Cationic liposome-mediated E1A gene transfer to human breast and ovarian cancer cells and its biologic effects: a phase I clinical trial

PURPOSE

Preclinical studies have demonstrated that the adenovirus type 5 E1A gene is associated with antitumor activities by transcriptional repression of HER-2/neu and induction of apoptosis. Indeed, E1A gene therapy is known to induce regression of HER-2/neu-overexpressing breast and ovarian cancers in nude mice. Therefore, we evaluated the feasibility of intracavitary injection of E1A gene complexed with DC-Chol cationic liposome (DCC-E1A) in patients with both HER-2/neu-overexpressing and low HER-2/neu-expressing breast and ovarian cancers in a phase I clinical trial.

PATIENTS AND METHODS

An E1A gene complexed with DCC-E1A cationic liposome was injected once a week into the thoracic or peritoneal cavity of 18 patients with advanced cancer of the breast (n = 6) or ovary (n = 12).

RESULTS

E1A gene expression in tumor cells was detected by immunohistochemical staining and reverse transcriptase-polymerase chain reaction. This E1A gene expression was accompanied by HER-2/neu downregulation, increased apoptosis, and reduced proliferation. The most common treatment-related toxicities were fever, nausea, vomiting, and/or discomfort at the injection sites.

CONCLUSION

These results argue for the feasibility of intracavitary DCC-E1A administration, provide a clear proof of preclinical concept, and warrant phase II trials to determine the antitumor activity of the E1A gene.

Effects of N-methyl-L-arginine on cardiac and regional blood flow in a dog endotoxin shock model

PURPOSE

Indirect evidence suggests a decrease in organ perfusion as a result of nitric oxide (NO) inhibition in endotoxic shock. Cardiac and regional hemodynamic responses to N-methyl-L-arginine (L-NMA), a nonspecific inhibitor of constitutive and inducible nitric oxide synthase (NOS), were assessed in nine conscious dogs subjected to endotoxin.

MATERIALS AND METHODS

Lipopolysaccharide (LPS) was titrated to a maximum of 200 microg/kg, IV, over 45 minutes. L-NMA was given in a dose of 20 mg/kg, IV. Hemodynamic parameters were recorded for 6 hours following L-NMA administration.

RESULTS

LPS induced significant decreases in mean arterial blood pressure (MAP), cardiac output (CO), first derivative of left ventricular pressure (dP/dt), coronary blood flow, carotid blood flow, mesenteric blood flow, renal blood flow, and a significant hepatic vasodilation. L-NMA fully reversed the effects of LPS on MAP, heart rate, dP/dt, coronary and carotid blood flow, and reversed mesenteric blood flow and hepatic blood flow at 1 and 3 hours, respectively. L-NMA partially overcame the LPS-induced decrease in renal blood flow at 30 minutes and 1 hour. Except for mesenteric and carotid circulation, L-NMA did not change regional vascular resistance.

CONCLUSIONS

It is likely that constitutive NOS is implicated in immediate cardiac, carotid, mesenteric, and renal vascular changes, whereas inducible NOS accounted for delayed responses in hepatic and coronary circulation.

Strategies to reduce side effects of interleukin-2: evaluation of the antihypotensive agent NG-monomethyl-L-arginine

PURPOSE

The clinical utility of high-dose intravenous recombinant interleukin (IL)-2 therapy is limited by severe toxicity including hypotension, fever, chills, pulmonary edema, and oliguria Hypotension has been previously shown to result from excessive vascular relaxation due to overproduction of the endogenous vasodilator nitric oxide. Nitric oxide production can be decreased by administration of the competitive enzyme inhibitor NG-monomethyl-L-arginine (NMA). A clinical trial to investigate the dose-dependent effects of NMA on blood pressure was undertaken in patients with metastatic renal cell carcinoma.

PATIENTS AND METHODS

Patients with metastatic renal cell carcinoma receiving a 5-day continuous infusion of IL-2 (18 million IU/m2/d) who developed hypotension were treated with increasing doses of NMA, ranging from 3 to 36 mg/kg.

RESULTS

Twenty-three patients received a total of 61 courses of IL-2; 18 of these patients developed hypotension and received NMA. Antihypotensive activity was observed at all dose levels, and the duration of the effect varied directly with the dose of NMA. At the higher dose levels tested (12 to 36 mg/kg), increased pulmonary vascular resistance and decreased cardiac output were observed. Patients experiencing a significant decrease in cardiac output received dobutamine (2.5 to 10 microg/kg/min). Pulmonary capillary wedge pressure was unaffected by administration of NMA. One patient treated at 24 mg/kg (bolus) experienced a major motor seizure, but no neurologic disorders were observed in other patients treated with NMA doses of 24 to 36 mg/kg. No other adverse events involving hepatic, renal, or hematologic systems were attributed to NMA. Three patients received NMA by an initial bolus followed by a continuous infusion. Similar antihypotensive effects were noted, and these patients were able to complete a full 5-day course of IL-2.

CONCLUSION

The antihypotensive effects of NMA appear to be optimal at a dose of 24 mg/kg, with maintenance doses of 8 mg/kg every 4 to 6 hours. At this dose level, blood pressure was restored, and IL-2-associated vasodilatation was fully reversed. Coincident with the reversal of hypotension, the state of high cardiac output was also reversed by NMA administration. These results suggest that NMA may be effective for alleviating the hypotensive effects of high-dose IL-2 therapy in cancer patients.

The role of nitric oxide in interleukin-2 therapy induced hypotension

Nitric oxide is an uncharged free radical that mediates a range of physiologic processes in the vasculature. As a principal determinant of vascular tone, the overproduction of nitric oxide has been implicated in the pathogenesis of sepsis- and cytokine-induced hypotension. The enzyme that produces nitric oxide, nitric oxide synthase, exists in three isoforms. One of the three isoforms, inducible nitric oxide synthase, is expressed in many cell types only after stimulation by cytokines and/or endotoxin. Compared to the constitutive nitric oxide synthase enzymes, the inducible enzyme generates larger quantities of nitric oxide for longer periods. Expression of the inducible isoform in vitro requires stimulation by a mixture of cytokines including interferon-gamma, tumor necrosis factor-alpha, and interleukin-1 beta. These proinflammatory cytokines are known mediators of sepsis and are also produced in the serum of cancer patients during interleukin-2 therapy, thereby leading to excessive production of nitric oxide. Interleukin-2 therapy is associated with a spectrum of cardiovascular toxicities and hemodynamic alterations that are indistinguishable from those seen in septic shock. Many of these hemodynamic effects have been linked to the overproduction of nitric oxide via a cytokine-inducible nitric oxide pathway. In this regard, inhibition of nitric oxide synthesis represents a novel approach to limit the cardiovascular toxicity associated with interleukin-2 therapy and to improve its therapeutic index. Clinical trials to evaluate the efficacy of nitric oxide synthase inhibitors in reversing the hypotension associated with IL-2 therapy are now underway.

