Hypertension and pregnancy-related hypertension

Motherhood: What every ophthalmologist needs to know

The aim of this review article is to summarize the available literature on physiologic and pathologic ocular changes during pregnancy and the effect of diseases in pregnancy. A literature search was conducted using PUBMED, MEDLINE, and Cochrane library in English. In addition, the cited references in the published articles were manually reviewed for the relevant results. Pregnancy encompasses a multitude of changes in all body systems, including the visual system of the female. The changes can be physiological, i.e., changes occurring in the lids and adnexa, cornea, conjunctiva, changes in tear film composition and intraocular pressure, retina, choroid, and visual field. Pathological changes in a pregnant woman's eye include changes related to preeclampsia and eclampsia, central serous chorioretinopathy, retinal artery or vein occlusions, and disseminated intravascular coagulation. Preexisting diseases like diabetic retinopathy, Graves' disease, idiopathic intracranial hypertension, various inflammatory conditions can undergo changes in their course during pregnancy. Ophthalmic medications can have an effect on both mother and the baby and hence should be used cautiously. In addition, intrauterine infections play a major role in causing inflammation in the eye of the baby. Hence, vaccination of the mother prior to pregnancy plays an important role in preventing intrauterine infections in the neonate. A regular eye examination in the perinatal period plays a vital role in recognizing ophthalmic pathologies which might require a prompt medical intervention. Pathological ocular diseases should be discriminated from physiologic changes to establish an individualized treatment or preventive plan. This approach to ocular benefits of treatment to the mother should always weigh against the potential harm to the fetus.

Differential expression of serum GBP-28, NBP-Cyc 3 and TIMP-1 complicates pregnancy in hypertensive disorder pregnancy

The current study is aimed at analyzing the correlation and differential expression of three entities namely, TIMP metallopeptidase inhibitor-1 (TIMP-1), a glycoprotein, serum adipokine (GBP-28), an amino acid protein and neuroendocrine basic polypeptide NBP-cystatin3 (NBP-Cyc 3) in HDP (Hypertensive Disorders complicating Pregnancy). A total of 63 patients, diagnosed with HDP at the study hospital during the study period, was placed under treatment (HDP) group. While healthy group had a total of 50 women with normal pregnancy during the same period. Both these groups were compared in terms of GBP-28, TIMP-1 and NBP-Cyc 3 levels. Further, the author also checked the correlation, diagnostic value and prognosis for the three factors and HDP. There was a significant increase observed in the expression levels of serum TIMP-1 and NBP-Cyc 3 in HDP during ELISA compared to GB. However, HDP group recorded low value of serum GBP-28 than healthy group (all P < 0.001). There is a relationship between the expressions of GBP-28, TIMP-1 and NBP-Cyc 3 and the abnormalities in lipid and glucose metabolisms, resulting in severe clinical conditions among HDP patients. The inference from spearman correlation analysis is that serum GBP-28 and the severity of HDP are negatively correlated. While Serum TIMP-1 and NBP-Cyc 3 had a positive correlation with the severity of HDP (all P < 0.001). When diagnosing HDP, the AUC values of both GBP-28 and NBP-Cyc 3 single diagnosis were above 0.8. Multivariate conditional logistic regression was deployed to assess the risk factors associated with HDP. The results listed the independent risk factors such as GBP-28, TIMP-1 and NBP-Cyc 3 and disease severity for the prognosis of HDP. Among HDP patients, upregulated expressions of serum TIMP-1and NBP-Cyc 3 were observed while in case of GBP-28, it was vice versa. The significant role, played by GBP-28, TIMP-1 and NBP-Cyc 3 in the progression of HDP, makes these entities potential serum biomarkers in diagnosis and assessment of HDP.

Posterior reversible encephalopathy syndrome in the setting of trauma: A case report

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Posterior reversible encephalopathy syndrome (PRES) in the setting of trauma and acute care surgery.

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Posterior reversible encephalopathy syndrome (PRES) in trauma patients with a specific pattern of neuroimaging and clinical symptoms.

