Current Therapies for Neonatal Hypoxic–Ischaemic and Infection-Sensitised Hypoxic–Ischaemic Brain Damage

Neonatal hypoxic–ischaemic brain damage is a leading cause of child mortality and morbidity, including cerebral palsy, epilepsy, and cognitive disabilities. The majority of neonatal hypoxic–ischaemic cases arise as a result of impaired cerebral perfusion to the foetus attributed to uterine, placental, or umbilical cord compromise prior to or during delivery. Bacterial infection is a factor contributing to the damage and is recorded in more than half of preterm births. Exposure to infection exacerbates neuronal hypoxic–ischaemic damage thus leading to a phenomenon called infection-sensitised hypoxic–ischaemic brain injury. Models of neonatal hypoxia–ischaemia (HI) have been developed in different animals. Both human and animal studies show that the developmental stage and the severity of the HI insult affect the selective regional vulnerability of the brain to damage, as well as the subsequent clinical manifestations. Therapeutic hypothermia (TH) is the only clinically approved treatment for neonatal HI. However, the number of HI infants needed to treat with TH for one to be saved from death or disability at age of 18–22 months, is approximately 6–7, which highlights the need for additional or alternative treatments to replace TH or increase its efficiency. In this review we discuss the mechanisms of HI injury to the immature brain and the new experimental treatments studied for neonatal HI and infection-sensitised neonatal HI.

The aetiology of medical device-related pressure ulcers and how to prevent them

This article provides an introduction to the aetiology of medical device-related pressure ulcers (MDRPUs), describes the vicious cycle that leads to these injuries and highlights bioengineering methodologies and findings that connect the aetiology to the clinical practice of preventing MDRPUs. Specifically, the vicious cycle of MDRPUs is triggered by the sustained tissue deformations induced by a skin-contacting device. The primary, deformation-inflicted cell damage leads to a secondary inflammatory-oedema-related damage and then to tertiary ischaemic damage. Each of these three factors contributes to cumulative cell death and tissue damage under and near the applied device. The damage therefore develops in an escalated manner, as a result of the added contributions of the above three factors. This phenomenon is exemplified through two common clinical scenarios. First, through the use of continuous positive airway pressure (CPAP) masks, which are being applied extensively in the current COVID-19 pandemic, and, second, through the use of doughnut-shaped head positioners, which are applied to surgical patients and sometimes to bedridden individuals who receive intensive care in a supine position. These two medical devices cause intense, localised mechanical loads in the facial skin and underlying tissues (CPAP mask) and at the occipital scalp (doughnut-shaped positioner), where the soft tissues cannot swell in response to the inflammatory oedema as, in both cases, the tissues are sandwiched between the device and the skull. Accordingly, the two device types result in characteristic MDRPUs that are avoidable through appropriate prophylactic interventions, that is, preventive dressings under the CPAP mask and replacement of the doughnut device by a soft, shape-conforming support aid to alleviate and disperse the localised soft tissue deformations. Hence, understanding the aetiology of MDRPUs targets and focuses effective clinical interventions.

Man with headache and altered mental status

PresentationAn 83-year-old man presented for headache and altered mental status. Four days prior, he underwent endoscopic sinus surgery for nasal polyps. Over the two previous days, he gradually developed a headache and was brought to the emergency department when his wife noted mild confusion and generalised weakness. His examination was notable for a heart rate of 101 beats per minute, clear nasal discharge, meningismus and confusion to the date with generalised weakness. A lumbar puncture revealed cloudy cerebrospinal fluid (CSF) with a white blood cell count of 3519x10ˆ9/L (95% neutrophils). A CT scan of the head was obtained (figure 1).Figure 1Non-contrast CT scan of the head in axial plane.QuestionWhat is the appropriate next step in management?Obtain MRI of the brain to localise ischaemic damage.Administer broad-spectrum antibiotics, including pseudomonal coverage.Consult otolaryngology to arrange functional endoscopic sinus surgery for CSF leak closure.Consult neurosurgery for surgical decompression of mass lesion(s).

No-touch saphenous vein grafts in coronary artery bypass surgery

After almost 30 years since the first harvesting of the saphenous vein graft with a pedicle of surrounding tissue (no-touch technique), there is no doubt that this method is superior to the conventional technique in which a denuded vein is harvested. In summary, the no-touch harvesting technique decreases risk of graft spasm and the requirement for manual dilatation, limiting endothelial cell loss and long-term damage. The preservation of the vasa vasorum allows retrograde blood flow from the graft lumen, thereby decreasing transmural ischaemic damage. This also preserves endothelial nitric oxide synthase, known to decrease intimal hyperplasia, atherosclerosis, and long-term graft failure. Furthermore, the perivascular tissue acts as a natural external stent reducing the neointimal and medial thickening of the vein graft and preventing it from kinking, which is especially vital for sequential grafts. Finally, target vessel size, quality, and degree of stenosis have little effect on the patency rates of no-touch saphenous vein grafts, in contrast to arterial grafts.

