Direct vascular effects of HMG-CoA reductase inhibitors

Several studies have demonstrated that any beneficial effect of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins) on coronary events are linked to their hypocholesterolemic properties. However, since mevalonic acid (MVA), the product of the enzyme reaction, is the precursor of numerous metabolites, inhibition of HMG-CoA reductase has the potential to result in pleiotropic effects. MVA and other intermediates of cholesterol synthesis (isoprenoids) are necessary for cell proliferation and other important cell functions, hence effects other than cholesterol reduction may help to explain the antiatherosclerotic properties of statins. Recently, we provided in vitro evidence that fluvastatin, simvastatin, lovastatin, cerivastatin, but not pravastatin, dose-dependently decrease smooth muscle cells (SMC) migration and proliferation, independently of their ability to reduce plasma cholesterol. Moreover, statins are able to reduce the in vitro cholesterol accumulation in macrophages, by blocking cholesterol esterification and endocytosis of modified lipoproteins. This in vitro inhibition was completely prevented by the addition of mevalonate and partially by all-trans farnesol and all-trans geranylgeraniol, confirming the specific role of isoprenoid metabolites--probably through a prenylated protein(s)--in regulating these cellular events. The inhibitory effect of lipophilic statins on SMC proliferation has been recently shown in different models of proliferating cells such as cultured arterial myocytes and rapidly proliferating carotid and femoral intimal lesions in rabbits. Finally, ex vivo studies recently showed that sera from fluvastatin-treated patients interfere with smooth muscle cell proliferation. These results suggest that HMG-CoA reductase inhibitors exert a direct antiatherosclerotic effect in the arterial wall, beyond their effects on plasma lipids, that could translate into a more significant prevention of cardiovascular disease.

Pharmacological control of the mevalonate pathway: effect on arterial smooth muscle cell proliferation

The mevalonate (MVA) pathway is involved in cell proliferation. We investigated drugs acting at different enzymatic steps on rat aorta smooth muscle cell (SMC) proliferation. Competitive inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase (0.1-10 microM) dose-dependently decreased (up to 90%) SMC proliferation. This effect was prevented by 100 microM MVA, 10 microM all-trans farnesol (F-OH) and 5 microM all-trans geranylgeraniol (GG-OH), precursors of protein prenyl groups, but not by 2-cis GG-OH, precursor of dolichols, squalene and ubiquinone. The same inhibitory effect was obtained with 6-fluoromevalonate (1-50 microM), an inhibitor of MVA-pyrophosphate decarboxylase. Partial recovery of cell proliferation was possible by all-trans F-OH and all-trans GG-OH, but not MVA. Squalestatin 1 (1-25 microM), a potent squalene synthase inhibitor, blocked cholesterol synthesis and slightly inhibited (21% decrease) SMC proliferation only at the highest tested concentration. NB-598 (1-10 microM), a potent squalene epoxidase inhibitor, blocked cholesterol synthesis without affecting SMC proliferation. Finally, the benzodiazepine peptidomimetic BZA-5B (10-100 microM), a specific inhibitor of protein farnesyltransferase, time- and dose-dependently decreased SMC proliferation (up to 62%) after 9 days. This effect of BZA-5B was prevented by MVA and all-trans GG-OH, but not by all-trans F-OH. SMC proliferation was not affected by the closely related compound BZA-7B, which does not inhibit protein farnesyltransferase. Altogether, these findings focus the role of the MVA pathway in cell proliferation and call attention to the involvement of specific isoprenoid metabolites, probably through farnesylated and geranylgeranylated proteins, in the control of this cellular event.

[Pharmacological control of biosynthesis pathway of mevalonate: effect on the proliferation of arterial smooth muscle cells]

