Kinetics of tissue oxygenation index during fast and slow cardiopulmonary bypass initiation.

INTRODUCTION: Despite being a daily clinical application in cardiac operating theaters, an evidence-based approach on how to optimally initiate the heart-lung machine (HLM) to prevent critical phases of cerebral ischemia is still lacking. We therefore designed a study comparing two different initiation times for starting the cardiopulmonary bypass (CPB). METHODS: We conducted a monocentric, randomized, and prospective study comparing the impact of two initiation times, a rapid initiation of 15 s and a slow initiation of 180 s to reach the full target flow rate of 2.5 L/min/m2 times the body surface area, on cerebral tissue oxygenation by near infrared spectroscopy measurements. RESULTS: The absolute values in tissue oxygenation index (TOI) showed no difference between the groups before and after the CPB with a 10% drop in oxygenation index in both groups due to the hemodilution through the HLM priming. Looking at the kinetics a rapid initiation of CPB produced a higher negative rate of change in TOI with a total of 21% in critical oxygenation readings compared to 6% in the slow initiation group. CONCLUSION: In order to avoid critical phases of cerebral ischemia during the initiation of CPB for cardiac procedures, we propose an initiation time of at least 90 s to reach the 100% of target flow rate of the HLM.

Prospective clinical study testing the efficacy and safety of a new formula to increase the precision of oxygen therapy in the initiation phase of cardiopulmonary bypass.

INTRODUCTION: During cardiopulmonary bypass (CPB), supranormal concentrations of oxygen are routinely administered with the intention to prevent cellular hypoxia. However, hyperoxemia may have adverse effects on patient outcome. Oxygen settings are based on the perfusionist's individual work experience rather than profound recommendations and studies analyzing the effect of oxygen levels are in need of methodological improvement. We aimed to advance perfusion technique by developing and clinically applying a formula for tailored oxygen therapy in CPB. METHODS: A formula to precalculate the oxygenator setting before CPB was developed. The newly-derived formula was then evaluated in a prospective, single-center pilot study to test whether a predefined arterial partial oxygen pressure (PaO2) of 150-250 mmHg could be reached. 80 patients were enrolled in the study between April and September 2021. RESULTS: The mean oxygen fraction calculated for the setting of the gas blender was 52% ±0,12. The mean PaO2 after initiation of the CPB was 193 ± 99 mmHg (min-max: 61-484, median 163 mmHg). 38.75% of the values were in the desired PaO2 corridor of 150 to 250 mmHg. 8.75% of all PaO2 values were below <79.9 mmHg, 31.25% between 80 and 149.9 mmHg, 38.75% between 150 and 249.9 mmHg and 21.25%>250 mmHg. CONCLUSIONS: Conceptually, perfusion technique should be goal-directed, guided by objective parameters and formulas. Although the optimal CPB oxygenation target remains unknown, it is nevertheless important to develop strategies to tailor oxygen therapy to aid in creating evidence as to what level of oxygen is best for patients during CPB. The formula we derived needs further adjustments to increase results in the target range.

Current Application of NIRS and CPB Initiation Times in German Cardiac Surgery Centers: A Survey.

Near-infrared spectroscopy (NIRS) has been widely used in cardiac surgery to monitor cerebral oxygen supply. The initiation and perioperative management of cardiopulmonary bypass (CPB) constitute critical events in modifying the normal physiology of adequate blood and oxygen supply to the brain. First, little is known about how frequent NIRS is really used. Second, there are varying practices on how to initiate CPB. We therefore conducted a survey in Germany to get an idea of NIRS usage in cardiac surgery for the duration of initiation of CPB protocols. A web-based e-mail survey using commercial SurveyMonkey® (SurveyMonkey, San Mateo, CA) software was conducted in August 2017 including all German cardiac surgery centers. About 75% of the perfusion departments do not use NIRS as a standard monitoring device. It is usually reserved for clinical scenarios where cerebral perfusion might be impaired such as aortic arch surgery or carotid artery stenosis. Only one-third of the departments use a standardized duration of initiation of CPB despite a common belief of potential harm with fast initiation. The usual applied time to initiate CPB ranges from 30 to 120 seconds. Our survey revealed that the NIRS technology is only used in specific types of cardiac surgery to this date. In addition, there is a clear need for scientific studies on how to initiate CPB in the best way for the patient.

