5-HT in systemic hypertension: foe, friend or fantasy?

Body distribution of infused serotonin in rats

1. Our goal was to investigate the body distribution of serotonin (5-hydroxytryptamine; 5-HT) in rats infused with 5-HT (25 microg/kg per min) for 7 days and the contribution of the 5-HT transporter (SERT) for 5-HT uptake into the tissues. 2. Mini-osmotic pumps containing 5-HT or vehicle were implanted in rats knocked out for SERT (SERT-KO) or in wild-type (WT) rats. On the 8th day, tissues were harvested for measurements of 5-HT by high-performance liquid chromatography (HPLC). The 5-HT metabolite 5-hydroxyindole acetic acid (5-HIAA) was also measured by HPLC, because an increase in 5-HIAA in tissues from rats receiving 5-HT reflects 5-HT uptake followed by metabolism. 3. In WT rats infused with 5-HT, an increase in 5-HT or 5-HIAA was observed in the heart, pancreas, thyroid, adrenal gland, kidney, seminal vesicle, bladder, prostate, liver, oesophagus, stomach, femur, trachea, lung and spleen compared with vehicle-infused rats. An increase in 5-HT and 5-HIAA was not observed in aorta, vena cava and jejunum. In tissues from SERT-KO rats infused with 5-HT, the content of 5-HT or 5-HIAA was decreased in most of the tissues studied compared with 5-HT-infused WT rats. Although 5-HT uptake in the kidney, seminal vesicle, prostate, jejunum and trachea is SERT dependent, it is SERT independent in the pancreas. The remaining tissues display SERT-dependent and -independent mechanisms for 5-HT uptake. 4. Altogether, tissues from different systems, such as the cardiovascular, endocrine, genitourinary and gastrointestinal, accumulate 5-HT mainly via SERT and, thus, these systems are potential targets for drugs that interfere with 5-HT homeostasis.

The beginning of a fantastic, unanswered question: is 5-HT involved in systemic hypertension?

This essay examines the historical significance of an APS classic paper that is freely available online:

The love of a lifetime: 5-HT in the cardiovascular system

Serotonin [5-hydroxytryptamine (5-HT)] is an amine made from the essential amino acid tryptophan. 5-HT serves numerous functions in the body, including mood, satiety, and gastrointestinal function. Less understood is the role 5-HT plays in the cardiovascular system, although 5-HT receptors have been localized to every important cardiovascular organ and 5-HT-induced changes in physiological function attributed to activation of these receptors. This manuscript relates a few scientific stories that test the idea that 5-HT is important to the control of normal vascular tone, more so in the hypertensive condition. Currently, our laboratory is faced with two different lines of experimentation from which one could draw vastly different conclusions as to the ability of 5-HT to modify endogenous vascular tone and blood pressure. Studies point to 5-HT being important in maintaining high blood pressure, but other studies solidly support the ability of 5-HT to reduce elevated blood pressure. This work underscores that our knowledge of the functions of 5-HT in the cardiovascular system is significantly incomplete. As such, this field is an exciting one in which to be, because there are superb questions to be asked.

c-Src tyrosine kinase, a critical component for 5-HT2A receptor-mediated contraction in rat aorta

