Relationship between circulating levels of calcitonin gene-related peptide, nitric oxide metabolites and hemodynamic changes in human septic shock

Inflammation and Organ Injury the Role of Substance P and Its Receptors

Tightly controlled inflammation is an indispensable mechanism in the maintenance of cellular and organismal homeostasis in living organisms. However, aberrant inflammation is detrimental and has been suggested as a key contributor to organ injury with different etiologies. Substance P (SP) is a neuropeptide with a robust effect on inflammation. The proinflammatory effects of SP are achieved by activating its functional receptors, namely the neurokinin 1 receptor (NK1R) receptor and mas-related G protein-coupled receptors X member 2 (MRGPRX2) and its murine homolog MRGPRB2. Upon activation, the receptors further signal to several cellular signaling pathways involved in the onset, development, and progression of inflammation. Therefore, excessive SP-NK1R or SP-MRGPRX2/B2 signals have been implicated in the pathogenesis of inflammation-associated organ injury. In this review, we summarize our current knowledge of SP and its receptors and the emerging roles of the SP-NK1R system and the SP-MRGPRX2/B2 system in inflammation and injury in multiple organs resulting from different pathologies. We also briefly discuss the prospect of developing a therapeutic strategy for inflammatory organ injury by disrupting the proinflammatory actions of SP via pharmacological intervention.

CGRP Plasma Levels Correlate with the Clinical Evolution and Prognosis of Hospitalized Acute COVID-19 Patients

SARS-CoV-2 is the etiological agent of COVID-19, an extremely heterogenous disease that can cause severe respiratory failure and critical illness. To date, reliable biomarkers allowing for early patient stratification according to disease severity are still lacking. Calcitonin gene-related peptide (CGRP) is a vasoactive neuropeptide involved in lung pathophysiology and immune modulation and is poorly investigated in the COVID-19 context. In this observational, prospective cohort study, we investigated the correlation between CGRP and clinical disease evolution in hospitalized moderate to severe COVID-19 patients. Between January and May 2021 (Italian third pandemic wave), 135 consecutive SARS-CoV-2 patients were diagnosed as being eligible for the study. Plasma CGRP level evaluation and routine laboratory tests were performed on blood samples collected at baseline and after 7 days of hospitalization. At baseline, the majority our patients had a moderate to severe clinical presentation, and higher plasma CGRP levels predicted a higher risk of in-hospital negative evolution (odds-ratio OR 2.84 [IQR 1.07-7.51]) and were correlated with pulmonary intravascular coagulopathy (OR 2.92 [IQR 1.19-7.17]). Finally, plasma CGRP levels were also correlated with plasma IP10 levels. Our data support a possible crosstalk between the lung and the neuroimmune axis, highlighting a crucial role for plasma CGRP in sustaining COVID-19-related hyperinflammation.

CGRP measurements in human plasma - a methodological study

Background

Calcitonin gene-related peptide plasma levels have frequently been determined as a biomarker for primary headaches. However, published data is often inconsistent resulting from different methods that are not precisely described in most studies.

Methods

We applied a well-proven enzyme-linked immunosorbent assay to measure calcitonin gene-related peptide concentrations in human blood plasma, we modified parameters of plasma preparation and protein purification and used calcitonin gene-related peptide-free plasma for standard solutions, which are described in detail.

Results

Calcitonin gene-related peptide levels are stable in plasma with peptidase inhibitors and after deep-freezing. Calcitonin gene-related peptide standard solutions based on synthetic intercellular fluid or pooled plasma with pre-absorbed calcitonin gene-related peptide influenced the measurements but yielded both comprehensible results. In a sample of 56 healthy subjects the calcitonin gene-related peptide plasma levels varied considerably from low (<50 pg/mL) to very high (>500 pg/mL) values. After a 12-hour exposure of these subjects to normobaric hypoxia the individual calcitonin gene-related peptide levels remained stable.

Conclusion

Buffering with peptidase inhibitors and immediate freezing or processing of plasma samples is essential to achieve reliable measurements. Individuals show considerable differences and partly high calcitonin gene-related peptide plasma levels without detectable pathological reason. Thus plasma measurements are suited particularly to follow calcitonin gene-related peptide levels in longitudinal studies.