Drug-induced vasodilation in an in vitro and in vivo study: the effects of nicardipine, papaverine, and lidocaine on the rabbit carotid artery

Extreme arterial vasoconstriction (vasospasm) is a common problem encountered in microvascular surgery. An ideal pharmacologic tool able to counteract ischemia during microsurgery should be easy to apply and exert its action both locally and distally in the microcirculation of the flap. We have compared in vitro and in vivo vascular properties of nicardipine, papaverine, and lidocaine in the rabbit carotid artery. In vitro, rings from the rabbit carotid artery (n = 7) were bathed in Krebs-Ringers solution and stretched progressively to an optimal tension of 3.7 to 4.2 g. The specimens were contracted with norepinephrine (1 microM), and a cumulative dose response curve was established. In vivo, microvascular anastomoses were performed bilaterally in the rabbit carotid artery in 35 animals using 9-0 nylon suture and standard microsurgical techniques. During and after the anastomoses, nicardipine (0.1, 0.01 mg topical, or 0.1 mg/hour IV), papaverine (30 mg/cc topical), and lidocaine (2% with and without epinephrine) were applied (blinded) at the anastomotic site in five rabbits each. Heparinized sodium chloride was used as topical irrigation for control and to clean the anastomosis. Blood flow changes were monitored continuously with the transonic Doppler for 30 minutes after the procedure. The systemic blood pressure was also monitored in a group of pilot experiments. A documented decrease in blood flow was noted in all animals after the microvascular anastomosis. Nicardipine and papaverine evoked a concentration-dependent relaxation to precontracted rings to norepinephrine. Nicardipine was greater than papaverine in inducing relaxation. Lidocaine demonstrated a biphasic response with low concentrations potentiating contraction. Systemic nicardipine and papaverine significantly increased the blood flow in the rabbit carotid artery. Topical application of nicardipine and lidocaine did not significantly alter the blood flow; however, the application of nicardipine demonstrates a trend toward increased flow. Lidocaine with epinephrine significantly decreased the blood flow. No drug was found to alter the blood pressure of the animals. Our results demonstrate that nicardipine and papaverine seem to be pharmacologic tools able to increase the blood flow in anastomotic arteries. In contrast, the use of 2% lidocaine as a spasmolytic agent should be re-evaluated, since this substance may act as a partial agonist.

Design of nitric oxide synthase inhibitors and their use to reverse hypotension associated with cancer immunotherapy

It is now just 10 years since it was first appreciated that NO is endogenously synthesized in mammals. In this period, two constitutive and one inducible isoform of NOS have been isolated, sequenced, and characterized with respect to their protein chemistry and catalytic mechanism. A wide variety of NOS inhibitors, most targeted to the arginine binding site in the oxygenase domain, have been synthesized and used to elucidate the physiological and pathophysiological roles of NO. It is now clear that NO is involved in signal transduction (e.g., in neurotransmission and blood pressure homeostasis), and that these roles are mediated by low concentrations of NO synthesized by nNOS or eNOS. The NO receptor is the heme cofactor of soluble isoform of guanylyl cyclase. Higher amounts of NO, typically but not always synthesized by iNOS, are often cytotoxic. At a minimum, high concentrations of NO derange the signal transduction pathways normally served by nNOS or eNOS. In addition, NO or its nitrosative products (RSNO, N2O3, or ONOO-) inhibit or damage cellular constituents, interfering with DNA synthesis, energy metabolism, and the structural integrity of the cell. Such cytotoxicity can be beneficial to the host if pathogens or tumor cells are destroyed, but is detrimental to the host if it results in inappropriate inflammation, hypotension, or immunosuppression. Therapeutic utility of NOS inhibitors has been demonstrated in sepsis and cytokine-induced hypotension; additional applications are being identified in a treatment of inflammatory and autoimmune disorders.

Nitric oxide and shock

Shock can be defined as the failure of the circulatory system to provide necessary cellular nutrients, including oxygen, and to remove metabolic wastes. Although it is now recognized that more than 100 different forms of shock exist, this recognition is more a reflection of the widespread use of the term to describe a variety of disease states. For the purpose of this monograph, we concentrate on various forms of cardiovascular shock, in particular, shock that may be linked to inappropriate vasodilation from overproduction of the endogenous vasodilator, nitric oxide. Some forms of shock have been extensively studied, and convincing evidence exists for the role of nitric oxide. Other disease states have been less well characterized in terms of their association with excess nitric oxide production. Available evidence of a role for nitric oxide is discussed in the hope of stimulating the interest of investigators to explore these areas more thoroughly.

Beneficial versus detrimental effects of nitric oxide synthase inhibitors in circulatory shock: lessons learned from experimental and clinical studies

Septic shock is a physiological derangement of the cardiovascular system characterized by pathological vasodilation. Recent studies have established a role for nitric oxide, previously known as endothelium-derived relaxing factor, in the vascular dysfunction of sepsis. This finding suggests that inhibition of nitric oxide synthase (NOS), the enzyme responsible for nitric oxide production, could be a target for therapeutic intervention. Animal studies have provided conflicting results, demonstrating both beneficial and detrimental effects. We provide here an overview of the preclinical studies of NOS inhibitors and an update of the clinical studies. The low toxicity and marked antihypotensive activity of NOS inhibitors in humans highlight some of the drawbacks of certain animal models and provide important insights into the experimental study of septic shock.

Tetrahydrobiopterin synthesis inhibitors induce nitric oxide synthesis in rat aorta

1. Incubation of rato aortic rings with tetrahydrobiopterin synthesis inhibitors (NAS or DAHP) significantly decreased contractions to phenylephrine. These two compounds significantly potentiated the vascular hyporeactivity induced by endotoxin. Inhibitors of nitric oxide synthesis (NLA or MLA) restored the contractile responses to this alpha 1-agonist in NAS- or DAHP-treated control rings and abolished the NAS- or DAHP-induced increased hyporeactivity to PE in endotoxin-treated aortic rings. These observations suggest that treatment of isolated blood vessels with BH4 synthesis inhibitors induces the production of NO.synthesis, resulting in turn in a vascular hyporeactivity to PE potentiated in endotoxin-treated preparations.

Potent inhibition of inducible nitric oxide synthase by geldanamycin, a tyrosine kinase inhibitor, in endothelial, smooth muscle cells, and in rat aorta

We have examined whether specific protein tyrosine kinase (PTK) inhibitors (genistein, tyrphostin, or geldanamycin) prevent nitric oxide (NO.) production in rat smooth muscle cells (SMC), in murine brain endothelial cells (MBE), and in isolated rat aortas treated with endotoxin (LPS) and/or cytokines. Tyrphostin failed to inhibit either the release of nitrite in both endothelial and smooth muscle cells or vascular hyporeactivity in rat aorta, caused by immunostimulants. Genistein decreased nitrite production in MBE only at high concentration but had no effect on nitrite production in SMC and on the hypocontractility in aortic rings. In contrast, low concentrations of geldanamycin abolished the release of nitrite in MBE and in SMC treated with endotoxin and/or cytokines. Geldanamycin inhibited also the hypocontractility to phenylephrine in aortic rings treated with LPS or interleukin-1. This inhibitor failed to inhibit the release of nitrite and the vascular hyporeactivity once nitric oxide synthase (NOS) was induced by immunostimulants whereas methyl-L-arginine, an inhibitor of NOS, had significant effects. These data suggest that LPS- and cytokines-induced NO. production initiate a common signaling pathway involving a PTK that is inhibited by geldanamycin but not or slightly by tyrphostin or genistein at a point that precedes the induction of NOS.