The role of mevalonic acid (MVA) and its products (isoprenoids) in cell proliferation prompted us to investigate the effect of drugs affecting diverse enzymatic steps of the MVA pathway on rat aorta smooth muscle cell (SMC) proliferation. Competitive inhibitors of HMG-CoA reductase (statins) decreased SMC proliferation in a dose-dependent manner. The inhibitory effect induced by simvastatin 3.5 microM (70% +/- 3.8 decrease) was prevented by addition of 100 microM MVA, (100% +/- 2.3), 10 microM farnesol (F-OH) (85% +/- 1.2) and 5 microM of all-trans geranylgeraniol (GG-OH) (precursor of prenylated proteins) (81% +/- 1.1), but not by 2-cis GG-OH (precursor of dolichols), squalene and ubiquinone. The same inhibitory effect was obtained with 6-fluoromevalonate (1-50 microM), an inhibitor of MVA-PP decarboxylase. Squalestatin 1 (1-25 microM) and NB-598 (1-10 microM), potent squalene synthase and epoxidase inhibitors, respectively, caused a complete inhibition of cholesterol synthesis without affecting SMC proliferation. Finally, BZA-5B (10-50 microM) a specific inhibitor of protein farnesyl tranferase (PFTase), inhibited SMC proliferation in a dose- (10-50 microM) and time-dependent manner, reaching 52% +/- 6.3 inhibition after 9 days, in the presence of 50 microM BZA-5B, without affecting cholesterol synthesis. This effect was partially prevented by mevalonate (76% +/- 3.2) and GG-OH (87% +/- 7.3) but not by F-OH. On the other hand, SMC proliferation was not affected by the closely related compound BZA-7B (93% +/- 4), which does not inhibit PFTase. Taken together, these findings support the involvement of specific isoprenoid metabolites, probably through farnesylated and geranylgeranylated proteins in cell proliferation.

Antimicrobial prophylaxis with ceftriaxone in neurosurgical procedures. A prospective study of 100 patients undergoing shunt operations

Shunt infection is a major complication of shunt implantation, with Staphylococcus epidermidis found in almost 45% of infected shunts. This pathogen produces an extracellular slime that enables it to adhere to implantable devices and resist antibiotic therapy. Antimicrobial prophylaxis can prevent slime production. In this paper we report the results of a prospective study involving 100 shunt operations. The objective was to evaluate the efficacy of a single preoperative dose of ceftriaxone (2 g, i.v.) in preventing shunt infection. Ceftriaxone was chosen for its pharmacokinetic properties. No shunt infection was observed over a 4-year follow-up period. On the basis of these results we recommend prophylaxis with ceftriaxone as a safe and effective way of preventing shunt infection. In addition, one-shot prophylaxis with ceftriaxone is more cost-effective than multiple-dose antibiotic regimens.

Effect of the new HMG-CoA reductase inhibitor cerivastatin (BAY W 6228)on migration, proliferation and cholesterol synthesis in arterial myocytes

The major relation existing between cell growth, migration and cholesterol homeostasis prompted us to investigate the effect of the new 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor cerivastatin (BAY W 6228) on these cellular events. The molecule inhibited in a dose-dependent manner the migration and the replication (evaluated as cell number and nuclear incorporation of 3H-thymidine) of rat arterial SMC with IC50 values of 2.7 microM and 0.5 microM, respectively. Among the tested statins BAY W 6228 resulted to be the most potent inhibitor of cholesterol synthesis and cell proliferation. Conditions producing 80-90% inhibition of cholesterol synthesis correlate with approximately 50% inhibition of cell growth. Similar results were obtained in SMC from human femoral artery. The in vitro inhibition of cell migration and proliferation induced by BAY W 6228 (80% decrease) was completely prevented by the addition of mevalonate and partially prevented (60-80%) by farnesol and geranylgeraniol, confirming the specific role of isoprenoid metabolites-probably through a prenylated protein(s)-in regulating these cellular events. The present results provide evidence that BAY W 6228 interferes, at least in vivo, with smooth muscle cells migration and proliferation, major processes involved in atherogenesis.

[The pharmacology of the statins: the evidence of a direct antiatherosclerotic action]

With the increasing knowledge on the pathogenesis of atherosclerosis, it appears that the prevention of cardiovascular disease in the future will involve, besides risk factor correction, direct pharmacological control of processes occurring in the arterial wall. Among them, a pivotal role is played by smooth muscle cell migration and proliferation that, together with lipid deposition, are prominent features of atherogenesis and restenosis after angioplasty. Mevalonate and other intermediates (isoprenoids) of cholesterol synthesis are essential for cell growth, hence drugs affecting this metabolic pathway are potential antiatherosclerotic agents. Recently we provided evidence that fluvastatin, simvastatin, lovastatin, but not pravastatin, dose-dependently decrease smooth muscle cell migration and proliferation, independently of their hypocholesterolemic properties. The in vitro inhibition of cell migration and proliferation induced by simvastatin and fluvastatin (70-90% decrease) was completely prevented by the addition of mevalonate and partially (80%) by farnesol and geranylgeraniol, confirming the specific role of isoprenoid metabolites--probably through prenylated proteins--in regulating these cellular events. The present results provide evidence that HMG-CoA reductase inhibitors interfere directly with processes involved in atherogenesis--beyond their effects on plasma lipids--partially through local inhibition of isoprenoid biosynthesis.

