Clopidogrel reduces the inflammatory response of lung in a rat model of decompression sickness

Recombinant human plasma gelsolin suppresses persistent neuroinflammation and restores hippocampal neurogenesis in murine model of decompression sickness

Loss of plasma gelsolin (pGSN), a protein that lyses actin filaments, is implicated in the pathology of inflammatory and neurodegenerative diseases. We hypothesized that because pGSN is depleted in a murine model of decompression sickness (DCS), supplementation by administration of human recombinant (rhu-) pGSN would ameliorate inflammatory events. We observed that pGSN levels were persistently decreased in mice for at least 12 days postexposure to 790 kPa of air for 2 h. This decline was associated with elevated levels of inflammatory microparticles (MPs) in the blood and cervical lymph nodes, which previously were shown to cause neuroinflammation. In addition, these mice exhibited reduced expression of synaptic proteins, impaired neurogenesis and impaired cognitive and motor functions. Rhu-pGSN ameliorated the inflammatory changes and resulted in restored synaptic protein expression, neurogenesis, and neurological function. These findings demonstrate that neuronal dysfunction in our murine model of DCS is mediated by MPs and that rhu-pGSN can ameliorate injury even when administered in a delayed fashion.NEW & NOTEWORTHY A decrease in plasma gelsolin levels and the release of inflammatory microparticles (MPs) occur in response to high pressure followed by decompression, with expression of filamentous (F)-actin leading to persistent neuroinflammation and functional deficits lasting at least 12 days. The infusion of recombinant human plasma gelsolin lyses these MPs in decompressed mice, thereby alleviating particle-associated neuronal dysfunction. Rhu-gelsolin infusion may be beneficial as a prophylactic or treatment for decompression sickness.

Influence of exposure duration on human pressure-induced inflammatory responses: Comparison between tunnel workers and underwater divers

Information is scarce on human responses to high pressure exposures out of water, such as related to tunnel construction workers. We hypothesized that differences in the longer durations of exposures for tunnel workers versus underwater divers results in greater inflammatory responses linked to the pathophysiology of decompression sickness (DCS). Blood was analyzed from 15 tunnel workers (36.1 ± 10.5 (SD) years old, 6 women) exposed to 142-156 kPa pressure for 4.1-4.9 h compared to 8 SCUBA divers (39.3 ± 13.3 (SD) years old, 6 women) exposed to 149 kPa for 0.61 hours. Despite differences in pressure duration between groups, elevations were the same for blood microparticles (MPs) (128 ± 28% MPs/μl) and intra-MPs interleukin (IL-1β) (376 ± 212% pg/million MPs), and for decreases of plasma gelsolin (pGSN, 31 ± 27% μg/mL). The number of circulating CD66b + neutrophils and evidence of cell activation, insignificant for divers, increased in tunnel workers. Across 3 exposures, the mean neutrophil count increased 150 ± 11%. Neutrophil activation increased by 1 to 2% of cells expressing cell surface CD18, myeloperoxidase, platelet-specific CD41, and decrease of cell bound pGSN. We conclude that MPs elevations occur rapidly in humans and reach steady state in minutes with pressure exposures and neutrophil activation requires significantly longer exposure times.

Persistent neuroinflammation and functional deficits in a murine model of decompression sickness

We hypothesized that early intra-central nervous system (CNS) responses in a murine model of decompression sickness (DCS) would be reflected by changes in the microparticles (MPs) that exit the brain via the glymphatic system, and due to systemic responses the MPs would cause inflammatory changes lasting for many days leading to functional neurological deficits. Elevations on the order of threefold of blood-borne inflammatory MPs, neutrophil activation, glymphatic flow, and neuroinflammation in cerebral cortex and hippocampus were found in mice at 12 days after exposure to 760 kPa of air for 2 h. Mice also exhibited a significant decline in memory and locomotor activity, as assessed by novel object recognition and rotarod testing. Similar inflammatory changes in blood, neuroinflammation, and functional impairments were initiated in naïve mice by injection of filamentous (F-) actin-positive MPs, but not F-actin-negative MPs, obtained from decompressed mice. We conclude that high pressure/decompression stress establishes a systemic inflammatory process that results in prolonged neuroinflammation and functional impairments in the mouse decompression model.NEW & NOTEWORTHY Elevated glymphatic flow due to astrocyte and microglial activation from high-pressure exposure triggers release of microparticles (MPs) to the circulation where neutrophil activation and production of filamentous (F)-actin expressing MPs result in a persistent feed-forward neuroinflammatory cycle and functional deficits lasting for at least 12 days.