The use of data for this study was approved by the Ethics Committee of the Medical

University of Innsbruck (https://www.i-med.ac.at/ethikkommission/; EK Nr: 1242/2017).

Identification of swine protein biomarkers of inflammation-associated pain

This study sought to determine if proteins associated with pain in humans could be measured using a swine in vitro model of inflammation. This would constitute the first step towards using them as surrogate endpoints to help support effectiveness indications for investigational new animal drugs to control pain in swine. Swine whole blood samples were cultured in vitro with E. coli derived-lipopolysaccharide (LPS) or without LPS for 24 h. Supernatants from these cultures were collected to determine the concentration of proteins associated with pain and whether the levels were altered in response to LPS-induced inflammation. Bradykinin protein levels steadily increased over time due to LPS stimulation and returned to 0 h levels after 6 h of culture. Corticotrophin-releasing factor protein levels were not affected by LPS. Substance-P protein trended towards increasing concentrations after LPS stimulation, following a time-concentration profile similar to that observed with bradykinin. These results suggest that 2 biomarkers may be useful as surrogate endpoints for evaluation of pain.

Evidence for a protective role for the rs805305 single nucleotide polymorphism of dimethylarginine dimethylaminohydrolase 2 (DDAH2) in septic shock through the regulation of DDAH activity

BACKGROUND

Dimethylarginine dimethylaminohydrolase 2 (DDAH2) regulates the synthesis of nitric oxide (NO) through the metabolism of the endogenous inhibitor of nitric oxide synthase, asymmetric dimethylarginine (ADMA). Pilot studies have associated the rs805305 SNP of DDAH2 with ADMA concentrations in sepsis. This study explored the impact of the rs805305 polymorphism on DDAH activity and outcome in septic shock.

METHODS

We undertook a secondary analysis of data and samples collected during the Vasopressin versus noradrenaline as initial therapy in septic shock (VANISH) trial. Plasma and DNA samples isolated from 286 patients recruited into the VANISH trial were analysed. Concentrations of L-Arginine and the methylarginines ADMA and symmetric dimethylarginine (SDMA) were determined from plasma samples. Whole blood and buffy-coat samples were genotyped for polymorphisms of DDAH2. Clinical data collected during the study were used to explore the relationship between circulating methylarginines, genotype and outcome.

RESULTS

Peak ADMA concentration over the study period was associated with a hazard ratio for death at 28 days of 3.3 (95% CI 2.0-5.4), p < 0.001. Reduced DDAH activity measured by an elevated ADMA:SDMA ratio was associated with a reduced risk of death in septic shock (p = 0.03). The rs805305 polymorphism of DDAH2 was associated with reduced DDAH activity (p = 0.004) and 28-day mortality (p = 0.02). Mean SOFA score and shock duration were also reduced in the less common G:G genotype compared to heterozygotes and C:C genotype patients (p = 0.04 and p = 0.02, respectively).

CONCLUSIONS

Plasma ADMA is a biomarker of outcome in septic shock, and reduced DDAH activity is associated with a protective effect. The polymorphism rs805305 SNP is associated with reduced mortality, which is potentially mediated by reduced DDAH2 activity.

TRIAL REGISTRATION

ISRCTN Registry, ISRCTN20769191 . Registered on 20 September 2012.

Transcerebral net exchange of vasoactive peptides and catecholamines during lipopolysaccharide-induced systemic inflammation in healthy humans

The systemic inflammatory response triggered by lipopolysaccharide (LPS) is associated with cerebral vasoconstriction, but the underlying mechanisms are unknown. We therefore examined whether a 4-hour intravenous LPS infusion (0.3 ng·kg^-1) induces any changes in the transcerebral net exchange of the vasoactive peptides endothelin-1 (ET-1) and calcitonin-gene related peptide (CGRP) and catecholamines in human volunteers. Cerebral blood flow was measured by the Kety-Schmidt technique, and paired arterial-to-jugular venous blood samples were obtained for estimating the transcerebral exchange of ET-1, CGRP, and catecholamines by the Fick principle in 12 volunteers before and after LPS infusion. The cerebrovascular release of ET-1 was enhanced, whereas the transcerebral net exchange of CGRP and catecholamines was unaffected. Our findings thus point towards locally produced ET-1 within the cerebrovasculature as a contributor to cerebral vasoconstriction after LPS infusion.