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T2 weighted diffusion hyperintensities were present on MRI of the brain in both cases.

Reports of posterior reversible encephalopathy syndrome (PRES) in the setting of trauma and acute care surgery are scarce. PRES presents rapidly with a variety of symptoms including headaches, visual disturbances, altered consciousness, and seizures. It is associated with acute hypertensive episodes. PRES is diagnosed with a specific neuroimaging pattern and a constellation of clinical symptoms. This case report presents two traumatically injured patients with one confirmed case of PRES and the other with a potential case of PRES. The diagnosis was made through neuroimaging showing patchy T2 and diffusion hyperintensity in the periphery of both occipital lobes and adjacent cerebellar hemispheres on MRI in one case. The other case highlights extensive stable white matter disease without evidence of acute infarct on MRI, as well as diminished attenuation within the cerebral white matter in the occipital lobes on CT scan. There was resolution of visual symptoms in one patient while the other patient's neurologic status did not allow for evaluation of symptom resolution. This report aims to emphasize the possibility of PRES in trauma patients with a specific pattern of neuroimaging and clinical symptoms, and to increase the index of suspicion in acute care providers.

[Posterior reversible encephalopathy syndrome and arterial hypertension]

OBJECTIVE

To identify a correlation between systolicdiastolic blood pressure (BP) and severity of clinical/radiological presentations in patients with posterior reversible encephalopathy syndrome (PRES).

MATERIAL AND METHODS

Clinical and paraclinic data of patients with PRES hospitalized in the Republican Clinical Hospital, Kazan in 2010-2018 were analyzed. Nineteen patients were found, all of them were women, aged 18-67 years, mean age 33.50±15.03 years. Clinical and paraclinic data included anamnesis, neurological examination, neuroimaging, first measurements of systolic and diastolic BP after symptoms'onset.

RESULTS AND CONCLUSION

Diastolic BP values can be associated with the incidence of depression of consciousness, systolic BP values - with the number of damaged structures. In total, BP is the significant factor implemented in the presence of endothelial dysfunction that defines the severity of encephalopathy.

Correlation between maternal anxiety, reactivity of fetal cerebral circulation to auditory stimulation, and birth outcome in normotensive and gestational hypertensive women

This study investigated the correlation between maternal anxiety and blood flow changes through the fetal middle cerebral artery (MCA) after defined acoustic stimulation in 43 normotensive (C) and 40 gestational hypertensive (GH) subjects. Neonatal outcomes (gestational age at birth, Apgar score, birth weight) in the C and GH groups were analyzed. State (STAI-S) and trait (STAI-T) anxiety was assessed using Spielberger's questionnaire. The MCA blood flow was assessed once between 28 and 41 weeks of gestation using color Doppler ultrasound before and after application of defined acoustic stimulus. Relative size of the Pulsatility index (Pi) change (RePi) was calculated. The general hypotheses were: (1) women in GH group would have higher anxiety; (2) higher anxiety correlates with higher RePi change and poorer neonatal outcome; (3) fetuses from the GH group would have poorer neonatal outcome. Subjects from the GH group had higher STAI-T and RePi compared to the C group. A positive correlation between RePi and STAI-S, STAI-T, and systolic/diastolic blood pressure was found in both groups. There were more preterm deliveries in the GH group compared to the C group. A significant effect of STAI-T on body weight was observed in the C and GH group. There was a predictive effect of STAI-T and RePi on the C group, and STAI-S, STAI-T, diastolic blood pressure, and RePi on the GH group in terms of neonatal body weight. This study demonstrates an association between antenatal anxiety in GH women and increased fetal cerebral circulation in response to defined auditory stimulation.

