Endothelial cell-derived extracellular vesicles exert cardio-protective effect via their protein cargo

Background

Extracellular vesicles (EV) are recognized as carriers of relevant biological effects and have been identified as regulators of cell-to-cell communication contributing to several patho-physiological processes. These processes include angiogenesis/coagulation/tissue repair/inflammation. In ischemia/reperfusion (I/R) settings, along with the direct effects of the I/R itself, paracrine mechanisms associated with the activation of the inflammatory response, primary involving endothelial cells, are crucial drivers of both vessel and cardiomyocyte damage.

Purpose

Since in models of myocardial I/R injury the role of EV released from endothelial cells is still unclear, our hypothesis was to provide insight on this specific topic. To this end, naïve endothelial cell (EC)-derived EV (eEV) and eEV released in response to the pro-inflammatory cytokine interleukin-3 (IL-3) (eEV-IL-3) have been evaluated on different I/R models.

Methods

eEV were characterized by MACSPlex-Exosome-Kit and western blot analysis. For the in-vitro hypoxia-reoxygenation (H/R) experiments, H9c2 or EC were pretreated with eEV, eEV-IL-3 (1x104 EV/cell) or IL-3 (10ng/ml) for 2 hours and then exposed to hypoxia (1% O2, 5% CO2) for additional 2 hours in the presence of eEV, eEV-IL-3 or IL-3 and subsequently reoxygenated (21% O2 and 5% CO2) for 1 hour. To verify the effect of EC treated with eEV, eEV-IL-3 or IL-3 on H9c2 and subjected to H/R protocol, transwell assay was used. At the end of the H/R protocol, cell viability was assessed. For ex-vivo experiments, isolated rat hearts, pretreated with a buffer containing EV (from EC pretreated or not with IL-3), were subjected to 30 minutes global normothermic ischemia and 1 hour reperfusion. Triton infusion was also used as a model of endothelial damage. At the end of I/R, the infarct size was measured and expressed as a percentage of total left ventricular mass (LVM). The role of eNOS/guanylyl-cyclase/MEK1/2 pathways in mediating eEV biological effects was also evaluated using different inhibitors both in in-vitro and ex-vivo models. Finally, protein profiles of eEV and eEV-IL-3 were analyzed using label free mass spectrometry.

Results

eEV and eEV-IL-3 protect EC, but not H9c2 exposed to H/R protocol, while eEV, but not eEV-IL-3-treatment limits I/R injury in the rat heart. Rat hearts pre-treated with triton significantly avoid eEV-induced cardio-protection. Transwell assay showed a reduction of H9C2 mortality after treatment with both eEV and eEV-IL-3. Proteomic analysis revealed that MEK1/2 and the endothelial-NOS (eNOS)-antagonist caveolin-1 were differentially expressed in eEV and eEV-IL-3. The use of eNOS/guanylyl-cyclase/MEK1/2 inhibitors prevented eEV-induced cardio-protection.

Conclusions

These observations indicate that eEV, but not eEV-IL-3, have cardio-protective effects when given as preconditioning agents. We have also shown that the activation of eNOS/GC/MEK1/2 pathway is crucial for eEV-mediated cardio-protection.

Funding Acknowledgement

Type of funding source: None

COVID-19-associated cardiovascular morbidity in older adults: a position paper from the Italian Society of Cardiovascular Researches

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infects host cells following binding with the cell surface ACE2 receptors, thereby leading to coronavirus disease 2019 (COVID-19). SARS-CoV-2 causes viral pneumonia with additional extrapulmonary manifestations and major complications, including acute myocardial injury, arrhythmia, and shock mainly in elderly patients. Furthermore, patients with existing cardiovascular comorbidities, such as hypertension and coronary heart disease, have a worse clinical outcome following contraction of the viral illness. A striking feature of COVID-19 pandemics is the high incidence of fatalities in advanced aged patients: this might be due to the prevalence of frailty and cardiovascular disease increase with age due to endothelial dysfunction and loss of endogenous cardioprotective mechanisms. Although experimental evidence on this topic is still at its infancy, the aim of this position paper is to hypothesize and discuss more suggestive cellular and molecular mechanisms whereby SARS-CoV-2 may lead to detrimental consequences to the cardiovascular system. We will focus on aging, cytokine storm, NLRP3/inflammasome, hypoxemia, and air pollution, which is an emerging cardiovascular risk factor associated with rapid urbanization and globalization. We will finally discuss the impact of clinically available CV drugs on the clinical course of COVID-19 patients. Understanding the role played by SARS-CoV2 on the CV system is indeed mandatory to get further insights into COVID-19 pathogenesis and to design a therapeutic strategy of cardio-protection for frail patients.

Apelin-induced cardioprotection against ischaemia/reperfusion injury: roles of epidermal growth factor and Src

AIM

Apelin, the ligand of the G-protein-coupled receptor (GPCR) APJ, exerts a post-conditioning-like protection against ischaemia/reperfusion injury through activation of PI3K-Akt-NO signalling. The pathway connecting APJ to PI3K is still unknown. As other GPCR ligands act through transactivation of epidermal growth factor receptor (EGFR) via a matrix metalloproteinase (MMP) or Src kinase, we investigated whether EGFR transactivation is involved in the following three features of apelin-induced cardioprotection: limitation of infarct size, suppression of contracture and improvement of post-ischaemic contractile recovery.

METHOD

Isolated rat hearts underwent 30 min of global ischaemia and 2 h of reperfusion. Apelin (0.5 μm) was infused during the first 20 min of reperfusion. EGFR, MMP or Src was inhibited to study the pathway connecting APJ to PI3K. Key components of RISK pathway, namely PI3K, guanylyl cyclase or mitochondrial K⁺ -ATP channels, were also inhibited. Apelin-induced EGFR and phosphatase and tensing homolog (PTEN) phosphorylation were assessed. Left ventricular pressure and infarct size were measured.

RESULTS

Apelin-induced reductions in infarct size and myocardial contracture were prevented by the inhibition of EGFR, Src, MMP or RISK pathway. The involvement of EGFR was confirmed by its phosphorylation. However, neither direct EGFR nor MMP inhibition affected apelin-induced improvement of early post-ischaemic contractile recovery, which was suppressed by Src and RISK inhibitors only. Apelin also increased PTEN phosphorylation, which was removed by Src inhibition.

CONCLUSION

While EGFR and MMP limit infarct size and contracture, Src or RISK pathway inhibition suppresses the three features of cardioprotection. Src does not only transactivate EGFR, but also inhibits PTEN by phosphorylation thus playing a crucial role in apelin-induced cardioprotection.