Effect of angiotensin II on irradiation exacerbated decompression sickness

In some complicated situations, decompression sickness (DCS) combined with other injuries, such as irradiation, will seriously endanger life safety. However, it is still unclear whether irradiation will increase the incidence of DCS. This study was designed to investigate the damage effects of irradiation on decompression injury and the underlying mechanism. Sprague-Dawley rats were exposed to irradiation followed by hyperbaric decompressing and the mortality and decompression symptoms were observed. Lung tissue and bronchoalveolar lavage fluid were collected to detect the lung lesion, inflammation response, activity of the angiotensin system, oxidative stress, and relative signal pathway by multiple methods, including Q-PCR, western blot, and ELISA. As a result, pre-exposure to radiation significantly exacerbated disease outcomes and lung lesions of DCS. Mechanically, the up-regulation of angiotensin-converting enzyme expression and angiotensin II levels was responsible for the exacerbated DCS and lung lesions caused by predisposing irradiation exposure. Oxidative stress and PI3K/AKT signal pathway activation in pulmonary tissue were enhanced after irradiation plus decompression treatment. In conclusion, our results suggested that irradiation could exacerbate lung injury and the outcomes of DCS by activating the angiotensin system, which included eliciting oxidative stress and activation of the PI3K/AKT signal pathway.

Effects of different simulated submarine escape depths by free ascent in animal models

Objective: If a damaged submarine cannot be rescued in time, it is necessary to carry out a submarine escape by free ascent. Decompression illness is the greatest threat to the safety of submariners. The maximum depth at which a safe escape can be carried out is unknown. This study intends to explore the maximum safe escape depth by observing the effects of simulated submarine escape at different depths on animal models. Methods: We evaluated pulmonary function indexes, blood gas values, blood cell counts, the myocardial enzyme spectrum, coagulation parameters, and proinflammatory cytokine levels in rats, electrocardiographic activity in rabbits after simulated 150-m, 200-m, 220-m, and 250-m submarine escape by free ascent. Results: An escape depth of 150 m did not cause significant changes in the indicators. An escape depth of >200 m led to pulmonary ventilation and gas diffusion dysfunction, hypoxemia, myocardial ischemia, and activation of the fibrinolytic and inflammatory systems. The magnitudes of the changes in the indicators were proportional to escape depth. Conclusion: An escape depth of 150 m in animal models is safe, whereas escape at > 200 m can be harmful.

Physiological effects of mixed-gas deep sea dives using a closed-circuit rebreather: a field pilot study

PURPOSE

Deep diving using mixed gas with closed-circuit rebreathers (CCRs) is increasingly common. However, data regarding the effects of these dives are still scarce. This preliminary field study aimed at evaluating the acute effects of deep (90-120 msw) mixed-gas CCR bounce dives on lung function in relation with other physiological parameters.

METHODS

Seven divers performed a total of sixteen open-sea CCR dives breathing gas mixture of helium, nitrogen and oxygen (trimix) within four days at 2 depths (90 and 120 msw). Spirometric parameters, SpO₂, body mass, hematocrit, short term heart rate variability (HRV) and critical flicker fusion frequency (CFFF) were measured at rest 60 min before the dive and 120 min after surfacing.

RESULTS

The median [1st-3rd quartile] of the forced vital capacity was lower (84% [76-93] vs 91% [74-107] of predicted values; p = 0.029), whereas FEV1/FVC was higher (98% [95-99] vs 95% [89-99]; p = 0.019) after than before the dives. The other spirometry values and SpO₂ were unchanged. Body mass decreased from 73.5 kg (72.0-89.6) before the dives to 70.0 kg (69.2-85.8) after surfacing (p = 0.001), with no change of hematocrit or CFFT. HRV was increased as indicated by the higher SDNN, RMSSD and pNN50 after than before dives.

CONCLUSION

The present observation represents the first original data regarding the effects of deep repeated CCR dives. The body mass loss and decrease of FVC after bounce dives at depth of about 100 msw may possibly impose an important physiological stress for the divers.

