Renin-angiotensin system inhibitors in management of hypertension during the COVID-19 pandemic

COVID-19, which is caused by the single-stranded RNA severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), has introduced significant therapeutic dilemmas in several areas. One of these is concern regarding the use of renin-angiotensin system (RAS) inhibitors. Dysfunction of the RAS has been observed in COVID-19 patients, but whether RAS inhibitors, such as angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II type-1 receptor blockers (ARBs), are associated with improved or worse clinical outcomes, remains unclear. RAS inhibitors are currently widely used in the treatment of hypertension. Emerging data suggest an increased association and a heightened mortality in patients of COVID-19 with co-morbidities such as hypertension, coronary heart disease, and diabetes mellitus, particularly in the elderly. Therefore, several recently published research papers have focused on the management of hypertension during the COVID-19 pandemic, as this co-morbidity was found to be the most common in patients with coronavirus infections. SARS-CoV-2 viral surface protein is known to attach angiotensin converting enzyme-2 (ACE-2) on the cell membrane to facilitate viral entry into the cytoplasm. While the SARS-CoV-2 viral load remains the highest in upper respiratory tract of COVID-19 patients, it has also been reported in multiple sites in COVID-19, and patients not infrequently require the Intensive Care Units (ICU) admission. However, despite the theoretical concerns of possible increased ACE2 expression by RAS blockade, there is no evidence that RAS inhibitors are harmful during COVID-19 infection, and indeed they have been shown to be beneficial in some animal studies. In this review we summarise the pathophysiology of the interaction between RAS, ACEIs/ARBs inhibitors and COVID-19, and conclude, on the basis of current data, that RAS blockade should be maintained during the current coronavirus pandemic.

Understanding mitotane mode of action

Adrenocortical carcinoma is a rare disease with poor prognosis. Mitotane is the most effective agent in post-operative treatment (or when inoperable). It selectively limits growth and bioactivity of adrenal tissue. Despite 60 years of use, the basis for its action has yet to be convincingly established. This review summarizes current knowledge of mitotane effects, based on studies on adrenal tissue and primary cell cultures, with emphasis on more recent studies of cell lines. We consider features of the adrenal cortex that might explain mitotane selectivity, and review effects on non-adrenal cells. Since the most clear-cut mitotane effects have been observed for mitochondria, this topic is the core of the review. Mitochondria present unique characteristics in steroidogenic tissue and are known to be important in malignancy development and apoptosis. We look at the evidence for mitotane activation within mitochondria, its impact on mitochondrial energy metabolism and other cellular processes as well as on downstream effects in the cell, such as apoptosis initiation. Further genomic and proteomic investigative studies are likely to yield useful results.

Effects of mitotane treatment on human steroid metabolism: implications for patient management

Mitotane (o,p'-DDD), an oral adrenolytic agent for treatment of advanced adrenocortical carcinoma (ACC), is reported to inhibit cortisol biosynthesis in vitro and enhance production from exogenous cortisol of urinary 6β-hydroxycortisol and unidentified polar unconjugated metabolites. We examined urinary steroid profiles by gas chromatography-mass spectrometry of patients with histologically confirmed ACC following surgery, receiving a) hydrocortisone alone (three males and three females) and b) mitotane and hydrocortisone (six males and 11 females). Samples were collected after plasma mitotane had reached the therapeutic range of 14-20 mg/l. Increased excretion of polar unconjugated steroids during mitotane treatment was confirmed, with 6β-hydroxycortisol and 6β-hydroxy-20-dihydrocortisols predominating. The proportion of additionally hydroxylated metabolites was <2% in untreated controls and 52, 35-52% (mean, range) in the mitotane plus hydrocortisone group. Ratios of 5α-/5β- and 20β-/20α-metabolites of administered cortisol were decreased 50-, 15-fold, and 14-, 8-fold respectively (males, females - mean values) but with no change in metabolite ratios that reflect oxidoreduction at C11 or C20. Patterns of decrease in 5α- relative to 5β-reduced metabolites were similar to those of patients with 5α-reductase 2 deficiency or on treatment with the 5α-reductase 2 inhibitor finasteride but different from those of patients on dutasteride, indicating specific inhibition of 5α-reductase 2. We conclude that mitotane causes consistent changes in cortisol catabolism, most of which have not been previously recognised. These need not interfere with early detection of ACC recurrence. Induction of 6β-hydroxylation offers an explanation for a reported decrease in cortisol bioavailability. Mitotane also has potential as a unique steroid metabolic probe for 20β-reduction.

