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Background Whole body ischemia-reperfusion injury (IRI) after cardiopulmonary resuscitation (CPR) induces a generalized inflammatory response which contributes to the development of post-cardiac arrest syndrome (PCAS). Recently, pattern recognition receptors (PRRs), such as toll-like receptors (TLRs) and inflammasomes, have been shown to mediate the inflammatory response in IRI. In this study we investigated monocyte PRR signaling and function in PCAS. Methods Blood samples were drawn in the first 12 hours, and at 24 and 48 hours following return of spontaneous circulation in 51 survivors after cardiac arrest. Monocyte mRNA levels of TLR2, TLR4, interleukin-1 receptor-associated kinase (IRAK)3, IRAK4, NLR family pyrin domain containing (NLRP)1, NLRP3, AIM2, PYCARD, CASP1, and IL1B were determined by real-time quantitative PCR. Ex vivo cytokine production in response to stimulation with TLR ligands Pam3CSK4 and lipopolysaccharide (LPS) was assessed in both whole blood and monocyte culture assays. Ex vivo cytokine production of peripheral blood mononuclear cells (PBMCs) from a healthy volunteer in response to stimulation with patients’ sera with or without LPS was assessed. The results were compared to 19 hemodynamically stable patients with coronary artery disease. Results Monocyte TLR2, TLR4, IRAK3, IRAK4, NLRP3, PYCARD and IL1B were initially upregulated in patients following cardiac arrest. The NLRP1 and AIM2 inflammasomes were downregulated in resuscitated patients. There was a significant positive correlation between TLR2, TLR4, IRAK3 and IRAK4 expression and the degree of ischemia as assessed by serum lactate levels and the time until return of spontaneous circulation. Nonsurvivors at 30 days had significantly lower mRNA levels of TLR2, IRAK3, IRAK4, NLRP3 and CASP1 in the late phase following cardiac arrest. We observed reduced proinflammatory cytokine release in response to both TLR2 and TLR4 activation in whole blood and monocyte culture assays in patients after CPR. Sera from resuscitated patients attenuated the inflammatory response in cultured PBMCs after co-stimulation with LPS. Conclusions Successful resuscitation from cardiac arrest results in changes in monocyte pattern recognition receptor signaling pathways, which may contribute to the post-cardiac arrest syndrome. Trial registration The trial was registered in the German Clinical Trials Register (DRKS00009684) on 27/11/2015. Electronic supplementary material The online version of this article (doi:10.1186/s13054-016-1340-3) contains supplementary material, which is available to authorized users.

Time-dependent monocyte mRNA expression in 30-day survivors following cardiac arrest. Shown are monocyte mRNA expression levels of TLR2, TLR4, IRAK3, IRAK4. NLRP1, NLRP3, AIM2, PYCARD, CASP1, and IL-1β in 30-day survivors in the first 12 h (CPR t1: n = 11), after 24 h (CPR t2: n = 11), and after 48 h (CPR t3: n = 12) following ROSC. Statistical hypothesis testing was performed using the Kruskal–Wallis test and post-hoc analysis with all-pairwise comparison using the Dunn–Bonferroni approach (*p value ≤0.05). (DOCX 36 kb)

Laboratory tests. Shown are patients’ inflammatory laboratory tests at admission, 24 and 48 h after ROSC. *Laboratory tests from patients after cardiopulmonary resuscitation (CPR) versus coronary artery disease (CAD) at admission. †Laboratory tests from patients after CPR versus CPR at admission. (DOCX 15 kb)

Correlation analyses of monocyte mRNA expression levels and clinical characteristics. Shown are correlation analyses of monocyte mRNA expression levels from patients in the first 12 h (CPR t1; n = 30), after 24 h (CPR t2; n = 29), and after 48 h (CPR t3; n = 23) following CPR, and the corresponding clinical characteristics. There was one patient lost to follow up after study enrollment. Statistical hypothesis testing was performed using Spearman’s rank correlation indicated as Spearman’s rho (r s) and the p values listed above. CPR cardiopulmonary resuscitation, ROSC return of spontaneous circulation, lactate serum lactate; t0 at admission, NE dosage of norepinephrine to maintain mean arterial blood pressure ≥80 mmHg. (DOCX 16 kb)

Cytokine production of cultured PBMCs in response to co-stimulation with patients’ sera and LPS. Shown is interleukin-1β (IL-1β) production of cultured PBMCs from a healthy volunteer in response to co-stimulation with 10 ng/ml LPS and 20 % serum either from patients with coronary artery disease (CAD: n = 7) or from resuscitated patients in the first 12 h (CPR t1: n = 14) and after 48 h following cardiac arrest (CPR t3: n = 9). Statistical hypothesis testing was performed using one-way ANOVA and post-hoc analysis with all-pairwise comparison using the Games-Howell approach (*p value ≤0.05; **p value ≤0.01). (DOCX 41 kb)

Time-dependent monocyte mRNA expression in 30-day nonsurvivors following cardiac arrest. Shown are monocyte mRNA expression levels of TLR2, TLR4, IRAK3, IRAK4. NLRP1, NLRP3, AIM2, PYCARD, CASP1, and IL-1β in 30-day nonsurvivors in the first 12 h (CPR t1: n = 18), after 24 h (CPR t2: n = 18), and after 48 h (CPR t3: n = 11) following ROSC. Statistical hypothesis testing was performed using the Kruskal–Wallis test and post-hoc analysis with all-pairwise comparison using the Dunn–Bonferroni approach (*p value ≤0.05; **p value ≤0.01; ***p value ≤0.001). (DOCX 42 kb)

