Phenylephrine impairs host defence mechanisms to infection: a combined laboratory study in mice and translational human study.

BACKGROUND: Immunosuppression after surgery is associated with postoperative complications, mediated in part by catecholamines that exert anti-inflammatory effects via the ß-adrenergic receptor. Phenylephrine, generally regarded as a selective α-adrenergic agonist, is frequently used to treat perioperative hypotension. However, phenylephrine may impair host defence through ß-adrenergic affinity. METHODS: Human leukocytes were stimulated with lipopolysaccharide (LPS) in the presence or absence of phenylephrine and α- and ß-adrenergic antagonists. C57BL/6J male mice received continuous infusion of phenylephrine (30-50 µg kg-1 min-1 i.v.) or saline via micro-osmotic pumps, before LPS administration (5 mg kg-1 i.v.) or caecal ligation and puncture (CLP). Twenty healthy males were randomised to a 5 h infusion of phenylephrine (0.5 µg kg-1 min-1) or saline before receiving LPS (2 ng kg-1 i.v.). RESULTS: In vitro, phenylephrine enhanced LPS-induced production of the anti-inflammatory cytokine interleukin (IL)-10 (maximum augmentation of 93%) while attenuating the release of pro-inflammatory mediators. These effects were reversed by pre-incubation with ß-antagonists, but not α-antagonists. Plasma IL-10 levels were higher in LPS-challenged mice infused with phenylephrine, whereas pro-inflammatory mediators were reduced. Phenylephrine infusion increased bacterial counts after CLP in peritoneal fluid (+42%, P=0.0069), spleen (+59%, P=0.04), and liver (+35%, P=0.09). In healthy volunteers, phenylephrine enhanced the LPS-induced IL-10 response (+76%, P=0.0008) while attenuating plasma concentrations of pro-inflammatory mediators including IL-8 (-15%, P=0.03). CONCLUSIONS: Phenylephrine exerts potent anti-inflammatory effects, possibly involving the ß-adrenoreceptor. Phenylephrine promotes bacterial outgrowth after surgical peritonitis. Phenylephrine may therefore compromise host defence in surgical patients and increase susceptibility towards infection. CLINICAL TRIAL REGISTRATION: NCT02675868 (Clinicaltrials.gov).

Norepinephrine Dysregulates the Immune Response and Compromises Host Defense during Sepsis.

Rationale: Sepsis is characterized by a dysregulated immune response to infection. Norepinephrine, the cornerstone vasopressor used in septic shock, may contribute to immune dysregulation and impact host defense.Objectives: To investigate effects of norepinephrine and the alternative vasopressor vasopressin on the immune response and host defense.Methods: Leukocytes from six to nine donors were stimulated in the presence or absence of norepinephrine and vasopressin. A total of 190 C57BL/6J mice received a continuous infusion of norepinephrine or vasopressin via microosmotic pumps and were challenged with LPS or underwent cecal ligation and puncture. Thirty healthy volunteers were randomized to a 5-hour infusion of norepinephrine, vasopressin, or saline and intravenously challenged with LPS. The relationship between the norepinephrine infusion rate and the use of ß-blockers and plasma cytokines was assessed in 195 patients with septic shock.Measurements and Main Results: Norepinephrine attenuated the production of proinflammatory mediators and reactive oxygen species and augmented antiinflammatory IL-10 production both in vitro and in LPS-challenged mice. Norepinephrine infusion during cecal ligation and puncture resulted in increased bacterial dissemination to the spleen, liver, and blood. In LPS-challenged volunteers, norepinephrine enhanced plasma IL-10 concentrations and attenuated the release of the proinflammatory cytokine IFN-γ-induced protein 10. Vasopressin exerted no immunomodulatory effects across these experimental setups. In patients, higher norepinephrine infusion rates were correlated with a more antiinflammatory cytokine balance, whereas ß-blocker use was associated with a more proinflammatory cytokine balance.Conclusions: Norepinephrine dysregulates the immune response in mice and humans and compromises host defense. Therefore, it may significantly contribute to sepsis-induced immunoparalysis, whereas vasopressin does not have untoward immunologic effects.

Potentially Inadvertent Immunomodulation: Norepinephrine Use in Sepsis.