The Role of Mitochondria in Brain Cell Protection from Ischaemia by Differently Prepared Propolis Extracts

Mitochondria are both the primary targets and mediators of ischaemic damage in brain cells. Insufficient oxygen causes reactive oxygen species that damage the mitochondria, leading to the loss of functionality and viability of highly energy-demanding neurons. We have recently found that aqueous (AqEP), polyethylene glycol-aqueous (Pg-AqEP) and ethanolic propolis extracts (EEP) can modulate mitochondria and ROS production in C6 cells of astrocytic origin. The aim of this study was to investigate the effect of the extracts on viability, mitochondrial efficiency and superoxide generation, and inflammatory cytokine release in primary rat cerebellar neuronal-glial cell cultures affected by ischaemia (mimicked by hypoxia +/− deoxyglucose). AqEP and Pg-AqEP (15–60 µg/mL of phenolic compounds, or PC) significantly increased neuronal viability in ischaemia-treated cultures, and this was accompanied by a reduction in mitochondrial superoxide levels. Less extended protection against ischaemia-induced superoxide production and death was exhibited by 2 to 4 µg/mL of PC EEP. Both Pg-AqEP and Ag-EP (but not EEP) significantly protected the cultures from hypoxia-induced elevation of TNF-α, IL-1β and IL-6. Only Pg-AqEP (but not AqEP or EEP) prevented hypoxia-induced loss of the mitochondrial basal and ATP-coupled respiration rate, and significantly increased the mitochondrial respiratory capacity. Summarising, the study revealed that hydrophilic propolis extracts might protect brain cells against ischaemic injury by decreasing the level of mitochondrial superoxide and preventing inflammatory cytokines, and, in the case of Pg-AqEP, by protecting mitochondrial function.

Cognitive impact of COVID-19: looking beyond the short term

COVID-19 is primarily a respiratory disease but up to two thirds of hospitalised patients show evidence of central nervous system (CNS) damage, predominantly ischaemic, in some cases haemorrhagic and occasionally encephalitic. It is unclear how much of the ischaemic damage is mediated by direct or inflammatory effects of virus on the CNS vasculature and how much is secondary to extracranial cardiorespiratory disease. Limited data suggest that the causative SARS-CoV-2 virus may enter the CNS via the nasal mucosa and olfactory fibres, or by haematogenous spread, and is capable of infecting endothelial cells, pericytes and probably neurons. Extracranially, SARS-CoV-2 targets endothelial cells and pericytes, causing endothelial cell dysfunction, vascular leakage and immune activation, sometimes leading to disseminated intravascular coagulation. It remains to be confirmed whether endothelial cells and pericytes in the cerebral vasculature are similarly targeted. Several aspects of COVID-19 are likely to impact on cognition. Cerebral white matter is particularly vulnerable to ischaemic damage in COVID-19 and is also critically important for cognitive function. There is accumulating evidence that cerebral hypoperfusion accelerates amyloid-β (Aβ) accumulation and is linked to tau and TDP-43 pathology, and by inducing phosphorylation of α-synuclein at serine-129, ischaemia may also increase the risk of development of Lewy body disease. Current therapies for COVID-19 are understandably focused on supporting respiratory function, preventing thrombosis and reducing immune activation. Since angiotensin-converting enzyme (ACE)-2 is a receptor for SARS-CoV-2, and ACE inhibitors and angiotensin receptor blockers are predicted to increase ACE-2 expression, it was initially feared that their use might exacerbate COVID-19. Recent meta-analyses have instead suggested that these medications are protective. This is perhaps because SARS-CoV-2 entry may deplete ACE-2, tipping the balance towards angiotensin II-ACE-1-mediated classical RAS activation: exacerbating hypoperfusion and promoting inflammation. It may be relevant that APOE ε4 individuals, who seem to be at increased risk of COVID-19, also have lowest ACE-2 activity. COVID-19 is likely to leave an unexpected legacy of long-term neurological complications in a significant number of survivors. Cognitive follow-up of COVID-19 patients will be important, especially in patients who develop cerebrovascular and neurological complications during the acute illness.