Redox signalling and cardioprotection: translatability and mechanism

The morbidity and mortality from coronary artery disease (CAD) remain significant worldwide. The treatment for acute myocardial infarction has improved over the past decades, including early reperfusion of culprit coronary arteries. Although it is mandatory to reperfuse the ischaemic territory as soon as possible, paradoxically this leads to additional myocardial injury, namely ischaemia/reperfusion (I/R) injury, in which redox stress plays a pivotal role and for which no effective therapy is currently available. In this review, we report evidence that the redox environment plays a pivotal role not only in I/R injury but also in cardioprotection. In fact, cardioprotective strategies, such as pre- and post-conditioning, result in a robust reduction in infarct size in animals and the role of redox signalling is of paramount importance in these conditioning strategies. Nitrosative signalling and cysteine redox modifications, such as S-nitrosation/S-nitrosylation, are also emerging as very important mechanisms in conditioning cardioprotection. The reasons for the switch from protective oxidative/nitrosative signalling to deleterious oxidative/nitrosative/nitrative stress are not fully understood. The complex regulation of this switch is, at least in part, responsible for the diminished or lack of cardioprotection induced by conditioning protocols observed in ageing animals and with co-morbidities as well as in humans. Therefore, it is important to understand at a mechanistic level the reasons for these differences before proposing a safe and useful transition of ischaemic or pharmacological conditioning. Indeed, more mechanistic novel therapeutic strategies are required to protect the heart from I/R injury and to improve clinical outcomes in patients with CAD.

Targeting the PI3K/Akt/mTOR signaling pathway in B-precursor acute lymphoblastic leukemia and its therapeutic potential

B-precursor acute lymphoblastic leukemia (B-pre ALL) is a malignant disorder characterized by the abnormal proliferation of B-cell progenitors. The prognosis of B-pre ALL has improved in pediatric patients, but the outcome is much less successful in adults. Constitutive activation of the phosphatidylinositol 3-kinase (PI3K), Akt and the mammalian target of rapamycin (mTOR) (PI3K/Akt/mTOR) network is a feature of B-pre ALL, where it strongly influences cell growth and survival. RAD001, a selective mTORC1 inhibitor, has been shown to be cytotoxic against many types of cancer including hematological malignancies. To investigate whether mTORC1 could represent a target in the therapy of B-pre ALL, we treated cell lines and adult patient primary cells with RAD001. We documented that RAD001 decreased cell viability, induced cell cycle arrest in G0/G1 phase and caused apoptosis in B-pre ALL cell lines. Autophagy was also induced, which was important for the RAD001 cytotoxic effect, as downregulation of Beclin-1 reduced drug cytotoxicity. RAD001 strongly synergized with the novel allosteric Akt inhibitor MK-2206 in both cell lines and patient samples. Similar results were obtained with the combination CCI-779 plus GSK 690693. These findings point out that mTORC1 inhibitors, either as a single agent or in combination with Akt inhibitors, could represent a potential therapeutic innovative strategy in B-pre ALL.

Cardioprotection against ischemia/reperfusion injury and chromogranin A-derived peptides

Chromogranin A (CgA) is produced by cells of the sympathoadrenal system and by human ventricular myocardium. In the clinical setting CgA has been mainly used as a marker of neuroendocrine tumors, but in the last decade a plenty of data have been published on the role of CgA and its derived peptides, particularly catestatin and vasostatin, in the regulation of cardiovascular function and diseases, including heart failure and hypertension. CgA-derived peptides, namely catestatin and vasostatin, may exert negative inotropic and lusitropic effects on mammalian hearts. As such CgA and its derived peptides may be regarded as mediators of a complex feedback system able to modulate the exaggerated release of catecholamines. This system may be also interpreted as an attempt for compensatory cardioprotective response against myocardial injury in the pre and postischemic scenarios. In fact, while vasostatin can trigger cardioprotective effects akin ischemic preconditioning (protection is triggered before ischemia), catestatin is a potent cardioprotective agent in the early post-ischemic phase, acting like a postconditioning agent (protection is triggered at the onset of reperfusion). Admittedly, the exact mechanism of cardioprotection of this system is far from being fully understood. Interestingly, both vasostatin and catestatin have shown to be able to activate multiple cardioprotective pathways. In particular, these two CgA-derived peptides may induce nitric oxide dependent pathway, which may play a pivotal role in cardioprotection against ischemia/reperfusion injury. Here, we review the literature about the cardiac effects of catestatin and vasostatin, the mechanisms of myocardial injury and protection and the role of CgA derived peptides in cardioprotection.

Cytotoxic activity of the novel Akt inhibitor, MK-2206, in T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive neoplastic disorder arising from T-cell progenitors. T-ALL accounts for 15% of newly diagnosed ALL cases in children and 25% in adults. Although the prognosis of T-ALL has improved, due to the use of polychemotherapy schemes, the outcome of relapsed/chemoresistant T-ALL cases is still poor. A signaling pathway that is frequently upregulated in T-ALL, is the phosphatidylinositol 3-kinase/Akt/mTOR network. To explore whether Akt could represent a target for therapeutic intervention in T-ALL, we evaluated the effects of the novel allosteric Akt inhibitor, MK-2206, on a panel of human T-ALL cell lines and primary cells from T-ALL patients. MK-2206 decreased T-ALL cell line viability by blocking leukemic cells in the G(0)/G(1) phase of the cell cycle and inducing apoptosis. MK-2206 also induced autophagy, as demonstrated by an increase in the 14-kDa form of LC3A/B. Western blotting analysis documented a concentration-dependent dephosphorylation of Akt and its downstream targets, GSK-3α/β and FOXO3A, in response to MK-2206. MK-2206 was cytotoxic to primary T-ALL cells and induced apoptosis in a T-ALL patient cell subset (CD34(+)/CD4(-)/CD7(-)), which is enriched in leukemia-initiating cells. Taken together, our findings indicate that Akt inhibition may represent a potential therapeutic strategy in T-ALL.

AMP-dependent kinase/mammalian target of rapamycin complex 1 signaling in T-cell acute lymphoblastic leukemia: therapeutic implications

The mammalian target of rapamycin (mTOR) serine/threonine kinase is the catalytic subunit of two multi-protein complexes, referred to as mTORC1 and mTORC2. Signaling downstream of mTORC1 has a critical role in leukemic cell biology by controlling mRNA translation of genes involved in both cell survival and proliferation. mTORC1 activity can be downmodulated by upregulating the liver kinase B1/AMP-activated protein kinase (LKB1/AMPK) pathway. Here, we have explored the therapeutic potential of the anti-diabetic drug, metformin (an LKB1/AMPK activator), against both T-cell acute lymphoblastic leukemia (T-ALL) cell lines and primary samples from T-ALL patients displaying mTORC1 activation. Metformin affected T-ALL cell viability by inducing autophagy and apoptosis. However, it was much less toxic against proliferating CD4(+) T-lymphocytes from healthy donors. Western blot analysis demonstrated dephosphorylation of mTORC1 downstream targets. Unlike rapamycin, we found a marked inhibition of mRNA translation in T-ALL cells treated with metformin. Remarkably, metformin targeted the side population of T-ALL cell lines as well as a putative leukemia-initiating cell subpopulation (CD34(+)/CD7(-)/CD4(-)) in patient samples. In conclusion, metformin displayed a remarkable anti-leukemic activity, which emphasizes future development of LKB1/AMPK activators as clinical candidates for therapy in T-ALL.

