Intraventricular ascorbic acid administration decreases hypoxic-ischemic brain injury in newborn rats

The pharmacology of vitamin C

Ascorbic acid, the reduced form of vitamin C, is a ubiquitous small carbohydrate. Despite decades of focused research, new metabolic functions of this universal electron donor are still being discovered and add to the complexity of our view of vitamin C in human health. Although praised as an unsurpassed water-soluble antioxidant in plasma and cells, the most interesting functions of vitamin C seem to be its roles as specific electron donor in numerous biological reactions ranging from the well-known hydroxylation of proline to cofactor for the epigenetic master regulators ten-eleven translocation enzymes and Jumonji domain-containing histone-lysine demethylases. Some of these functions may have important implications for disease prevention and treatment and have spiked renewed interest in, eg, vitamin C's potential in cancer therapy. Moreover, some fundamental pharmacokinetic properties of vitamin C remain to be established including if other mechanisms than passive diffusion governs the efflux of ascorbate anions from the cell. Taken together, there still seems to be much to learn about the pharmacology of vitamin C and its role in health and disease. This review explores new avenues of vitamin C and integrates our present knowledge of its pharmacology. SIGNIFICANCE STATEMENT: Vitamin C is involved in multiple biological reactions of which most are essential to human health. Hundreds of millions of people are considered deficient in vitamin C according to accepted guidelines, but little is known about the long-term consequences. Although the complexity of vitamin C's physiology and pharmacology has been widely disregarded in clinical studies for decades, it seems clear that a deeper understanding of particularly its pharmacology holds the key to unravel and possibly exploit the potential of vitamin C in disease prevention and therapy.

Antioxidant Therapy in Neonatal Hypoxic Ischemic Encephalopathy: Adjuvant or Future Alternative to Therapeutic Hypothermia?

BACKGROUND

Oxidative stress-related diseases in newborns arise from pro-oxidant/antioxidant imbalance in both term and preterm neonates. Pro-oxidant/antioxidant imbalance has shown to be present in different pathological conditions such as hypoxic ischemic encephalopathy (HIE), retinopathy of prematurity (ROP), bronchopulmonary dysplasia (BPD), necrotizing enterocolitis (NEC), and patent ductus arteriosus (PDA).

METHODS AND RESULTS

We performed a narrative review according to the most recent available literature (2012-2024), using Scopus and PubMed as electronic databases. Many observational and experimental studies in vitro and in vivo have evaluated the effectiveness of antioxidant therapies such as melatonin, erythropoietin (EPO), allopurinol, N-acetylcisteine (NAS), and nitric oxide synthase (NOS) inhibitors in these diseases. Perinatal asphyxia is one of the most important causes of mortality and morbidity in term and near-term newborns. Therapeutic hypothermia (TH) is the gold standard treatment for neonates with moderate-severe perinatal asphyxia, resulting in a reduction in the mortality and neurodevelopmental disability rates.

CONCLUSIONS

According to the most recent literature and clinical trials, melatonin, allopurinol, NAS, NOS inhibitors, magnesium sulfate, and stem cells stand out as promising as both adjuvants and future probable alternatives to TH in the treatment of HIE.

Vitamin C Intake and Ischemic Stroke

Vitamin C is an essential micronutrient with important antioxidant properties. Ischemic stroke is a major public health problem worldwide. Extensive evidence demonstrates that vitamin C has protective effects against cardiovascular disease, and there is a close relationship between vitamin C intake and ischemic stroke risk. Based on the evidence, we conducted this umbrella review to clarify the relationship between vitamin C intake and ischemic stroke risk from four perspectives: cellular mechanisms, animal experiments, clinical trials, and cohort studies.

Ascorbate deficiency confers resistance to hippocampal neurodegeneration after asphyxial cardiac arrest in juvenile rats

BACKGROUND

Asphyxial cardiac arrest (CA) is a significant cause of death and disability in children. Using juvenile Osteogenic disorder Shionogi (ODS) rats that, like humans, do not synthesize ascorbate, we tested the effect of ascorbate deficiency on functional and histological outcome after CA.

METHODS

Postnatal day 16-18 milk-fed ODS and wild-type Wistar rats underwent 9-min asphyxial CA (n = 8/group) or sham surgery (n = 4/group). ODS mothers received ascorbate in drinking water to prevent scurvy. Levels of ascorbate and glutathione (GSH) were measured in plasma and hippocampus at baseline and after CA. Neurologic deficit score (NDS) was measured at 3, 24, and 48 h and hippocampal neuronal counts, neurodegeneration, and microglial activation were assessed at day 7.