Nitric oxide: moving towards the clinic

This meeting showed how the surge of research in the field of NO biology has led to novel therapeutic approaches in multiple clinical disciplines. Some approaches have already advanced towards clinical applications. Continued research efforts will undoubtedly lead to new applications.

Cardiac and regional hemodynamic interactions between halothane and nitric oxide synthase activity in dogs

BACKGROUND

In vitro, halothane appears to affect the role played by nitric oxide in the regulation of vascular tone and cardiac function. In vivo, the results of the interactions between halothane and the nitric oxide pathway remain controversial. The authors investigated the effects of halothane on the cardiac and regional hemodynamic properties of N-methyl-L-arginine (NMA), a specific nitric oxide synthase inhibitor, in dogs.

METHODS

Twenty-five dogs were chronically instrumented. Aortic pressure, the first derivative of left ventricular pressure, cardiac output, heart rate, and carotid, coronary, mesenteric, hepatic, portal and renal blood flows were continuously recorded. N-methyl-L-arginine was infused intravenously at 20 mg/kg over 1 min in awake dogs (n = 11) and in 1.2% halothane-anesthetized dogs (n = 10). As a control group, the remaining four dogs were studied awake and during 1.2% halothane for 2 h in the absence of NMA.

RESULTS

In awake dogs, NMA produced a sustained pressor response (34%) and systemic vasoconstriction (40%) associated with a decrease in cardiac output (16%). Regional circulation changes included an immediate and transient increase in carotid (43%) and coronary (237%) blood flows and a subsequent decrease in carotid blood flow (25%). Hepatic and mesenteric blood flows also decreased, by 43% and 16%, respectively. Except for the coronary circulation, regional vascular resistance increased significantly. Halothane did not affect the pressor response to NMA but did blunt the cardiac output changes. Consequently, the systemic vasoconstriction after nitric oxide synthase inhibition was of shorter duration and of lesser magnitude during halothane anesthesia. Halothane also blunted the carotid, mesenteric, and renal vasoconstriction induced by NMA. Finally, in 1.2% halothane-anesthetized dogs, NMA induced a coronary vasoconstriction.

CONCLUSIONS

Halothane minimally interferes with the systemic and regional hemodynamic consequences of nitric oxide synthase blockade. The nature and magnitude of the interaction depend on the territory in which they occur.

Changes in regional hemodynamics after nitric oxide inhibition during ovine bacteremia

We studied the action of nitric oxide synthase (NOS) inhibition on changes in regional blood flow during a continuous infusion of live bacteria. Eighteen ewes were chronically instrumented. After a 7-day recovery period, an infusion of 10(6) colony-forming units/min Pseudomonas aeruginosa was begun. At 24 h, cardiac output increased significantly above baseline in all groups (5.9 +/- 0.4 vs. 8.2 +/- 0.6 l.min 1.m-2), systemic vascular resistance decreased (1,362 +/- 120 vs. 821 +/- 145 dyn.g.cm-5.m-2), and cerebral, cephalic mesenteric, and hindlimb blood flows increased. The animals were then equally and randomly assigned to a bolus of a NOS inhibitor, either 25 mg/kg N omega-nitro-L-arginine methyl ester (L-NAME) or 20 mg/kg N omega-monomethyl-L-arginine (L-NMMA), followed by a continuous infusion of 7 mg.kg-1.min-1 L-NMMA or saline. After NOS inhibition, cardiac index decreased [5.6 +/- 0.1 (L-NAME) and 5.5 +/- 0.4 l.min-1.m-2 (L-NMMA)] and remained significantly decreased for 12 h. 1-NAME decreased carotid and mesenteric blood flows to 64% of the preseptic baseline, and they remained below baseline for 20 h. L-NMMA decreased blood flows only to preseptic baseline values. NOS inhibitors may affect blood flows independently of their hemodynamic effects.

Escalated MVAC with or without recombinant human granulocyte-macrophage colony-stimulating factor for the initial treatment of advanced malignant urothelial tumors: results of a randomized trial

PURPOSE

Hematopoietic growth factors have been shown to ameliorate the side effects of chemotherapy. Here we assess the ability of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) to increase the dose-intensity and reduce the side effects of escalated methotrexate, vinblastine, doxorubicin, and cisplatin (MVAC) chemotherapy.

PATIENTS AND METHODS

A prospective randomized trial to compare escalated MVAC versus escalated MVAC with rhGM-CSF was conducted. All patients were treated at The University of Texas M.D. Anderson Cancer Center (UTMDACC) and had a metastatic or unresectable urothelial tumor. Forty-eight patients were randomized (25 to MVAC with rhGM-CSF and 23 to escalated MVAC alone). The clinical characteristics of the study populations were similar (ie, degree of tumor dissemination and performance status).

RESULTS

The dose-intensity in the two arms of the study did not differ significantly. No difference in the frequency of bacteriologically documented infections occurred between the two study arms.

CONCLUSION

The use of the hematopoietic growth factor rhGM-CSF did not result in an increased dose-intensity of escalated MVAC. The inability to increase the dose-intensity of MVAC further was a result of nonhematologic side effects of the chemotherapy. Escalation of treatment delivered at its median-tolerated dose is unlikely to result in additional therapeutic benefit for patients with common solid tumors. Future development of therapy may require the development of new agents or concepts, rather than modification of existing therapies.