Plasma nitrate/nitrite concentrations in dogs with naturally developing sepsis and non-infectious forms of the systemic inflammatory response syndrome

The aim of this prospective observational study was to evaluate the differences in plasma nitrate/nitrite concentrations between dogs with sepsis and those with non-infectious forms of the systemic inflammatory response syndrome (SIRS). Eighteen dogs with sepsis, 20 dogs with SIRS and 29 healthy control dogs were enrolled. Blood samples were obtained from the dogs within 12 hours of admission to the University of Missouri Veterinary Medical Teaching Hospital (MU VMTH) Intensive Care Unit (ICU) in lithium heparin blood tubes. Plasma nitrate/nitrite concentrations were measured using the Greiss reaction. Plasma nitrate/nitrite concentrations at presentation, clinical parameters, organ dysfunction and in-hospital mortality were compared between groups. Plasma total nitrate/nitrite was significantly greater in the sepsis group compared with the control group (P=0.005) and SIRS group (P=0.037). There was no statistical difference in plasma nitrate/nitrite concentration between the SIRS and control groups (P=0.489). The sensitivity was 66.7 per cent (95 per cent CI, 41 to 87 per cent) and the specificity was 75.5 per cent (95 per cent CI, 61 to 87 per cent) for differentiating dogs with sepsis from dogs without sepsis.

Disruption of the transient receptor potential vanilloid 1 can affect survival, bacterial clearance, and cytokine gene expression during murine sepsis

BACKGROUND

Previous studies suggest that the transient receptor potential vanilloid 1 (TRPV1) channel has a role in sepsis, but it is unclear whether its effect on survival and immune response is beneficial or harmful.

METHODS

We studied the effects of genetic (Trpv1-knockout vs. wild-type [WT] mice) and pharmacologic disruption of TRPV1 with resiniferatoxin (an agonist) or capsazepine (an antagonist) on mortality, bacterial clearance, and cytokine expression during lipopolysaccharide or cecal ligation and puncture-induced sepsis.

RESULTS

After cecal ligation and puncture, genetic disruption of TRPV1 in Trpv1-knockout versus WT mice was associated with increased mortality risk (hazard ratio, 2.17; 95% CI, 1.23-3.81; P = 0.01). Furthermore, pharmacologic disruption of TRPV1 with intrathecal resiniferatoxin, compared with vehicle, increased mortality risk (hazard ratio, 1.80; 95% CI, 1.05-3.2; P = 0.03) in WT, but not in Trpv1-knockout, mice. After lipopolysaccharide, neither genetic (Trpv1 knockout) nor pharmacologic disruption of TRPV1 with resiniferatoxin had significant effect on survival compared with respective controls. In contrast, after lipopolysaccharide, pharmacologic disruption of TRPV1 with capsazepine, compared with vehicle, increased mortality risk (hazard ratio, 1.92; 95% CI, 1.02-3.61; P = 0.04) in WT animals. Furthermore, after cecal ligation and puncture, increased mortality in resiniferatoxin-treated WT animals was associated with higher blood bacterial count (P = 0.0004) and higher nitrate/nitrite concentrations and down-regulation of tumor necrosis factor α expression (P = 0.004) compared with controls.

CONCLUSIONS

Genetic or pharmacologic disruption of TRPV1 can affect mortality, blood bacteria clearance, and cytokine response in sepsis in patterns that may vary according to the sepsis-inducing event and the method of TRPV1 disruption.