Reversible posterior leukoencephalopathy syndrome following combinatorial cisplatin and pemetrexed therapy for lung cancer in a normotensive patient: A case report and literature review

Reversible posterior leukoencephalopathy syndrome (RPLS) is a rare neurological syndrome of the brain, causing symptoms such as headaches, seizures, altered mental status and visual disturbances. The condition is predominantly associated with hypertension, eclampsia, renal impairment, cytotoxic drugs, immunosuppressive agents and molecular targeted agents, but the precise underlying mechanism of RPLS is not fully understood. The present study describes the case of a 65-year-old female patient with stage IIA non-small cell lung cancer who received cisplatin/pemetrexed treatment at the Leo W. Jenkins Cancer Center. Following 3 cycles of this therapy, the patient was referred to the Emergency Department of Vidant Medical Center with an altered mental status, subsequently presenting with epileptic seizures, a fever and a headache. A neurological examination revealed generalized hyperreflexia and paraparesis, with extensor posturing of the bilateral lower extremities. The lumbar puncture and electroencephalography results were normal, but cranial computed tomography (CT) scans revealed attenuation abnormalities in the bilateral parietal region and the left occipital lobe, with suspected metastasis. Cranial T2-weighted magnetic resonance imaging (MRI) indicated bilateral regions of increased signal intensity in the occipital, temporal and periventricular white matter. The patient was treated with anticonvulsants, steroids and antihypertensive drugs, recovered gradually from the symptoms and regained full consciousness. However, the patient reported residual weakness, presenting with an Eastern Cooperative Oncology Group score of 3, reflective of an inability to independently perform daily activities and self-care. A brain MRI performed 10 days later demonstrated that the subcortical edema had partially subsided. The patient was discharged on day 15 post-admission. A follow-up cranial CT examination 1 month later indicated a partial resolution of the abnormalities. The present report reviews similar associated cases, and also discusses the clinical features and mechanisms underlying RPLS. Although it is typically reversible, RPLS is a serious and potentially life-threatening adverse condition if left untreated. Early recognition of this condition is crucial for the prompt control of the patient's blood pressure or withdrawal of cytotoxic drugs in order to reverse this syndrome.

Bilateral Vision Loss after Delivery in Two Cases: Severe Preeclampsia and HELLP Syndrome

Two patients with no symptoms of hypertension in their medical history before pregnancy were referred to the obstetrics emergency clinic with hypertension and visual complaints. After physical examination and laboratory tests, one of the patients was diagnosed with severe preeclampsia while the other was diagnosed with HELLP syndrome (Hemolysis-Elevated Liver enzymes-Low Platelets). Ocular examinations were performed after delivery due to the patients’ worsening visual complaints. The severe preeclamptic patient showed bilateral serous retinal detachment (SRD) while the patient with HELLP syndrome showed bilateral macular hemorrhage. Systemic blood pressure control was advised. The patients’ ocular findings and visual acuities improved in the follow-up periods. SRD and macular hemorrhage can be observed in patients with preeclampsia and HELLP syndrome as a result of the disruption of retinal and choroidal vasculature.

Permanent Bilateral Vision Loss in Eclamptic Posterior Reversible Encephalopathy Syndrome

Posterior reversible encephalopathy syndrome (PRES) classically consists of reversible vasogenic oedema in the posterior circulation territories, which is reversible both clinically and radiologically in the majority of patients after the control of hypertension. The authors describe a 27-year-old eclamptic patient with PRES in accelerated hypertension who revealed permanent vision loss associated with bilateral Purtscher retinopathy. One of the two competing theories that explain vasogenic brain oedema in PRES is excessive autoregulation leading to the dilation of cerebral arterial vessels, particularly in the occipito-parietal vasculatures. Dysfunction of endothelial cells that results in constriction of vessels has also been hypothesised as a cause of PRES. The concurrence of bilateral vaso-occlusive retinopathy and PRES supports the hypothesis that vasoconstriction is a more plausible mechanism of vasogenic oedema in PRES.