Characterization of the effects of two new arginine/citrulline analogues on constitutive and inducible nitric oxide synthases in rat aorta

1. New potent inhibitors of nitric oxide synthase (NOS) may be useful in the treatment of septic shock, a disorder characterized by a vascular hyporeactivity to catecholamines caused by an overproduction of nitric oxide (NO-). We examined the effects of L-thiocitrulline (L-TC) and S-methyl-L-thiocitrulline (L-SMTC), novel NOS inhibitors, on the constitutive and inducible NOS in rat aorta and compared those effects with inhibition due to NG-methyl-L-arginine (L-NMA). 2. Phenylephrine evoked similar concentration-contraction curves in the control rings and in the rings treated with these different NOS inhibitors (10 microM), whereas 100 microM of L-NMA, L-TC or L-SMTC increased significantly, and to a similar extent, contractions evoked by phenylephrine in aortic rings with endothelium without significantly affecting the maximal responses. 3. Relaxations evoked by acetylcholine, adenosine triphosphate, or calcium ionophore were significantly inhibited in a dose-dependent manner by L-NMA, L-SMTC, or L-TC (10-100 microM). The potencies of these inhibitors in reducing the relaxations of these vasodilators were not significantly different. 4. In endotoxin-treated preparations with endothelium, the three L-arginine analogues (10 microM) significantly potentiated contractile responses to phenylephrine (pEC50: 6.73 +/- 0.12 and 7.3 +/- 0.12, 7.34 +/- 0.13, or 7.22 +/- 0.14; in the absence and the presence of L-NMA, L-TC, or L-SMTC respectively) and increased maximal contractions from 1.53 +/- 0.15 g to 1.95 +/- 0.13 g, 2.08 +/- 0.12 g, and 2.03 +/- 0.13 g with L-NMA, L-TC, and L-SMTC respectively. A higher concentration of these NOS inhibitors (100 microM)further increased contractions evoked by this alpha1-agonist without further enhancing the maximal contractions; however, contractions evoked by 10 nM phenylephrine were significantly greater in the presence of L-SMTC or L-TC than in the presence of L-NMA (100 microM) (L-NMA: 0.4 +/- 0.11 g; L-TC:0.78 +/- 0.14 g and L-SMTC: 0.82+/-0.17 g). The effects of these inhibitors on NO- synthesis induced by endotoxin were significantly reversed by addition of L-arginine (1 mM) but not by L-citrulline (1 mM). InLPS-treated rings with endothelium, all three NOS inhibitors (100 microM) shifted the concentration contraction curves evoked by phenylephrine significantly to the left (pEC5o: 7.19 +/- 0.03 and 7.79 +/- 0.08,8.01 +/- 0.07, or 8.02 +_ 0.07, in the absence and the presence of L-NMA, L-TC, or L-SMTC, respectively)and increased significantly maximal contractions from 2.05 +/- 0.05 g to 2.38 +/- 0.14 g, 2.5 +/- 0.12 g, and 2.4 +_ 0.21 g with L-NMA, L-TC, and L-SMTC, respectively. L-TC and L-SMTC were significantly more potent than L-NMA in potentiating contractions evoked by 10 nM and 30 nM phenylephrine.5. L-TC and L-SMTC produced dose-dependent increases in tone in LPS-treated aortic rings with and without endothelium. In LPS-treated rings with endothelium, L-NMA induced contractions but in preparations without endothelium low concentrations of L-NMA induced small contractions while high concentrations of this inhibitor evoked relaxations. In both preparations L-TC and L-SMTC were significantly more potent than L-NMA in increasing vascular tone.6. These results suggest that L-SMTC, L-TC and L-NMA were equipotent on basal and agonist stimulated NO- synthesis produced by the constitutive isoform of NOS, whereas the two new L-arginine analogues were more potent than L-NMA in inhibiting the production of NO- induced by endotoxin in rat aorta.

NG-methyl-L-arginine, an inhibitor of nitric oxide synthase, reverses interleukin-2-induced hypotension

OBJECTIVE

To evaluate the role of NG-methyl-L-arginine as a modulator of the hyperdynamic shock induced by the administration of interleukin-2 (IL-2).

DESIGN

A prospective, pilot clinical study.

SETTING

Intensive care unit of a tertiary care center.

PATIENTS

Three sequential patients with metastatic renal cell carcinoma who developed hypotension during their first course of treatment with high-dose IL-2 (18 x 10(6) IU/m2/day by continuous infusion for 5 days).

INTERVENTIONS

Upon developing hypotension during their subsequent therapy with IL-2, patients were administered 12 mg/kg of NG-methyl-L-arginine. Thereafter, a dose of 4 mg/kg was given every 4 hrs, as needed, to maintain the systolic blood pressure above 100 mm Hg.

MEASUREMENTS AND MAIN RESULTS

Invasive hemodynamic monitoring was instituted before the initiation of treatment with IL-2. Differences noted before, and 15 mins after, the administration of NG-methyl-L-arginine were analyzed using the paired t-test. NG-methyl-L-arginine (12 mg/kg) induced a significant antihypotensive effect (mean blood pressure increased from 87 +/- 4 to 121 +/- 7 mm Hg), accompanied by an increase of the systemic vascular resistance (549 +/- 51 to 860 +/- 167 dyne.sec/cm5) and pulmonary vascular resistance (81 +/- 16 to 117 +/- 29 dyne.sec/cm5). A decrease in the cardiac index was also documented (4.5 +/- 0.5 to 3.6 +/- 0.3 L/min/m2). No significant changes in pulmonary artery occlusion and central venous pressures were observed. Maintenance doses of 4 mg/kg of NG-methyl-L-arginine induced similar hemodynamic results, although the duration of the antihypotensive effect of NG-methyl-L-arginine decreased with sequential doses.

CONCLUSIONS

The hemodynamic effects induced by IL-2 administration are reversed by NG-methyl-L-arginine, a nitric oxide synthesis inhibitor. These results provide evidence for the biological activity of NG-methyl-L-arginine when administered alone to hypotensive patients. While no adverse effects were observed in this preliminary study, issues of toxicity and effectiveness need to be defined further in formal clinical trials. NG-methyl-L-arginine may play a therapeutic role in the modulation of the extreme vasodilation induced by cytokine administration or in septic shock.

S-alkyl-L-thiocitrullines. Potent stereoselective inhibitors of nitric oxide synthase with strong pressor activity in vivo

Nitric oxide synthase catalyzes the oxidation of a guanidino nitrogen of L-arginine to nitric oxide with concomitant formation of citrulline. Enzyme activity is inhibited by a variety of N omega-monosubstituted L-arginine analogs including N omega-alkyl-, N omega-amino-, and N omega-nitro-L-arginine derivatives. We report here that both constitutive and inducible isoforms of nitric oxide synthase are strongly inhibited by S-alkyl-L-thiocitrullines (N delta-(S-alkyl)isothioureido-L-ornithines) with n-alkyl groups of one to three carbons. These compounds represent a novel class of inhibitors and are the most potent nitric oxide synthase-inhibiting amino acids described to date. Inhibition is reversible, stereoselective, and competitive with L-arginine. Spectral studies show no direct interaction of inhibitor sulfur with heme iron, a result in contrast to that seen previously with the parent compound, L-thiocitrulline. The S-alkyl-L-thiocitrullines have strong pressor activity in normotensive control rats; S-methyl-L-thiocitrulline reverses hypotension in a rat model of septic peritonitis and in dogs administered endotoxin. These latter findings suggest that the inhibitors may have therapeutic utility in treating hypotension due to the overproduction of nitric oxide.