Serotonin (5-hydroxytryptamine, 5-HT) receptors (5-HTRs) play critical roles in brain and cardiovascular functions. In the vasculature, 5-HT induces potent vasoconstrictions, which in aorta are mainly mediated by activation of the 5-HT(2A)R subtype. We previously proposed that one signalling mechanism of 5-HT-induced vasoconstriction could be c-Src, a member of the Src tyrosine kinase family. We now provide evidence for a central role of c-Src in 5-HT(2A)R-mediated contraction. Inhibition of Src kinase activity with 10 mum 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2) prior to contraction resulted in approximately 90-99% inhibition of contractions induced by 5-HT or by alpha-methyl-5-HT (5-HT(2)R agonist). In contrast, PP2 pretreatment only partly inhibited contractions induced by angiotensin II and the thromboxane A(2) mimetic, U46619, and had no significant action on phenylephrine-induced contractions. 5-Hydroxytryptamine increased Src kinase activity and PP2-sensitive tyrosine-phosphorylated proteins. As expected for c-Src identity, PP2 pretreatment inhibited 5-HT-induced contraction with an IC(50) of approximately 1 mum. Ketanserin (10 nm), a 5-HT(2A) antagonist, but not antagonists of 5-HT(2B)R (100 nm SB204741) or 5-HT(2C)R (20 nm RS102221), prevented 5-HT-induced contractions, mimicking PP2 and implicating 5-HT(2A)R as the major receptor subtype coupled to c-Src. In HEK 293T cells, c-Src and 5-HT(2A)R were reciprocally co-immunoprecipitated and co-localized at the cell periphery. Finally, 5-HT-induced Src activity was unaffected by inhibition of Rho kinase, supporting a role of c-Src upstream of Rho kinase. Together, the results highlight c-Src activation as one of the early and pivotal mechanisms in 5-HT(2A)R contractile signalling in aorta.

Lack of the serotonin transporter does not prevent mineralocorticoid hypertension in rat and mouse

We hypothesized that lack of a functional serotonin transporter (SERT) would increase basal blood pressure and enhance the development of deoxycorticosterone acetate (DOCA)-salt hypertension compared to wild type (WT) controls. Mean arterial blood pressure was measured in WT and SERT knockout (KO) mice and rat models through radiotelemetry. Basal blood pressures were not different between respective WT and KO. Moreover, blood pressure elevated similarly (~50 mm Hg) in all strains given DOCA and salt. Thus, the lack of functional SERT did not prevent development of DOCA-salt induced hypertension or modify basal blood pressure significantly.

The existence of a local 5-hydroxytryptaminergic system in peripheral arteries

BACKGROUND AND PURPOSE

5-HT is a vasoconstrictor exhibiting enhanced effects in systemic arteries from subjects with cardiovascular disease. The effect of endogenous 5-HT on arteries is controversial, because the concentration of free circulating 5-HT is low and a 5-hydroxytryptaminergic system has not been identified in peripheral arteries. We hypothesized that a local 5-hydroxytryptaminergic system (including 5-HT synthesis, metabolism, uptake and release) with physiological function exists in peripheral arteries.

EXPERIMENTAL APPROACH

The presence of key components of a 5-hydroxytryptaminergic system in rat aorta and superior mesenteric artery was examined using western blot analyses, immunohistochemistry and immunocytochemistry. The function of the rate-limiting enzyme in 5-HT biosynthesis, tryptophan hydroxylase (TPH), and 5-HT transporter was tested by measuring enzyme activity and 5-HT uptake, respectively. Isometric contraction of arterial strips was used to demonstrate the function of released endogenous 5-HT in arterial tissues.

KEY RESULTS

mRNA for TPH-1 was present in arteries, with low levels of TPH protein and TPH activity. Expression and function of MAO A (5-HT metabolizing enzyme) was supported by immunohistochemistry, western analyses and the elevation of concentrations of 5-hydroxyindoleacetic acid (5-HT metabolite) after exposure to exogenous 5-HT. The 5-HT transporter was localized to the plasma membrane of freshly isolated aortic smooth muscle cells. Peripheral arteries actively took up 5-HT in a time-dependent and 5-HT transporter-dependent manner. The 5-HT transporter substrate, (+)-fenfluramine, released endogenous 5-HT from peripheral arteries, which potentiated noradrenaline-induced arterial contraction.

CONCLUSIONS AND IMPLICATIONS

This study revealed the existence of a local 5-hydroxytryptaminergic system in peripheral arteries.