Decompressive Pathology in Cetaceans Based on an Experimental Pathological Model

Decompression sickness (DCS) is a widely known clinical syndrome in human medicine, mainly in divers, related to the formation of intravascular and extravascular gas bubbles. Gas embolism and decompression-like sickness have also been described in wild animals, such as cetaceans. It was hypothesized that adaptations to the marine environment protected them from DCS, but in 2003, decompression-like sickness was described for the first time in beaked whales, challenging this dogma. Since then, several episodes of mass strandings of beaked whales coincidental in time and space with naval maneuvers have been recorded and diagnosed with DCS. The diagnosis of human DCS is based on the presence of clinical symptoms and the detection of gas embolism by ultrasound, but in cetaceans, the diagnosis is limited to forensic investigations. For this reason, it is necessary to resort to experimental animal models to support the pathological diagnosis of DCS in cetaceans. The objective of this study is to validate the pathological results of cetaceans through an experimental rabbit model wherein a complete and detailed histopathological analysis was performed. Gross and histopathological results were very similar in the experimental animal model compared to stranded cetaceans with DCS, with the presence of gas embolism systemically distributed as well as emphysema and hemorrhages as primary lesions in different organs. The experimental data reinforces the pathological findings found in cetaceans with DCS as well as the hypothesis that individuality plays an essential role in DCS, as it has previously been proposed in animal models and human diving medicine.

Systematic review on the effects of medication under hyperbaric conditions: consequences for the diver

BACKGROUND

Physiological changes are induced by immersion, swimming and using diving equipment. Divers must be fit to dive. Using medication may impact the capacity to adapt to hyperbaric conditions. The aim of this systematic review is to assess the interaction of diving/hyperbaric conditions and medication and to provide basic heuristics to support decision making regarding fitness to dive in medicated divers.

METHODS

This was a systematic review of human and animal studies of medications in the hyperbaric environment. Studies were subdivided into those describing a medication/hyperbaric environment interaction and those concerned with prevention of diving disorders. Studies without a relation to diving with compressed air, and those concerning oxygen toxicity, hyperbaric oxygen therapy or the treatment of decompression sickness were excluded.

RESULTS

Forty-four studies matched the inclusion criteria. Animal studies revealed that diazepam and valproate gave limited protection against the onset of the high-pressure neurological syndrome. Lithium had a protective effect against nitrogen-narcosis and losartan reduced cardiac changes in repetitive diving. Human studies showed no beneficial or dangerous pressure-related interactions. In prevention of diving disorders, pseudoephedrine reduced otic barotrauma, vitamins C and E reduced endothelial dysfunction after bounce diving and hepatic oxidative stress in saturation diving.

DISCUSSION AND CONCLUSIONS

Animal studies revealed that psycho-pharmaceuticals can limit the onset of neurologic symptoms and cardiovascular protective drugs might add a potential protective effect against decompression sickness. No evidence of significant risks due to changes in pharmacologic mechanisms were revealed and most medication is not a contraindication to diving. For improving decision making in prescribing medicine for recreational and occupational divers and to enhance safety by increasing our understanding of pharmacology in hyperbaric conditions, future research should focus on controlled human studies.

Provocative decompression causes diffuse vascular injury in mice mediated by microparticles containing interleukin-1β

Inflammatory mediators are known to be elevated in association with decompression from elevated ambient pressure, but their role in tissue damage or overt decompression sickness is unclear. Circulating microparticles (MPs) are also know to increase and because interleukin (IL)-1β is packaged within these particles, we hypothesized that IL-1β was responsible for tissue injuries. Here, we demonstrate that elevations of circulating MPs containing up to 9-fold higher concentrations of IL-1β occur while mice are exposed to high air pressure (790 kPa), whereas smaller particles carrying proteins specific to exosomes are not elevated. MPs number and intra-particle IL-1β concentration increase further over 13 hours post-decompression. MPs also exhibit intra-particle elevations of tumor necrosis factor-α, caspase-1, inhibitor of κB kinase -β and -γ, and elevated IL-6 is adsorbed to the surface of MPs. Contrary to lymphocytes, neutrophil NLRP3 inflammasome oligomerization and cell activation parameters occur during high pressure exposure, and additional evidence for activation are manifested post-decompression. Diffuse vascular damage, while not apparent immediately post-decompression, was present 2 hours later and remained elevated for at least 13 hours. Prophylactic administration of an IL-1β receptor inhibitor or neutralizing antibody to IL-1β inhibited MPs elevations, increases of all MPs-associated pro-inflammatory agents, and vascular damage. We conclude that an auto-activation process triggered by high pressure stimulates MPs production and concurrent inflammasome activation, and IL-1β is a proximal factor responsible for further cytokine production and decompression-associated vascular injuries.

Protective effects of diketopiperazines from Moslae Herba against influenza A virus-induced pulmonary inflammation via inhibition of viral replication and platelets aggregation

ETHNOPHARMACOLOGICAL RELEVANCE

Moslae Herba (MH) is broadly used as an antiviral, antipyretic and anticoagulant drug which effectively treats respiratory diseases including cough, asthma, throat, cold and flu.