The molecular pathogenesis of pituitary tumors: implications for clinical management

Pituitary adenomas are unique in several ways, and while they are rarely malignant they may be invasive and/or recurrent. Several attempts have been made to determine the growth potential of pituitary adenomas. Pituitary tumors predominantly arise in a sporadic setting or more rarely as part of hereditary genetic syndromes. Molecular analysis of these familial pituitary adenomas has provided significant insight into pituitary tumorigenesis. Some specific genes have been identified that predispose to pituitary neoplasia, but these are rarely involved in the pathogenesis of sporadic tumors. The number of genes or molecular alterations involved in pituitary tumorigenesis is progressively increasing, providing a hope for development of new predictive and prognostic markers. The aim of this review is to focus on the molecular pathology of pituitary adenomas in the context of their implications on management and targeted therapy. We have summarized our current knowledge on the molecular biology in familial and sporadic pituitary adenomas, and we subsequently focus on prognostic factors as well as specific predictive markers for new promising targeted therapies.

Temozolomide in the management of dopamine agonist-resistant prolactinomas

BACKGROUND

The majority of prolactinomas respond to dopamine agonist therapy, but a proportion are resistant, requiring other treatments including surgery and/or radiotherapy. Temozolomide is an oral chemotherapy agent, which has been used as a salvage therapy to treat aggressive pituitary adenomas and carcinomas, including prolactinomas, unresponsive to all conventional treatment.

CASE SERIES

We report three patients where temozolomide was used in the treatment of refractory prolactinomas. Case 1 describes a patient with a highly invasive prolactinoma, resistant to all conventional therapy, which responded dramatically to temozolomide used as a salvage treatment. In case 2, temozolomide was used after incomplete surgical resection to relieve chiasmal compression and avoid chiasm exposure to radiotherapy. In case 3, temozolomide enabled radiotherapy to be deferred in a 16-year old with a resistant prolactinoma. In all three cases, the tumours were negative by immunostaining for methylguanine methyltransferase (MGMT).

LITERATURE REVIEW AND DISCUSSION

A review of the published literature reveals 51 reported cases of temozolomide treatment for pituitary tumours, including 20 prolactinomas. Fifteen of the 20 prolactinomas showed a good response to temozolomide. Our analysis demonstrates a strong association between MGMT-negative staining and a good response to temozolomide (OR 9.35, P = 0.0030). Current clinical practice is to use temozolomide as a salvage therapy after all conventional modalities of treatment have failed. We suggest that, in selected cases, consideration should be given to using temozolomide earlier in the treatment algorithm.

Repeated colonoscopic screening of patients with acromegaly: 15-year experience identifies those at risk of new colonic neoplasia and allows for effective screening guidelines

OBJECTIVE

It is suggested that patients with acromegaly have an increased risk of colorectal cancer and pre-malignant adenomatous polyps. However, the optimum frequency with which colonoscopic screening should be offered remains unclear.

DESIGN

To determine the optimum frequency for repeated colonoscopic surveillance of acromegalic patients.

METHODS

We retrospectively reviewed the case records of all patients with acromegaly seen in our centre since 1992: 254 patients had at least one surveillance colonoscopy, 156 patients had a second surveillance colonoscopy, 60 patients had a third surveillance colonoscopy and 15 patients had a fourth surveillance colonoscopy.

RESULTS

The presence of hyperplastic or adenomatous polyps was assessed in all patients, while one cancer was detected at the second surveillance. At the third surveillance, mean (+/-s.d.) serum IGF1 levels (ng/ml) in patients with hyperplastic polyps were significantly higher than those with normal colons (P<0.05). The presence of an adenoma rather than a normal colon at the first colonoscopy was associated with a significantly increased risk of adenoma at the second (odds ratio (OR) 4.4, 95% confidence interval (CI) 1.9-10.4) and at the third (OR 8.8, 95% CI 2.9-26.5) screens. Conversely, a normal colon at the first surveillance gave a high chance of normal findings at the second (78%) or third surveillance (78%), and a normal colon at the second colonoscopy was associated with normality at the third colonoscopy (81%).

CONCLUSIONS

Repeated colonoscopic screening of patients with acromegaly demonstrated a high prevalence of new adenomatous and hyperplastic colonic polyps, dependent on both the occurrence of previous polyps and elevated IGF1 levels.