Profound hypothermia after adenosine kinase inhibition in A1AR-deficient mice suggests a receptor-independent effect of intracellular adenosine.

Administration of the nucleoside adenosine has been shown to induce hypothermia in a number of species, an effect mediated predominantly by the adenosine 1 receptor (A1AR) subtype. The present experiments were performed to explore the possibility that the rise of intracellular adenosine levels expected to accompany adenosine administration may contribute to the hypothermic effect of adenosine independent of A1AR activation. Since phosphorylation of adenosine by adenosine kinase (ADK) is causal in the maintenance of low intracellular adenosine, we have examined the effect of ADK inhibition on core body temperature (CBT). Our data show that inhibition of ADK by A-134974 causes a long-lasting deep hypothermia in wild-type mice. Since there was an about 4-fold increase of adenosine plasma levels, experiments were repeated in A1AR-/- mice. ADK inhibition caused deep hypothermia despite the absence of A1AR, although the effect was significantly reduced compared to WT. Furthermore, the dose-dependent hypothermia caused by adenosine administration in WT mice was found to be reduced, but not abolished in A1AR-/- mice. To assess the possible role of A2AR and A3AR activation in our experimental setting, we compared the effects of the agonists CPA (A1AR), CGS21680 (A2AR), and IB-MECA (A3AR) on CBT. Hypothermia induced by CPA was much greater than that caused by CGS21680 or IB-MECA indicating that A1AR activation is the major receptor-dependent pathway for adenosine-induced hypothermia under our experimental conditions. Induction of deep hypothermia by inhibition of ADK, maintenance of this effect in A1AR-/- mice, and maintenance of adenosine-induced hypothermia in A1AR-deficient mice suggest that a receptor-independent action of adenosine requiring intact function of adenosine kinase contributes importantly to the hypothermia induced by adenosine.

Cerebral Oxygen Saturation Associates with Changes in Oxygen Transport Parameters during Cardiopulmonary Bypass.

(1) Background: Adequate organ perfusion during cardiopulmonary bypass (CPB) requires accurate estimation and adjustment of flow rates which conventional methods may not always achieve. Perioperative monitoring of cerebral oxygen saturation (ScO2) may detect changes in oxygen transport. This study aims to compare estimated and measured perfusion flow rates and assess the capacity of ScO2 to detect subtle changes in oxygen transport during CPB. (2) Methods: This observational study included 50 patients scheduled for elective coronary artery bypass grafting (CABG) surgery, all of whom provided written informed consent. Perfusion flow rates were estimated using the DuBois formula and measured using echocardiography and a flow probe in the arterial line of the CPB system. ScO2 was continuously monitored, alongside intermittent measurements of oxygen delivery and extraction ratios. (3) Results: Significant discrepancies were found between estimated flow rates (5.2 [4.8-5.5] L/min) and those measured at the start of the surgery (4.6 [4.0-5.0] L/min). These discrepancies were flow rate-dependent, being more pronounced at lower perfusion rates and diminishing as rates increased. Furthermore, ScO2 showed a consistent correlation with both oxygen delivery (r = 0.48) and oxygen extraction ratio (r = 0.45). (4) Conclusions: This study highlights discrepancies between estimated and actual perfusion flow rates during CPB and underscores the value of ScO2 monitoring as a continuous, noninvasive tool for maintaining adequate organ perfusion, suggesting a need for improved, patient-tailored perfusion strategies.

Direct assessment of tubuloglomerular feedback responsiveness in connexin 40-deficient mice.