Phase I study of tumor necrosis factor plus actinomycin D in patients with androgen-independent prostate cancer

Based on preclinical studies which reveal enhanced antitumor activity of tumor necrosis factor (TNF) when combined with actinomycin D in human prostate cancer cell lines, we performed a phase I clinical study combining TNF and actinomycin D. All patients had metastatic prostatic carcinoma exhibiting androgen-independent growth. Patients were treated with a combination of a short infusion of actinomycin D followed by a TNF infusion daily for five consecutive days. Soluble TNF receptor p60 was not modulated by treatment but p80 receptor increased significantly following treatment with a combination of TNF and actinomycin D (baseline median 3.4 ng/ml) range 2.5-6.6 ng/ml follow up (9.3 ng/ml) range 6-24 ng/ml. We concluded that the maximum tolerated dose of continuous infusion TNF and short infusion actinomycin D is 400 micrograms/m2 of actinomycin D and 400 micrograms/m2 of TNF. The increased soluble receptor isoform (p80) may account for the lack of clinical activity seen in this trial. Should these results be confirmed, a strategy focused on overcoming the upregulation of the TNF soluble receptor will be required before further study of TNF should be considered.

NG-methyl-L-arginine, an inhibitor of nitric oxide formation, acts synergistically with dobutamine to improve cardiovascular performance in endotoxemic dogs

OBJECTIVE

To evaluate the hemodynamic effects of the nitric oxide inhibitor, NG-methyl-L-arginine, and dobutamine during experimental endotoxemia.

DESIGN

Prospective, randomized, controlled animal study.

SETTING

University research laboratory.

SUBJECTS

Adult, male mongrel dogs.

INTERVENTIONS

After catheterization with a flow-directed, thermal-dilution pulmonary artery flotation catheter and arterial catheter, awake dogs received either NG-methyl-L-arginine or dobutamine alone or in combination (controls; n = 5). Other animals were administered endotoxin (50 micrograms/kg), then received either NG-methyl-L-arginine alone or in combination with dobutamine after the onset of hypotension (endotoxin-treated; n = 5).

MEASUREMENTS AND MAIN RESULTS

Both dobutamine and NG-methyl-L-arginine alone had a small, but significant vasopressor effect on control animals. In contrast, administration of the combination of NG-methyl-L-arginine and dobutamine resulted in a 48.6% increase in mean arterial pressure, an effect which was dose-dependent with respect to NG-methyl-L-arginine. In dogs treated with 50 micrograms/kg of endotoxin, hypotension could be only partially reversed by NG-methyl-L-arginine, mainly due to a decline in cardiac output. Co-infusion of dobutamine reversed this depression of cardiac output and resulted in a complete restoration of blood pressure.

CONCLUSIONS

Later stages of septic shock are characterized by hypotension and decreased myocardial performance. A major mediator of hypotension is nitric oxide, a vasodilatory agent derived from L-arginine. Administration of the arginine derivative, NG-methyl-L-arginine, improved systemic vascular resistance but not myocardial performance. The addition of an inotropic agent to NG-methyl-L-arginine, a nitric oxide synthase inhibitor, resulted in an enhancement of the antihypotensive action of NG-methyl-L-arginine through the restoration of cardiac output. The synergistic action between dobutamine and NG-methyl-L-arginine may be of therapeutic value in the treatment of septic shock.

Phase II trial of low dose gamma-interferon in metastatic renal cell carcinoma

We conducted a phase II trial to confirm the activity of fixed, low dose gamma-interferon in metastatic renal cell carcinoma. A total of 35 patients with metastatic renal cell carcinoma, who had not received prior immunotherapy and who had a Zubrod performance status of 2 or less, was enrolled in this study. Primary tumors were controlled by nephrectomy or embolization before treatment began. gamma-Interferon was administered weekly as a subcutaneous injection at a fixed dose of 100 micrograms. Toxic effects were limited to low grade fever, chills and myalgias within 24 hours of injection. There were no incidences of grade 3 or 4 toxicity. Responses could be evaluated in 34 patients. There were 1 complete and 4 partial responses, for an objective response rate of 15% (95% confidence interval 5 to 32%). Durations of response to date are 21+, 17+, 13+, 9 and 2 months. We conclude that gamma-interferon is an active agent for metastatic renal cell carcinoma when administered according to this dose and schedule. The response rate compares favorably with those of alpha-interferon and interleukin-2, and toxicity is minimal. gamma-Interferon has excellent potential for use in combination with other biological or chemotherapeutic agents and in the adjuvant setting.

Cardiovascular effects of NG-methyl-L-arginine in chronically instrumented conscious dogs

The cardiovascular effects of nitric oxide blockade were examined in five conscious chronically instrumented dogs. The hypothesis tested was that nitric oxide release plays a role in vascular tone and regional organ blood flow under physiological conditions. Aortic pressures; the first derivative of the left ventricular pressure; cardiac output (CO); heart rate; and carotid, coronary, renal, hepatic, and portal blood flows were recorded before and after bolus injection of 5, 10, and 20 mg/kg of NG-methyl-L-arginine (L-NMA). In response to L-NMA, mean arterial pressure increased by 7, 20, and 35%, respectively, in a dose-dependent manner, whereas CO decreased. CO reduction was sustained at the highest dose, whereas peripheral blood flows were not altered. These data suggest that blocking basal nitric oxide synthesis by administering L-NMA leads to a modest dose-dependent pressor response despite a marked and sustained reduction in CO recorded at the highest dose of L-NMA. Moreover, within our dose range, although the nitric oxide synthase inhibition provides a significant pressor response, it does not alter the resting carotid, coronary, renal, hepatic, and portal blood flows.

NG-methyl-L-arginine, an inhibitor of nitric oxide formation, reverses IL-2-mediated hypotension in dogs

The effects of NG-methyl-L-arginine (L-NMA), an inhibitor of nitric oxide formation, were studied in dogs treated with interleukin-2 (IL-2). The administration of IL-2 to dogs resulted in hypotension within 3 days of treatment. The development of hypotension correlated with accumulation in the serum of nitrate, which is a stable breakdown product of nitric oxide. Administration of L-NMA decreased serum nitrate levels and increased the mean arterial pressure. The antihypotensive effect was dose dependent with a maximum effect observed at a dose of 20 mg/kg. Administration of a continuous infusion of L-NMA (5 mg.kg-1.h-1) maintained the mean arterial pressure for 48 h with concurrent administration of IL-2. Evaluation of IL-2-induced lymphokine-activated killer cell proliferation and tumoricidal activity toward a canine glioblastoma target cell line was unaffected by L-NMA. These studies imply that L-NMA may effectively ameliorate the dose-limiting hypotension associated with administration of IL-2 without adversely affecting the antitumor effects.