Sirtuin 1-dependent regulation of high mobility box 1 in hypoxia–reoxygenated brain microvascular endothelial cells: roles in neuronal amyloidogenesis

Hypoxia–reperfusion injury is one of the major risk factors for neurodegeneration. However, it is unclear whether ischaemic damage in brain microvascular endothelial cells plays roles in neurodegeneration, particularly in the amyloidogenic changes contributing to the development of Alzheimer’s disease (AD) pathologies. Therefore, we investigated the roles of hypoxia–reoxygenation (H/R)-induced release of high mobility group box protein 1 (HMGB1), a risk molecule for AD pathogenesis in the ischaemic damaged brain, from human brain microvascular endothelial cells (HBMVECs) in neuronal amyloid-beta (Aβ) production. H/R increased nuclear–cytosolic translocation and secretion of HMGB1 in HBMVECs, along with increased permeability and HMGB1-dependent p-c-Jun activation. In addition, H/R increased the expression of Sirtuin 1 (Sirt1), coincident with an increase of intracellular Sirt1–HMGB1 binding in HBMVECs. H/R increased the acetylation of HMGB1 and extracellular secretion, which was significantly inhibited by Sirt1 overexpression. Furthermore, Sirt1 contributed to autophagy-mediated endogenous HMGB1 degradation. More importantly, treatment of neuronal cells with conditioned medium from H/R-stimulated HBMVECs (H/R-CM) activated their amyloidogenic pathways. The neuronal amyloidogenic changes (i.e. increased levels of extracellular Aβ40 and Aβ42) by H/R-CM from HBMVECs were further increased by Sirt1 inhibition, which was significantly suppressed by neutralization of the HMGB1 in H/R-CM. Collectively, our results suggest that HMGB1 derived from H/R-stimulated HBMVECs contributes to amyloidogenic pathways in neurons playing roles in the pathogenesis of AD, which are regulated by endothelial Sirt1.

P1600KIDNEY PERFUSION WITH MESENCHYMAL STROMAL CELLS OR EXTRACELLULAR VESICLES PREVENTS ISCHAEMIC DAMAGE THROUGH CD73/ADO SYSTEM IN A RAT MODEL OF DCD DONATION

Background and Aims Adenosine (Ado), the main substrate of ATP, is a potent endogenous anti-inflammatory nucleoside. Hypoxia induces ATP depletion, AMP extracellular increase that is phosphohydrolyzed to ADO by the enzyme ecto-5′-nucleotidase (CD73). Constitutive CD73 expression is higher in deep cortex outer medulla that is the most vulnerable region to ischemic injury. Notably CD73 is also expressed on Mesenchymal Stromal Cell (MSC) and is essential phenotypic marker. Previously in a rat model of Donation after Circulatory Death (DCD), we demonstrated that the perfusion of ischemic kidney with MSC or MSC derived Extracellular Vesicles (EV) protects tissue up regulating mitochondrial energetic metabolism genes. The aim of this study was to investigate the role of CD73/Ado system in MSC/EV protection from ischemia. Method Fisher rats were used as kidney donors and Lewis rats as MSC donors. MSC missing CD73 were produced by electroporation in the presence of specific siRNA to block CD73 expression (siMSC). EV were isolated from supernatants of MSC and siMSC (siEV) medium through differential ultracentrifugations. Size distribution and enumeration analysis were performed using NanoSight NS300. EV phenotypic characterization was performed in flow cytometer using CD45, CD49e, CD63, CD9, CD81 and CD73 monoclonal antibodies. DCD model was obtained by renal artery clamping for 20 minutes. This warm ischemia time represents the “no touch period” imposed by the Italian law to death declaration. After nephrectomy, kidneys were perfused in hypothermia (4°C) with Belzer Solution (BS), or BS supplemented with 3x106 MSC (MSC) or BS supplemented with 28,5x109 EV/siEV (EV/siEV). The effluent fluid (EF) was collected at the beginning (T0), every hours (T1, T2, T3) and at the end of the perfusion (T4). Ado and ATP determinations in EF and tissues were performed by HPLC and ELISA, respectively. Results EF Ado was significantly higher in MSC vs BS from T1 and in EV vs BS from T0 to T4 (p<0,05). Only in EV, EF Ado concentration increased over time from T2 to T4 ( p<0,05), while in BS, MSC and siEV there was a steady trend over time. There was a negative correlation between EF and tissue levels of Ado (r=0,67 p=0,01). Tissue ATP was higher in EV and significantly in MSC vs BS (p<0,01). There was a negative correlation between tissue ATP and EF ADO levels (r= 0,79 p< 0,0001). Tissue ATP/Ado ratio was significantly higher in EV vs BS (p<0,01). There was a negative correlation between tissue ATP/Ado ratio and EF Ado (r= 0,84 p < 0.0001). siEV cancelled EV effects on ATP and Ado levels in EF and renal tissue. Conclusion CD73 expressed on MSC /EV impacts on cell energy metabolism pathway and ATP generation. This is the first evidence that MSC/EV act through CD73/Ado system to prevent ischaemic damage.