A serotonergic system in veins: serotonin transporter-independent uptake

We hypothesized that the 5-hydroxytryptamine (5-HT; serotonin) system is present and functional in veins. In vena cava (VC), the presence of the 5-HT synthesis rate-limiting enzyme tryptophan hydroxylase-1 mRNA and accumulation of the 5-HT synthesis intermediate 5-hydroxytryptophan after incubation with tryptophan supported the ability of veins to synthesize 5-HT. The presence of 5-HT and its metabolite 5-hydroxyindole acetic acid was measured by high-performance liquid chromatography in VC and jugular vein (JV), and it was compared with similarly sized arteries aorta (RA) and carotid (CA), respectively. In rats treated with the monoamine oxidase-A (MAO-A) inhibitor pargyline to prevent 5-HT metabolism, basal 5-HT levels were higher in veins than in arteries. 5-HT uptake was observed after exposure to exogenous 5-HT in all vessels. The presence of MAO-A and the 5-HT transporter (SERT) in VC was observed by immunohistochemistry and Western analysis. However, 5-HT uptake was not inhibited by the SERT inhibitors fluoxetine and/or fluvoxamine in VC and JV, as opposed to the inhibition in RA and CA. Moreover, studies performed in VC from mutant rats lacking SERT showed no differences in 5-HT uptake compared with VC from wild type. These data suggest the SERT is not functional under physiological conditions in veins. The differences in 5-HT handling between veins and arteries may represent alternative avenues for targeting the 5-HT system in the peripheral circulation for controlling vascular tone.

Maternal serotonin influences cardiac function in adult offspring

Using the Tph1-invalidated mouse line, in which blood is depleted in serotonin (5-hydroxytryptamine, 5-HT), we have demonstrated previously that maternal 5-HT is required for normal embryonic development. Here, we address the issue of the influence of the maternal 5-HT concentration on the cardiac function of the offspring as adults. We investigated the cardiac phenotype of Tph1-invalidated mice born to Tph1 heterozygous and null mothers. Functionally, all mutants display a significant decrease of cardiac contractility, indicative of impaired left ventricular function. They exhibit progressive dilated cardiomyopathy and are unable to adapt appropriately to a pharmacological stress. Moreover, we show that the cardiopathy is more severe in adult Tph1(-/-) mice born to homozygous mothers than to heterozygous mothers. Importantly, the severity of the cardiac phenotype is inversely correlated with the plasma 5-HT concentration but not the whole-blood 5-HT concentration. Thus, plasma 5-HT concentration may be a useful index of heart failure. These findings show that cardiac function, through the plasma 5-HT concentration, is influenced by the maternal serotonergic status.

Vascular reactivity, 5-HT uptake, and blood pressure in the serotonin transporter knockout rat

The handling of serotonin [5-hydroxytryptamine (5-HT)] depends on the serotonin transporter (SERT). A SERT knockout (KO) rat is a useful model to test the hypothesis that SERT is the primary mechanism for arterial 5-HT uptake and to investigate the impact of SERT removal on blood pressure. Wild-type (WT) and KO rats were used to measure 5-HT content (plasma, raphe, aorta, carotid, and mesenteric artery), aortic isometric contraction, and blood pressure. HPLC supported the lack of circulating 5-HT in plasma (ng/ml plasma, WT, 310 +/- 96; and KO, 1.0 +/- 0.5; P < 0.05). Immunohistochemistry and Western blot analyses validated the presence of the SERT protein in the WT rats and a lesser expression in the KO rat. The aorta isolated from KO rats had a normal contraction to phenylephrine and norepinephrine and a normal relaxation to the endothelium-dependent agonist acetylcholine compared with the aorta from WT. In contrast, the potency of 5-HT was increased in the aorta from KO rats compared with WT rats [-log EC(50) (M); WT, 5.71 +/- 0.08; and KO, 6.7 +/- 0.18] and maximum contraction was reduced [%phenylephrine (10 muM) contraction, WT, 113 +/- 6%; and KO, 52 +/- 12%]. 5-HT uptake was reduced but not abolished in arteries of the KO compared with the WT rats. Diurnal mean arterial blood pressure, heart rate, and locomotor activity level of the KO rats were similar to the WT rats. These data suggest that there are other mechanisms of 5-HT uptake in the arteries of the rat and that although the absence of circulating 5-HT and/or SERT function sensitizes arteries to 5-HT, SERT dysfunction does not impair normal blood pressure.