Activation of RAF/MEK/ERK and PI3K/AKT/mTOR pathways in pituitary adenomas and their effects on downstream effectors

Raf/MEK/ERK and phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) cascades are key signalling pathways interacting with each other to regulate cell growth and tumourigenesis. We have previously shown B-Raf and Akt overexpression and/or overactivation in pituitary adenomas. The aim of this study is to assess the expression of their downstream components (MEK1/2, ERK1/2, mTOR, TSC2, p70S6K) and effectors (c-MYC and CYCLIN D1). We studied tissue from 16 non-functioning pituitary adenomas (NFPAs), six GH-omas, six prolactinomas and six ACTH-omas, all collected at transsphenoidal surgery; 16 normal autopsy pituitaries were used as controls. The expression of phospho and total protein was assessed with western immunoblotting, and the mRNA expression with quantitative RT-PCR. The expression of pSer217/221 MEK1/2 and pThr183 ERK1/2 (but not total MEK1/2 or ERK1/2) was significantly higher in all tumour subtypes in comparison to normal pituitaries. There was no difference in the expression of phosphorylated/total mTOR, TSC2 or p70S6K between pituitary adenomas and controls. Neither c-MYC phosphorylation at Ser 62 nor total c-MYC was changed in the tumours. However, c-MYC phosphorylation at Thr58/Ser62 (a response target for Akt) was decreased in all tumour types. CYCLIN D1 expression was higher only in NFPAs. The mRNA expression of MEK1, MEK2, ERK1, ERK2, c-MYC and CCND1 was similar in all groups. Our data indicate that in pituitary adenomas both the Raf/MEK/ERK and PI3K/Akt/mTOR pathways are upregulated in their initial cascade, implicating a pro-proliferative signal derangement upstream to their point of convergence. However, we speculate that other processes, such as senescence, attenuate the changes downstream in these benign tumours.

Clinical significance of apoptotic index in non-small cell lung cancer: correlation with p53, mdm2, pRb and p21WAF1/CIP1 protein expression

PURPOSE

The aim of this study was to assess the prognostic relevance of apoptotic index (AI), considered alone or together with expression of several proteins controlling G1 check point (p53, mdm2, pRb and p21WAF1/CIP1) in non-small cell lung cancer (NSCLC) patients.

METHODS

Study group included 50 NSCLC patients who underwent curative pulmonary resection. Apoptosis was detected with the use of TUNEL technique and AI was defined as the number of apoptotic cells per 1,000 tumor cells. The expression of p53, mdm2, pRb and p21WAF1/CIP1 was assessed immunohistochemically.

RESULTS

The mean and median AI calculated for all 50 patients was 14 and 9, respectively. Patients with lower (<14) and higher (> or =14) AI constituted 35 (70%) and 15 (30%) of cases, respectively. AI was not correlated with patient clinical characteristics, and expression of p53, pRb and p21WAF1/CIP1 . However, lower AI was correlated with over-expression of mdm2 protein (P=0.04). Median survival for patients with lower and higher AI was 43 months and 22 months, respectively, and 5-year survival probability-60 and 25%, respectively (P=0.03). In multivariate analysis, the only variable associated with shortened survival was AI (P=0.03, HR=2.9, 95% CI 1.95-3.86).

CONCLUSIONS

These results suggest that AI correlates with mdm2 protein expression and influences survival in NSCLC.

Prognostic relevance of proliferating cell nuclear antigen and p53 expression in non-small cell lung cancer

Prognostic value of p53 and PCNA expression in non-small cell lung cancer (NSCLC) remains controversial. In this study we determined the relevance of these abnormalities in terms of overall survival and disease-free survival in 95 NSCLC patients who underwent curative pulmonary resection. Expression of p53 was found in 44 samples (45%), expression of PCNA-in 79 samples (83%), and expression of both markers-in 35 samples (36%). There was no relationship between expression of either protein and major clinicopathological characteristics. Median survival for patients with and without p53 expression was 36 and 33 months, respectively and 5-year survival probability-29 and 37%, respectively (P=0.73). Median survival for patients with and without PCNA expression was 36 and 27 months, respectively and 5-year survival probability-35 and 25%, respectively (P=0.60). There was no significant difference in overall survival between particular groups of patients with tumors carrying four possible p53/PCNA phenotypes. In multivariate analysis including patient age, sex, tumor stage, tumor type and differentiation, p53 and PCNA expression, the only variable important for survival was stage of disease. These results suggest the lack of prognostic relevance of p53 and PCNA expression in surgically treated NSCLC patients.