RESULTS

ODS rats showed depletion of plasma and hippocampal ascorbate, attenuated hippocampal neurodegeneration and microglial activation, and increased CA1 hippocampal neuron survival vs. Wistar rats while NDS were similar. Hippocampal GSH levels were higher in ODS vs. Wistar rats at baseline and 10 min, whereas hypoxia-inducible factor-1α levels were higher in Wistar vs. ODS rats at 24 , after CA.

CONCLUSION

Ascorbate-deficient juvenile ODS rats appear resistant to neurodegeneration produced by asphyxia CA, possibly related to upregulation of the endogenous antioxidant GSH in brain.

IMPACT

Like humans and unlike other rodents, osteogenic disorder Shionogi (ODS) rats do not synthesize ascorbate, and thus may serve as a useful model for studying the role of ascorbate in human disease. Conflicting evidence exists regarding ascorbate's protective versus detrimental effects in animal models and clinical studies. Ascorbate-deficient ODS rats are resistant to neurodegeneration after experimental cardiac arrest.

Mechanisms of Vitamin C Regulating Immune and Inflammation Associated with Neonatal Hypoxic-Ischemic Encephalopathy Based on Network Pharmacology and Molecular Simulation Technology

Background

There are still controversies about the curative effect of vitamin C in treating HIE, and its mechanism of action is not entirely clear. This study is designed to explore the potential molecular mechanism of vitamin C in treating neonatal hypoxic ischemic encephalopathy (HIE).

Methods

The effect targets of vitamin C and the pathogenic targets of neonatal HIE were obtained via retrieval of public databases to screen out the molecular targets of vitamin C acting on neonatal HIE. Gene Ontology (GO) functional annotations and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed on the main targets. Vitamin C and the optimum target structural components are subjected to molecular docking and molecular dynamics simulation analysis via computer software so as to verify their binding activity and stability.

Result

Based on 16 overlapping targets of vitamin C and HIE, seven main targets were identified in this study. According to GO and KEGG analysis, molecular functions (top 25 items) and signal pathways (21 items) related to inflammatory reaction, immune response, and cell transcriptional control may be potential pathways for vitamin C to treat neonatal HIE. Molecular docking and molecular dynamics simulation were adopted to definitively determine the 4 optimum core target spots.

Conclusion

The efficacy of vitamin C on HIE is involved in the immunoregulation and inflammation-related functional processes and signal pathways. These molecular mechanisms, including core targets, will contribute to the clinical practice of neonatal HIE in the future.

Therapies for neonatal encephalopathy: Targeting the latent, secondary and tertiary phases of evolving brain injury

In term and near-term neonates with neonatal encephalopathy, therapeutic hypothermia protocols are well established. The current focus is on how to improve outcomes further and the challenge is to find safe and complementary therapies that confer additional protection, regeneration or repair in addition to cooling. Following hypoxia-ischemia, brain injury evolves over three main phases (latent, secondary and tertiary), each with a different brain energy, perfusion, neurochemical and inflammatory milieu. While therapeutic hypothermia has targeted the latent and secondary phase, we now need therapies that cover the continuum of brain injury that spans hours, days, weeks and months after the initial event. Most agents have several therapeutic actions but can be broadly classified under a predominant action (e.g., free radical scavenging, anti-apoptotic, anti-inflammatory, neuroregeneration, and vascular effects). Promising early/secondary phase therapies include Allopurinol, Azithromycin, Exendin-4, Magnesium, Melatonin, Noble gases and Sildenafil. Tertiary phase agents include Erythropoietin, Stem cells and others. We review a selection of promising therapeutic agents on the translational pipeline and suggest a framework for neuroprotection and neurorestoration that targets the evolving injury.