Participation of connexin 40 (Cx40) in the regulation of renin secretion and in the tubuloglomerular feedback (TGF) component of renal autoregulation suggests that gap junctional coupling through Cx40 contributes to the function of the juxtaglomerular apparatus. In the present experiments, we determined the effect of targeted Cx40 deletion in C57BL/6 and FVB mice on TGF responsiveness. In C57BL/6 mice, stop-flow pressure (PSF) fell from 40.3 ± 2 to 34.5 ± 2 mmHg in wild-type (WT) and from 31 ± 1.06 to 26.6 ± 0.98 mmHg in Cx40-/- mice. PSF changes of 5.85 ± 0.67 mmHg in WT and of 4.3 ± 0.55 mmHg in Cx40-/- mice were not significantly different (P = 0.08). In FVB mice, PSF fell from 37.4 ± 1.5 to 31.6 ± 1.5 mmHg in WT and from 28.1 ± 1.6 to 25.4 ± 1.7 mmHg in Cx40-/-, with mean TGF responses being significantly greater in WT than Cx40-/- (5.5 ± 0.55 vs. 2.7 ± 0.84 mmHg; P = 0.002). In both genetic backgrounds, PSF values were significantly lower in Cx40-/- than WT mice at all flow rates. Arterial blood pressure in the animals prepared for micropuncture was not different between WT and Cx40-/- mice. We conclude that the TGF response magnitude in superficial cortical nephrons is reduced by 30-50% in mice without Cx40, but that with the exception of a small number of nephrons, residual TGF activity is maintained. Thus gap junctional coupling appears to modulate TGF, perhaps by determining the kinetics of signal transmission.

Tubuloglomerular feedback and renal function in mice with targeted deletion of the type 1 equilibrative nucleoside transporter.

A(1) adenosine receptors (A1AR) are required for the modulation of afferent arteriolar tone by changes in luminal NaCl concentration implying that extracellular adenosine concentrations need to change in synchrony with NaCl. The present experiments were performed in mice with a null mutation in the gene for the major equilibrative nucleoside transporter ENT1 to test whether interference with adenosine disposition by cellular uptake of adenosine may modify TGF characteristics. Responses of stop flow pressure (P(SF)) to maximum flow stimulation were measured in mice with either C57Bl/6 or SWR/J genetic backgrounds. Maximum flow stimulation reduced P(SF) in ENT1(-/-) compared with wild-type (WT) mice by 1.6 ± 0.4 mmHg (n = 28) and 5.8 ± 1.1 mmHg (n = 17; P < 0.001) in C57Bl/6 and by 1.4 ± 0.4 mmHg (n = 15) and 9 ± 1.5 mmHg (n = 9; P < 0.001) in SWR/J. Plasma concentrations of adenosine and inosine were markedly higher in ENT1(-/-) than WT mice (ado: 1,179 ± 78 and 225 ± 48 pmol/ml; ino: 179 ± 24 and 47.5 ± 9 pmol/ml). Renal mRNA expressions of the four adenosine receptors, ENT2, and adenosine deaminase were not significantly different between WT and ENT1(-/-) mice. No significant differences of glomerular filtration rate or mean arterial blood pressure were found while plasma renin concentration, and heart rates were significantly lower in ENT1(-/-) animals. In conclusion, TGF responsiveness is significantly attenuated in the absence of ENT1, pointing to a role of nucleoside transport in the NaCl-synchronous changes of extracellular adenosine levels in the juxtaglomerular apparatus interstitium.

Out-of-hospital cardiac arrest treated with prehospital double sequential external defibrillation during eCPR in refractory VF - a case report.

BACKGROUND: Double sequential external defibrillation (DSED) has demonstrated increased survival with good neurological outcome in a recent randomized controlled trial. DSED has not been studied in patients with extracorporeal cardiopulmonary resuscitation (eCPR). CASE: We present the first case of prehospital eCPR with ongoing refractory ventricular fibrillation (VF), terminated by DSED. After six shocks, return of spontaneous circulation was initially achieved; however, the patient went into recurrent VF. ECPR was performed prehospital, with VF still refractory after three more shocks. DSED successfully terminated VF and showed a further increase in etCO2 and near-infrared spectroscopy cerebral oximetry values. CONCLUSION: DSED can be a sufficient strategy for patients in refractory VF while on eCPR and should be evaluated in further studies.

