Cerebral Vasoactivity and Oxygenation with Oxygen Carrier M101 in Rats

EFFECTS OF M101-AN EXTRACELLULAR HEMOGLOBIN-APPLIED DURING CARDIOPULMONARY RESUSCITATION: AN EXPERIMENTAL RODENT STUDY

ABSTRACT

During and immediately after cardiac arrest, cerebral oxygen delivery is impaired mainly by microthrombi and cerebral vasoconstriction. This may narrow capillaries so much that it might impede the flow of red blood cells and thus oxygen transport. The aim of this proof-of-concept study was to evaluate the effect of M101, an extracellular hemoglobin-based oxygen carrier (Hemarina SA, Morlaix, France) derived from Arenicola marina , applied during cardiac arrest in a rodent model, on markers of brain inflammation, brain damage, and regional cerebral oxygen saturation. Twenty-seven Wistar rats subjected to 6 min of asystolic cardiac arrest were infused M101 (300 mg/kg) or placebo (NaCl 0.9%) concomitantly with start of cardiopulmonary resuscitation. Brain oxygenation and five biomarkers of inflammation and brain damage (from blood, cerebrospinal fluid, and homogenates from four brain regions) were measured 8 h after return of spontaneous circulation. In these 21 different measurements, M101-treated animals were not significantly different from controls except for phospho-tau only in single cerebellum regions ( P = 0.048; ANOVA of all brain regions: P = 0.004). Arterial blood pressure increased significantly only at 4 to 8 min after return of spontaneous circulation ( P < 0.001) and acidosis decreased ( P = 0.009). While M101 applied during cardiac arrest did not significantly change inflammation or brain oxygenation, the data suggest cerebral damage reduction due to hypoxic brain injury, measured by phospho-tau. Global burden of ischemia appeared reduced because acidosis was less severe. Whether postcardiac arrest infusion of M101 improves brain oxygenation is unknown and needs to be investigated.

Therapeutic Potential of Hemoglobin Derived from the Marine Worm Arenicola marina (M101): A Literature Review of a Breakthrough Innovation

Oxygen (O₂) is indispensable for aerobic respiration and cellular metabolism. In case of injury, reactive oxygen species are produced, causing oxidative stress, which triggers cell damaging chemical mediators leading to ischemic reperfusion injuries (IRI). Sufficient tissue oxygenation is necessary for optimal wound healing. In this context, several hemoglobin-based oxygen carriers have been developed and tested, especially as graft preservatives for transplant procedures. However, most of the commercially available O₂ carriers increase oxidative stress and show some adverse effects. Interestingly, the hemoglobin derived from the marine lugworm Arenicola marina (M101) has been presented as an efficient therapeutic O₂ carrier with potential anti-inflammatory, anti-bacterial, and antioxidant properties. Furthermore, it has demonstrated promise as a supplement to conventional organ preservatives by reducing IRI. This review summarizes the properties and various applications of M101. M101 is an innovative oxygen carrier with several beneficial therapeutic properties, and further research must be carried out to determine its efficacy in the management of different pathologies.

Characterization of a hyaluronic acid-based hydrogel containing an extracellular oxygen carrier (M101) for periodontitis treatment: An in vitro study

Periodontitis is an inflammatory disease associated with anaerobic bacteria leading to the destruction of tooth-supporting tissues. Porphyromonas gingivalis is a keystone anaerobic pathogen involved in the development of severe lesions. Periodontal treatment aims to suppress subgingival biofilms and to restore tissue homeostasis. However, hypoxia impairs wound healing and promotes bacterial growth within periodontal pocket. This study aimed to evaluate the potential of local oxygen delivery through the local application of a hydrogel containing Arenicola marina's hemoglobin (M101). To this end, a hydrogel (xanthan (2%), hyaluronic acid (1%)) containing M101 (1-2 g/L) (Xn(2%)-HA(1%)-M101) was prepared and characterized. Rheological tests revealed the occurrence of high deformation without the loss of elastic properties. Dialysis experiment revealed that incorporation of M101 within the gel did not modify its oxygen transportation properties. Samples of release media of the gels (1 g/L (10%) and 2 g/L (10%) M101) decreased significantly the growth of P. gingivalis after 24 h validating its antibacterial effect. Metabolic activity measurement confirmed the cytocompatibility of Xn(2%)-HA(1%)-M101. This study suggests the therapeutic interest of Xn(2%)-HA(1%)-M101 gel to optimize treatment of periodontitis with a non-invasive approach.