Septic shock is a major cause of death worldwide and a considerable healthcare burden in the twenty-first century. Attention has shifted from damaging effects of the proinflammatory response to the detrimental role of antiinflammation, a phenomenon known as sepsis-induced immunoparalysis. Sepsis-induced immunoparalysis may render patients vulnerable to secondary infections and is associated with impaired outcome. The immunoparalysis hypothesis compels us to reevaluate the current management of septic shock and to assess whether we are inadvertently compromising or altering the host immune response. In this perspective, we discuss the potential detrimental role of norepinephrine, the cornerstone treatment for septic shock, in sepsis-induced immunoparalysis. We provide a short overview of the current understanding of the immunologic pathophysiology of sepsis, followed by a detailed description of the immunomodulatory effects of norepinephrine and alternative vasopressors. We conclude that although the development of novel therapies aimed at reversing immunoparalysis is underway, the use of norepinephrine may aggravate the development, extent, and duration of sepsis-induced immunoparalysis. Current in vitro and animal data indicate that norepinephrine treatment exerts immunosuppressive and bacterial growth-promoting effects and may increase susceptibility toward infections. However, evidence in humans is circumstantial, as immunologic effects of norepinephrine have not been investigated properly in experimental or clinical studies. Alternatives such as vasopressin/selepressin, angiotensin II, and phenylephrine could have a fundamental advantage over norepinephrine with respect to their immunologic properties. However, also for these agents, in vivo immunologic data in humans are largely lacking. As such, human studies on the immunomodulatory properties of norepinephrine and viable alternatives are highly warranted.

The impact of ADRB2 polymorphisms on immune responses and norepinephrine-induced immunosuppression.

RATIONALE: To evaluate whether common nonsynonymous variants [single-nucleotide polymorphisms (SNPs) or SNP haplotypes] in the ß2-adrenergic receptor render subjects more susceptible to norepinephrine-induced immunosuppression and whether they are associated with dysregulated ex vivo and in vivo inflammatory responses. METHODS: Peripheral blood mononuclear cells from healthy volunteers (main cohort: n = 106, secondary cohort: n = 408) were ex vivo stimulated with various stimuli and production of cytokines was assessed. Additionally, ex vivo modulation of cytokine production by norepinephrine was evaluated in the main cohort. Volunteers from the main cohort also underwent experimental endotoxemia (administration of 1 ng/kg lipopolysaccharide), during which in vivo plasma cytokine concentrations and clinical inflammatory parameters were measured. Subjects were genotyped, common SNPs in the ADRB2 gene were extracted (rs1042711, rs1042713, and rs1042714), and the presence of haplotypes was identified (CysGlyGln, CysArgGln, and ArgGlyGlu). RESULTS: In both cohorts, presence of ADRB2 SNPs or haplotypes was not associated with altered ex vivo cytokine responses. Norepinephrine attenuated production of the proinflammatory cytokines TNF and IL-6 [-26% (-22% to -30%) and -14% (-9% to -18%), respectively, both P < 0.0001] and enhanced release of the anti-inflammatory IL-10 [+9% (+3% to +15%), P = 0.003]. These effects were not modulated by the presence of ADRB2 SNPs or haplotypes (all P values >0.37). In addition, no influence of SNPs or haplotypes on in vivo cytokine concentrations or clinical inflammatory parameters was observed (P values >0.14). CONCLUSIONS: Common nonsynonymous variants in the ADRB2 gene influence neither ex vivo cytokine production or norepinephrine-mediated immunosuppression nor the systemic in vivo inflammatory response induced by lipopolysaccharide administration in healthy volunteers.

No interplay between gut microbiota composition and the lipopolysaccharide-induced innate immune response in humans in vivo.

OBJECTIVE: Animal studies have demonstrated the extensive interplay between the gut microbiota and immunity. Moreover, in critically ill patients, who almost invariably suffer from a pronounced immune response, a shift in gut microbiota composition is associated with infectious complications and mortality. We examined the relationship between interindividual differences in gut microbiota composition and variation in the in vivo cytokine response induced by bacterial lipopolysaccharide (LPS). Furthermore, we evaluated whether an LPS challenge alters the composition of the gut microbiota. METHODS: Healthy male volunteers received an intravenous bolus of 2 ng kg-1 LPS (n = 70) or placebo (n = 8). Serial plasma concentrations of tumor necrosis factor-α, interleukin (IL)-6, IL-8 and IL-10 were measured, and subjects were divided into high and low cytokine responders. Gut microbiota composition was determined using 16s RNA gene sequencing of faecal samples obtained 1 day before (baseline) and 1 day and 7 days following the LPS challenge. RESULTS: Baseline microbiota composition, analysed by principal coordinate analysis and random forest analysis, did not differ between high and low responders for any of the four measured cytokines. Furthermore, baseline microbiota diversity (Shannon and Chao indices) was similar in high and low responders. No changes in microbiota composition or diversity were observed at 1 and 7 days following the LPS challenge. CONCLUSION: Our results indicate that existing variation in gut microbiota composition does not explain the observed variability in the LPS-induced innate immune response. These findings strongly argue against the interplay between the gut microbiota composition and the innate immune response in humans.