Neuroprotective Properties of Vitamin C: A Scoping Review of Pre-Clinical and Clinical Studies

There is a need for novel neuroprotective therapies. We aimed to review the evidence for exogenous vitamin C as a neuroprotective agent. MEDLINE, Embase, and Cochrane library databases were searched from inception to May 2020. Pre-clinical and clinical reports evaluating vitamin C for acute neurological injury were included. Twenty-two pre-clinical and 11 clinical studies were eligible for inclusion. Pre-clinical studies included models of traumatic and hypoxic brain injury, subarachnoid and intracerebral hemorrhage, and ischemic stroke. The median [IQR] maximum daily dose of vitamin C in animal studies was 120 [50-500] mg/kg. Twenty-one animal studies reported improvements in biomarkers, functional outcome, or both. Clinical studies included single reports in neonatal hypoxic encephalopathy, traumatic brain injury, and subarachnoid hemorrhage and eight studies in ischemic stroke. The median maximum daily dose of vitamin C was 750 [500-1000] mg, or ∼10 mg/kg for an average-size adult male. Apart from one case series of intracisternal vitamin C administration in subarachnoid hemorrhage, clinical studies reported no patient-centered benefit. Although pre-clinical trials suggest that exogenous vitamin C improves biomarkers of neuroprotection, functional outcome, and mortality, these results have not translated to humans. However, clinical trials used approximately one tenth of the vitamin C dose of animal studies.

Effect of intrahippocampal administration of vitamin C and progesterone on learning in a model of multiple sclerosis in rats

PURPOSE

The purpose of this study was to evaluate the effect of intrahippocampal injection of vitamin C and progesterone, alone or in combination, on passive avoidance learning (PAL) in multiple sclerosis.

METHODS

Sixty- three male wistar rats were divided into nine groups (n=7) as following: control (saline), lesion, vitamin C (0.2, 1, 5 mg/kg), progesterone (0.01, 0.1, 1 µg/µl) and combination therapy. Lesion was induced by intrahippocampal injection of ethidium bromide. In combination therapy, animals were treated with vitamin C (5 mg/kg) plus progesterone (0.01 mg/kg). Animals in experimental groups received different treatments for 7 days, and then all groups were tested for step through latency (STL).

RESULTS

Our results showed that intrahippocampal injection of ethidium bromide destroys PAL significantly (p<0.001). Treatment with vitamin C (5mg/kg) significantly (p<0.05) improved PAL. Lower doses of progesterone did not affect latency but dose of 1 µg/µl significantly (p<0.05) increased STL. In combination therapy group STL was significantly (p<0.05) more than in the lesion group, although it was not significantly different from the vitamin C group.

CONCLUSION

Based on our results, we concluded that intrahippocampal injection of vitamin C improves memory for PAL, but progesterone alone or in combination with vitamin C had no improving effects on memory.

Dehydroascorbic Acid Attenuates Ischemic Brain Edema and Neurotoxicity in Cerebral Ischemia: An in vivo Study

Ischemic stroke results in the diverse phathophysiologies including blood brain barrier (BBB) disruption, brain edema, neuronal cell death, and synaptic loss in brain. Vitamin C has known as the potent anti-oxidant having multiple functions in various organs, as well as in brain. Dehydroascorbic acid (DHA) as the oxidized form of ascorbic acid (AA) acts as a cellular protector against oxidative stress and easily enters into the brain compared to AA. To determine the role of DHA on edema formation, neuronal cell death, and synaptic dysfunction following cerebral ischemia, we investigated the infarct size of ischemic brain tissue and measured the expression of aquaporin 1 (AQP-1) as the water channel protein. We also examined the expression of claudin 5 for confirming the BBB breakdown, and the expression of bcl 2 associated X protein (Bax), caspase-3, inducible nitric oxide synthase (iNOS) for checking the effect of DHA on the neurotoxicity. Finally, we examined postsynaptic density protein-95 (PSD-95) expression to confirm the effect of DHA on synaptic dysfunction following ischemic stroke. Based on our findings, we propose that DHA might alleviate the pathogenesis of ischemic brain injury by attenuating edema, neuronal loss, and by improving synaptic connection.

Effects of antioxidant vitamins on newborn and placental traits in gestations at high altitude: comparative study in high and low altitude native sheep