N-nitroso-melatonin releases nitric oxide in the presence of serotonin and its derivatives

A novel reaction was observed between 5-hydroxytryptophan derivatives like serotonin and N-nitroso-melatonin (NOMela). This reaction decreased the concentration of serotonin by about 50% and generated initially as detectable products nitric oxide and melatonin with stoichiometrical yields. The other expected product, a serotonin-derived radical, could not be detected by electron spin resonance (ESR) spectrometry, probably because the self-decay of phenoxyl type radicals proceed at the diffusion-controlled limit. From the facts that the decay rate of NOMela corresponded very well with the nitric oxide releasing rate and that nitrite was the only thermodynamically stable nitrogen oxide-containing product, it is concluded that the NOMela-serotonin reaction proceeded quantitatively. The observed reaction might be a possibility to counteract a pharmacologically abnormal high serotonin concentration in various diseases.

5-hydroxytryptamine in the cardiovascular system: focus on the serotonin transporter (SERT)

1. The function of the serotonin transporter (SERT) is to take up and release serotonin (5-hydroxytyptamine (5-HT)) from cells and this function of SERT in the central nervous system (CNS) is well-documented; SERT is the target of selective serotonin reuptake inhibitors used in the treatment of CNS disorders, such as depression. 2. The aim of the present review is to discuss our current knowledge of 5-HT and SERT in the cardiovascular (CV) system, as well as their function in physiological and pathophysiological states. 3. The SERT protein has been located in multiple CV tissues, including the heart, blood vessels, brain, platelets, adrenal gland and kidney. Modification of SERT function occurs at both transcriptional and translational levels. The functions of SERT in these tissues is largely unexplored, but includes modulation of cardiac and smooth muscle contractility, platelet aggregation, cellular mitogenesis, modulating neuronal activity and urinary excretion. 4. Recent studies have uncovered potential relationships between the expression of SERT gene promoter variants (long (l) or short (s)) with CV diseases. Specifically, the risk of myocardial infarction and pulmonary hypertension is increased with expression of the ll promoter, a variant associated with increased expression and function of SERT. The relationship between promoter variants and other CV diseases has not been investigated. 5. Newly available experimental tools, such as pharmacological compounds and genetically altered mice, should prove useful in the investigation of the function of SERT in the CV system. 6. In summary, the function of SERT in the CV system is just beginning to be revealed.

Serotonin (5-HT) in veins: not all in vain

The circulatory system consists of veins and arteries. Compared with arteries, veins have been neglected in cardiovascular research. Although veins are significantly less muscular than similarly sized arteries, the contribution of veins to cardiovascular homeostasis cannot be left un-noted because veins accommodate 70% of the circulating blood. Circulating blood platelets contain the majority of systemic 5-HT (5-hydroxytryptamine; serotonin). Similar to venous function, the physiological role of 5-HT in the cardiovascular system is not well understood. Here, we present not only a review on 5-HT and veins but ways in which these two topics might intersect in a physiologically relevant manner. Here we show the novel findings that veins exhibit higher amounts of intracellular 5-HT than arteries. Moreover, we also show evidence that, similar to arteries, veins have the ability to uptake 5-HT. In this review, we introduce the venous system as a reservoir for 5-HT in the periphery, suggesting that veins, in addition to arteries, may represent an important target for drugs that interfere with the serotonergic system. In addition, the serotonergic system from synthesis to metabolism, 5-HT receptor activation and venous diseases will also be discussed.