Monocyte mRNA expression in patients who had suffered cardiac arrest and the control group. Shown are kinetics of monocyte mRNA expression levels, expressed as mean relative copy numbers ± standard deviation (SD), in patients who had suffered cardiac arrest in the first 12 h (CPR t1; n = 30), after 24 h (CPR t2; n = 29) and after 48 h (CPR t3; n = 23) following CPR, and in the control group with coronary artery disease (CAD; n = 19). Statistical hypothesis testing was performed using the Kruskal–Wallis test and post-hoc analysis with all-pairwise comparison using the Dunn–Bonferroni approach indicated as the p values listed above. (DOCX 15 kb)

Primer list. Accession number = Refseq accession number, web page access date 3 July 2014 ( http://www.ncbi.nlm.nih.gov/refseq/ ). TA annealing temperature, Conc. concentration of each primer pair, Amplicon length of replicated DNA sequence in base pairs (bp). (DOCX 16 kb)

In der vorliegenden Arbeit wurde die Verteilung der SAH-Hydrolase in der Niere der Ratte unter Kontroll- und pathologischen Bedingungen untersucht. Das zytosolische Enzym ist in tierischem Gewebe ubiquitär vorhanden und spielt eine wichtige Rolle in der Regulation von Transmethylierungsreaktionen des Organismus. Die Lokalisation der SAH-Hydrolase wurde mit Hilfe von Immunfluoreszenz-Markierung nachgewiesen. Dazu wurden Kryostatschnitte von Nieren männlicher Sprague-Dawley-Ratten unter Kontrollbedingungen, mit Streptozotocin-induziertem Diabetes mellitus ohne Insulinsubstitution nach 2 und 4 Wochen, 7 und 14 Tage nach unilateraler Nephrektomie, unter experimenteller Hypoxie, sowie salzarmer und -reicher Diät untersucht. Die SAH-Hydrolase konnte unter Kontrollbedingungen außer in den Tubuluszellen im Glomerulum und zwar in den Mesangiumzellen sowie den Podozyten, hier vor allem im Zytosol der Zellkörper und den Abgängen der Zellfortsätze lokalisiert werden. Es war kein Enzym in der Macula densa und den Zellkernen nachweisbar. Unter diabetischen Bedingungen war zusätzlich 2 Wochen nach Diabetesbeginn, SAH-Hydrolase mit den Zellkernen der tubulären Zellen des Nierenmarks assoziiert nachweisbar. In der hypoxischen Niere war die SAH-Hydrolase in Zellkernen im Interstitium von Nierenmark und -rinde, sowie in kortikalen Tubuli nachweisbar. Auch in der Niere 7 Tage nach unilateraler Nephrektomie konnte die SAH-Hydrolase in den Zellkernen der proximalen und distalen Tubuli der Nierenrinde nachgewiesen werden. Eine Co-Lokalisation der SAH-Hydrolase mit COX-2 ließ sich auch in der Macula densa von Nieren nach 7-tägiger salzarmer Diät nicht nachweisen. Mit dem Western Blot ließ sich kein SAH-Hydrolase-Protein aus den Zellkernen von Kontrollnieren und Nieren der verschiedenen pathologischen Zustände nachweisen. The aim of the present study was the localization of the cytoplasmic enzyme S-adenosylhomocysteine (SAH) hydrolase in rat kidneys under physiological and pathological conditions. SAH hydrolase is ubiquitously distributed in animal tissues and plays an important role in the regulation of transmethylation reactions. Using two-channel immunofluorescence confocal laser scan microscope the SAH hydrolase was visualized by double-immunofluorescence staining with a high specific antibody in cryostat sections of control rat kidneys. These were compared with the localization of SAH hydrolase in kidneys two and four weeks after induction of insulin dependent diabetes mellitus, after hypoxia, the remaining kidneys seven and fourteen days after uninephrectomy and after high and low salt intake. Immunostaining of SAH hydrolase in control kidneys showed a relatively uniform distribution of the enzyme in glomeruli, proximal and distal tubules of the cortex and medulla. It could be located in mesangial cells, and podocytes, where it appeared to be mainly perinuclear in the cytoplasm of the cell bodies and in the branches of their foot processes. There was no detectable amount of SAH hydrolase in the macula densa and in the nuclei of the proximal and distal tubules of the renal cortex and medulla. In the kidney of two weeks IDDM rats SAH hydrolase was detectable in a certain amount of nuclei of tubular cells of the medulla. A very bright immunofluorescence of SAH hydrolase could be localized in the nuclei of interstitial cells of renal cortex and medulla and the cortical tubules in the rat kidneys after hypoxia. SAH hydrolase immunostaining was also observed in the nuclei of tubular cells of the proximal and distal tubules of the renal cortex seven days after uninephrectomy. There was no detectable co-localization of SAH hydrolase and COX-2 in the macula densa cells neither under high, nor under low salt intake conditions. We could not detect a soluble franction of SAH hydrolase in the nuclei of kidney cells neither under physiological nor pathological conditions.