Outcomes in hypertensive disorders of pregnancy in the North Indian population

INTRODUCTION

Hypertensive disorders complicating pregnancy seriously endanger the safety of the mother and fetus during pregnancy. Very few studies have explored hypertensive disorders of pregnancy in India, even though this disease has been associated with adverse maternal and perinatal outcomes. This study aimed to analyze the disease pattern and risk factors associated with the disorder and assess the maternal and fetal outcomes in cases of hypertensive disorders of pregnancy.

SUBJECTS AND METHODS

This case-control study was carried out over 1 year from 2011 to 2012 at the Department of Obstetrics and Gynecology, King George's Medical University, Lucknow, Uttar Pradesh, India. A total of 149 patients were enrolled in the study. As seven were lost to follow-up, analysis was carried out on 142 cases. Patients were further classified according to the National High Blood Pressure Education Program Working Group (2000) as having mild preeclampsia (65 cases), severe preeclampsia (32 cases), or eclampsia (45 cases). Thirty-one healthy pregnant non-hypertensive women were enrolled into the study as controls.

RESULTS

The most common manifestation was edema, seen in 90% of cases. Proteinuria was also relatively common, 26.76% of patients with proteinuria of ≥300 mg/24 hours, 47.88% with proteinuria of ≥2 g/24 hours, and 25.35% with a urinary protein excretion of 3-5 g/24 hours. Central nervous system involvement was observed in 42.2% of cases, elevated bilirubin levels in 47.0%, visual symptoms in 6.4%, vaginal bleeding in 11.3%, and HELLP (hemolysis, elevated liver enzymes, and low platelet count) syndrome was reported in 2.80%. Maternal deaths occurred in 2.8% of cases, all of which were from the eclampsia group. Stillbirths occurred in 16.9% of cases, and overall neonatal death observed in 4.23% of cases.

CONCLUSION

Women with hypertensive disorders of pregnancy were more prone to adverse maternal and fetal outcomes than normotensive pregnant women, but we observed a decreasing trend in the present study compared with that reported in other studies, which might be due to the increased number of hospital deliveries that occurred in our study.

The Effect of Glyceryl Trinitrate on Hypertension in Women with Severe Preeclampsia, HELLP Syndrome, and Eclampsia

OBJECTIVE

The goal of this study is to evaluate the effect of glyceryl trinitrate (GTN) in the management of hypertension in women with preeclampsia, eclampsia, and HELLP syndrome.

STUDY DESIGN

Fifty five women with preeclampsia, eclampsia, and HELLP syndrome administered GTN infusion for the management of hypertension were studied. Demographic, clinical, and perinatal outcome findings were collected for analyses. We recorded initial and maintenance doses of GTN, and duration of its use in prepartum and postpartum periods. We collected systolic and diastolic blood pressures (BPs) at admission and before the administration of GTN infusion. During the GTN infusion, we calculated average diastolic and systolic blood pressures 6 hours apart on the first day, 12 hours apart on the second day, and 24 hours apart on the third day.

RESULTS

Of 55 women, 24 with severe preeclampsia, 16 with HELLP syndrome, and 15 with eclampsia were included in this study. In severe preeclampsia group, GTN infusion significantly reduced systolic and diastolic BPs beginning from the second quarter and third quarter, respectively, of first day (p < 0.05). In the HELLP syndrome group, GTN infusion significantly decreased systolic and diastolic blood pressures beginning from the third quarter and second quarter, respectively, of the first day (p < 0.05). In the eclampsia group, GTN infusion significantly reduced systolic and diastolic blood pressures beginning from the third quarter and first quarter, respectively, of the first day (p < 0.05).

CONCLUSION

In women with severe preeclampsia, eclampsia, and HELLP syndrome, infusion of GTN can be used as an alternative agent to well-known drugs and causes no significant adverse effect to the mother and fetus.