Circulating levels of vasoactive peptides in patients with acute bacterial meningitis

PURPOSE

The underlying mechanisms for cerebral blood flow (CBF) abnormalities in acute bacterial meningitis (ABM) are largely unknown. Putative mediators include vasoactive peptides, e.g. calcitonin-gene related peptide (CGRP), vasoactive intestinal peptide (VIP), and endothelin-1 (ET-1), all of which may be affected by therapeutic interventions used in the intensive care unit. We measured arterial levels as well as the net cerebral flux of these peptides in patients with ABM, and in healthy volunteers undergoing interventions relevant to intensive care.

METHODS

Seven patients with severe ABM and sepsis and fifteen healthy volunteers were included after informed consent. The net cerebral fluxes of vasoactive peptides were measured by the Kety-Schmidt technique in ABM patients (baseline study only), as well as in volunteers at baseline, during voluntary hyperventilation, after an intravenous injection of lipopolysaccharide (LPS), and during norepinephrine infusion.

RESULTS

The arterial levels of CGRP, but not of VIP or ET-1, were elevated in patients with ABM, but no net cerebral flux was present. CGRP levels decreased during hyperventilation and after LPS injection. No net cerebral flux of VIP occurred in any group at any time. A cerebral efflux of ET-1, which occurred in volunteers at baseline, was neither present in volunteers after LPS injection nor in patients with ABM.

CONCLUSION

The arterial concentration of the vasodilatory peptide, CGRP, but of neither VIP nor the vasoconstrictor ET-1, is elevated in patients with ABM and sepsis. A constitutive cerebral output of ET-1 appears to be present in healthy humans, but is abolished after LPS injection.

Direct hemoperfusion with polymyxin-B-immobilized fiber columns improves septic hypotension and reduces inflammatory mediators in septic patients with colorectal perforation

PURPOSE

Although some studies have reported favorable effects of direct hemoperfusion with polymyxin-B-immobilized fiber columns (PMX) for the treatment of septic shock, few studies have demonstrated the efficacy of PMX in studies with a uniform case definition and without any other blood purification techniques.

MATERIALS AND METHODS

Fifty-two patients with severe sepsis or septic shock secondary to colorectal perforation were treated with PMX. Hemodynamic alterations and plasma concentrations of endotoxin, interleukin (IL)-1beta, IL-1 receptor antagonist (IL-1Ra), IL-6, IL-8, and IL-10 were evaluated following PMX treatment.

RESULTS

We observed a significant reduction in plasma endotoxin in the nonsurvivors immediately after PMX treatment compared to before treatment. Systolic blood pressure was markedly increased and circulating levels of IL-1beta, IL-1Ra, and IL-8 were significantly reduced during a 2-h interval of PMX.

CONCLUSIONS

Our findings suggested that PMX treatment appears to adsorb endotoxin and also modulates circulating cytokine during a 2-h interval of direct hemoperfusion in septic patients with such condition.

The transient receptor potential vanilloid 1 (TRPV1) receptor protects against the onset of sepsis after endotoxin

Transient potential vanilloid 1 (TRPV1) receptor is an ion channel receptor primarily localized on sensory nerves and activated by specific stimuli to initiate and amplify pain and inflammation, as typified by murine models of scald and arthritis. Little is known of the role of TRPV1 in sepsis, an infective disease associated with inflammation. Through use of a sublethal murine model of lipopolysaccharide-induced peritoneal sepsis, we provide novel evidence that genetic deletion of TRPV1 leads to an enhanced onset of various pathological components of systemic endotoxemia. Paired studies of TRPV1 knockout (KO) and wild-type mice demonstrate significantly enhanced hypotension (56+/-2% vs. 38+/-6% decrease in blood pressure, n=12), hypothermia (13+/-3% vs. 7+/-1% decrease in core temperature, n=6), and peritoneal exudate mediator levels (TNF-alpha, 0.78+/-0.2 vs. 0.38+/-0.1 ng/ml; nitrite, for NO, 35+/-10 vs. 15+/-3 microM; n=8) in TRPV1 KO mice, indicating loss of protective effect. Findings correlated with liver edema and raised plasma levels of aspartate aminotransferase in TRPV1 KO mice. These data suggest that TRPV1 may play an important regulatory role in sepsis independent of the major sensory neuropeptide substance P. The findings are relevant to developing strategies that increase the beneficial, and reduce the harmful, components of sepsis to prevent and treat this often fatal condition.