Mechanisms of U46619- and 5-HT-induced contraction of bovine pulmonary arteries: role of chloride ions

BACKGROUND AND PURPOSE

Thromboxane A(2) and 5-hydroxytryptamine (5-HT) are implicated in pulmonary hypertension. The involvement of chloride, voltage-operated calcium channels (VOCCs), store-operated calcium channels (SOCCs) and the Rho kinase in the contractile response of bovine pulmonary arteries (BPA) to the thromboxane A(2) mimetic U46619 and 5-HT was investigated.

EXPERIMENTAL APPROACH

Endothelium-intact ring segments of BPA were mounted in Krebs/Henseleit buffer (37 degrees C) under a tension of 2g and gassed with 95%O(2)/5%CO(2).

KEY RESULTS

Depletion or removal of extracellular chloride, inhibition of chloride and SOCC, Na:K:2Cl, Cl/HCO(3), Rho kinase inhibited contractions to U46619. Combining Rho kinase inhibition and chloride channel blockade (with NPPB) almost abolished the contractions to U46619. In contrast 5-HT-induced contraction was inhibited by verapamil and mibefradil. Depletion of stored calcium with caffeine almost abolished the response to U46619 but not 5-HT. The contraction by the sarco(endo)plasmic reticulum Ca(2+)-ATPase inhibitor CPA was abolished by SOCC and chloride channel blockade (with NPPB) and by chloride depletion.

CONCLUSIONS AND IMPLICATIONS

This study suggests that the contractile response of BPA to U46619 involves Rho kinase together with a chloride-sensitive mechanism, which does not involve VOCC but may have a role in calcium release and calcium entry via SOCC. In contrast contraction of the BPA by 5-HT appears to involve verapamil- and mibefradil-sensitive VOCC. This study may indicate that the use of calcium channel blockers in the management of pulmonary hypertension may not always be effective and that Rho kinase and chloride channels may be targets for the development of new therapies.

Antenatal dexamethasone treatment leads to changes in gene expression in a murine late placenta

Antenatal steroids like dexamethasone (DEX) are used to augment fetal lung maturity and there is a major concern that they impair fetal growth. If delivery is delayed after using antenatal DEX, placental function and hence fetal growth may be compromised even further. To investigate the effects of DEX on placental function, we treated 9 pregnant C57/BL6 mice with DEX and 9 pregnant mice were injected with saline to serve as controls. Placental gene expression was studied using microarrays in 3 pairs and other 6 pairs were used to confirm microarray results by semi-quantitative RT-PCR, real-time PCR, in situ hybridization, western blot analysis and Oligo ApopTaq assay. DEX-treated placentas were hydropic, friable, pale, and weighed less (80.0+/-15.1mg compared to 85.6.8+/-7.6mg, p=0.05) (n=62 placentas). Fetal weight was significantly reduced after DEX use (940+/-32mg compared to 1162+/-79mg, p=0.001) (n=62 fetuses). There was >99% similarity within and between the three gene chip data sets. DEX led to down-regulation of 1212 genes and up-regulation of 1382 genes. RT-PCR studies showed that DEX caused a decrease in expression of genes involved in cell division such as cyclins A2, B1, D2, cdk 2, cdk 4 and M-phase protein kinase along with growth-promoting genes such as EGF-R, BMP4 and IGFBP3. Oligo ApopTaq assay and western blot studies showed that DEX-treatment increased apoptosis of trophoblast cells. DEX-treatment led to up-regulation of aquaporin 5 and tryptophan hydroxylase genes as confirmed by real-time PCR, and in situ hybridization studies. Thus antenatal DEX treatment led to a reduction in placental and fetal weight, and this effect was associated with a decreased expression of several growth-promoting genes and increased apoptosis of trophoblast cells.