Are platelets activated after a rapid, one-step density gradient centrifugation? Evidence from flow cytometric analysis

This procedure describes the preparation of platelets from whole blood of healthy donors and pregnancy-induced hypertensive (PIH) patients by a rapid, one-step density gradient centrifugation, and the direct immunofluorescence staining of obtained platelets (CD63). Platelets are relatively fragile structures. Consequently, for the investigation of their biochemical properties it is recommended to isolate them by a simple method that does not damage their functional parameters and induce their activation. During platelet activation, several changes occur at the platelet surface. CD63 is the receptor for a lysosomal glycoprotein expressed in activated platelets. Currently, flow cytometry (fluorescence-activated cell sorting) is the most sensitive method to detect increased surface exposure of activation antigens on the platelet surface. The present technical note describes that compared with other whole blood flow cytometric techniques, our one-step density-gradient centrifugation method using OptiPrep can also prevent artificial, sample manipulation-related platelet activation.

The possible role of prolactin in preeclampsia: 2001, a hypothesis revisited a quarter of century later

A genetic predisposition (theory 1) to preeclampsia in a woman with or without risk factors, may lead to an immune maladaptation to pregnancy (theory 2) (Th1 type of immune response predominance over Th2). In turn, they may contribute to an early defective 'switch' (quantitatively or out of timing) with a predominant decidual production of 16-kDa PRL over that of a 23-kDa PRL (our hypothesis), which induces an antiangiogenic process with a shallow invasion of the spiral arteries by the endovascular cytotrophoblast. Afterwards, a high-resistance arteriolar system and placental ischemia or hypoxia ensue, leading to endothelial cell dysfunction (theory 3) and an increased oxidative stress (theory 4). We are not proposing any strict chronological sequence of events, but the early occurrence (first 10 weeks) during pregnancy of the predominant decidual secretion of a 16-kDa PRL over that of 23-kDa PRL inducing a defective angiogenic process. No other specific mechanism(s) to explain the 'shallow' invasion of the spiral arteries has been previously proposed. Furthermore, it seems to happen early enough in pregnancy, as a 'very early change which may give a clue to the etiology,' as first suggested 25 years ago by Horrobin.

An exploratory study of fetal behavior at 33 and 36 weeks gestational age in hypertensive women

The relationship between maternal blood pressure (BP) and fetal behaviors as well as differential spontaneous and vibroacoustic elicited fetal behaviors were examined in hypertensive (n = 21) compared to normotensive (n = 22) women at 33 and 36 weeks gestational age (GA). Maternal BP was negatively related to GA at birth and birth weight. On average, fetuses of hypertensive women were born 2 weeks earlier (38 weeks GA) and 340 g lighter. Maternal systolic BP was negatively related to the number of spontaneous body movements observed on ultrasound scan over 20 min and the magnitude of the fetal heart rate (FHR) acceleration elicited by a vibroacoustic stimulus. At 36 weeks GA, vibroacoustic stimulation elicited differential responding with fetuses in the hypertensive compared to the normotensive group having fewer body movements, a lower magnitude of FHR acceleration, and a lack of cardiac-body movement coupled responses. These findings suggest a relationship between maternal BP and fetal behaviors and differential functional development of sensory-motor response systems which need to be characterized in the subgroups of hypertensive disorders observed during pregnancy.

Fas and Fas ligand expression in maternal blood and in umbilical cord blood in preeclampsia

The Fas-Fas ligand (FasL) pathway of apoptosis is abnormally activated in diseases associated with impaired immune tolerance or chronic inflammation. Pregnancy-related hypertension is a spectrum of disease that commonly causes significant morbidity in women and in their newborn infants, is associated with generalized inflammation, and may be causally related to impaired maternal-fetal tolerance. Our recent observation of enhanced trophoblast expression of FasL in one form of pregnancy-related hypertension led us to hypothesize that this group of disorders might be associated with abnormal activation of the Fas-FasL pathway. To test this hypothesis, we prospectively quantified soluble and leukocyte-associated Fas receptor and FasL in the maternal and umbilical cord blood (CB) sera of 20 gestations complicated by preeclampsia and of 18 normal control gestations, using ELISA and flow cytometric analyses. We determined higher soluble FasL levels in paired maternal and CB sera of hypertensive gestations compared with control gestations (p < 0.01); in contrast, soluble Fas levels were similar between groups. Surface expression of FasL was lower on maternal (p < 0.01) and CB (p < 0.05) neutrophils from affected gestations, whereas surface Fas expression was lower on maternal (p < 0.02), but not CB, neutrophils and lymphocytes. We conclude that expression of Fas and FasL in sera and on leukocytes is altered in gestations complicated by preeclampsia, and speculate that activation of the Fas-FasL pathway mediates associated pathologic processes in affected women and in their neonates.