Activity of endothelial factors on myocardial inotropy

Both nitric oxide (NO) and endothelins can either increase or decrease myocardial contractility. A positive inotropic effect occurs in response to low NO concentrations, whereas a negative effect is brought about by high concentrations. Activation of protein kinase A and protein kinase G accounts for the increase and decrease in contractility respectively. Basal NO concentration is virtually unknown so that when NO-donors and NOS stimulators add newly released NO, the most frequent effect is a decrease in contractility. This negative inotropic effect represents a protection against the maladaptative activity of the increased production of angiotensin II and cathecholamines in heart failure. Unlike NO, the main effect of endothelins is an increase in contractility. While the increase in contractility is attributed to an activation of Na+/H+ and Na+/Ca2+ exchangers a decrease seems to depend on the triggering of NO-cGMP pathway by endothelin receptors B. Since endothelin concentration increases in several cardiovascular diseases, the blockade of endothelin receptors has been suggested as a therapeutic tool. The study of the endothelial-dependent repolarizing factors revealed the inotropic activity of 14,15 isoform of epoxi-eicosatrienoic acids.

Low concentrations of an nitric oxide-donor combined with a liposoluble antioxidant compound enhance protection against reperfusion injury in isolated rat hearts

Nitric oxide (NO) and reactive oxygen species (ROS) are double-edged swords in reperfused hearts. The effects of a NO-donor and an antioxidant compound against ischemia/reperfusion were studied. The compounds were tested separately, as a mixture and as a new hybrid molecule containing both leads. Isolated rat hearts underwent 30 min global ischemia and 2 hrs reperfusion. Compounds were infused either at 1 or 10 microM concentrations during the first 20 min of reperfusion. Hybrid was also tested in the presence of mitochondrial K(+) ATP-sensitive (mKATP) channel blockade by 5-HD (100 microM). Reduction of infarct size and recovery of left ventricular developed pressure during reperfusion were evaluated. When given at 1 microM concentration, hybrid significantly improved all indices of protection; its beneficial effects were abolished by mKATP channel blockade. At the same concentration, mixture and NO-donor alone improved recovery of left ventricular developed pressure but did not reduce infarct size; antioxidant was ineffective. When given at 10 microM concentration, antioxidant and mixture improved all parameters of protection; NO-donor and hybrid were ineffective. Our data suggest that different signaling cascades could be elicited by low and high concentrations of antioxidant compound and/or NO-donor. It is likely that a different NO-induced release of reactive oxygen species via mKATP channel activation may play a pivotal role in affecting infarct size and post-ischemic contractile recovery.

Post-ischaemic activation of kinases in the pre-conditioning-like cardioprotective effect of the platelet-activating factor

AIM

Platelet-activating factor (PAF) triggers cardiac pre-conditioning against ischemia/reperfusion injury. The actual protection of ischaemic pre-conditioning occurs in the reperfusion phase. Therefore, we studied in this phase the kinases involved in PAF-induced pre-conditioning.

METHODS

Langendorff-perfused rat hearts underwent 30 min of ischaemia and 2 h of reperfusion (group 1, control). Before ischaemia, group 2 hearts were perfused for 19 min with PAF (2 x 10(-11) M); groups 3-5 hearts were co-infused during the initial 20 min of reperfusion, with the protein kinase C (PKC) inhibitor chelerythrine (5 x 10(-6) M) or the phosphoinositide 3-kinase (PI3K) inhibitor LY294002 (5 x 10(-5) M) and atractyloside (2 x 10(-5) M), a mitochondrial permeability transition pore (mPTP) opener respectively. Phosphorylation of PKCepsilon, PKB/Akappat, GSK-3beta and ERK1/2 at the beginning of reperfusion was also checked. Left ventricular pressure and infarct size were determined.

RESULTS

PAF pre-treatment reduced infarct size (33 +/- 4% vs. 64 +/- 5% of the area at risk of control hearts) and improved pressure recovery. PAF pre-treatment enhanced the phosphorylation/activation of PKCepsilon, PKB/Akappat and the phosphorylation/inactivation of GSK-3beta at reperfusion. Effects on ERK1/2 phosphorylation were not consistent. Infarct-sparing effect and post-ischaemic functional improvement induced by PAF pre-treatment were abolished by post-ischaemic infusion of either chelerythrine, LY294002 or atractyloside.

CONCLUSIONS

The cardioprotective effect exerted by PAF pre-treatment involves activation of PKC and PI3K in post-ischaemic phases and might be mediated by the prevention of mPTP opening in reperfusion via GSK-3beta inactivation.

Mesenchymal stem cell interaction with a non-woven hyaluronan-based scaffold suitable for tissue repair

The fabrication of biodegradable 3-D scaffolds enriched with multipotent stem cells seems to be a promising strategy for the repair of irreversibly injured tissues. The fine mechanisms of the interaction of rat mesenchymal stem cells (rMSCs) with a hyaluronan-based scaffold, i.e. HYAFF(R)11, were investigated to evaluate the potential clinical application of this kind of engineered construct. rMSCs were seeded (2 x 10(6) cells cm(-2)) on the scaffold, cultured up to 21 days and analysed using appropriate techniques. Light (LM), scanning (SEM) and transmission (TEM) electron microscopy of untreated scaffold samples showed that scaffolds have a highly porous structure and are composed of 15-microm-thick microfibres having a rough surface. As detected by trypan blue stain, cell adhesion was high at day 1. rMSCs were viable up to 14 days as shown by CFDA assay and proliferated steadily on the scaffold as revealed by MTT assay. LM showed rMSCs in the innermost portions of the scaffold at day 3. SEM revealed a subconfluent cell monolayer covering 40 +/- 10% of the scaffold surface at day 21. TEM of early culture showed rMSCs wrapping individual fibres with regularly spaced focal contacts, whereas confocal microscopy showed polarized expression of CD44 hyaluronan receptor; TEM of 14-day cultures evidenced fibronexus formation. Immunohistochemistry of 21-day cultures showed that fibronectin was the main matrix protein secreted in the extracellular space; decorin and versican were seen in the cell cytoplasm only and type IV collagen was minimally expressed. The expression of CD90, a marker of mesenchymal stemness, was found unaffected at the end of cell culture. Our results show that HYAFF(R)11 scaffolds support the adhesion, migration and proliferation of rMSCs, as well as the synthesis and delivery of extracellular matrix components under static culture conditions without any chemical induction. The high retention rate and viability of the seeded cells as well as their fine modality of interaction with the substrate suggest that such scaffolds could be potentially useful when wide tissue defects are to be repaired as in the case of cartilage repair, wound healing and large vessel replacement.