Cell-free hemoglobin reverses the endotoxin-mediated hyporesponsivity of rat aortic rings to alpha-adrenergic agents

Hemoglobin (Hbg) and lysates of red blood cells act as vasoconstrictors in isolated vessels by a mechanism that may involve nitric oxide (NO.) scavenging. To determine if such a mechanism indeed occurs, we investigated the effects of cell-free Hgb, modified Hgp (met Hgb and cyan met Hgb), and red blood cells on the formation of NO. induced by endotoxin in rat aorta. Incubation of rat aortic rings with endotoxin induced a delayed and prolonged release of NO. that resulted in a decrease in the contractile response to phenylephrine. Hgb significantly potentiated contractions to phenylephrine in control rings and also reversed the hyporeactivity to this alpha 1-agonist in endotoxin-treated rings with and without endothelium. Lysed red blood cells but not whole red blood cells shifted the concentration-contraction response curves to phenylephrine significantly to the right in endotoxin-treated preparations. Neither picket-fence porphyrin-albumin (PFP-albumin) or metheme-albumin affected the contractile response to phenylephrine. Oxidation of Hgb to met Hgb did not alter the contractions to an alpha 1-agonist in endotoxin-treated rings. In contrast, the formation of cyan met Hgb abolished the action of Hgb on the vascular reactivity of endotoxin-treated preparations. Together, these results demonstrate that free Hgb can scavenge NO. produced in endotoxin-treated vascular tissue and that the ability to bind NO. requires a cell-free form of Hgb with an intact heme center capable of undergoing redox reactions.

Effects of NG-methyl-L-arginine, NG-nitro-L-arginine, and aminoguanidine on constitutive and inducible nitric oxide synthase in rat aorta

A new selective inhibitor of the inducible nitric oxide synthase in the treatment of pathogenesis characterized by overproduction of nitric oxide may be useful. Therefore, we have examined the effects of two L-arginine analogues, NG-methyl-L-arginine (L-NMA) and NG-nitro-L-arginine (L-NNA), and aminoguanidine (AG) on the constitutive and inducible nitric oxide synthase in rat aorta. L-NNA induced greater contractions to phenylephrine than L-NMA whereas AG had no effect on dose-response curves to this alpha 1-agonist in rat aorta with endothelium. Relaxations to acetylcholine, adenosine triphosphate, and A 23187 were fully abolished by L-NNA, while L-NMA partially inhibited and AG did not affect the relaxations to these three vasodilators. L-NNA, L-NMA, and AG were equipotent in inhibiting the vascular hyporeactivity to phenylephrine induced by endotoxin in rat aortic rings with endothelium; however, the rate of onset of the maximum inhibitory effects of AG was slower than that obtained with L-NNA and L-NMA. L-arginine completely abolished the effects of AG, but only partially reversed the effects of L-NNA and L-NMA in LPS-treated rings. These results suggest that AG selectively inhibits inducible nitric oxide synthase, whereas L-NNA and L-NMA exert their effects on both the constitutive and inducible nitric oxide synthase.

Phase I study of interleukin-2 combined with interferon-alpha and 5-fluorouracil in patients with metastatic renal cell cancer

Interferon-alpha (IFN-alpha) and interleukin-2 (IL-2) each has produced a 15%-20% response in metastatic renal cell cancer. Combining IFN-alpha with either IL-2 or 5-fluorouracil (5-FU) enhanced IFN-alpha activity. We have therefore conducted a Phase I Study combining IL-2, IFN-alpha, and 5-FU. The patients were continuously infused with IL-2 (1-3 x 10(6) u/m2) and 5-FU (600-750 mg/m2) for a 5-day period every 28 days, and IFN-alpha (4-5 x 10(6) u/m2) was injected subcutaneously daily. Lymphokine-activated killer (LAK) and natural killer (NK) cell activity was measured on days 0 and 8. Twenty-one patients received 76 courses. All primary tumors were controlled by surgery (81%) or angioinfarction. Hematologic toxicity was mild; median nadir of platelets was 117 K/microL and of granulocytes was 1.2 K/microL. Dose-limiting toxicity included mucositis, liver damage, and hypotension. No treatment-related death occurred, and only one patient required intensive-care-unit support. Two patients had an objective response, one of which was a complete response. Increased LAK cell and NK cell activity occurred at all IL-2 dose levels. Simultaneous delivery of IL-2, IFN-alpha, and 5-FU is safe and shows antitumor and biologic activity. 5-FU did not appear to suppress IL-2-induced LAK and NK cell activation. Maximum tolerated dose of the three-drug combination is IL-2, 2 x 10(6) u/m2, 5-FU 600 mg/m2, and IFN-alpha, 4 x 10(6) u/m2.

Inhibition of interleukin-1-alpha-induced nitric oxide synthase in vascular smooth muscle and full reversal of interleukin-1-alpha-induced hypotension by N omega-amino-L-arginine

BACKGROUND

Interleukin-1-alpha (IL-1) is a cytokine with potentially therapeutic immunoproliferative and tumoricidal activities. Preliminary clinical studies suggest that use of IL-1 may be restricted by dose-limiting hypotension.

PURPOSE

The purpose of this study was to investigate the role of nitric oxide (NO.) as a possible mediator of this hypotension.

METHODS

Cytokine-treated rat aortic smooth muscle cells were assayed for nitrite production, a stable breakdown product of nitric oxide. Nitric oxide synthase from smooth muscle cells was partially characterized in cytosol preparations using a novel Fe(2+)-myoglobin method to test for nitric oxide production. To determine the role of NO. on the immunorestorative and antineoplastic activity of IL-1, N omega-amino-L-arginine (NAA) or N omega-monomethyl-L-arginine (NMA), inhibitors of nitric oxide synthase, were added to either cultures of IL-1-dependent T cells or A375 melanoma cells exposed to IL-1. To investigate the effects of NAA in vivo, pentobarbital anesthetized dogs, which were made hypotensive by administration of IL-1, received a single intravenous bolus dose of NAA. The effects of NAA were then reversed by the administration of L-arginine.

RESULTS

Our results show that cultured IL-1-activated rat aortic smooth muscle cells synthesize nitric oxide, a potent vasodilator. Induction of nitric oxide synthase is augmented by interferon-gamma and blocked by IL-1 receptor antagonist and by inhibitors of RNA or protein synthesis. Nitric oxide synthesis by IL-1-activated smooth muscle cells is inhibited by NAA, NMA, and N omega-nitro-L-arginine (NNA) with ED50 (i.e., effective dose for 50% inhibition) values of 20, 60, and 1000 microM, respectively; this rank order of inhibition is characteristic of an agonist-unregulated, inducible isoform of nitric oxide synthase. In smooth muscle cells, inhibition of NO. synthesis by NAA is reversed by excess L-arginine. Consistent with the induction of unregulated NO. synthesis in vascular smooth muscle in vivo, administration of IL-1 (50 micrograms/kg) to dogs caused a 33.5% decrease in systemic vascular resistance and a 28% decrease in blood pressure within 3 hours. Subsequent administration of NAA (20 mg/kg) rapidly and completely reversed the hypotension and increased systemic vascular resistance; these effects of NAA were reversed by L-arginine. Neither the immunoproliferative nor the tumoricidal activity of IL-1 was diminished by NAA.

CONCLUSIONS

Our results indicate that (a) vascular smooth muscle is a likely source as well as a target of IL-1-induced NO. synthesis, causing vasodilatation and hypotension, (b) nitric oxide synthase inhibitors can fully reverse this hypotension, and (c) the therapeutically useful properties of IL-1 are not diminished by nitric oxide synthase inhibitors.