CGP 41251, a new potential anticancer drug, improves contractility of rat isolated cardiac muscle subjected to hypoxia

The aim of the present work was to examine the effects of 4'-N-benzoyl staurosporine (CGP 41251), a protein kinase C inhibitor with broad antiproliferative activity in many cell lines, on the rat isolated heart contractility under normoxic and hypoxic conditions. Additionally, we examined the effects of CGP 41251, WB-4101 (alpha1a -adrenoceptor antagonist), chloroethylclonidine (CEC) (alpha1b-adrenoceptor antagonist) and selective damage of endocardial endothelium by Triton X-100 on the protection against hypoxia induced by preconditioning of rat heart tissue. Experiments were performed on rat isolated left ventricular papillary muscle. The following parameters were measured: force of contraction (Fc), velocity of contraction (+dF/dt) and velocity of relaxation (-dF/dt). The temperature of the bath solution was 37 degrees C +/- 0.5 degrees C, and rate of electrical stimulation was 0.5 Hz. At concentrations less than 1 microM CGP 41251 did not cause any changes in contractility of rat heart. At 1 and 3 microM, significant positive inotropic action was observed. Treatment of rat papillary muscle by CGP 41251 at 3 microM reduced decreasing of contractility by simulated hypoxia and reperfusion. Moreover, protective effects of preconditioning was not affected by addition of CGP 41251 neither at 1 nor at 3 microM. Pretreatment with CEC at 3 microM, and selective damage of endocardial endothelium induced by fast (1-s) immersion of papillary muscle in 0.5% Triton X-100, but not pretreatment with WB-4101, abolished the protective effects of preconditioning. The results imply that CGP 41251 improves contractility of heart muscle under normoxic and hypoxic conditions, and does not alter hypoxic preconditioning in rat isolated cardiac tissue. Moreover, it was shown that alpha1b-adrenoceptors and endocardial endothelium are involved in triggering of preconditioning in rat isolated heart muscle.

Experimental hyperlipidemia prevents the protective effect of ischemic preconditioning on the contractility and responsiveness to phenylephrine of rat-isolated stunned papillary muscle

This study was designed to establish a hyperlipidemic diet (significant increase in the cholesterol and triglycerides blood levels, but without atherogenic changes in heart muscle and coronary vessels) and to investigate the influence of experimental hyperlipidemia on the effects of ischemic preconditioning (PC) of rat-isolated papillary muscle on the time course of contractility during simulated ischemia and reperfusion and responsiveness to phenylephrine under such a condition. The animals were divided in four experimental groups: standard diet-fed control group (SD), SD underwent ischemic preconditioning (SD-PC), hyperlipidemic diet-fed group (HLD) and HLD underOFFt PC (HLD-PC). Force of contraction (Fc), velocity of contraction (+dF/dt), and velocity of relaxation (-dF/dt) were measured. HLD preparations were more sensitive to ischemia then SD ones. PC, performed by 5-min perfusion with no-substrate solution gassing with 95% N2/5% CO2 in the presence of fast electrical stimulation, and 10 min of reperfusion with normal solution and rate of stimulation, significantly increased the resistance of isolated cardiac tissues to simulated ischemia in SD-PC group, but not in HLD-PC group. Negative inotropic action of phenylephrine occured in SD group of preparations after simulated-ischemia/reperfusion period was also prevented by PC. Therefore, we conclude that experimental hyperlipidemia significantly influenced the function of rat heart muscle including the higher sensitivity to ischemia and different reaction to the same PC procedure.

4-Aminopyridine induces positive lusitropic effects and prevents the negative inotropic action of phenylephrine in the rat cardiac tissue subjected to ischaemia