Synergistic effects against post-ischemic cardiac dysfunction by sub-chronic nandrolone pretreatment and postconditioning: role of beta2-adrenoceptor

Beta(2)-adrenoreceptor overexpression is beneficial against ischemia/reperfusion (I/R) injury. Whether beta-adrenoreceptors are involved in postconditioning (PostC) is unknown. We investigated whether nandrolone-decanoate (ND)-pretreatment can modulate (1) beta-adrenoreceptor expression and (2) post-ischemic cardiac function in response to I/R and PostC. Finally, we tested whether cardioprotection can be prevented by the inhibition of beta(2)-adrenoreceptors. Isolated rat hearts from ND pretreated (15 mg/kg/day i.m., for 14 days) and untreated-animals underwent 30-min ischemia and 120-min reperfusion. In subgroups, at the end of ischemia a PostC protocol (five cycles of 10-s reperfusion and 10-s ischemia) was applied and/or a beta(2)-adrenoreceptor blocker, ICI-118.551 (10 microM), was infused. Left ventricular pressure (LVP) was measured with an electromanometer, and infarct-size was evaluated using nitro-blue-tetrazolium staining. ND-pretreatment increased beta(2)-adrenoreceptor expression, but did not alter cardiac-weight, LVP and maximum rate of increase of LVP (dP/dt(max)). After I/R, infarct-size was smaller in ND-pretreatment than in untreated-animals. Infarct-size was also reduced by PostC, both in untreated and ND-pretreated animals. Contracture was less marked in ND-pretreated animals. PostC reduced contracture in both ND-pretreated and untreated hearts. Moreover, PostC improved post-ischemic recovery of developed LVP and dP/dt(max) much more in earts of ND-pretreated than untreated-animals. ICI-118.551 abolished ND protection and PostC-protection both in ND-pretreated and untreated hearts. Data show that two-weeks ND-pretreatment induces 1) an overexpression of beta(2)-ARs without cardiac hypertrophy and 2) improves the post-ischemic diastolic and systolic cardiac function. Intriguingly, ND-pretreatment potentiates the improvement of systolic function induced by postconditioning via beta(2)-adrenoreceptor activation.

The platelet activating factor triggers preconditioning-like cardioprotective effect via mitochondrial K-ATP channels and redox-sensible signaling

Endogenous platelet activating factor (PAF) is involved in heart ischemic preconditioning. PAF can also afford pharmacological preconditioning. We studied whether mitochondrial-ATP-sensitive K(+) (mK(ATP)) channels and reactive oxygen species (ROS) are involved in PAF-induced cardioprotection. In Group 1 control hearts, Langendorff-perfused rat hearts underwent 30 min ischemia and 2 hours of reperfusion. Group 2 hearts, before ischemia, were perfused for 19 min with PAF (2x10(-11) M); Groups 3 and 4 hearts were co-infused with PAF and N-acetyl-L-cysteine or 5-hydroxydecanoate to scavenge ROS or to block mK(ATP) channels, respectively. Left ventricular pressure and infarct size were determined. PAF-pretreatment reduced infarct size (33 +/- 4% vs 64 +/- 4.6 % of the area at risk of control hearts) and improved pressure recovery. Infarct-sparing effect of PAF was abolished by N-acetyl-L-cysteine and 5-hydroxydecanoate. Thus, the cardioprotective effect exerted by PAF-pretreatment involves activation of mK(ATP) channels and redox signaling in pre-ischemic phase.

The paradigm of postconditioning to protect the heart

Ischaemic preconditioning limits the damage induced by subsequent ischaemia/reperfusion (I/R). However, preconditioning is of little practical use as the onset of an infarction is usually unpredictable. Recently, it has been shown that the heart can be protected against the extension of I/R injury if brief (10–30 sec.) coronary occlusions are performed just at the beginning of the reperfusion. This procedure has been called postconditioning (PostC). It can also be elicited at a distant organ, termed remote PostC, by intermittent pacing (dyssynchrony-induced PostC) and by pharmacological interventions, that is pharmacological PostC. In particular, brief applications of intermittent bradykinin or diazoxide at the beginning of reperfusion reproduce PostC protection. PostC reduces the reperfusion-induced injury, blunts oxidant-mediated damages and attenuates the local inflammatory response to reperfusion. PostC induces a reduction of infarct size, apoptosis, endothelial dysfunction and activation, neutrophil adherence and arrhythmias. Whether it reduces stunning is not clear yet. Similar to preconditioning, PostC triggers signalling pathways and activates effectors implicated in other cardioprotective manoeuvres. Adenosine and bradykinin are involved in PostC triggering. PostC triggers survival kinases (RISK), including A t and extracellular signal-regulated kinase (ERK). Nitric oxide, via nitric oxide synthase and non-enzymatic production, cyclic guanosine monophosphate (cGMP) and protein kinases G (PKG) participate in PostC. PostC-induced protection also involves an early redox-sensitive mechanism, and mitochondrial adenosine-5′ -triphosphate (ATP)-sensitive K⁺ and PKC activation. Protective pathways activated by PostC appear to converge on mitochondrial permeability transition pores, which are inhibited by acidosis and glycogen synthase kinase-3β (GSK-3β). In conclusion, the first minutes of reperfusion represent a window of opportunity for triggering the aforementioned mediators which will in concert lead to protection against reperfusion injury. Pharmacological PostC and possibly remote PostC may have a promising future in clinical scenario.

Nitric oxide and cardiac function

Nitric oxide (NO) participates in the control of contractility and heart rate, limits cardiac remodeling after an infarction and contributes to the protective effect of ischemic pre- and postconditioning. Low concentrations of NO, with production of small amounts of cGMP, inhibit phosphodiesterase III, thus preventing the hydrolysis of cAMP. The subsequent activation of a protein-kinase A causes the opening of sarcolemmal voltage-operated and sarcoplasmic ryanodin receptor Ca(2+) channels, thus increasing myocardial contractility. High concentrations of NO induce the production of larger amounts of cGMP which are responsible for a cardiodepression in response to an activation of protein kinase G (PKG) with blockade of sarcolemmal Ca(2+) channels. NO is also involved in reduced contractile response to adrenergic stimulation in heart failure. A reduction of heart rate is an evident effect of NO-synthase (NOS) inhibition. It is noteworthy that the direct effect of NOS inhibition can be altered if baroreceptors are stimulated by increases in blood pressure. Finally, NO can limit the deleterious effects of cardiac remodeling after myocardial infarction possibly via the cGMP pathway. The protective effect of NO is mainly mediated by the guanylyl cyclase-cGMP pathway resulting in activation of PKG with opening of mitochondrial ATP-sensitive potassium channels and inhibition of the mitochondrial permeability transition pores. NO acting on heart is produced by vascular and endocardial endothelial NOS, as well as neuronal and inducible synthases. In particular, while in the basal control of contractility, endothelial synthase has a predominant role, the inducible isoform is mainly responsible for the cardiodepression in septic shock.

Transfusion recipient identification

Recent reports from different haemovigilance systems indicate that errors in the whole-blood transfusion chain - from initial recipient identification to final blood administration - occur with a frequency of approximately 1 in 1000 events. Although mistakes occur also within the blood transfusion service, about two-thirds of errors are associated with incorrect blood recipient identification at the patient's bedside. To prevent the potentially fatal consequences of such mistakes, specific tools have been developed, including patient identification bracelets with barcodes and/or radio frequency identification devices, mechanical or electronic locks preventing access to bags assigned to other patients, and palm computers suitable for transferring blood request and administration data from the patient's bedside to the blood transfusion service information system in real time. The effectiveness of these systems in preventing mistransfusion has been demonstrated in a number of studies.