Renal afferent arteriolar and tubuloglomerular feedback reactivity in mice with conditional deletions of adenosine 1 receptors.

Adenosine 1 receptors (A1AR) have been shown in previous experiments to play a major role in the tubuloglomerular feedback (TGF) constrictor response of afferent arterioles (AA) to increased loop of Henle flow. Overexpression studies have pointed to a critical role of vascular A1AR, but it has remained unclear whether selective deletion of A1AR from smooth muscle cells is sufficient to abolish TGF responsiveness. To address this question, we have determined TGF response magnitude in mice in which vascular A1AR deletion was achieved using the loxP recombination approach with cre recombinase being controlled by a smooth muscle actin promoter (SmCre/A1ARff). Effective vascular deletion of A1AR was affirmed by absence of vasoconstrictor responses to adenosine or cyclohexyl adenosine (CHA) in microperfused AA. Elevation of loop of Henle flow from 0 to 30 nl/min caused a 22.1 ± 3.1% reduction of stop flow pressure in control mice and of 7.2 ± 1.5% in SmCre/A1ARff mice (P < 0.001). Maintenance of residual TGF activity despite absence of A1AR-mediated responses in AA suggests participation of extravascular A1AR in TGF. Support for this notion comes from the observation that deletion of A1ARff by nestin-driven cre causes an identical TGF response reduction (7.3 ± 2.4% in NestinCre/A1ARff vs. 20.3 ± 2.7% in controls), whereas AA responsiveness was reduced but not abolished. A1AR on AA smooth muscle cells are primarily responsible for TGF activation, but A1AR on extravascular cells, perhaps mesangial cells, appear to contribute to the TGF response.

Functional expression of the olfactory signaling system in the kidney.

Olfactory-like chemosensory signaling occurs outside of the olfactory epithelium. We find that major components of olfaction, including olfactory receptors (ORs), olfactory-related adenylate cyclase (AC3) and the olfactory G protein (G(olf)), are expressed in the kidney. AC3 and G(olf) colocalize in renal tubules and in macula densa (MD) cells which modulate glomerular filtration rate (GFR). GFR is significantly reduced in AC3(-/-) mice, suggesting that AC3 participates in GFR regulation. Although tubuloglomerular feedback is normal in these animals, they exhibit significantly reduced plasma renin levels despite up-regulation of COX-2 expression and nNOS activity in the MD. Furthermore, at least one member of the renal repertoire of ORs is expressed in a MD cell line. Thus, key components of olfaction are expressed in the renal distal nephron and may play a sensory role in the MD to modulate both renin secretion and GFR.

Stimulation of renin secretion by angiotensin II blockade is Gsalpha-dependent.

Angiotensin II converting enzyme inhibitors (ACEI) or angiotensin II receptor blockers (ARB) presumably stimulate renin secretion by interrupting angiotensin II feedback inhibition. The increase in cytosolic calcium caused by activation of Gq-coupled AT1 receptors may mediate the renin-inhibitory effect of angiotensin II at the cellular level, implying that ACEI and ARB may work by reducing intracellular calcium. Here, we investigated whether angiotensin II blockade acts predominantly through Gs-mediated stimulation of adenylyl cyclase (AC) by testing the effect of ACEI and ARB in mice with juxtaglomerular cell-specific deficiency of the AC-stimulatory Gsalpha. The ACEI captopril and quinaprilate and the ARB candesartan significantly increased plasma renin concentration (PRC) to 20 to 40 times basal PRC in wild-type mice but did not significantly alter PRC in Gsalpha-deficient mice. Captopril also completely abrogated renin stimulation in wild-type mice after co-administration of propranolol, indomethacin, and L-NAME. Treatment with enalapril and a low-NaCl diet for 7 days led to a 35-fold increase in PRC among wild-type mice but no significant change in PRC among Gsalpha-deficient mice. Three different pharmacologic inhibitors of AC reduced the stimulatory effect of captopril by 70% to 80%. In conclusion, blockade of angiotensin II stimulates renin synthesis and release indirectly through the action of ligands that activate the cAMP/PKA pathway in a Gsalpha-dependent fashion, including catecholamines, prostaglandins, and nitric oxide.