[Ceftriaxone prophylaxis in cerebrospinal fluid shunts. Motivation and results of the choice of prophylaxis with this cephalosporin in 100 patients]

Staphylococcus epidermidis is a bacterial organism found in almost 75% of such shunts becoming infected. This is due to its production of an extracellular slime responsible of adherence to implantable devices and resistance to antibiotic therapy. Use of antimicrobial prophylaxis prevents production of such slime. In 100 shunt operations the A. used antimicrobial prophylaxis with ceftriaxone (2 g before operation). Follow up of 3 years showed no shunt infection. Choice of ceftriaxone was due to its pharmacokinesis.

Splenic haemodynamics and portal hypertension in patients with liver cirrhosis and spleen enlargement

The relationships between portal hypertension and spleen enlargement, in patients with liver cirrhosis, are not clearly defined; as well as those between splenic haemodynamics and portal hypertension. In 25 cirrhotics with spleen enlargement and portal hypertension and in seven controls, the following parameters were determined: estimated splenic volume (ESV) from the radiographic view of the spleen, according to Blendis, Williams and Kreel (1969), specific splenic blood-flow (SSBF), total splenic blood-flow (TSBF), porto-hepatic gradient (PHG), specific splenic resistance (SSR) and total splenic resistance (TSR). Moreover, the size and extension of oesophageal varices, at oesophagoscopy, were classified according to Dagradi (1973). PHG, ESV and TSBF were increased in all subjects, SSBF was increased in two cases, SSR was increased in two cases and decreased in two cases, TSR was decreased in all cases and ESV was not correlated to the level of portal hypertension. Neither TSBF nor TSR were found to be correlated to the level of portal hypertension, as estimated by PHG or by oesophageal varices. It is concluded that, in patients with liver cirrhosis and spleen enlargement, splenomegaly is likely to be the consequence of pulp hyperplasia and not of passive congestion, and that increases in splenic blood-flow do not contribute significantly to portal hypertension.

[Effect of somatostatin on splanchnic hemodynamics in liver cirrhosis]

The effect of somatostatin on splanchnic haemodynamics in patients with liver cirrhosis is not clearly defined, as some Authors reported a decrease in portal pressure and in liver blood flow during i.v. administration of this hormone, while others did not. In 19 subjects with liver cirrhosis and portal hypertension the following parameters were measured before and during i.v. infusion of somatostatin (7.5 micrograms/min): porto-hepatic gradient, effective hepatic plasma flow, specific splenic blood flow, cardiac output. Moreover the gastrin-G-17 plasma levels, those of insulin and growth hormone were measured. Effective hepatic plasma flow decreased significantly during somatostatin infusion (P less than 0.05), averaging a 15% decrease. Porto-hepatic gradient, specific splenic blood flow, cardiac output did not vary significantly. Gastrin, insulin and growth hormone plasma levels decreased significantly (P less than 0.02, 0.01, 0.05). These data indicate that somatostatin infused at the dose of 7.5 micrograms/min provokes endocrine effects, but as far as the splanchnic circulation is concerned, it induces a slight decrease in liver blood flow without affecting portal hypertension.

Surgical treatment of cerebrospinal fluid otorrhea. Translabyrinthine approach in posterior petrous bone fractures

The authors intend to define the treatment of cerebrospinal fluid otorrhea according to the type of fracture involving the petrous bone. Fractures of the petrous bone causing cerebrospinal fluid otorrhea can be classified in two types: (1) fractures extending anteriorly toward the anterior foramen lacerus; (2) fractures extending posteriorly through the labyrinth to the internal auditory meatus. The former usually resolve spontaneously; the latter, because of different anatomy and embryogenesis, require a surgical procedure using a translabyrinthine approach.