Endothelial cytochrome P450 contributes to the acetylcholine-induced cardiodepression in isolated rat hearts

AIMS

Acetylcholine (ACh) is known to reduce the contractility of the heart by acting on myocardial muscarinic M2 receptors. ACh induces also an endothelial-dependent vasodilatation by causing the release of nitric oxide (NO), prostacyclin and endothelium-derived hyperpolarizing factors from the vascular endothelium. It has been proposed that ACh elicits a hyperpolarization of the coronary endothelial cells which may be accompanied by the activation of cytochrome P450 (CYP) and the resulting release of epoxyeicosatrienoic acids (EETs). The study aims at investigating whether endothelial CYP is involved in the cardiodepression by ACh.

METHODS AND RESULTS

In isolated rat hearts, cardiodepression by ACh (i.e. 25-30% reduction of developed left ventricular pressure) was partially attenuated either by inhibition of CYP with 1-aminobenzotriazole (ABT) or by endothelial dysfunction obtained with Triton X-100. No attenuation of cardiodepression was seen after nitric oxide synthase and cyclooxygenase inhibition by L-nitro-arginine methyl ester and indomethacin, respectively.

CONCLUSION

The results suggest that the negative inotropic effect of ACh depends not only on a direct myocardial effect but also on the endothelial CYP activation.

Role of the fuel utilized by tissues on coronary vessel response to physical stimuli in isolated rat hearts

In isolated rat hearts which can or cannot utilize fatty acids (FA) as substrates the coronary responses to an increase in flow were studied under three different conditions: a) control, during perfusion with glucose-enriched Tyrode solution which allowed the hearts to utilize long-chain FA from the endogenous pool, b) during forced utilization of glucose obtained with oxfenicine, an inhibitor of long-chain FA oxidation, and c) during restored utilization of FA obtained with the addition of hexanoic acid which bypasses the blockade induced by oxfenicine. A step increase in coronary flow (50 %) induced an increase in coronary perfusion pressure whose initial slope (first 60-80 s) was similar in all the conditions of buffer perfusion, thereafter the pressure tended to further increase under control conditions (buffer a), but to decrease during oxfenicine (buffer b). The addition of hexanoic acid to the perfusion solution (buffer c) abolished the effect of oxfenicine. Steady-state conditions were reached after four minutes of increased flow, when perfusion pressure increased by about 70 and 65 % under control conditions and during hexanoate, respectively, but only by 45 % during oxfenicine. In isolated rat hearts during inhibition of FA utilization, an increase in flow elicited a reduced increase in perfusion pressure that resulted in delayed coronary dilation. It follows that the resulting shear stress is substrate-sensitive.

Fatty acids are important for the Frank-Starling mechanism and Gregg effect but not for catecholamine response in isolated rat hearts

In some pathophysiological conditions myocardial metabolism can switch from mainly long chain fatty acid (LCFA) oxidation to mainly glucose oxidation. Whether the predominant fatty acid or glucose oxidation affects cardiac performance has not been defined. In a buffer perfused isovolumetrically contracting rat heart, oxidation of endogenous pool LCFA was avoided by inhibiting carnitine-palmitoyl-transferase I (CPT-I) with oxfenicine (2 mM). In order to restore fatty acid oxidation, hexanoate (1 mM), which bypasses CPT-I inhibition, was added to the perfusate. Three groups of hearts were subjected to either an increase in left ventricular volume (VV, +25%) or an increase in coronary flow (CF, +50%), or inotropic stimulation with isoproterenol (10(-8) and 10(-6) m). The increase in VV (the Frank-Starling mechanism) increased rate-pressure product (RPP) by 21 +/- 2% under control conditions, but only by 6 +/- 2% during oxfenicine-induced CPT-I inhibition. The contractile response to changes in VV recovered after the addition of hexanoate. Similar results were obtained in hearts, in which an increase in CF was elicited (the Gregg phenomenon). Isoproterenol caused a similar increase in contractility regardless of the presence of oxfenicine or hexanoate. In all groups, a commensurate increase in oxygen consumption accompanied the increase in contractility. The fatty acid oxidation is necessary for an adequate contractile response of the isolated heart to increased pre-load or flow, whereas the inotropic response to adrenergic beta-receptor stimulation is insensitive to changes in substrate availability.

Mitochondrial ATP-sensitive channel opener does not induce vascular preconditioning, but potentiates the effect of a preconditioning ischemia on coronary reactive hyperemia in the anesthetized goat

Preconditioning ischemia (PI) increases the speed of the initial vasodilatation (vascular preconditioning) of a subsequent coronary reactive hyperemia (CRH) and reduces total hyperemic flow (THF). We investigated whether changes in CRH similar to those induced by PI are obtained with diazoxide, a mitochondrial ATP-sensitive K+ channel opener, and whether diazoxide influences the effects of a subsequent PI on CRH. In anesthetized goats, flow was recorded from the left circumflex coronary artery (LCCA). CRH and PI were obtained with 15-s and 5-min LCCA occlusions, respectively. CRH was studied before and after PI, before and after diazoxide (2.5 mg/kg i.v.) as well as before and after PI was induced after diazoxide pre-treatment. After PI, the time to peak (ttp) of CRH and THF decreased by 51+/-13% and 23+/-8%, respectively. Diazoxide did not change CRH. After diazoxide and PI, when basal flow had returned to the control level, the ttp of CRH was reduced as after PI alone (-45+/-12%), whereas THF was reduced to a greater extent (-41+/-9% versus -23+/-8%; P<0.01). In conclusion, PI alters CRH by decreasing THF and reducing the ttp of CRH. Whilst diazoxide does not reproduce the effects of PI on CRH, pre-treatment with diazoxide potentiates the effects of PI on THF.

Involvement of nitric oxide in ischemic preconditioning

In ischemic preconditioning, nitric oxide (NO) limits the extension of a subsequent infarct and protects against ischemia/reperfusion-induced endothelial dysfunction, arrhythmias and myocardial stunning. The protective activity concerns both the first and the second window of protection. The antiarrhythmic effect is attributed to microvessel dilation and to the production of cyclic guanosine monophosphate in the myocardium. The limitation of the infarct size is likely to depend on the opening of the mitochondrial adenosine triphosphate-sensitive potassium channels, to which NO participates via the activation of a protein kinase C (PKC). The endothelial protection involves an NO-mediated reduction in neutrophil adherence to the coronary endothelium and platelet aggregation and is accompanied by an enhanced response to vasodilator stimuli. During preconditioning ischemia, NO is released from the coronary endothelium as a result of bradykinin-induced activation of B2 endothelial receptors. In addition to the early protection, endothelium-derived NO is also responsible for a signaling cascade which leads to the activation of myocardial inducible NO synthase, which in turn is responsible for the release of NO involved in the delayed protection. The signaling cascade includes the activation of PKC-epsilon, tyrosine kinase and some mitogen-activated protein kinases. It has been suggested that the activation of PKC-epsilon is mediated by peroxynitrite produced by the combination of NO and the superoxide anion, the latter being generated during reperfusion which follows preconditioning ischemia.

