Ischaemic stroke and the recanalization drug tissue plasminogen activator interfere with antibacterial phagocyte function

Abstract

BackgroundStroke induces immune alterations such as impaired oxidative burst and reduced release of neutrophil extracellular traps (NETs). We hypothesised that key enzymes of these defence mechanisms may be altered in ischaemic stroke. Therefore, we analysed the intra- and extracellular amounts of myeloperoxidase (MPO) and neutrophil elastase (NE) in patient sera and granulocytes and monocytes. Because the autonomous nervous system is thought to mediate stroke-induced immune alterations, we also studied the influence of stress hormones and acetylcholine on MPO and NE.Rapid recanalization by recombinant tissue plasminogen activator (r-tPA) is the only available treatment for ischaemic stroke besides thrombectomy, and its influence on antibacterial defence mechanisms of granulocytes and monocytes were addressed here.MethodsEx vivo: Intracellular and serum MPO and NE were measured on days 0, 1, 3 and 5 post-stroke by either flow cytometry or enzyme-linked immunosorbent assay (ELISA) and compared to controls. In vitro: Blood from healthy donors was incubated with catecholamines, dexamethasone and acetylcholine, and the percentage of NET-producing cells and the area covered by NETs were quantified immunohistochemically. Intra- and extracellular MPO and NE were quantified by flow cytometry or ELISA. Blood samples from healthy donors were incubated with r-tPA, and oxidative burst, phagocytosis, NETosis, cytokine release, MPO and NE were quantified by flow cytometry, ELISA and microscopy.ResultsMPO was reduced in granulocytes but increased in sera obtained from stroke patients compared to controls. NE was not altered intracellularly but was elevated in patient sera. The percentage of NET-producing neutrophils was decreased by stress hormones and increased by acetylcholine. Neither intracellular MPO nor NE was altered by hormone treatment; however, adrenaline and acetylcholine induced NE release.r-tPA led to reduced phagocytosis and oxidative burst in granulocytes and monocytes in vitro. NETosis, MPO release and cytokines were not altered, whereas NE release was enhanced by r-tPA.ConclusionsIntracellular reduction of MPO might be responsible for reduced NETosis in stroke patients. The impact of enhanced MPO and NE serum levels in stroke patients should be addressed in future studies.r-tPA impaired antibacterial defence function in vitro. Therefore, patients who undergo unsuccessful recanalization therapy might be at higher risk for infection, which should be analysed in future investigations. Immune alterations due to r-tPA effects in stroke patients should also be investigated.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-017-0914-6) contains supplementary material, which is available to authorized users.

Harmful neutrophil subsets in patients with ischemic stroke

“…Because neutrophil degranulation can also result in rapid release of neutrophil serine proteases from azurophilic granules into the extracellular medium and circulation, we measured the level of circulating neutrophil elastase. Consistently with previous data, 20 serum neutrophil elastase levels were significantly higher in patients with IS than HCs (figure 1C).…”

The Timing of Stroke Care Processes and Development of Stroke Associated Pneumonia: A National Registry Cohort Study

“…Our findings in real-world practice could be explained by early improvement in stroke severity (including level of alertness and dysphagia) in those with faster door to needle times. Another possible explanation is that immunosuppression induced by thrombolysis with tissue plasminogen activator, might potentially increase the susceptibility to SAP with treatment later rather than earlier in the thrombolysis time window ( 17 , 18 ).…”

Association of Neutrophil Serine Proteinases Levels with the Outcomes of Acute Ischemic Stroke: A Prospective Cohort Study

“…In IS, DAMPs and other lifesaving signals released from the dying cerebral tissues trigger intracytoplasmic granules in mounting neutrophils to translocate to the phagosomes and to the plasma membrane, which resultantly makes NSPs detectable in the plasma of IS patients. In line with it, a study reported that serum NE level in AIS patients was signi cantly altered compared to controls [34]. A recent clinical study enrolled 41 AIS patients and matched healthy controls reported that plasma NE levels were signi cantly increased in AIS patients compared to controls, and NE levels were associated with stroke severity [10].…”