IMPLICATIONS

Administration of inhibitors of nitric oxide synthase can reverse the pathological cardiovascular effects of IL-1 at concentrations that do not interfere with the potentially useful immunoproliferative or tumoricidal effects of this cytokine. In the context of the current clinical trials of IL-1, this finding would represent a very significant advantage.

Cytokine-activated endothelial cells express an isotype of nitric oxide synthase which is tetrahydrobiopterin-dependent, calmodulin-independent and inhibited by arginine analogs with a rank-order of potency characteristic of activated macrophages

We have previously reported that cultured murine brain endothelial cells (MBE) produce large quantities of nitric oxide (NO) after activation with interferon-gamma in combination with any of several immunoactivators including: bacterial endotoxin, tumor necrosis factor and interleukin-1. Since endothelial cells are the first example of a cell-type which may possess both a constitutive and an inducible type of NO synthase, it was of interest to compare the requirements of these two enzyme activities. Induction of NO synthesis in MBE by cytokines was abolished by the protein synthesis inhibitor, cycloheximide, and by 2,4-diamino-6-hydroxypyridine (DAHP), a selective inhibitor of GTP cyclohydrolase I, the rate-limiting enzyme for de novo synthesis of tetrahydrobiopterin (THB). In the presence of DAHP, NO synthesis was restored by sepiapterin (SEP), a substrate for the alternative pathway of THB synthesis occurring via pterin salvage. Moreover, SEP increased NO synthesis to greater than 150% of control values, suggesting that THB availability is rate-limiting for NO synthesis by cytokine-induced MBE. Methotrexate, an inhibitor of the pterin salvage pathway of THB synthesis, completely reversed the stimulation of NO synthesis by sepiapterin. Thus, cytokine-induced MBE NO synthase appears to have an absolute requirement for THB as cofactor. In additional studies we found that NO synthesis by cytokine-activated MBE was inhibited by NG-monosubstituted arginine analogs with a rank-order of potency NH2 greater than CH3 greater than NO2, in contrast with the rank-order of NO2 greater than NH2 greater than CH3 previously described for inhibition of the constitutive endothelial cell enzyme. Using a kinetic assay for NO synthase activity, based on oxidation of myoglobin heme-iron, we have found that these rank orders of potency also apply to cytosol preparations of cytokine-induced and untreated endothelial cells, respectively. Further differences between constitutive and cytokine-induced NO synthase were observed with regard to calmodulin requirements. Whereas constitutive NO synthase was potently inhibited by the calmodulin antagonists mellitin and trifluoperazine, cytokine-induced NO synthase was unaffected. In summary, NO synthesis by cytokine-activated MBE is THB-dependent, calmodulin-independent and inhibited by NG-substituted arginine analogs with a rank-order profile distinct from that for untreated endothelial cells but identical to that for cytokine-activated macrophages.

Role of nitric oxide in lysis of tumor cells by cytokine-activated endothelial cells

The purpose of these studies was to determine whether nitric oxide produced by cytokine-activated murine lung vascular endothelial cells plays a role in their lytic destruction of M-5076 reticulum cell sarcoma. Vascular endothelial cells harvested from perfused lungs of mice were adapted to grow in culture. Cloned lines ascertained to be of endothelial origin were incubated in vitro with interferon gamma and tumor necrosis factor. Lysis of radiolabeled tumor cells and accumulation of nitrite in the culture medium were determined at several time points. The concentration of nitrite in the culture medium directly correlated with endothelial cell-mediated tumor cell lysis. Endothelial cells cultured in L-arginine-free medium did not produce significant tumor cell lysis nor accumulation of nitrite in the medium. Both tumor cell lysis and nitrite accumulation were observed when the deficient medium was reconstituted with L-arginine, suggesting that endothelial cell-mediated tumor lysis was dependent on L-arginine, a precursor of nitric oxide. Moreover, specific inhibition of nitric oxide synthesis by NG-methyl-L-arginine resulted in complete inhibition of endothelial cell-mediated lysis of the M-5076 reticulum cell sarcoma. Similarly, treatment of cytokine-activated endothelial cells with dexamethasone inhibited both target cell lysis and production of nitrite. Collectively, these results suggest that nitric oxide plays a major role in the lysis of tumor cells mediated by cytokine-activated endothelial cells.

Reversal of endotoxin-mediated shock by NG-methyl-L-arginine, an inhibitor of nitric oxide synthesis

Septic shock is a life-threatening condition that results from exposure to bacterial endotoxin. It is manifested by cardiovascular collapse and mediated by the release of cytokines such as tumor necrosis factor. Some of these cytokines cause the release of vasoactive substances. In the present study, administration of 40 microgram/kg of bacterial endotoxin to dogs caused a 33% decrease in peripheral vascular resistance and a 54% fall in mean arterial blood pressure within 30 to 90 minutes. Vascular resistance and systemic arterial pressure returned to normal within 1.5 minutes after intravenous administration of NG-methyl-L-arginine (20 mg/kg), a potent and selective inhibitor of nitric oxide synthesis. L-Arginine reversed the effect of L-NMA and restored the endotoxin-induced hypotension. Although NG-methyl-L-arginine injection increased blood pressure in control dogs, the hypertensive effect was much greater in endotoxemic dogs (24.8 +/- 2.7 mmHg vs 47.8 +/- 6.8 mmHg, p = 0.01, n = 4). NG-Methyl-L-arginine caused only a modest increase in blood pressure in dogs made hypotensive by continuous intravenous infusion of nitroglycerin (17.1 +/- 5.0 mm Hg, n = 3). These findings suggest that nitric oxide overproduction is an important contributor to endotoxic shock. Moreover, our findings demonstrate for the first time, the utility of nitric oxide synthesis inhibitors in endotoxic shock and suggest that such inhibitors may be of therapeutic value in the treatment of septic shock.

A prospective randomized trial comparing MVAC and CISCA chemotherapy for patients with metastatic urothelial tumors

To evaluate the relative efficacy of cisplatin, cyclophosphamide, and Adriamycin (doxorubicin; Adria Laboratories, Columbus, OH) (CISCA) versus methotrexate, vinblastine, Adriamycin, and cisplatin (MVAC), a prospective randomized trial was performed in patients with advanced metastatic urothelial tumors. Patients were stratified by histologic disease type and degree of tumor dissemination. Equal distribution of the clinical characteristics was achieved. One hundred ten patients with metastatic disease of the urinary tract (86 bladder, 16 renal pelvis, seven ureter, one prostatic urethra) met eligibility criteria and were enrolled on study. These represented 82% of the total patients seen during the study period in the Section of Genitourinary Oncology who met the eligibility criteria. The combined complete and partial response rate was significantly higher for patients treated with MVAC than for those treated with CISCA (65% v 46%; P less than .05). The survival duration of MVAC-treated patients was significantly longer than that of CISCA-treated patients (mean, 62.6 weeks; median, 48.3; range, 5.0+ to 162.3+ v mean, 40.4 weeks; median, 36.1; range, 7+ to 147.1+). We conclude that MVAC chemotherapy is superior to CISCA chemotherapy, achieving a higher response rate and a longer survival for equivalent patients with metastatic urothelial tumors.