The present study evaluated the hypothesis that the effects of hypoxia on sheep pregnancies at high altitude (HA) are mediated by oxidative stress and that antioxidant vitamins may prevent these effects. Both HA native and newcomer ewes were maintained at an altitude of 3,589 m during mating and pregnancy. Control low altitude (LA) native ewes were maintained at sea level. Half of each group received daily oral supplements of vitamins C (500 mg) and E (350 IU) during mating and gestation. Near term, maternal plasma vitamin levels and oxidative stress biomarkers were measured. At delivery, lambs were weighed and measured, and placentas were recovered for macroscopic and microscopic evaluation. Vitamin concentrations in supplemented ewes were two- or threefold greater than in non-supplemented ewes. Plasma carbonyls and malondialdehyde in non-supplemented ewes were consistent with a state of oxidative stress, which was prevented by vitamin supplementation. Vitamin supplementation increased lamb birthweight and cotyledon number in both HA native and newcomer ewes, although placental weight and cotyledon surface were diminished. Placentas from vitamin-supplemented HA ewes were similar to those from ewes at sea level, making these placental traits (weight, number and diameter of cotyledons) similar to those from ewes at sea level. Vitamin supplementation had no effect on LA pregnancies. In conclusion, supplementation with vitamins C and E during pregnancy at HA prevents oxidative stress, improving pregnancy outcomes.

Ascorbic acid and α-tocopherol supplement starting prenatally enhances the resistance of nucleus tractus solitarius neurons to hypobaric hypoxic challenge

Hypobaric hypoxia, encountered at high altitude, could result in severe consequences. Ascorbic acid (AA) and α-tocopherol (αTC), the two readily available over-the-counter antioxidants, are known to protect nervous tissue against oxidative stress. Here we study whether AA or αTC supplement starting prenatally protects animals against hypobaric hypoxic challenge at adulthood. Expressions of c-fos and the NR1 subunit of the N-methyl-D-aspartate receptors in the nucleus tractus solitarius (NTS) subserving cardiorespiratory functions were investigated. AA and αTC supplement reduced the number of c-fos immunoreactive neurons and intensity of NR1 expression in young and adult animals under normoxia. The treatment, in addition, attenuated the activation of NTS neurons, in terms of c-fos and NR1 expressions, and reduced the anxiety behaviors of adult rats subjected to hypobaric hypoxic challenge. Reduction of c-fos immunoreactive neurons was found concentrated in the chemoreceptor, baroreceptor, and tracheobronchial tree NTS subnuclei that receive corresponding afferents. The protective effect was not found in normal adult animals supplemented with AA or αTC a week before hypobaric hypoxic challenge. In short, prenatal and sustained AA or αTC supplement altered NTS substrate and ameliorated animals' reactions to hypobaric hypoxic insult, suggesting that this may be considered to protect animals from hypoxic insults from young to adult.

Effects of co-administration of dopamine and vitamin C on ischaemia-reperfusion injury after experimental testicular torsion-detorsion in rats

The objective of this study was to investigate the effects of dopamine as vasodilator, vitamin C as an antioxidant and combined administration of them on ischaemia-reperfusion (I-R) injury following testicular torsion (TT). Thirty adult male rats were divided into six groups each containing five rats. Testicular ischaemia was achieved by twisting the left testis for 4 h. Group 1 was for determination of the basal values. Group 2 had 4 h TT. Group 3 had 4 h TT and was then treated with dopamine. Group 4 had 4 h TT and was then treated with vitamin C. Group 5 had 4 h TT and was then treated with dopamine and vitamin C. Group 6 was designed as a sham operated group. Testicular torsion caused a significant decrease in the percentage of spermatogenesis and seminiferous tubules diameters compared with the control and sham groups. Administration of dopamine, vitamin C and their combination increased above mentioned parameters and decreased serum malondialehyde levels significantly. However, vitamin C had better results than the other treatments (P < 0.05). In conclusion, a potent antioxidant like vitamin C was found to be more effective than increasing blood flow by a vasodilator like dopamine on improving I-R injury following TT.

Ascorbic acid combined with ibuprofen in hypoxic ischemic encephalopathy: a randomized controlled trial

OBJECTIVE

Free oxygen radicals and proinflammatory cytokines are important causes for brain injury in neonates with hypoxic ischemic encephalopathy (HIE). Our objectives were to test the hypothesis that a combination of antioxidants (ascorbic acid) and anti-inflammatory agents (ibuprofen) can ameliorate the brain injury in HIE and improve neurodevelopmental outcomes when given to term infants immediately after birth.

STUDY DESIGN

In a prospective, randomized, double-blinded controlled trial, 60 asphyxiated term infants were assigned to one of two groups, intervention and control. The intervention group (n=30) received intravenous ascorbic acid and oral ibuprofen for 3 days; and the control group (n=30) received similar volumes of a placebo. We measured a panel of cytokines at enrollment and administered the treatment drugs within 2 h after birth. Neurological evaluations and developmental screenings were performed for all survivors at 6 months of age.