Vasoactive peptides in cardiovascular (patho)physiology

Numerous vasoactive agents play an important physiological role in regulating vascular tone, reactivity and structure. In pathological conditions, alterations in the regulation of vasoactive peptides result in endothelial dysfunction, vascular remodeling and vascular inflammation, which are important processes underlying vascular damage in cardiovascular disease. Among the many vasoactive agents implicated in vascular (patho)biology, angiotensin II (Ang II), endothelin (ET), serotonin and natriuretic peptides appear to be particularly important because of their many pleiotropic actions and because they have been identified as potential therapeutic targets in cardiovascular disease. Ang II, ET-1, serotonin and natriuretic peptides mediate effects via specific receptors, which belong to the group of G-protein-coupled receptors. ET, serotonin and Ang II are primarily vasoconstrictors with growth-promoting actions, whereas natriuretic peptides, specifically atrial, brain and C-type natriuretic peptides, are vasodilators with natriuretic effects. Inhibition of vasoconstrictor actions with drugs that block peptide receptors, compounds that inhibit enzymes that generate vasoactive peptides or agents that increase levels of natriuretic peptides are potentially valuable therapeutic tools in the management of cardiovascular diseases. This review focuses on ET, natriuretic peptides and serotonin. The properties and distribution of these vasoactive agents and their receptors, mechanisms of action and implications in cardiovascular (patho)physiology will be discussed.

Plasma serotonin levels and the platelet serotonin transporter

Serotonin (5HT) is a platelet-stored vasoconstrictor. Altered concentrations of circulating 5HT are implicated in several pathologic conditions, including hypertension. The actions of 5HT are mediated by different types of receptors and terminated by a single 5HT transporter (SERT). Therefore, SERT is a major mechanism that regulates plasma 5HT levels to prevent vasoconstriction and thereby secure a stable blood flow. In this study, the response of platelet SERT to the plasma 5HT levels was examined within two models: (i) in subjects with chronic hypertension or normotension; (ii) on platelets isolated from normotensive subjects and pretreated with 5HT at various concentrations. The platelet 5HT uptake rates were lower during hypertension due to a decrease in Vmax with a similar Km; also, the decrease in Vmax was primarily due to a decrease in the density of SERT on the platelet membrane, with no change in whole cell expression. Additionally, while the platelet 5HT content decreased 33%, the plasma 5HT content increased 33%. Furthermore, exogenous 5HT altered the 5HT uptake rates by changing the density of SERT molecules on the plasma membrane in a biphasic manner. Therefore, we hypothesize that in a hypertensive state, the elevated plasma 5HT levels induces a loss in 5HT uptake function in platelets via a decrease in the density of SERT molecules on the plasma membrane. Through the feedback effect of this proposed mechanism, plasma 5HT controls its own concentration levels by modulating the uptake properties of platelet SERT.

Increased 5-HT contractile response in late pregnant rat myometrium is associated with a higher density of 5-HT2A receptors

The 5-hydroxytryptamine (5-HT) type 2 receptor family is involved in multiple physiological functions in smooth muscle including proliferation, differentiation and contraction. In myometrium, 5-HT2 receptors not only play a role in contraction but also regulate the activity of hypertrophic genes during pregnancy. Here we investigated whether 5-HT2A receptors were up-regulated during gestation and whether changes in expression could be correlated with changes in 5-HT-induced contractions in late pregnant myometrium. 5-HT tension dose-response curves showed that 5-HT-induced myometrial contractility is drastically increased in late pregnancy when compared to non-pregnant conditions. The 5-HT maximum tension (% of 80 mM KCl contracture) increased from 17 +/- 2% in non-pregnant to 54 +/- 7% in late pregnant myometrium. This tension increase took place without significant changes in the 5-HT sensitivity as EC50 values were similar in non-pregnant and late pregnant myometrium (0.11 +/- 0.03 microM and 0.17 +/- 0.02 microM, respectively). The increased 5-HT-induced contraction at the end of pregnancy was associated with up-regulation of 5-HT2A transcript (approximately 5-fold) and protein (approximately 6-fold) levels. These functional and biochemical studies provide evidence that myometrium remodelling during pregnancy is in part associated with up-regulation of 5-HT2A transcript and protein levels resulting in higher 5-HT-induced contractile responses. We conclude that the higher 5-HT-induced contractile response results from a higher density of 5-HT2A receptors having the same properties as in non-pregnant myometrium.