Comparison between the effects of pentobarbital or ketamine/nitrous oxide anesthesia on metabolic and endothelial components of coronary reactive hyperemia

Barbiturates induce reduction of myocardial contractility and metabolism, whereas ketamine exerts a sympathomimetic effect that can mask its direct depressant effect on contractility. However, it is unclear whether barbiturates, which interfere with the cytochrome P-450 pathway, or ketamine, which inhibits nitric oxide synthesis, also alter the responsiveness of the coronary vessels to vasodilator stimuli. We hypothesized that the parameters of coronary reactive hyperemia (CRH), which reflect both the degree of myocardial metabolism and vascular reactivity, could be modified by the type of anesthesia used. In two groups of goats, anesthesia was induced either using ketamine plus nitrous oxide or pentobarbital alone. To record coronary flow an electromagnetic flow-probe was placed around the left circumflex coronary artery. In the ketamine group (n = 14) and in the pentobarbital group (n = 16) CRH was studied using the indices of myocardial metabolism and vascular dilator responsiveness. In the pentobarbital group all of the indices of myocardial metabolism were lower than in the ketamine group (i.e. the excess to debt flow ratio was 2.3+/-0.8 vs. 4.6+/-2.4; p< 0.001). Yet, some indices of vascular responsiveness (time derivative of coronary flow and the peak to basal flow ratio) were not different in the two groups. Moreover, the duration of the reactive hyperemia was shorter in the ketamine than in the pentobarbital group (118+/-47 vs. 153+/-45 s, p<0.05). It is suggested that pentobarbital decreases the indices of CRH related to metabolic activity, whereas ketamine reduces the duration of the hyperemic response, which suggests an impairment of endothelial function.

Cytochrome P-450 metabolite of arachidonic acid mediates bradykinin-induced negative inotropic effect

This study focused on the mechanisms of the negative inotropic response to bradykinin (BK) in isolated rat hearts perfused at constant flow. BK (100 nM) significantly reduced developed left ventricular pressure (LVP) and the maximal derivative of systolic LVP by 20-22%. The cytochrome P-450 (CYP) inhibitors 1-aminobenzotriazole (1 mM and 100 microM) or proadifen (5 microM) abolished the cardiodepression by BK, which was not affected by nitric oxide and cyclooxygenase inhibitors (35 microM NG-nitro-L-arginine methyl ester and 10 microM indomethacin, respectively). The CYP metabolite 14,15-epoxyeicosatrienoic acid (14,15-EET; 50 ng/ml) produced effects similar to those of BK in terms of the reduction in contractility. After the coronary endothelium was made dysfunctional by Triton X-100 (0.5 microl), the BK-induced negative inotropic effect was completely abolished, whereas the 14,15-EET-induced cardiodepression was not affected. In hearts with normal endothelium, after recovery from 14,15-EET effects, BK reduced developed LVP to a 35% greater extent than BK in the control. In conclusion, CYP inhibition or endothelial dysfunction prevents BK from causing cardiodepression, suggesting that, in the rat heart, endothelial CYP products mediate the negative inotropic effect of BK. One of these mediators appears to be 14,15-EET.

Ischemic preconditioning: from the first to the second window of protection

In many species one or more brief coronary occlusions limit the injuries which a subsequent ischemia-reperfusion can produce in the myocardium. A similar protection has been observed in the majority of organ systems. A first period or window of protection can lasts up to 3 hours and is followed by a second window of protection (SWOP) which begins about 24 hours after the brief coronary occlusions and lasts about 72 hours. Increase of the release of endogenous agents such as adenosine and nitric oxide (NO) may be responsible for both windows through the activation of a protein-kinase C (PKC) which in turn activates ATP sensitive potassium (K+(ATP)) channels. Nitric oxide is also reported to act directly on K+(ATP) channels. Recently, it has been suggested that the channels involved in the protection are mitochondrial rather than sarcolemmal. In SWOP the origin of NO is attributed to the activity of an inducible NO-synthase. Free oxygen radicals released during preconditioning are likely to take part in the delayed protection through the production of peroxynitrite which activates PKC and through the increase of the activity of antioxidant enzymes such as Mn superoxide-dismutase. The production of heat shock proteins is considered a marker rather than a mechanism of SWOP.

Role of calcium-sensitive K(+) channels and nitric oxide in in vivo coronary vasodilation from enhanced perfusion pulsatility

BACKGROUND

In vitro studies support K(+)(Ca) channel-induced smooth muscle hyperpolarization as underlying acetylcholine-mediated (or bradykinin-mediated) vasodilation that persists despite combined nitric oxide (NO) and PGI(2) inhibition. We tested the hypothesis that these channels are activated by enhanced pulsatile perfusion in vivo and contribute substantially to vasodilation from this stimulus.

METHODS AND RESULTS

The canine left descending coronary artery was perfused with whole blood at constant mean pressure, and physiological flow pulsatility was set at 40 or 100 mm Hg by computer servo-pump. Cyclooxygenase was inhibited by indomethacin. Mean flow increased +18+/-2% (P:<0.0001) with enhanced pulsatility. This response declined approximately 50% by blocking NO synthase (L-NMMA) or K(+)(Ca) [charybdotoxin (CbTX)+apamin (AP)]. Combining both inhibitors virtually eliminated the flow rise. Inhibiting either or both pathways minimally altered basal coronary flow, whereas agonist-stimulated flow was blocked. Bradykinin-induced dilation declined more with CbTX+AP than with L-NMMA (-66% versus -46%, P:=0.03) and was fully blocked by their combination. In contrast, acetylcholine-induced dilation was more blunted by L-NMMA than by CbTX+AP (-71% versus -44%, P:<0.002) and was not fully prevented by the combination. Substituting iberiotoxin (IbTX) for CbTX greatly diminished inhibition of pulse pressure and agonist flow responses (with or without NOS inhibition). Furthermore, blockade by IbTX+AP was identical to that by AP alone, supporting a minimal role of IbTX-sensitive large-conductance K(+)(Ca) channels.

CONCLUSIONS

K(+)(Ca) activation and NO comodulate in vivo pulsatility-stimulated coronary flow, supporting an important role of a hyperpolarization pathway in enhanced mechanovascular signaling. Small- and intermediate-conductance K(+)(Ca) channels are the dominant species involved in modulating both pulse pressure- and bradykinin-induced in vivo coronary dilation.

Model-based assessment of pressure and flow-dependent coronary responses following abrupt pressure drops

The response of the coronary vasculature to an experimental manoeuvre of step-like decrease of the perfusion pressure has been investigated with a model. The coronary vasculature was simulated using a 'windkessel' scheme. Proximal resistance and compliance were assumed to be pressure-independent. The distal resistance, on the contrary, was controlled by a feed-back loop which accounts for the smooth muscle activation induced by the pressure variation. Three more parameters were introduced, and namely the smooth muscle activation time constant and the pressure-induced and flow-induced gains. The parameter values were assessed by comparing the model predicted coronary flow with the one actually measured in animals.

The endothelium-derived hyperpolarizing factor: does it play a role in vivo and is it involved in the regulation of vascular tone only?