RESULT

The Intervention and Control groups did not differ in the severity of HIE at enrollment, the concentrations of IL-1 beta and IL-6, the incidence of mortality (37 vs 33%), the incidence of neurological abnormalities at hospital discharge (47 vs 55%) and the incidence of developmental delay at 6 months of age (32 vs 40%), respectively. None of the observed complications were related to intervention. Serum interleukin (IL)-1 beta and IL-6 concentrations correlated positively with the severity of HIE at birth (P<0.01), whereas only serum IL-6 correlated with neurodevelopmental outcome at 6 months (P<0.001).

CONCLUSION

Early administration of ascorbic acid and ibuprofen did not affect outcomes in infants with perinatal asphyxia. This study does not explain whether our intervention was not effective in blocking free radicals and inflammatory cytokines, if the dosing and route of administration were inadequate, or if other mediators existed that could have a more powerful role in brain injury during hypoxia-ischemia.

Ascorbic acid protects the newborn rat brain from hypoxic-ischemia

Ascorbic acid (AA) is a potent antioxidant, and its neuroprotective effect has not been established yet. Using the Rice-Vannucci model, we examined the effect of AA on hypoxic-ischemic (HI) injury in the immature rat brain. Under isoflurane anesthesia, 7-day-old rat pups received 750 mg/kg of AA by intraperitoneal injection just before hypoxic exposure; 8% oxygen for 90 min. Vehicle controls received an equal volume of saline. AA decreased a macroscopic brain injury score at 48 and 168 h post-HI compared with vehicle controls (48 h post-HI, AA 1.38+/-0.45 vs. controls 2.94+/-0.24, p<0.05; 168 h post-HI, 1.13+/-0.44 vs. 2.50+/-0.25, p<0.05). AA injection significantly decreased the number of both necrotic and apoptotic cells in cortex, caudate putamen, thalamus and hippocampus, and also seemed to reduce the number of TUNEL-positive cells. Western blot analysis showed that AA significantly suppressed 150/145 kDa subunits of alpha-fodrin breakdown products (FBDP) in cortex, striatum, thalamus and hippocampus at 24 and 48 h post-HI, and also 120 kDa subunit of FBDP in all examined regions except for thalamus, which indicated that AA injection inhibited both calpain and caspase-3 activation. Western blot analysis of nitrotyrosine failed to show inhibition of free radical production by AA, however, our results show that AA inhibits both necrotic and apoptotic cell death and that AA is neuroprotective after HI in immature rat brain.

Photoreceptor cell death mechanisms in inherited retinal degeneration

Photoreceptor cell death is the major hallmark of a group of human inherited retinal degenerations commonly referred to as retinitis pigmentosa (RP). Although the causative genetic mutations are often known, the mechanisms leading to photoreceptor degeneration remain poorly defined. Previous research work has focused on apoptosis, but recent evidence suggests that photoreceptor cell death may result primarily from non-apoptotic mechanisms independently of AP1 or p53 transcription factor activity, Bcl proteins, caspases, or cytochrome c release. This review briefly describes some animal models used for studies of retinal degeneration, with particular focus on the rd1 mouse. After outlining the major features of different cell death mechanisms in general, we then compare them with results obtained in retinal degeneration models, where photoreceptor cell death appears to be governed by, among other things, changes in cyclic nucleotide metabolism, downregulation of the transcription factor CREB, and excessive activation of calpain and PARP. Based on recent experimental evidence, we propose a putative non-apoptotic molecular pathway for photoreceptor cell death in the rd1 retina. The notion that inherited photoreceptor cell death is driven by non-apoptotic mechanisms may provide new ideas for future treatment of RP.

Calpain activity in retinal degeneration

Retinal degenerations such as retinitis pigmentosa (RP) or glaucoma are a major cause of blindness in humans. Understanding the mechanisms underlying the various types of retinal degeneration is a pre-requisite for the development of rational therapies for these diseases. Activation of the calcium dependent protease, calpain, has been suggested to play an important role in cell death in various neuronal tissues including the retina. Improved detection and analysis of calpain activity during degenerative processes is likely to expand the list of pathological conditions with calpain involvement. We give a short overview of the methods available for the detection of calpain activity, and briefly discuss properties of calpain inhibitors. We then discuss the role of calpains in different cell death mechanisms and review existing work on retinal degeneration and the possible involvement of calpains therein. The implication of calpains in retinal cell death raises the possibility to use calpain inhibitors to prevent or delay retinal degeneration.