Angiotensin II overcomes strain-dependent resistance of rapid CKD progression in a new remnant kidney mouse model.

The remnant kidney model in C57BL/6 mice does not develop progressive chronic kidney disease (CKD). In this study we modified the model to mimic features of human CKD and to define accelerants of disease progression using three strains of mice. Following the procedure, there was a progressive increase in albuminuria, progressive loss in renal function, severe glomerulosclerosis and interstitial fibrosis, hypertension, cardiac fibrosis, and anemia by 4 weeks in CD-1 mice and by 12 weeks in 129S3 mice. In contrast, even after 16 weeks, the C57BL/6 mice with a remnant kidney had modestly increased albuminuria without increased blood pressure and without developing CKD or cardiac fibrosis. The baseline blood pressure, determined by radiotelemetry in conscious animals, correlated with CKD progression rates in each strain. Administering angiotensin II overcame the resistance of C57BL/6 mice to CKD following renal mass reduction, displaying high blood pressure and albuminuria, severe glomerulosclerosis, and loss of renal function by 4 weeks. Decreasing blood pressure with olmesartan, but not hydralazine, in CD-1 mice with a remnant kidney reduced CKD progression and cardiac fibrosis. C57BL/6 mice with a remnant kidney and DOCA-salt hypertension developed modest CKD. Each strain had similar degrees of interstitial fibrosis in three different normotensive models of renal fibrosis. Thus, reducing renal mass in CD-1 or 129S3 mice mimics many features of human CKD. Angiotensin II can convert the C57BL/6 strain from CKD resistant to susceptible in this disease model.

Major contribution of tubular secretion to creatinine clearance in mice.

This study was performed to quantify the fraction of excreted creatinine not attributable to creatinine filtration for accurately determining the glomerular filtration rate in mice. To measure this we compared creatinine filtration with the simultaneous measurement of inulin clearance using both single-bolus fluorescein isothiocyanate (FITC)-inulin elimination kinetics and standard FITC-inulin infusion. During anesthesia, creatinine filtration was found to be systematically higher than inulin clearance in both male and female C57BL/6J mice. The secretion fraction was significantly less in female mice. Administration of either cimetidine or para-aminohippuric acid, competitors of organic cation and anion transport respectively, significantly reduced the secretion fraction in male and female mice and both significantly increased the plasma creatinine level. Creatinine secretion in both genders was not mediated by the organic cation transporters OCT1 or OCT 2 since secretion fraction levels were identical in FVB wild-type and OCT1/2 knockout mice. Thus, secretion accounts for about 50 and 35% of excreted creatinine in male and female mice, respectively. Increasing plasma creatinine threefold by infusion further increased the secretion fraction. Renal organic anion transporter 1 mRNA expression was higher in male than in female mice, reflecting the gender difference in creatinine secretion. Hence we show that there is a major secretory contribution to creatinine excretion mediated through the organic anion transport system. This feature adds to problems associated with measuring endogenous creatinine filtration in mice.

Deletion of the secretory vesicle proteins IA-2 and IA-2beta disrupts circadian rhythms of cardiovascular and physical activity.

Targeted deletion of IA-2 and IA-2beta, major autoantigens in type 1 diabetes and transmembrane secretory vesicle proteins, results in impaired secretion of hormones and neurotransmitters. In the present study, we evaluated the effect of these deletions on daily rhythms in blood pressure, heart rate, core body temperature, and spontaneous physical and neuronal activity. We found that deletion of both IA-2 and IA-2beta profoundly disrupts the usual diurnal variation of each of these parameters, whereas the deletion of either IA-2 or IA-2beta alone did not produce a major change. In situ hybridization revealed that IA-2 and IA-2beta transcripts are highly but nonrhythmically expressed in the suprachiasmatic nuclei, the site of the brain's master circadian oscillator. Electrophysiological studies on tissue slices from the suprachiasmatic nuclei showed that disruption of both IA-2 and IA-2beta results in significant alterations in neuronal firing. From these studies, we concluded that deletion of IA-2 and IA-2beta, structural proteins of secretory vesicles and modulators of neuroendocrine secretion, has a profound effect on the circadian system.