Fluids of the Future

Fluids are a vital tool in the armament of acute care clinicians in both civilian and military resuscitation. We now better understand complications from inappropriate resuscitation with currently available fluids; however, fluid resuscitation undeniably remains a life-saving intervention. Military research has driven the most significant advances in the field of fluid resuscitation and is currently leading the search for the fluids of the future. The veterinary community, much like our civilian human counterparts, should expect the fluid of the future to be the fruit of military research. The fluids of the future not only are expected to improve patient outcomes but also be field expedient. Those fluids should be compatible with military environments or natural disaster environments. For decades, military personnel and disaster responders have faced the peculiar demands of austere environments, prolonged field care, and delayed evacuation. Large scale natural disasters present field limitations often similar to those encountered in the battlefield. The fluids of the future should, therefore, have a long shelf-life, a small footprint, and be resistant to large temperature swings, for instance. Traumatic brain injury and hemorrhagic shock are the leading causes of preventable death for military casualties and a significant burden in civilian populations. The military and civilian health systems are focusing efforts on field-expedient fluids that will be specifically relevant for the management of those conditions. Fluids are expected to be compatible with blood products, increase oxygen-carrying capabilities, promote hemostasis, and be easy to administer in the prehospital setting, to match the broad spectrum of current acute care challenges, such as sepsis and severe systemic inflammation. This article will review historical military and civilian contributions to current resuscitation strategies, describe the expectations for the fluids of the future, and describe select ongoing research efforts with a review of current animal data.

Combating hypoxemia in COVID-19 patients with a natural oxygen carrier, HEMO2Life® (M101)

BACKGROUND

Infection with SARS-CoV-2 is responsible for the COVID-19 crisis affecting the whole world. This virus can provoke acute respiratory distress syndrome (ARDS) leading to overcrowed the intensive care unit (ICU). Over the last months, worldwide experience demonstrated that the ARDS in COVID-19 patients are in many ways "atypical". The mortality rate in ventilated patients is high despite the application of the gold standard treatment (protective ventilation, curare, prone position, inhaled NO). Several studies suggested that the SARS-CoV-2 could interact negatively on red blood cell homeostasis. Furthermore, SarsCov2 creates Reactive Oxygen Species (ROS), which are toxic and generate endothelial dysfunction. Hypothesis/objective(s) We hypothesis that HEMO2Life® administrated intravenously is safe and could help symptomatically the patient condition. It would increase arterial oxygen content despite lung failure and allow better tissue oxygenation control. The use of HEMO2Life® is also interesting due to its anti-oxidative effect preventing cytokine storm induced by the SARS-CoV-2. Evaluation of the hypothesis: Hemarina is based on the properties of the hemoglobin of the Arenicola marina sea-worm (HEMO2Life®). This extracellular hemoglobin has an oxygen capacity 40 times greater than the hemoglobin of vertebrates. Furthermore, the size of this molecule is 250 times smaller than a human red blood cell, allowing it to diffuse in all areas of the microcirculation, without diffusing outside the vascular sector. It possesses an antioxidative property du a Superoxide Dismutase Activity. This technology has been the subject of numerous publications and HEMO2Life® was found to be well-tolerated and did not induce toxicity. It was administered intravenously to hamsters and rats, and showed no acute effect on heart rate and blood pressure and did not cause microvascular vasoconstriction. In preclinical in vivo models (mice, rats, and dogs), HEMO2Life® has enabled better tissue oxygenation, especially in the brain. This molecule has already been used in humans in organ preservation solutions and the patients showed no abnormal clinical signs.

CONSEQUENCES OF THE HYPOTHESIS

The expected benefits of HEMO2Life® for COVID-19 patients are improved survival, avoidance of tracheal intubation, shorter oxygen supplementation, and the possibility of treating a larger number of patients as molecular respirator without to use an invasive machine.

Generating brain matrices for zebra finch brain sectioning using three-dimensional printing technology

BACKGROUND

The demand to sample brain regions in non-model species is increasing as more studies are integrating neurological data into behavioural, ecological or evolutionary analysis. However, the sampling operation is difficult for researchers without neuroscience background. It is also a challenge to collect neuroanatomical regions from animals in the field.