AIM OF THIS STUDY

The excessive inflammation of the lungs is the hallmark of severe influenza A virus (IAV) infection, while platelet aggregation and its subsequent microvascular thrombosis can exacerbate IAV-induced lung injury. Thus, inhibition of platelet aggregation can be a potential target for IAV treatment. Previous studies focus on the flavonoids from MH and their anti-inflammatory activities, but the anticoagulant compounds and potential molecular mechanism of MH remains unclear. This study was to isolate and characterize diketopiperazines (DKPs) from MH and to explore the underlying anticoagulant mechanism on IAV infection models.

MATERIALS AND METHODS

EtOAc sub-extract separated from MH ethanolic extract was subjected to fractionation through column chromatography. The chemical structures of pure compounds were characterized by the spectral analysis. Antiviral activities of DKPs were assayed in IAV-infected Madin-Darby canine kidney (MDCK) cells and mice. Anticoagulant effects of DKPs were investigated on adenosine 5'-diphosphate (ADP)-induced acute pulmonary embolism and IAV-induced lung injury in vivo, as well as the inhibition on platelet activating factor (PAF), arachidonic acid (AA) and ADP-induced platelet aggregation in vitro. The serum levels of thromboxane B₂ (TXB₂) and 6-keto-PGF_1α were detected by ELISA. The expressions of key proteins in CD41-mediated PI3K/AKT pathways were determined by western blotting analysis.

RESULTS

Six DKPs were, for the first time, isolated from MH and identified as cyclo(Tyr-Leu) (1), cyclo(Phe-Phe) (2), cyclo(Phe-Tyr) (3), cyclo(Ala-Ile) (4), cyclo(Ala-Leu) (5) and Bz-Phe-Phe-OMe (6). Among these DKPs, cyclo(Ala-Ile) and Bz-Phe-Phe-OMe possessed low cytotoxicities and significant inhibition against cytopathic effects induced by IAV (H1N1 and H3N2) replication in MDCK cells. Furthermore, cyclo(Ala-Ile) and Bz-Phe-Phe-OMe significantly alleviated IAV-induced platelet activation and lung inflammation in mice. They could reduce the expression of CD41 and the phosphorylation of PI3K and AKT in PLTs of IAV-infected mice.

CONCLUSION

These results suggested that cyclo(Ala-Ile) and Bz-Phe-Phe-OMe isolated from MH have antiviral and anticoagulant effects against IAV-induced PLT aggregation and lung inflammation via regulating CD41/PI3K/AKT pathway, and could be used as the potential agents for IAV treatment.

Angiotensin Converting Enzyme Inhibitor Has a Protective Effect on Decompression Sickness in Rats

Introduction: Commercial divers, high altitude pilots, and astronauts are exposed to some inherent risk of decompression sickness (DCS), though the mechanisms that trigger are still unclear. It has been previously showed that diving may induce increased levels of serum angiotensin converting enzyme. The renin angiotensin aldosterone system (RAAS) is one of the most important regulators of blood pressure and fluid volume. The purpose of the present study was to control the influence of angiotensin II on the appearance of DCS.

Methods: Sprague Dawley rats have been pre-treated with inhibitor of angiotensin II receptor type 1 (losartan; 10 mg/kg), angiotensin-converting enzyme (ACE) inhibitor (enalapril; 10 mg/kg), and calcium-entry blocker (nifedipine; 20 mg/kg). The experimental groups were treated for 4 weeks before exposure to hyperbaric pressure while controls were not treated. Seventy-five rats were subjected to a simulated dive at 1000 kPa absolute pressure for 45 min before starting decompression. Clinical assessment took place over a period of 60 min after surfacing. Blood samples were collected for measurements of TBARS, interleukin 6 (IL-6), angiotensin II (ANG II) and ACE.

Results: The diving protocol induced 60% DCS in non-treated animals. This ratio was significantly decreased after treatment with enalapril, but not other vasoactive drugs. Enalapril did not change ANG II or ACE concentration, while losartant decreased post dive level of ACE but not ANG II. None of the treatment modified the effect of diving on TBARS and IL-6 values.

Conclusion: Results suggests that the rennin angiotensin system is involved in a process of triggering DCS but this has to be further investigated. However, a vasorelaxation mediated process, which potentially could increase the load of inert gas during hyperbaric exposure, and antioxidant properties were excluded by our results.