Association Between Use of a Flying Intervention Team vs Patient Interhospital Transfer and Time to Endovascular Thrombectomy Among Patients With Acute Ischemic Stroke in Nonurban Germany.

Importance: The benefit of endovascular thrombectomy (EVT) for acute ischemic stroke is highly time-dependent, and it is challenging to expedite treatment for patients in remote areas. Objective: To determine whether deployment of a flying intervention team, compared with patient interhospital transfer, is associated with a shorter time to endovascular thrombectomy and improved clinical outcomes for patients with acute ischemic stroke. Design, Setting, and Participants: This was a nonrandomized controlled intervention study comparing 2 systems of care in alternating weeks. The study was conducted in a nonurban region in Germany including 13 primary telemedicine-assisted stroke centers within a telestroke network. A total of 157 patients with acute ischemic stroke for whom decision to pursue thrombectomy had been made and deployment of flying intervention team or patient interhospital transfer was initiated were enrolled between February 1, 2018, and October 24, 2019. The date of final follow-up was January 31, 2020. Exposures: Deployment of a flying intervention team for EVT in a primary stroke center vs patient interhospital transfer for EVT to a referral center. Main Outcomes and Measures: The primary outcome was time delay from decision to pursue thrombectomy to start of the procedure in minutes. Secondary outcomes included functional outcome after 3 months, determined by the distribution of the modified Rankin Scale score (a disability score ranging from 0 [no deficit] to 6 [death]). Results: Among the 157 patients included (median [IQR] age, 75 [66-80] y; 80 [51%] women), 72 received flying team care and 85 were transferred. EVT was performed in 60 patients (83%) in the flying team group vs 57 (67%) in the transfer group. Median (IQR) time from decision to pursue EVT to start of the procedure was 58 (51-71) minutes in the flying team group and 148 (124-177) minutes in the transfer group (difference, 90 minutes [95% CI, 75-103]; P < .001). There was no significant difference in modified Rankin Scale score after 3 months between patients in the flying team (n = 59) and transfer (n = 57) groups who received EVT (median [IQR] score, 3 [2-6] vs 3 [2-5]; adjusted common odds ratio for less disability, 1.91 [95% CI, 0.96-3.88]; P = .07). Conclusions and Relevance: In a nonurban stroke network in Germany, deployment of a flying intervention team to local stroke centers, compared with patient interhospital transfer to referral centers, was significantly associated with shorter time to EVT for patients with acute ischemic stroke. The findings may support consideration of a flying intervention team for some stroke systems of care, although further research is needed to confirm long-term clinical outcomes and to understand applicability to other geographic settings.

Clinical outcome of rural in-hospital-stroke patients after interhospital transfer for endovascular therapy within a telemedical stroke network in Germany: a registry-based observational study.

OBJECTIVES: Little is known about in-hospital-stroke (IHS) patients with large vessel occlusion and subsequent transfer to referral centres for endovascular therapy (EVT). However, this subgroup is highly relevant given the substantial amount of IHS, the ongoing trend towards greater use of EVT and lack of EVT possibilities in rural hospitals. The study objective is to explore the clinical outcomes of this vulnerable patient group, given that both IHS and interhospital transfer are associated with worse clinical outcomes due to a higher proportion of pre-existing conditions and substantial time delays during transfer. DESIGN AND SETTING: Prospectively collected data of patients receiving EVT after interhospital transfer from 14 rural hospitals of the Telemedical Stroke Network in Southeast Bavaria (TEMPiS) between February 2018 and July 2020 was analysed. PARTICIPANTS: 49 IHS and 274 out-of-hospital-stroke (OHS) patients were included. OUTCOME MEASURES: Baseline characteristics, treatment times and outcomes were compared between IHS and OHS. The primary endpoint was a 3-month modified Rankin Scale (mRS). RESULTS: In IHS patients, atrial fibrillation (55.3% vs 35.9%, p=0.012), diabetes (36.2% vs 21.1%, p=0.024) and use of oral anticoagulants (44.7% vs 20.8%, p<0.001) were more frequent. Stroke severity was similar in both groups. Treatment times from symptom onset to first brain imaging, therapy decision or EVT were shorter for IHS patients. IHS patients displayed worse clinical outcomes: 59.2% of IHS patients died within 3 months compared with 28.5% of OHS patients (p<0.001). They were less likely to achieve moderate outcomes (mRS 0-3) 3 months after stroke (20.4% vs 39.8%, p=0.010). After controlling for possible confounding variables, IHS was associated with worse clinical outcomes (adjusted OR 3.04 (95% CI 1.57 to 6.04), p<0.001). CONCLUSIONS: The mortality of IHS patients after interhospital transfer and EVT was high and functional outcomes were worse compared with those of OHS patients. Further research is needed to ascertain whether IHS patients benefit from this therapeutic approach. A more careful selection of IHS patients for transfer and means to enable faster treatment should be considered. TRIAL REGISTRATION NUMBER: NCT04270513; Post-results.