Increases in vanilloid TRPV1 receptor protein and CGRP content during endotoxemia in rats

The aim of the present study was to determine whether the transient receptor potential vanilloid (TRPV1) receptor protein as well as the calcitonin gene-related peptide (CGRP) content could be enhanced after the i.p. administration of 5 mg/kg lipopolysaccharide (LPS) to Sprague-Dawley rats. In tongue tissue, used as a representative model of TRPV1 receptors expression, there was a significant increase in the abundance of TRPV1 receptor protein 6 h after LPS administration. In mesenteric arteries, the density of the CGRP-positive nerves as well as the release of CGRP induced by 10 microM anandamide was also significantly increased 6 h after LPS administration. The relaxant responses induced by anandamide in mesenteric beds isolated from either untreated or LPS-treated rats were abolished after a 2 h exposure to 10 microM capsaicin. Moreover, anandamide-induced relaxations of untreated mesenteries were potentiated by the protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA, 0.1 microM), but not by its inactive analogue 4alpha-phorbol (0.1 microM). The potentiation of anandamide effects caused by the PKC activator was accompanied by a significant increase in the overflow of CGRP induced by anandamide in the untreated rats. It is proposed that the overexpression of the TRPV1 receptors and the increased content of CGRP could contribute to the enhancement of anandamide effects during the endotoxemic shock. An eventual phosphorylation event linked to the overflow of CGRP could also participate in the enhanced relaxation caused by anandamide in endotoxemia.

Regulation of immune tolerance by anti-inflammatory neuropeptides

The induction of antigen-specific tolerance is essential to maintain immune homeostasis, control autoreactive T cells, prevent the onset of autoimmune diseases and achieve tolerance of transplants. Inflammation is a necessary process for eliminating pathogens, but can lead to serious deleterious effects in the host if left unchecked. Identifying the endogenous factors that control immune tolerance and inflammation is a key goal in the field of immunology. In the last decade, various neuropeptides that are produced by immune cells with potent anti-inflammatory actions were found to participate in the maintenance of tolerance in different immunological disorders.

Endotoxin apheresis for sepsis

The principle use of apheresis in the treatment of sepsis may be summarized as the removal of toxic substances and the restoration of normal organs function. It is ideal to control the early phases of inflammatory cascade when treating sepsis by removing microbial components, such as endotoxin or peptidoglycan. This review discusses endotoxin apheresis with particular emphasis on treatment using polymyxin B immobilized fiber columns (Toraymyxin) which are used widely in Japan for endotoxin removal therapy in patients with septic shock. Lixelle and CTR which have recently been shown to remove circulating bacterial components are also included in this review.

The Preclinical Pharmacology of BIBN4096BS, a CGRP Antagonist

CGRP is an important neuropeptide found throughout the cardiovascular system. However, until recently it has been difficult to define its pharmacology or physiological role because of the lack of suitable antagonists. BIBN4096BS is a high-affinity, nonpeptide antagonist that shows much greater selectivity for human CGRP1 receptors compared to any other drug. Its pharmacology has been defined with studies on transfected cells or cell lines endogenously expressing receptors of known composition. These have allowed confirmation that in many human blood vessels, CGRP is working via CGRP1 receptors. However, it also interacts with other CGRP-activated receptors, of unknown composition. In vivo, clinical studies have shown that BIBN4096BS is likely to be useful in the treatment of migraine. It has also been used to define the role of CGRP in phenomena such as plasma extravasation and cardioprotection following ischemia.