A new signaling paradigm for serotonin: use of Crk-associated substrate in arterial contraction

Crk-associated substrate (CAS), a 130-kDa adaptor protein, was discovered as a tyrosine kinase substrate of Src that was important to cellular motility and actin filament formation. As the tyrosine kinase Src is utilized by the 5-hydroxytryptamine (5-HT)2A receptor in arterial contraction, we tested the hypothesis that CAS was integral to 5-HT2A receptor-mediated vasoconstriction. Rat thoracic aorta was used as a model of the arterial 5-HT2A receptor. Western and immunohistochemistry analyses validated the presence of CAS in the aorta, and tissue bath experiments demonstrated reduction of contraction to 5-HT (13.5 ± 5% control maximum) and the 5-HT2 receptor agonist α-methyl-5-HT (6 ± 2% maximum) by latrunculin B (10−6 mol/l), an actin disruptor. In aorta contracted with 5-HT (10−5 mol/l), tyrosine phosphorylation (Tyr410) of CAS was significantly increased (∼225%), and both contraction and CAS phosphorylation were reduced by the 5-HT2A/2C receptor antagonist ketanserin (3 × 10−8 mol/l). Src is one candidate for 5-HT-stimulated CAS tyrosyl-phosphorylation as 5-HT promoted interaction of Src and CAS in coimmunoprecipitation experiments, and the Src tyrosine kinase inhibitor PP1 (10−5 mol/l) abolished 5-HT-induced tyrosyl-phosphorylation of CAS and reduced 5-HT- and α-methyl-5-HT-induced contraction. Antisense oligodeoxynucleotides delivered to the aorta reduced CAS expression (33% control) and arterial contraction to α-methyl-5-HT (45% of control), independent of changes in myosin light chain phosphorylation. These data are the first to implicate CAS in the signal transduction of 5-HT.

Severe anaphylactic reactions in patients receiving oxaliplatin therapy: a rare but potentially fatal complication

GOALS

The most well-known adverse events of oxaliplatin are hematologic toxicity, gastrointestinal tract toxicity, and sensory neuropathy. However, hypersensitivity reaction of oxaliplatin, especially severe anaphylactic reactions (SAR), was less often reported.

MATERIALS AND METHODS

Three hundred and three patients with colon cancer treated by oxaliplatin-containing chemotherapy in one institution were analyzed. Patients were considered to have oxaliplatin-induced SAR if they suffered from at least one of the following symptoms after oxaliplatin infusion: symptomatic bronchospasm, allergy-related edema/angioedema, unstable blood pressure, or anaphylaxis. The reported cases in published literatures that met our definition were also reviewed.

RESULT

There were 4 out of 303 patients suffering from SAR after receiving oxaliplatin infusion, with an estimated incidence of 1.32%. Two of them became unconscious and had hypertensive crisis, and one patient had consciousness loss with hypotension. All four patients needed various level of oxygen support. Twenty-seven cases of oxaliplatin-induced SAR were found from Medline. Among the 31 reported cases, the most frequent SAR symptom was hypotension. However, we reported two unique SAR cases with hypertension crisis. In only four out of ten cases, patients could tolerate rechallenge of oxaliplatin. There is no association between the occurrence of oxaliplatin-induced SAR and metastatic sites.

CONCLUSION

Oxaliplatin-induced SAR is a rare but potentially fatal complication. Hypertension crisis can be one of the oxaliplatin anaphylactic reactions. Only few patients suffering this complication could tolerate subsequent treatment of oxaliplatin by prolonged infusion time or using a desensitization schedule, thus changing regimen might be a better alternative for them.