Several investigations performed in vitro have shown that vascular endothelia can release diffusible compounds capable of inducing hyperpolarization of the smooth muscle fibers. Experiments in vitro have shown that these compounds can cause coronary vasodilation and alter cardiac performance. Experiments in vivo only showed the occurrence of vasodilation. While it has been shown that the release of these endothelium-derived hyperpolarizing factors (EDHFs) is not impaired by the inhibition of nitric oxide synthase and cyclooxygenase, the precise nature of the compound(s) has not yet been identified. It is possible that they vary depending on the organ and animal species. However, a common feature of the activity of EDHFs is the activation of calcium-dependent potassium channels, inhibitable by charybdotoxin and apamin. Furthermore in the coronary circulation of many species EDHF seems to be a cytochrome P450-dependent non-prostanoid metabolite of arachidonic acid activated by a number of chemical and physical stimuli similar to those which are known to activate endothelial nitric oxide synthase. Using compounds which inhibit cytochrome P450 and blockers of the calcium-dependent potassium channels, researchers can study the physiological and pathophysiological relevance of EDHF in vivo thus disclosing the potential therapeutic applications of the basic knowledge in this field.

Reversal of glibenclamide-induced coronary vasoconstriction by enhanced perfusion pulsatility: possible role for nitric oxide

OBJECTIVES

ATP-sensitive potassium channels (K+ATP) prominently contribute to basal coronary tone; however, flow reserve during exercise remains unchanged despite channel blockade with glibenclamide (GLI). We hypothesized that increasing perfusion pulsatility, as accompanies exercise, offsets vasoconstriction from K+ATP-channel blockade, and that this effect is blunted by nitric oxide synthase (NOS) inhibition.

METHODS

In 31 anaesthetized dogs the left anterior descending artery was blood-perfused by computer-controlled servo-pump, with real-time arterial perfusion pulse pressure (PP) varied from 40 and 100 mm Hg at a constant mean pressure and cardiac workload.

RESULTS

At control PP (40 mm Hg), GLI (50 micrograms/min/kg, i.c.) lowered mean regional coronary flow from 37 +/- 5 to 25 +/- 4 ml/min (P < 0.001). However, this was not observed at 100 mm Hg PP (41 +/- 2 vs. 45 +/- 4). NOS inhibition by NG-monomethyl-L-arginine (L-NMMA) did not alter basal flow at 40 mm Hg PP, but modestly lowered flow (-5%, P < 0.001) at higher PP (100 mm Hg), reducing PP-flow augmentation by -36%, and acetylcholine (ACh) induced flow elevation by -39%. Co-infusion of L-NMMA with GLI resulted in net vasoconstriction at both PP levels (-60% and -40% at 40 and 100 mm Hg PP, respectively). Unlike GLI, vasoconstriction by vasopressin (-43 +/- 3% flow reduction at 40 mm Hg PP) or quinacrine (-23 +/- 7%) was not offset at higher pulsatility (-44 +/- 4 and -23 +/- 6%, respectively). Neither of the latter agents inhibited ACh- or PP-induced flow responses, nor did they modify the effect of L-NMMA on these responses.

CONCLUSIONS

Increased coronary flow pulsatility offsets vasoconstriction from K+ATP blockade by likely enhancing NO release. This mechanism may assist exercise-mediated dilation in settings where K+ATP opening is partially compromised.

New insights into nitric oxide and coronary circulation

Since its discovery over 20 years ago as an intercellular messenger, nitric oxide (NO), has been extensively studied with regard to its involvement in the control of the circulation and, more recently, in the prevention of atherosclerosis. The importance of NO in coronary blood flow control has also been recognized. NO-independent vasodilation causes increased shear stress within the blood vessel which, in turn, stimulates endothelial NO synthase activation, NO release and prolongation of vasodilation. Reactive hyperemia, myogenic vasodilation and vasodilator effects of acetylcholine and bradykinin are all mediated by NO. Ischemic preconditioning, which protects the myocardium from cellular damage and arrhythmias, is itself linked with NO and both the first and second windows of protection may be due to NO release. Exercise increases NO synthesis via increases in shear stress and pulse pressure and so it is likely that NO is an important blood flow regulatory mechanism in exercise. This phenomenon may account for the beneficial effects of exercise seen in atherosclerotic individuals. Whilst NO plays a protective role in preventing atherosclerosis via superoxide anion scavenging, risk factors such as hypercholesterolemia reduce NO release leading the way for endothelial dysfunction and atherosclerotic lesions. Exercise reverses this process by stimulating NO synthesis and release. Other factors impacting on the activity of NO include estrogens, endothelins, adrenomedullin and adenosine, the last appearing to be a compensatory pathway for coronary control in the presence of NO inhibition. These studies reinforce the pivotal role played by the substance in the control of coronary circulation.

Specificity of synergistic coronary flow enhancement by adenosine and pulsatile perfusion in the dog

1. Coronary flow elevation from enhanced perfusion pulsatility is synergistically amplified by adenosine. This study determined the specificity of this interaction and its potential mechanisms. 2. Mean and phasic coronary flow responses to increasing pulsatile perfusion were assessed in anaesthetized dogs, with the anterior descending coronary artery servoperfused to regulate real-time physiological flow pulsatility at constant mean pressure. Pulsatility was varied between 40 and 100 mmHg. Hearts ejected into the native aorta whilst maintaining stable loading. 3. Increasing pulsatility elevated mean coronary flow +11.5 +/- 1.7 % under basal conditions. Co-infusion of adenosine sufficient to raise baseline flow 66 % markedly amplified this pulsatile perfusion response (+82. 6 +/- 14.3 % increase in mean flow above adenosine baseline), due to a leftward shift of the adenosine-coronary flow response curve at higher pulsatility. Flow augmentation with pulsatility was not linked to higher regional oxygen consumption, supporting direct rather than metabolically driven mechanisms. 4. Neither bradykinin, acetylcholine nor verapamil reproduced the synergistic amplification of mean flow by adenosine and higher pulsatility, despite being administered at doses matching basal flow change with adenosine. 5. ATP-sensitive potassium (KATP) activation (pinacidil) amplified the pulse-flow response 3-fold, although this remained significantly less than with adenosine. Co-administration of the phospholipase A2 inhibitor quinacrine virtually eliminated adenosine-induced vasodilatation, yet synergistic interaction between adenosine and pulse perfusion persisted, albeit at a reduced level. 6. Thus, adenosine and perfusion pulsatility specifically interact to enhance coronary flow. This synergy is partially explained by KATP agonist action and additional non-flow-dependent mechanisms, and may be important for modulating flow reserve during exercise or other high output states where increased flow demand and higher perfusion pulsatility typically co-exist.

An Italian national multicenter study for the definition of reference ranges for normal values of peripheral blood lymphocyte subsets in healthy adults

BACKGROUND AND OBJECTIVE

Reference ranges are necessary in clinical chemistry and hematology to compare an observed value and to provide meaningful information. The aim of this multicenter study was the definition of reference ranges of the relative and absolute numbers of lymphocyte subsets by evaluating a large cohort of healthy adults and by using a standard protocol to reduce the variability in both sample preparation methodology and flow cytometer operation. Other aims of this study were the evaluation of the influence of sex, age, obesity, smoking, sport and some methodological variables on lymphocyte subsets and the comparison of differential white blood cell values obtained by flow cytometry and those obtained by hematology counters.