Reduced production of creatinine limits its use as marker of kidney injury in sepsis.

Although diagnosis and staging of acute kidney injury uses serum creatinine, acute changes in creatinine lag behind both renal injury and recovery. The risk for mortality increases when acute kidney injury accompanies sepsis; therefore, we sought to explore the limitations of serum creatinine in this setting. In mice, induction of sepsis by cecal ligation and puncture in bilaterally nephrectomized mice increased markers of nonrenal organ injury and serum TNF-alpha. Serum creatinine, however, was significantly lower in septic animals than in animals subjected to bilateral nephrectomy and sham cecal ligation and puncture. Under these conditions treatment with chloroquine decreased nonrenal organ injury markers but paradoxically increased serum creatinine. Sepsis dramatically decreased production of creatinine in nephrectomized mice, without changes in body weight, hematocrit, or extracellular fluid volume. In conclusion, sepsis reduces production of creatinine, which blunts the increase in serum creatinine after sepsis, potentially limiting the early detection of acute kidney injury. This may partially explain why small absolute increases in serum creatinine levels are associated with poor clinical outcomes. These data support the need for new biomarkers that provide better measures of renal injury, especially in patients with sepsis.

Enhanced tubuloglomerular feedback in mice with vascular overexpression of A1 adenosine receptors.

Adenosine 1 receptors (A1AR) in the kidney are expressed in the vasculature and the tubular system. Pharmacological inhibition or global genetic deletion of A1AR causes marked reductions or abolishment of tubuloglomerular feedback (TGF) responses. To assess the function of vascular A1AR in TGF, we generated transgenic mouse lines in which A1AR expression in smooth muscle was augmented by placing A1AR under the control of a 5.38-kb fragment of the rat smooth muscle alpha-actin promoter and first intron (12). Two founder lines with highest expression in the kidney [353 +/- 42 and 575 +/- 43% compared with the wild type (WT)] were used in the experiments. Enhanced expression of A1AR at the expected site in these lines was confirmed by augmented constrictor responses of isolated afferent arterioles to administration of the A1AR agonist N6-cyclohexyladenosine. Maximum TGF responses (0-30 nl/min flow step) were increased from 8.4 +/- 0.9 mmHg in WT (n = 21) to 14.2 +/- 0.7 mmHg in A1AR-transgene (tg) 4 (n = 22; P < 0.0001), and to 12.6 +/- 1.2 mmHg in A1AR-tg7 (n = 12; P < 0.02). Stepwise changes in perfusion flow caused greater numerical TGF responses in A1AR-tg than WT in all flow ranges with differences reaching levels of significance in the intermediate flow ranges of 7.5-10 and 10-15 nl/min. Proximal-distal single-nephron glomerular filtration rate (SNGFR) differences (free-flow micropuncture) were also increased in A1AR-tg, averaging 6.25 +/- 1.5 nl/min compared with 2.6 +/- 0.51 nl/min in WT (P = 0.034). Basal plasma renin concentrations as well as the suppression of renin secretion after volume expansion were similar in A1AR-tg and WT mice, suggesting lack of transgene expression in juxtaglomerular cells. These data indicate that A1AR expression in vascular smooth muscle cells is a critical component for TGF signaling and that changes in renal vascular A1AR expression may determine the magnitude of TGF responses.

Decrease in adhesion molecules on polymorphonuclear leukocytes of patients with fibromyalgia.