Effect of Vasopressors on the Macro- and Microcirculation During Systemic Inflammation in Humans In Vivo.

AIM: Comparing the effects of different vasopressors in septic shock patients is hampered by high heterogeneity and the fact that current guidelines dictate the use of norepinephrine. Herein, we studied the effects of three vasopressor agents, norepinephrine, phenylephrine, and vasopressin, on the macro- and microcirculation during experimental human endotoxemia, a standardized, controlled model of systemic inflammation in humans in vivo. METHODS: We performed a randomized controlled study in which 40 healthy male volunteers were assigned to a 5-h infusion of either 0.05 µg/kg/min norepinephrine (n = 10), 0.5 µg/kg/min phenylephrine (n = 10), 0.04 IU/min vasopressin (n = 10), or saline (n = 10), starting 1 h before intravenous administration of 2 ng/kg lipopolysaccharide (LPS). The macrocirculation was monitored using arterial catheter-derived parameters with additional blood pressure waveform contour analysis (PCA) until 4.5 h following LPS administration. Sublingual microcirculatory density and flow were assessed using a handheld video microscope until 6 h post-LPS. RESULTS: LPS administration affected all macrocirculatory and microcirculatory parameters. The LPS-induced decrease in blood pressure and systemic vascular resistance (SVR) was refractory to low-dose norepinephrine and phenylephrine, and to a lesser extent, to vasopressin. Only vasopressin exerted effects on PCA parameters compared with placebo, by mitigating the LPS-induced decrease in diastolic blood pressure by stabilizing SVR and cardiac output. The endotoxemia-induced decreased indices of microvascular flow and density were not influenced by vasopressor therapy. CONCLUSIONS: In a highly controlled model of systemic inflammation in humans in vivo, a 5-h infusion of various vasopressors revealed distinctive effects on macrohemodynamic variables without affecting the sublingual microcirculation.

Is the excess cardiovascular morbidity in pheochromocytoma related to blood pressure or to catecholamines?

BACKGROUND: It is generally accepted that pheochromocytoma is associated with an increased cardiovascular risk. This is however not based on studies with an appropriate control group of patients with essential hypertension. AIM OF THE STUDY: We examined whether patients with pheochromocytoma have an excess cardiovascular morbidity as compared to hypertensive patients. METHODS: In a retrospective case-control study we reviewed the medical charts of 109 pheochromocytoma patients for cardiovascular events within 5 years prior to the diagnosis. These patients were matched to control patients with essential hypertension for gender and year of birth and diagnosis. Outcome variables were ischemic heart disease, cerebrovascular accidents, and transient ischemic attacks. Classical cardiovascular risk factors were also assessed. RESULTS: A significantly higher rate of patients with pheochromocytoma suffered a cardiovascular event (13.8%; 95% confidence interval: 7.9%-21.6%) as compared to hypertensive patients (1.1%, 95% confidence interval: 0.1%-3.9%) (P < .001). Blood pressure level was lower in pheochromocytoma patients (153/91 ± 35/15 mm Hg) than in hypertensive patients (170/103 ± 18/8 mm Hg) (P < .001), even after correction for use of antihypertensive medication (P < .02). The difference in event rates could not be attributed to differences in other cardiovascular risk factors. CONCLUSIONS: Pheochromocytoma patients have a clearly higher rate of cardiovascular events than patients with essential hypertension. This cannot be attributed to differences in blood pressure or other cardiovascular risk factors. The most likely explanation for the excess event rate is the prolonged exposure to the toxic effects of tumoral catecholamines. These data underpin the importance of a timely diagnosis and treatment of pheochromocytoma.