NEW METHOD

Here we developed a new brain matrix for guiding researchers to section zebra finches' (Taeniopygia guttata) brains more steadily than by freehand trimming. Based on the 3D printing technology, we produced the zebra finch brain matrix from scratch. We also provided a step-by-step protocol to make brain matrices for any species with a brain size between that of shrews and dogs.

RESULTS

The brain matrix could guide us to find the zebra finch's neuroanatomical landmarks, such as the hypothalamus, optic chiasm and occulomotor nerve. The matrix's channels near these landmarks could be used to section brains steadily and rapidly.

COMPARISON WITH EXISTING METHODS

Standardized brain sectioning often requires expensive machines that may not be available in most laboratories or in the field, such as microtomes. In addition, machine-based trimming is time-consuming. Although commercial brain matrices can overcome these problems, they are only available for rats and mice. The brain matrices we developed are affordable to most laboratories and can be customised for non-model species in both lab and field experiments.

CONCLUSIONS

The matrix-guided approach requires a relatively short training period and can allow researchers to properly and quickly sample brains, and thus will facilitate neuroscience-based interdisciplinary research.

Cerebral Microvascular Injury: A Potentially Treatable Endophenotype of Traumatic Brain Injury-Induced Neurodegeneration

Traumatic brain injury (TBI) is one the most common human afflictions, contributing to long-term disability in survivors. Emerging data indicate that functional improvement or deterioration can occur years after TBI. In this regard, TBI is recognized as risk factor for late-life neurodegenerative disorders. TBI encompasses a heterogeneous disease process in which diverse injury subtypes and multiple molecular mechanisms overlap. To develop precision medicine approaches where specific pathobiological processes are targeted by mechanistically appropriate therapies, techniques to identify and measure these subtypes are needed. Traumatic microvascular injury is a common but relatively understudied TBI endophenotype. In this review, we describe evidence of microvascular dysfunction in human and animal TBI, explore the role of vascular dysfunction in neurodegenerative disease, and discuss potential opportunities for vascular-directed therapies in ameliorating TBI-related neurodegeneration. We discuss the therapeutic potential of vascular-directed therapies in TBI and the use and limitations of preclinical models to explore these therapies.

Exposure to Blast Overpressure Impairs Cerebral Microvascular Responses and Alters Vascular and Astrocytic Structure

Exposure to blast overpressure may result in cerebrovascular impairment, including cerebral vasospasm. The mechanisms contributing to this vascular response are unclear. The aim of this study was to evaluate the relationship between blast and functional alterations of the cerebral microcirculation and to investigate potential underlying changes in vascular microstructure. Cerebrovascular responses were assessed in sham- and blast-exposed male rats at multiple time points from 2 h through 28 days after a single 130-kPa (18.9-psi) exposure. Pial microcirculation was assessed through a cranial window created in the parietal bone of anesthetized rats. Pial arteriolar reactivity was evaluated in vivo using hypercapnia, barium chloride, and serotonin. We found that exposure to blast leads to impairment of arteriolar reactivity >24 h after blast exposure, suggesting delayed injury mechanisms that are not simply attributed to direct mechanical deformation. Observed vascular impairment included a reduction in hypercapnia-induced vasodilation, increase in barium-induced constriction, and reversal of the serotonin effect from constriction to dilation. A reduction in vascular smooth muscle contractile proteins consistent with vascular wall proliferation was observed, as well as delayed reduction in nitric oxide synthase and increase in endothelin-1 B receptors, mainly in astrocytes. Collectively, the data show that exposure to blast results in delayed and prolonged alterations in cerebrovascular reactivity that are associated with changes in the microarchitecture of the vessel wall and astrocytes. These changes may contribute to long-term pathologies involving dysfunction of the neurovascular unit, including cerebral vasospasm.