The effects of 4-aminopyridine (4-AP) at concentration of 1 mM on the contractility of rat isolated papillary muscle subjected to simulated ischaemia has been evaluated. Additionally, the effects of 4-AP on the phenylephrine inotropic action (a selective agonist of alpha1-adrenergic receptor) on rat isolated cardiac tissue underwent simulated ischaemia and reperfusion was studied. Experiments were performed on rat isolated papillary muscles obtained from left ventricle. The following parameters have been measured: force of contraction (Fc), velocity of contraction (+dF/dt), velocity of relaxation (-dF/dt) and the ratio between time to peak contraction (ttp) and relaxation time at the level of 10% of total contraction amplitude (tt10) as an index of lusitropic effects. Simulated ischaemia lasting 45 min was induced by replacement of standard normoxic solution by no-substrat one gassing with 95% N2/5%CO2. Although 4-AP exerted a slight, but significant positive inotropic action itself, pretreatment with 1 mM of this compound significantly depressed a recovery of Fc and +dF/dt, but improves recovery of -dF/dt in the rat papillary muscle during reperfusion as compared with control group of preparations. Moreover, the paradoxical negative inotropic action of phenylephrine observed in rat stunned papillary muscle was prevented in preparations previously treated by 4-AP. These findings suggest that an inhibition of outward K+ current (probably transient outward and rapid component of delayed rectifying currents at 1 mM of 4-AP) aggravates ischaemia-induced failure in contractility but prevents changes in alpha1-adrenergic receptor signaling pathway occuring during ischaemia.

The influence of experimental hyperlipidemia on the time course of contractility during simulated ischaemia and reperfusion and responsiveness to phenylephrine of rat heart papillary muscle

The aim of this study was to examine the influence of simulated ischaemia on the contractility and responsiveness to phenylephrine of rat isolated papillary muscle in standard diet fed (SD) and hyperlipidemic diet fed (HLD) rats. The following parameters were measured: force of contraction (Fc), rate of rise (+dF/dt) and rate of fall (-dF/dt) of force of contraction, time to peak contraction (ttp) and relaxation time at 10% of total amplitude of contraction (tt10). The baseline values of Fc and +dF/dt, but, not -dF/dt, were significantly lower in HLD group than in SD group. Tissues from HLD rats were more sensitive to ischaemia regarding Fc, +dF/dt and -dF/dt. Moreover, reprefusion completely reversed the effects of ischaemia only in SD rats, but not in HLD rats, regarding Fc and +dF/dt. In contrast, a recovery of -dF/dt during reperfusion occurred only in the HLD group. In SD rats, phenylephrine (10 and 30 microM) had no effect on the contractility or induced megative inotropic effects (100 and 300 microM). Propranolol (1 microM), a non-selective blocker of beta-adrenoceptors, had no effects on this action. Chloroethylclonidine (CEC) (1 microM), a selectivw blocker of alpha 1b-adrenoceptor subtype, but not WB-4101(2-((2,6-dimethoxyphenoxyethyl)amino-methyl-1,4-benzodioxane), a selective blocker of alpha 1a adrenoceptor subtype, abolishes the negative inotropic action of phenylephrine. In HLD rats, phenylephrine had positive inotropic action (10 and 30 microM). The results indicate that hyperlipidemic diet in rats leads to the suppression of force of contraction and velocity of contraction, but not velocity of relaxation of isolated heart muscle. Under such a condition, heart muscle is more sensitive to ischaemia, but has better responsiveness to phenylephrine after ischeamia-reperfusion period.

Different aspects of the effects of thapsigargin on automatism, contractility and responsiveness to phenylephrine in cardiac preparations from rats and guinea pigs

Sarcoplasmic reticulum (SR) Ca(2+)-ATPase play a very important role in excitation-contraction coupling in the heart. The effects of thapsigargin (TG), a selective inhibitor of SR Ca(2+)-ATPase in the heart muscle, on automatism and contractility of the rat and guinea pig heart were examined. Experiments were performed on isolated right auricula and right ventricle papillary muscle. The following parameters were registered: force of contraction (Fc); rate of rise of force (+dF/dt); rate of fall of force (-dF/dt); time to peak contraction (ttp); duration of relaxation phase of contraction at the level of 10% of total amplitude (tt10); and automatism (b.p.m.). Additionally, the influence of thapsigargin on the effects of phenylephrine on the above mentioned parameters were studied. It was found that TG (1 microM) decreased only the automatism in rat heart, but increased automatism and ttp duration and decreased Fc in guinea pig heart. The positive force-frequency relation in the guinea pig heart was attenuated. The effects of phenylephrine in the rat heart were not significantly different before and after pretreatment with TG. Alternatively, pretreatment with TG exerted a profound influence on the effects of phenylephrine in the guinea pig heart. The results indicate that TG has different effects on the guinea pig and rat hearts. The reason for this could be due to species differences, i.e. the weaker crossing of TG through the membrane of rat myocytes or a different mechanism of Ca2+ homeostasis in rat and guinea pig hearts.