Rapid and transient stimulation of intracellular reactive oxygen species by melatonin in normal and tumor leukocytes.

Melatonin is a modified tryptophan with potent biological activity, exerted by stimulation of specific plasma membrane (MT1/MT2) receptors, by lower affinity intracellular enzymatic targets (quinone reductase, calmodulin), or through its strong anti-oxidant ability. Scattered studies also report a perplexing pro-oxidant activity, showing that melatonin is able to stimulate production of intracellular reactive oxygen species (ROS). Here we show that on U937 human monocytes melatonin promotes intracellular ROS in a fast (<1 min) and transient (up to 5-6 h) way. Melatonin equally elicits its pro-radical effect on a set of normal or tumor leukocytes; intriguingly, ROS production does not lead to oxidative stress, as shown by absence of protein carbonylation, maintenance of free thiols, preservation of viability and regular proliferation rate. ROS production is independent from MT1/MT2 receptor interaction, since a) requires micromolar (as opposed to nanomolar) doses of melatonin; b) is not contrasted by the specific MT1/MT2 antagonist luzindole; c) is not mimicked by a set of MT1/MT2 high affinity melatonin analogues. Instead, chlorpromazine, the calmodulin inhibitor shown to prevent melatonin-calmodulin interaction, also prevents melatonin pro-radical effect, suggesting that the low affinity binding to calmodulin (in the micromolar range) may promote ROS production.

Melatonin antagonizes the intrinsic pathway of apoptosis via mitochondrial targeting of Bcl-2.

We have recently shown that melatonin antagonizes damage-induced apoptosis by interaction with the MT-1/MT-2 plasma membrane receptors. Here, we show that melatonin interferes with the intrinsic pathway of apoptosis at the mitochondrial level. In response to an apoptogenic stimulus, melatonin allows mitochondrial translocation of the pro-apoptotic protein Bax, but it impairs its activation/dimerization The downstream apoptotic events, i.e. cytochrome c release, caspase 9 and 3 activation and nuclear vesiculation are equally impaired, indicating that melatonin interferes with Bax activation within mitochondria. Interestingly, we found that melatonin induces a strong re-localization of Bcl-2, the main Bax antagonist to mitochondria, suggesting that Bax activation may in fact be antagonized by Bcl-2 at the mitochondrial level. Indeed, we inhibit the melatonin anti-apoptotic effect (i) by silencing Bcl-2 with small interfering RNAs, or with small-molecular inhibitors targeted at the BH3 binding pocket in Bcl-2 (i.e. the one interacting with Bax); and (ii) by inhibiting melatonin-induced Bcl-2 mitochondrial re-localization with the MT1/MT2 receptor antagonist luzindole. This evidence provides a mechanism that may explain how melatonin through interaction with the MT1/MT2 receptors, elicits a pathway that interferes with the Bcl-2 family, thus modulating the cell life/death balance.