Cerebral Microvascular and Systemic Effects Following Intravenous Administration of the Perfluorocarbon Emulsion Perftoran

Oxygen-carrying perfluorocarbon (PFC) fluids have the potential to increase tissue oxygenation during hypoxic states and to reduce ischemic cell death. Regulatory approval of oxygen therapeutics was halted due to concerns over vasoconstrictive side effects. The goal of this study was to assess the potential vasoactive properties of Perftoran by measuring brain pial arteriolar diameters in a healthy rat model. Perftoran, crystalloid (saline) or colloid (Hextend) solutions were administered as four sequential 30 min intravenous (IV) infusions, thus allowing an evaluation of cumulative dose-dependent effects. There were no overall changes in diameters of small-sized (<50 μm) pial arterioles within the Perftoran group, while both saline and Hextend groups exhibited vasoconstriction. Medium-sized arterioles (50–100 μm) showed minor (~8–9%) vasoconstriction within saline and Hextend groups and only ~5% vasoconstriction within the Perftoran group. For small- and medium-sized pial arterioles, the mean percent change in vessel diameters was not different among the groups. Although there was a tendency for arterial blood pressures to increase with Perftoran, pressures were not different from the other two groups. These data show that Perftoran, when administered to healthy anesthetized rats, does not cause additional vasoconstriction in cerebral pial arterioles or increase systemic blood pressure compared with saline or Hextend.

The Emulsified PFC Oxycyte® Improved Oxygen Content and Lung Injury Score in a Swine Model of Oleic Acid Lung Injury (OALI)

PURPOSE

Perfluorocarbons (PFCs) can transport 50 times more oxygen than human plasma. Their properties may be advantageous in preservation of tissue viability in oxygen-deprived states, such as in acute lung injury. We hypothesized that an intravenous dose of the PFC emulsion Oxycyte^® would improve tissue oxygenation and thereby mitigate the effects of acute lung injury.

METHODS

Intravenous oleic acid (OA) was used to induce lung injury in anesthetized and instrumented Yorkshire swine assigned to three experimental groups: (1) PFC post-OA received Oxycyte^® (5 ml/kg) 45 min after oleic acid-induced lung injury (OALI); (2) PFC pre-OA received Oxycyte^® 45 min before OALI; and (3) Controls which received equivalent dose of normal saline. Animals were observed for 3 h after OALI began, and then euthanized.

RESULTS

The median survival times for PFC post-OA, PFC pre-OA, and control were 240, 87.5, and 240 min, respectively (p = 0.001). Mean arterial pressure and mean pulmonary arterial pressure were both higher in the PFC post-OA (p < 0.001 for both parameters). Oxygen content was significantly different between PFC post-OA and the control (p = 0.001). Histopathological grading of lung injury indicated that edema and congestion was significantly less severe in the PFC post-OA compared to control (p = 0.001).

CONCLUSION

The intravenous PFC Oxycyte^® improves blood oxygen content and lung histology when used as a treatment after OALI, while Oxycyte^® used prior to OALI was associated with increased mortality. Further exploration in other injury models is indicated.

Sanguinate's effect on pial arterioles in healthy rats and cerebral oxygen tension after controlled cortical impact

Sanguinate, a polyethylene glycol-conjugated carboxyhemoglobin, was investigated for cerebral vasoactivity in healthy male Sprague-Dawley rats (Study 1) and for its ability to increase brain tissue oxygen pressure (PbtO2) after controlled cortical impact (CCI) - traumatic brain injury (TBI) (Study 2). In both studies ketamine-acepromazine anesthetized rats were ventilated with 40% O2. In Study 1, a cranial window was used to measure the diameters of medium - (50-100μm) and small-sized (<50μm) pial arterioles before and after four serial infusions of Sanguinate (8mL/kg/h, cumulative 16mL/kg IV), volume-matched Hextend, or normal saline. In Study 2, PbtO2 was measured using a phosphorescence quenching method before TBI, 15min after TBI (T15) and then every 10min thereafter for 155min. At T15, rats received either 8mL/kg IV Sanguinate (40mL/kg/h) or no treatment (saline, 4mL/kg/h). Results showed: 1) in healthy rats, percentage changes in pial arteriole diameter were the same among the groups, 2) in TBI rats, PbtO2 decreased from 36.5±3.9mmHg to 19.8±3.0mmHg at T15 in both groups after TBI and did not recover in either group for the rest of the study, and 3) MAP increased 16±4mmHg and 36±5mmHg after Sanguinate in healthy and TBI rats, respectively, while MAP was unchanged in control groups. In conclusion, Sanguinate did not cause vasoconstriction in the cerebral pial arterioles of healthy rats but it also did not acutely increase PbtO2 when administered after TBI. Sanguinate was associated with an increase in MAP in both studies.