DESIGN AND METHODS

Blood samples from 1311 healthy adults (blood donors and volunteers chosen according to the Italian law for donor selection) were analyzed to study, by flow cytometry, the immunophenotype of lymphocyte subsets and their distribution in terms of percentages and absolute values. Pre-analytical and analytical phases were performed according to the guidelines of the International Federation of Clinical Chemistry (IFCC) and the Italian Group of Cytometry (GIC). T cells were defined by the expression of CD3; T subpopulations by the coexpression of CD4 or CD8 or HLA-DR; B-lymphocytes were identified by the expression of CD19 while natural killer lymphocytes were identified by positivity of CD16 and/or CD56 without CD3. We calculated, for each laboratory and for all data collected, the frequency distribution percent values and absolute values of each lymphocyte subset. The influence of age, sex, smoking, obesity and sport was calculated by the t-test. The influence of some methodological variables was calculated by the t-test and multiple regression test.

RESULTS

Fifty-three flow cytometry laboratories at different institutions in Italy participated in this study. Data was obtained from 1311 healthy adults aged from 18 to 70; 968 phenotype analyses (74%) were considered eligible for statistical analysis. Significant results were found as regards sex, smoking and some methodological variables (quantity of sample, washing procedures, brand of monoclonal antibodies and kind of instruments used). The comparison between hematology counters and cytometers showed no difference for any of the parameters considered.

INTERPRETATION AND CONCLUSIONS

The large number of cases, the different kinds of laboratories and their distribution throughout the country make our sample representative of the Italian adult population. The standardization criteria of pre-analytical and analytical phases (the most important issues in evaluating reference values for an indicator) assured good reproducibility among laboratories so that the obtained reference ranges may be useful for interlaboratory comparison of results. Instruments and the brand of monoclonal antibodies may represent an inevitable cause of variability.

The effects of ischemic preconditioning on resting coronary flow and reactive hyperemia: involvement of A1 adenosine receptors

During the myocardial protection induced by ischemic preconditioning a reduction in myocardial metabolism occurs due to activation of the A1 adenosine receptors. This study investigates whether preconditioning changes both resting coronary flow and the magnitude of coronary reactive hyperemia and whether A1 adenosine receptors are involved in the observed changes. Experiments were performed in 14 goats (30-50 kg body weight). After the animals were anesthetized with ketamine, an electromagnetic flow-probe was used to record blood flow in the left circumflex coronary artery. Distal to the probe, an occluder was placed to produce ischemic preconditioning and reactive hyperemia. Preconditioning was obtained with two periods of 2.5 min of coronary occlusion separated from each other by 5 min of reperfusion. Coronary reactive hyperemia was obtained with 15 s of occlusion of the artery before and after preconditioning. In a group of goats before preconditioning 0.2 mg kg(-1) of 8-cyclopentyl-dipropylxanthine (CPX), an A1 adenosine receptor blocker, were given intravenously. In all animals ischemic preconditioning did not alter resting coronary flow, but, in the absence of A1 adenosine receptor blockade, reduced the reactive hyperemic response. The total hyperemic flow and the excess/debt flow ratio were reduced by about 25% and 30% respectively. The A1 adenosine receptor blockade "per se" did not cause any change in the resting flow and in the parameters of the reactive hyperemia. Unlike what observed in the absence of blockade, after CPX ischemic preconditioning was unable to reduce total hyperemic flow and the excess/debt flow ratio. The results suggest that ischemic preconditioning reduces the coronary hyperemic response by decreasing the myocardial metabolism through the activation of the A1 adenosine receptors.

Quantitative evaluation of the stretch reflex before and after hydro kinesy therapy in patients affected by spastic paresis

The aim of this study was the quantitative evaluation of the myotatic reflex in a group of 26 patients affected by stationary spastic paresis (6: hemiparesis; 5: paraparesis; 8: tetraparesis; 7: multiple sclerosis) before and after a treatment of hydro-kinesy therapy. The treatment was carried out in an indoor pool containing warm (32 degrees C) sea water and consisted of active and passive motion exercises, coordination exercises and immersion walking. The measured parameters were: (i) the peak input force (FpH) measured by means of an instrumented hammer with which the patellar tendon was hit; and (ii) the peak value of the corresponding reflex force of the quadriceps femoris (FpQ) measured by means of a load cell connected to the subject's ankle. The peak values of the reflex response (FpQ) were found to increase as a function of the intensity of the imposed stimulus and to reach a plateau between 15 and 30 N of FpH. A Student's t test applied to the paired values of FpQ (as measured at plateau conditions) on both the lower limbs, before and after therapy, showed no significant changes due to the treatment in the four groups of subjects. However, if all subjects were grouped regardless the type of illness: 1) the average reflex response of the affected limb (the one characterized before therapy by the higher FpQ values) was found to decrease following the treatment (75.1+/-26.7 N pre therapy and 69.1+/-29.3 N post therapy, p = 0.07, n = 26); and 2) the effect of the treatment was found to be significantly larger (p = 0.04, n = 26) on the affected limb (delta FpQ = 6.07+/-16.5 N) as respect with the contra lateral one (delta FpQ = -0.16+/-12.1 N).

Ischaemic preconditioning changes the pattern of coronary reactive hyperaemia in the goat: role of adenosine and nitric oxide

OBJECTIVES

After ischaemic preconditioning (IP), obtained by short episodes of ischaemia, cardiac protection occurs due to a reduction in myocardial metabolism through the activation of A1 adenosine receptors. The antiarrhythmic effect of IP is attributed to an increase in the release of nitric oxide (NO) by the endothelium. On the basis of the above consideration the present investigation studies the changes induced by preconditioning in coronary reactive hyperaemia (RH) and how blockade of A1 receptors and inhibition of NO synthesis can modify these changes.

METHODS

In anaesthetised goats, an electromagnetic flow-probe was placed around the left circumflex coronary artery. Preconditioning was obtained with two episodes of 2.5 min of coronary occlusion, separated by 5 min of reperfusion. RH was obtained with a 15 s occlusion. In a control group (n = 7) RH was studied before and after IP. In a second group (n = 7), 0.2 mg kg-1 of 8-cyclopentyl-dipropylxanthine, an A1 receptor blocker, and in a third group (n = 7) 10 mg kg-1 of NG-nitro-L-arginine (LNNA), an NO inhibitor, were given before IP. Reactive hyperaemia was again obtained before and after IP.

RESULTS

In the control group, after IP, the time to peak hyperaemic flow and total hyperaemic flow decreased by about 50% and 25%, respectively. The A1 receptor blockade alone did not change RH. During A1 blockade, IP reduced the time to peak of RH similar as in control (45%), but did not alter total hyperaemic flow. LNNA alone reduced resting flow and total hyperaemic flow. After NO inhibition, IP only reduced total hyperaemic flow by about 15%, but the time to peak flow was not affected.

CONCLUSIONS

IP alters RH by decreasing total hyperaemic flow and reducing the time to peak hyperaemic flow. While the former effect is attributed to a reduction in myocardial metabolism through the activation of the A1 receptors, the latter is likely to be due to an increased endothelial release of NO, suggesting that in addition to a protective effect on the myocardium, IP also exerts a direct effect on the responsiveness of the coronary vasculature (vascular preconditioning).