Urocortin and adrenomedullin prevent lethal endotoxemia by down-regulating the inflammatory response

Urocortin 1 (UCN) and adrenomedullin (AM) are two neuropeptides that have emerged as potential endogenous anti-inflammatory factors based on their production by and binding to immune cells. Because human septic shock involves excessive inflammatory cytokine production, we investigated the effect of UCN and AM in the production of inflammatory mediators and their therapeutic actions in two models of septic shock. Both peptides down-regulated the production of inflammatory mediators by endotoxin-activated macrophages. The administration of UCN or AM protected against lethality after cecal ligation and puncture or after injection of bacterial endotoxin and prevented septic shock-associated histopathology, such as infiltration of inflammatory cells and intravascularly disseminated coagulation in various target organs. The therapeutic effect of UCN and AM was mediated by decreasing the local and systemic levels of a wide spectrum of inflammatory mediators, including cytokines, chemokines, and the acute phase protein serum amyloid A. Importantly, UCN or AM treatment was therapeutically effective in established endotoxemia. In conclusion, UCN and AM could represent two multistep therapeutic agents for human septic shock to be used in combination with other immunomodulatory agents or complementary as anti-inflammatory factors to other therapies.

Calcitonin gene related peptide and N-procalcitonin modulate CD11b upregulation in lipopolysaccharide activated monocytes and neutrophils

OBJECTIVE

Circulating levels of calcitonin gene related peptide (CGRP) and calcitonin precursors, including procalcitonin (PCT) and its free aminopeptide N-procalcitonin (N-PCT), have been found dramatically increased in septic patients. PCT is known to attenuate the chemotaxis of monocytes in response to chemoattractants. This study examined whether CGRP and N-PCT modulate the LPS-induced expression of CD11b, which is one of the major integrins involved in monocyte and neutrophil chemotaxis during a response to microbial infections.

DESIGN AND SETTING

In vitro cell culture study in the immunology laboratory of a university hospital.

PARTICIPANTS

Healthy volunteers.

MEASUREMENTS AND RESULTS

We assessed the effects of N-PCT and CGRP on CD11b expression on monocytes and neutrophils after LPS (2 ng/ml) or fMLP (10(-8) M) challenges. We used a human whole blood model, and measurements were made by flow cytometry. Both peptides in a dose-dependent manner decreased the LPS- and fMLP-induced rise in CD11b in monocytes and neutrophils. As these peptides are thought to act by raising cAMP, we also mimicked their effects with the use of rolipram and forskolin and found similar results.

CONCLUSIONS

These findings are in line with recent studies demonstrating anti-inflammatory properties for this family of peptides. CGRP and calcitonin precursors may function as factors suppressing the propagation of inflammation through the inhibition of several processes involved during a response to a bacterial stimulus.

Immunologic and hemodynamic effects of "low-dose" hydrocortisone in septic shock: a double-blind, randomized, placebo-controlled, crossover study

Within the last few years, increasing evidence of relative adrenal insufficiency in septic shock evoked a reassessment of hydrocortisone therapy. To evaluate the effects of hydrocortisone on the balance between proinflammatory and antiinflammation, 40 patients with septic shock were randomized in a double-blind crossover study to receive either the first 100 mg of hydrocortisone as a loading dose and 10 mg per hour until Day 3 (n = 20) or placebo (n = 20), followed by the opposite medication until Day 6. Hydrocortisone infusion induced an increase of mean arterial pressure, systemic vascular resistance, and a decline of heart rate, cardiac index, and norepinephrine requirement. A reduction of plasma nitrite/nitrate indicated inhibition of nitric oxide formation and correlated with a reduction of vasopressor support. The inflammatory response (interleukin-6 and interleukin-8), endothelial (soluble E-selectin) and neutrophil activation (expression of CD11b, CD64), and antiinflammatory response (soluble tumor necrosis factor receptors I and II and interleukin-10) were attenuated. In peripheral blood monocytes, human leukocyte antigen-DR expression was only slightly depressed, whereas in vitro phagocytosis and the monocyte-activating cytokine interleukin-12 increased. Hydrocortisone withdrawal induced hemodynamic and immunologic rebound effects. In conclusion, hydrocortisone therapy restored hemodynamic stability and differentially modulated the immunologic response to stress in a way of antiinflammation rather than immunosuppression.

Is nitric oxide overproduction the target of choice for the management of septic shock?