Inspiratory flow limitation during sleep in pre-eclampsia: comparison with normal pregnant and nonpregnant women

Self-reported snoring is common in pregnancy, particularly in females with pre-eclampsia. The prevalence of inspiratory flow limitation during sleep in preeclamptic females was objectively assessed and compared with normal pregnant and nonpregnant females. Fifteen females with pre-eclampsia were compared to 15 females from each of the three trimesters of pregnancy, as well as to 15 matched nonpregnant control females (total study population, 75 subjects). All subjects had overnight monitoring of respiration, oxygen saturation, and blood pressure (BP). No group had evidence of a clinically significant sleep apnoea syndrome, but patients with pre-eclampsia spent substantially more time (31+/-8.4% of sleep period time, mean+/-SD) with evidence of inspiratory flow limitation compared to 15.5+/-2.3% in third trimester subjects and <5% in the other three groups (p=0.001). In the majority of preeclamptics, the pattern of flow limitation was of prolonged episodes lasting several minutes without associated oxygen desaturation. As expected, systolic and diastolic BPs were significantly higher in the pre-eclamptic group (p<0.001), but all groups showed a significant fall (p< or =0.05) in BP during sleep. Inspiratory flow limitation is common during sleep in patients with pre-eclampsia, which may have implications for the pathophysiology and treatment of this disorder.

Elevated levels of S-nitrosoalbumin in preeclampsia plasma

The availability of nitric oxide (NO), which is required for the normal regulation of vascular tone, may be decreased in preeclampsia, thus contributing to the vascular pathogenesis of this pregnancy disorder. Because ascorbate is essential for the decomposition of S-nitrothiols and the release of NO, we speculated that the ascorbate deficiency typical of preeclampsia plasma might result in decreased rates of decomposition of S-nitrosothiols. We tested the hypothesis that total S-nitrosothiol and S-nitrosoalbumin concentrations are increased in preeclampsia plasma, reflecting a decreased release of NO from these major reservoirs of NO. Gestationally matched plasma samples were obtained (before labor or intravenous MgSO(4)) from 21 women with preeclampsia and 21 women with normal pregnancy, and plasma samples were also obtained from 12 nonpregnant women of similar age and body mass index during the follicular phase of the menstrual cycle. All were nonsmokers. The assay included ultraviolet-induced decomposition of S-nitrosothiols to liberate NO captured by a florigenic reagent, 4,5-diaminofluoresceine, to produce diaminofluoresceine-Triazole. Preeclampsia plasma contained significantly higher concentrations of total S-nitrosothiols (11.1+/-2.9 nmol/mL) than normal pregnancy samples (9.4+/-1.5 nmol/mL). Even greater differences were found between preeclampsia plasma and plasma samples from normal pregnancies and nonpregnant women (294+/-110, 186+/-25, and 151+/-25 pmol/mg protein, respectively) when S-nitrosothiol content was expressed per milligram protein. The albumin fraction contained 49.4% of total plasma S-nitrosothiols in the control samples and 53.7% and 56.8% of plasma S-nitrosothiols in normal pregnancy and preeclampsia, respectively. The level of S-nitrosoalbumin was significantly higher in preeclampsia than in normal pregnancy or nonpregnancy plasma (6.3+/-1.4, 5.1+/-0.7, and 4.2+/-1.0 nmol/mL, respectively). The increased concentration of S-nitrosoalbumin in preeclampsia almost completely accounted for the increased levels of S-nitrosothiols in total plasma. Due to combined increases in nitrosothiols and decreases in protein, the preeclampsia plasma concentration of S-nitrosoalbumin was greatly increased on a per milligram of protein basis (271% and 186% compared with normal nonpregnancy and normal pregnancy plasma, respectively). We conclude that S-nitrosoalbumin and total S-nitrosothiol concentrations are significantly increased in preeclampsia plasma and may reflect insufficient release of NO groups in this condition.