Fibromyalgia (FM) is a chronic widespread pain condition in highly stressed humans. Because stress is known to modulate adhesion molecule expression, we determined L: -selectin (CD62L) and beta(2)-integrin (CD11b/CD18) expression on the surface of polymorphonuclear leukocytes in 22 patients with FM. As compared to age and sex-matched healthy controls, FM patients showed a significantly decreased expression of CD62L (p < 0.01) and CD11b/CD18 (p < 0.05) on polymorphonuclear leukocytes. These changes might lower the rate of polymorphonuclear leukocyte migration to sites of inflammation and thereby compromise defense against infections and pain control.

Pre-existing renal disease promotes sepsis-induced acute kidney injury and worsens outcome.

While it is known that risk of death from sepsis is higher in patients with pre-existing chronic kidney disease its mechanism is unknown. To study this we established a two-stage mouse model where renal disease was first induced by folic acid injection followed by sub-lethal cecal ligation and puncture to induce sepsis. Septic mice with pre-existing renal disease had significantly higher mortality, serum creatinine, vascular permeability, plasma vascular endothelial growth factor (VEGF) levels, bacteremia, serum IL-10, splenocyte apoptosis and more severe septic shock when compared to septic mice without pre-existing disease. To evaluate the contribution of vascular and immunological dysfunction, we treated the folate-septic mice with soluble Flt-1 to bind VEGF and chloroquine to reduce splenocyte apoptosis. These treatments together resulted in a significant improvement in kidney injury, hemodynamics and survival. Our study shows that the sequential mouse model mimics human sepsis frequently complicated by pre-existing renal disease and might be useful in evaluating preventive and therapeutic strategies.

Anandamide and neutrophil function in patients with fibromyalgia.

Fibromyalgia (FM) is a common stress-related painful disorder. There is considerable evidence of neuroimmunologic alterations in FM which may be the consequence of chronic stress and pain or causally involved in the development of this disorder. The endocannabinoid system has been shown to play a pivotal role in mammalian nociception, is activated under stressful conditions and can be an important signaling pathway for immune modulation. The endocannabinoid system could therefore be involved in the complex pathophysiology of FM. We tested this hypothesis by evaluating the effects of stress hormones and the endocannabinoid anandamide on neutrophil function in patients with FM. We determined plasma levels of catecholamines, cortisol and anandamide in 22 patients with primary FM and 22 age- and sex-matched healthy controls. Neutrophil function was characterized by measuring the hydrogen peroxide (H2O2) release (oxidative stress) and the ingestion capabilities of neutrophils (microbicidal function). FM patients had significantly higher norepinephrine and anandamide plasma levels. Neutrophils of FM patients showed an elevated spontaneous H2O2 production. The ability of neutrophils to adhere was negatively correlated with serum cortisol levels. Adhesion and phagocytosis capabilities of neutrophils correlated positively with anandamide plasma levels. In conclusion, patients with FM might benefit from pharmacologic manipulation of endocannabinoid signaling which should be tested in controlled studies.

Lymphocyte subsets and the role of TH1/TH2 balance in stressed chronic pain patients.

BACKGROUND: The complex regional pain syndrome (CRPS) and fibromyalgia (FM) are chronic pain syndromes occurring in highly stressed individuals. Despite the known connection between the nervous system and immune cells, information on distribution of lymphocyte subsets under stress and pain conditions is limited. METHODS: We performed a comparative study in 15 patients with CRPS type I, 22 patients with FM and 37 age- and sex-matched healthy controls and investigated the influence of pain and stress on lymphocyte number, subpopulations and the Th1/Th2 cytokine ratio in T lymphocytes. RESULTS: Lymphocyte numbers did not differ between groups. Quantitative analyses of lymphocyte subpopulations showed a significant reduction of cytotoxic CD8+ lymphocytes in both CRPS (p < 0.01) and FM (p < 0.05) patients as compared with healthy controls. Additionally, CRPS patients were characterized by a lower percentage of IL-2-producing T cell subpopulations reflecting a diminished Th1 response in contrast to no changes in the Th2 cytokine profile. CONCLUSIONS: Future studies are warranted to answer whether such immunological changes play a pathogenetic role in CRPS and FM or merely reflect the consequences of a pain-induced neurohumoral stress response, and whether they contribute to immunosuppression in stressed chronic pain patients.