Melatonin as an apoptosis antagonist.

The pineal hormone melatonin (Mel), in addition to having a well-established role as a regulator of circadian rhythms, modulates nonneural compartments by acting on specific plasma membrane receptors (MT1/MT2) present in many different cell types. Mel plays immunomodulatory roles and is an oncostatic and antiproliferative agent; this led to the widespread belief that Mel may induce or potentiate apoptosis on tumor cells, even though no clear indications have been presented so far. Here we report that Mel is not apoptogenic on U937 human monocytic cells, which are known to possess MT1 receptors at the times (up to 48 h) and doses (up to 1 mM) tested. Mel does not even potentiate apoptosis, but instead, significantly reduces apoptosis induced by both cell-damaging agents (intrinsic pathway) and physiological means (extrinsic pathway). The doses required for the antiapoptotic effect (>or=100 microM) are apparently not compatible with receptor stimulation (receptor affinity<1 nM). However, receptor involvement cannot be ruled out, because we discovered that the actual Mel concentration active on cells was lower than the nominal one because of sequestration by fetal calf serum (FCS). Accordingly, in FCS-free conditions, Mel doses required for a significant antiapoptotic effect are much lower.

Intracellular pro-oxidant activity of melatonin deprives U937 cells of reduced glutathione without affecting glutathione peroxidase activity.

It was long believed that melatonin might counteract intracellular oxidative stress because it was shown to potentiate antioxidant endogenous defences, and to increase the activity of many antioxidant enzymes. However, it is now becoming evident that when radicals are measured within cells, melatonin increases, rather than decreasing, radical production. Herein we demonstrate a pro-oxidant effect of melatonin in U937 cells by showing an increase of intracellular oxidative species and a depletion of glutathione (GSH). The activity of glutathione peroxidase is not modified by melatonin treatment as it does occur in other experimental models.

Melatonin as a modulator of apoptosis in B-lymphoma cells.

Melatonin is considered a promising antitumor agent, promoting apoptosis in tumor cells and contrasting it in normal cells. The basis for this selectivity is presumed to be the ability of melatonin to stimulate reactive oxygen species (ROS) production in tumor cells. Here we investigate the effect of melatonin on three types of human lymphocytes: normal blood lymphocytes, BL41 Burkitt lymphoma, and the cognate Epstein-Barr virus (EBV)-converted E2r. We found that melatonin promotes ROS production in all these cells. Melatonin protects BL41 from apoptosis in the same manner as normal lymphocytes, whereas E2r are unaffected. These results show that ROS production is not limited to tumor lymphocytes nor it is involved in apoptosis promotion; that melatonin does not promote apoptosis in tumor lymphocytes, but EBV inhibits melatonin anti-apoptotic effects; and that the anti-apoptotic effect of melatonin does not depend on the well-known chemical antioxidant properties of melatonin.

Melatonin antagonizes apoptosis via receptor interaction in U937 monocytic cells.

Among the non-neurological functions of melatonin, much attention is being directed to the ability of melatonin to modulate the immune system, whose cells possess melatonin-specific receptors and biosynthetic enzymes. Melatonin controls cell behaviour by eliciting specific signal transduction actions after its interaction with plasma membrane receptors (MT(1), MT(2)); additionally, melatonin potently neutralizes free radicals. Melatonin regulates immune cell loss by antagonizing apoptosis. A major unsolved question is whether this is due to receptor involvement, or to radical scavenging considering that apoptosis is often dependent on oxidative alterations. Here, we provide evidence that on U937 monocytic cells, apoptosis is antagonized by melatonin by receptor interaction rather than by radical scavenging. First, melatonin and a set of synthetic analogues prevented apoptosis in a manner that is proportional to their affinity for plasma membrane receptors but not to their antioxidant ability. Secondly, melatonin's antiapoptotic effect required key signal transduction events including G protein, phospholipase C and Ca(2+) influx and, more important, it is sensitive to the specific melatonin receptor antagonist luzindole.