx2 and Trx1 contribute significantly to neuronal integrity and could be clinically relevant in neuronal damage following perinatal asphyxia and other neuronal disorders.

Oxygen sensing neurons and neuropeptides regulate survival after anoxia in developing C. elegans

Hypoxic brain injury remains a major source of neurodevelopmental impairment for both term and preterm infants. The perinatal period is a time of rapid transition in oxygen environments and developmental resetting of oxygen sensing. The relationship between neural oxygen sensing ability and hypoxic injury has not been studied. The oxygen sensing circuitry in the model organism C. elegans is well understood. We leveraged this information to investigate the effects of impairments in oxygen sensing on survival after anoxia. There was a significant survival advantage in developing worms specifically unable to sense oxygen shifts below their preferred physiologic range via genetic ablation of BAG neurons, which appear important for conferring sensitivity to anoxia. Oxygen sensing that is mediated through guanylate cyclases (gcy-31, 33, 35) is unlikely to be involved in conferring this sensitivity. Additionally, animals unable to process or elaborate neuropeptides displayed a survival advantage after anoxia. Based on these data, we hypothesized that elaboration of neuropeptides by BAG neurons sensitized animals to anoxia, but further experiments indicate that this is unlikely to be true. Instead, it seems that neuropeptides and signaling from oxygen sensing neurons operate through independent mechanisms, each conferring sensitivity to anoxia in wild type animals.