Sepsis is a heterogeneous class of syndromes caused by a systemic inflammatory response to infection. Septic shock, a severe form of sepsis, is associated with the development of progressive damage in multiple organs, and is a leading cause of patient mortality in intensive care units. Despite important advances in understanding its pathophysiology, therapy remains largely symptomatic and supportive. A decade ago, the overproduction of nitric oxide (NO) had been discovered as a potentially important event in this condition. As a result, great hopes arose that the pharmacological inhibition of NO synthesis could be developed into an efficient, mechanism-based therapeutic approach. Since then, an extraordinary effort by the scientific community has brought a deeper insight regarding the feasibility of this goal. Here we present in summary form the present state of knowledge of the biological chemistry and physiology of NO. We then proceed to a systematic review of experimental and clinical data, indicating an up-regulation of NO production in septic shock; information on the role of NO in septic shock, as provided by experiments in transgenic mice that lack the ability to up-regulate NO production; effects of pharmacological inhibitors of NO production in various experimental models of septic shock; and relevant clinical experience. The accrued evidence suggests that the contribution of NO to the pathophysiology of septic shock is highly heterogeneous and, therefore, difficult to target therapeutically without appropriate monitoring tools, which do not exist at present.

Nitric oxide indices in human septic shock

OBJECTIVES

To study the relation between nitrite, nitrate, nitrotyrosine, and nitrosothiols as NO indices in human septic shock.

DESIGN

A prospective clinical study.

SETTING

Intensive care units in a university hospital and a central county hospital.

PATIENTS

Sixteen patients admitted for septic shock. Nine healthy volunteers served as controls.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Patients with septic shock had a hyperdynamic circulatory response and required infusion of at least two vasopressors to maintain systemic blood pressure. Four episodes of recurrent shock occurred in two patients. Heparinized plasma was collected once daily for analysis of NO indices. Peak plasma concentrations of nitrite + nitrate (NOx) were elevated in first episodes of septic shock; 144+/-39 microM vs. controls, 20+/-3 microM (p < .05). Peak plasma NOx concentrations in recurrent shocks were; 160+/-19 microM. Peak plasma concentrations of 3-nitrotyrosine (NT) were elevated in primary septic shock 102+/-19 pmol x mL(-1) vs. controls 14+/-6 pmol x mL(-1) (p < .05). Peak NT concentrations were 117+/-37 pmol x mL(-1) in recurrent septic shock. Peak plasma NT concentrations did not coincide with peak NOx concentrations in half of the episodes of septic shock. Plasma NT was elevated (59+/-15 pmol x mL(-1) vs. controls 14+/-6 pmol x mL(-1), p < .05) in patients with normal plasma NOx concentrations throughout septic shock. Plasma concentrations of nitrosothiols did not change during septic shock.

CONCLUSIONS

Plasma concentrations of NOx and NT are elevated in primary episodes of septic shock and may also be elevated in secondary septic shock, but too few episodes of recurrent septic shock occurred to allow firm conclusions. Plasma concentrations of NT are elevated in patients with septic shock with normal plasma NOx concentrations, indicating that plasma concentrations of NOx may not always accurately reflect NO production. Reactive nitrogen species may be formed in septic shock, and measuring both NOx and NT may give a better indication of NO production in septic shock than NOx alone. Plasma levels of nitrosothiols did not change during septic shock.

Procalcitonin and calcitonin gene-related peptide decrease LPS-induced tnf production by human circulating blood cells

The pathogenesis of septic shock is mainly due to unregulated tumour necrosis factor-alpha (TNF-alpha) production. Procalcitonin (PCT) and calcitonin gene-related peptide (CGRP) are alternative transcription products of the calcitonin gene. Since high PCT levels have been described in human sepsis, and since CGRP inhibits TNF synthesis in rats, we examined the role of these peptides in the regulation of the inflammatory response during septic shock. LPS-induced TNF production was assessed using a human whole blood model. In this model, PCT (10(-7) M) and CGRP (10(-6) M) significantly inhibit TNF production by 27 and 24 % respectively. The effect of CGRP was reversed by CGRP 8-37 (10 microM), an antagonist of CGRP receptor. No effect on interleukin (IL)-1, IL-6 and IL-8 was found. This is the first description of an anti-inflammatory role for PCT and CGRP in humans.