Posterior leukoencephalopathy syndrome

Posterior leukoencephalopathy syndrome is a newly recognised brain disorder that predominantly affects the cerebral white matter. Oedematous lesions particularly involve the posterior parietal and occipital lobes, and may spread to basal ganglia, brain stem, and cerebellum. This rapidly evolving neurological condition is clinically characterised by headache, nausea and vomiting, seizures, visual disturbances, altered sensorium, and occasionally focal neurological deficit. Posterior leukoencephalopathy syndrome is often associated with an abrupt increase in blood pressure and is usually seen in patients with eclampsia, renal disease, and hypertensive encephalopathy. It is also seen in the patients treated with cytotoxic and immunosuppressive drugs such as cyclosporin, tacrolimus, and interferon alfa. The lesions of posterior leukoencephalopathy are best visualised with magnetic resonance (MR) imaging. T2 weighted MR images, at the height of symptoms, characteristically show diffuse hyperintensity selectively involving the parieto-occipital white matter. Occasionally the lesions also involve the grey matter. Computed tomography can also be used satisfactorily to detect hypodense lesions of posterior leukoencephalopathy. Early recognition of this condition is of paramount importance because prompt control of blood pressure or withdrawal of immunosuppressive agents will cause reversal of the syndrome. Delay in the diagnosis and treatment can result in permanent damage to affected brain tissues.

Endothelial dysfunction and hypertensive vasoconstriction

A change in endothelial function is a common phenomenon in patients with essential hypertension and in animals with hypertension, whether primary or induced by a salt-rich diet. In hypertensive subjects, there may be a change in the synthesis, or the effect, of nitric oxide. Nevertheless, hypertensive vasoconstriction is at present associated, above all, with the degradation of this mediator by free radicals, such as the superoxide anion, released in the dysfunctional vascular endothelium. These radicals are also formed when hypoxanthine is turned into xanthine, and when the latter becomes uric acid, both having been catalysed by the enzyme xanthine oxidase. In physiological conditions, the concentration of superoxide radicals remains low within the organism as a result of its reaction with the superoxide dismutase enzyme. However, in pathological situations, such as arterial hypertension, there may be an increase in the production of these radicals or a deficiency of the superoxide dismutase enzyme. In hypertensive patients, the release of vasoconstrictor peroxides derived from the activity of cyclo-oxygenase in the endothelium and the vascular smooth muscle is also important. The excess free radicals released by the dysfunctional endothelium also stimulate the synthesis of these contracting agents. Moreover, it should not be forgotten that endothelin-1, which is similarly synthesized and released in the vascular endothelium, is the most powerful known endogenous vasoconstrictor. This peptide would therefore play a prominent part in some forms of hypertension. Although no changes in endothelin plasma levels have been found in essential hypertension, there may be an increase in its local concentration. It should be borne in mind that endothelin could strengthen the effect of other vasoconstrictors. Moreover, it may also provoke the release of free radicals and of cyclo-oxygenase-derived vasoconstrictor factors. The latest theories therefore indicate that the increase in vasoconstriction, which characterizes arterial hypertension, is associated with a greater production of free radicals. At the present time, antioxidant agents and xanthine oxydase-inhibiting compounds are being used to treat hypertension and other pathologies linked to endothelial dysfunction. In addition, it is thought that the therapeutic benefit of some anti-hypertensive drugs, such as calcium antagonists and angiotensin-converting enzyme inhibitors, could be in part due to the inhibition of the production of free radicals that they provoke.