Bio-energetic response of the heart to dopamine following brain death-related reduced myocardial workload: a phosphorus-31 magnetic resonance spectroscopy study in the cat

OBJECTIVE

Long-term exposure of the donor heart to high dosages of dopamine in the treatment of brain death-related hemodynamic deterioration has been shown to reduce myocardial phosphocreatine (PCr) and adenosine triphosphate (ATP) in myocardial biopsy specimens and may preclude heart donation for transplantation. Short-term exposure to the acute catecholamine release during the onset of brain death has shown an unchanged PCr/ATP ratio using in vivo phosphorus-31 magnetic resonance spectroscopy (31P MRS). In this study 31P MRS was used to evaluate in vivo myocardial energy metabolism during long-term dopamine treatment.

METHODS

Twelve cats were studied in a 4.7 Tesla magnet for 360 minutes. At t = 0 minutes, brain death was induced (n = 6). At 210 minutes, when myocardial workload in the brain-death group was reduced significantly, dopamine was infused (n = 12) at 5 microg/kg/min and its dose was consecutively doubled every 30 minutes and was withheld during the last 30 minutes of the experiment. Phosphorus-31 magnetic resonance spectra were obtained from the left ventricular wall during 5-minute time frames, and PCr/ATP ratios were calculated. The hearts were histologically examined.

RESULTS

Although significant changes in myocardial workload were observed after the induction of brain death and during support and withdrawal of dopamine in both groups, the initial PCr/ATP ratio of 2.00+/-0.12 and the contents of PCr and ATP did not vary significantly. Histologically identified sub-endocardial hemorrhage was observed in 3 of 6 of the brain-dead animals and in 1 of 6 of the control animals.

CONCLUSIONS

High dosages of dopamine in the treatment of brain death-related reduced myocardial workload do not alter PCr/ATP ratios and the contents of PCr and ATP of the potential donor heart despite histologic damage.

Nitric oxide release from the liver surface to the intraabdominal cavity during acute endotoxemia in rats

Nitric oxide (NO) is produced by the liver during lipopolysaccharide (LPS)-induced endotoxemia. The aim of this study was to examine whether NO, which is produced in the liver, is released from the liver surface to the intraabdominal cavity during endotoxemia. NO was quantitatively determined by chemiluminescence and a newly developed gas purge technique was used to directly measure NO released from the liver surface and the intraabdominal cavity of rats before and after LPS (0.1 mg/kg, intraperitoneally) or saline administration. The expression of inducible NO synthase (iNOS) mRNA in the liver was detected by Northern blot analysis. NO levels from both the liver surface and in the intraabdominal cavity were elevated at 2 h after LPS injection and peaked at 10 h and both the time course of NO level were well correlated with each other. Both NO levels were below the detectable range before LPS and after saline administration. Inducible NOS mRNA in the liver exhibited a sharp increase to a maximum level at 4 h after LPS injection. The present study indicates that the hepatic NO, which might have been produced by iNOS in the liver, is released from the liver surface to the intraabdominal cavity during endotoxemia.

Vasoactive Intestinal Peptide (VIP) and Pituitary Adenylate Cyclase-Activation Polypeptide (PACAP) Protect Mice from Lethal Endotoxemia Through the Inhibition of TNF-α and IL-6

The neuropeptides vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) down-regulate cytokine production. Because human septic shock involves excessive cytokine production, the effect of VIP/PACAP was investigated in a high endotoxemia murine model. Both peptides protect against endotoxin-induced lethality and prevent septic shock-associated histopathological alterations. VIP/PACAP reduce serum and peritoneal TNF-α and IL-6, suggesting that the protective effect is exerted by inhibiting the production of endogenous TNF-α/IL-6. Consistent with this mechanism, VIP does not protect against septic shock induced by exogenous TNF-α. The immunomodulatory role of VIP in vivo is supported by the appearance of high levels of VIP in serum and peritoneal fluid following LPS administration. Thus, the neuropeptides VIP/PACAP protect from the lethal effect of high endotoxemia, presumably by down-regulating TNF-α and IL-6 production, and may offer an alternative in the treatment of human septic shock syndrome.