Endothelial cell production of nitrogen oxides in response to interferon gamma in combination with tumor necrosis factor, interleukin-1, or endotoxin

Clinical studies using biological response modifiers in cancer therapy have shown that the major dose-limiting toxic effects are hypotension and diffuse microvascular leakage. The cause and pathophysiology of this hypotension remains unknown. Previous experiments have demonstrated that a number of cell types, including endothelial cells, neutrophils, and macrophages, can secrete a potent hypotensive agent--endothelium-derived relaxing factor, which has recently been identified as nitric oxide. In this study, we tested interferon gamma, tumor necrosis factor, interleukin-1, interleukin-2, muramyl dipeptide, and endotoxin for their effects on production of nitrogen oxides by endothelial cells. Interferon gamma, in combination with tumor necrosis factor, interleukin-1 (IL-1), or endotoxin, induced murine brain endothelial cells to secrete nitrites (20-45 microM within 48 hr), which are breakdown products of nitric oxide. Nitrite production was blocked by incubation of endothelial cells in medium without L-arginine, a substrate for nitric-oxide synthase. Accumulation of nitrites was also inhibited by addition of NG-monomethyl-L-arginine (L-NMMA), which acts as a competitive inhibitor of this enzyme. The inhibitory effects of L-NMMA were reversed by addition of excess L-arginine. These results suggest (a) that endothelial cells produce nitric oxide in response to immunomodulators and (b) that endothelial cell-derived nitric oxide plays a role in the development of hypotension in patients treated with tumor necrosis factor or interleukins. Furthermore, administration of substrate analogues such as L-NMMA may favorably alter the toxicity associated with these immunomodulators and result in a higher maximum tolerated dose, with subsequent improvement in the antitumor activity.

NG-methyl-L-arginine inhibits tumor necrosis factor-induced hypotension: implications for the involvement of nitric oxide

Clinical assessment of the activity of tumor necrosis factor (TNF) against human cancer has been limited by a dose-dependent cardiovascular toxicity, most frequently hypotension. TNF is also thought to mediate the vascular collapse resulting from bacterial endotoxin. The present studies address the mechanism by which TNF causes hypotension and provide evidence for elevated production of nitric oxide, a potent vasodilator initially characterized as endothelium-derived relaxing factor. Nitric oxide is synthesized by several cell types, including endothelial cells and macrophages, from the guanidino nitrogen of L-arginine; the enzymatic pathway is competitively inhibited by NG-methyl-L-arginine. We found that hypotension induced in pentobarbital-anesthetized dogs by TNF (10 micrograms/kg, i.v., resulting in a fall in mean systemic arterial pressure from 124.7 +/- 7 to 62.0 +/- 22.9 mmHg; 1 mmHg = 133 Pa) was completely reversed within 2 min following administration of NG-methyl-L-arginine (4.4 mg/kg, i.v.). In contrast, NG-methyl-L-arginine failed to reverse the hypotensive response to an equivalent depressor dose of nitroglycerin, a compound that acts by forming nitric oxide by a nonenzymatic, arginine-independent mechanism. The effect of NG-methyl-L-arginine on TNF-induced hypotension was antagonized, and the hypotension restored, by administration of excess L-arginine (100 mg/kg, i.v.). Our findings suggest that excessive nitric oxide production mediates the hypotensive effect of TNF.

Escalated therapy for refractory urothelial tumors: methotrexate-vinblastine-doxorubicin-cisplatin plus unglycosylated recombinant human granulocyte-macrophage colony-stimulating factor

Thirty-two assessable patients with metastatic urothelial tumors refractory to standard chemotherapy with methotrexate, vinblastine, doxorubicin, and cisplatin (MVAC) were treated with escalated doses of MVAC plus unglycosylated recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF). Results of this phase I trial revealed that escalated MVAC (30 mg of methotrexate/m2, 4 mg of vinblastine/m2, 60 mg of doxorubicin/m2, and 100 mg of cisplatin/m2) can be tolerated by heavily pretreated patients. The side effects of rhGM-CSF are dose- and schedule-dependent. The maximum tolerated dose is 250 micrograms/m2 per day as a single dose administered subcutaneously (SC) for 10 consecutive days. This dose is well tolerated in outpatients, resulting in only modest fever and few side effects. The same dose delivered as a continuous infusion or a higher dose delivered either as a continuous infusion or SC caused significant side effects. For phase II trials, the starting dose of rhGM-CSF when combined with escalated MVAC is 120 micrograms/m2 per day SC for 10 consecutive days. forty percent of the treated patients responded, seven (23%) with complete remission and five (17%) with partial remission. This response rate is higher than anticipated from such a modest dosage escalation in chemotherapy-refractory patients.

Rapid, quantitative microassay for the monokine respiration inhibitory factor

The murine monokine respiration inhibitory factor (RIF) induces lesions at Complex I and Complex II of the mitochondrial electron transport chain (ETC) of tumor cells; these lesions in the ETC appear closely linked with cytostasis of the targets. In this report we describe the use of the sensitive murine mammary adenocarcinoma line EMT-6 in a colorimetric microassay for the effects of RIF on the ETC and target replication. The participation of cytolytic molecules in this assay system was excluded because of the resistance of the target to their effects. The endpoint for the assay was the ETC-mediated reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) to its colored formazan. The two major coupling sites of MTT in the ETC of EMT-6 cells are shown to be proximal to Coenzyme Q, detected either by malate oxidation through Complex I or succinate oxidation through Complex II. The assay was sensitive to both RIF-induced lesions at these dehydrogenases and to the cytostasis-linked reduction in target cell number. The assessment of ETC lesions by this microassay correlated directly with that determined by the less sensitive polarimetric assay based on oxygen consumption. We demonstrate the application of this microassay to parameters for the production of RIF by activated murine macrophages, and to initial molecular characterization of this mediator.

Activated macrophages secrete a soluble factor that inhibits mitochondrial respiration of tumor cells

Conditioned supernatants (CS) obtained from activated murine peritoneal macrophages inhibit tumor cell mitochondrial respiration. EMT-6 cells exposed to CS were markedly inhibited in their ability to oxidize succinate (11.8 ng-atoms 02/min/10(6) cells base line; 3.2 CS treated), malate (15.4 base line, 3.6 CS treated), and tetramethylphenylenediamine (27.6 base line, 10.6 CS treated). The CS was also found to inhibit DNA synthesis in EMT-6 cells (98.9% inhibition of [3H]thymidine incorporation), but did not cause cell lysis. Mitochondrial respiration inhibition activity was not detected in CS until 4 hr; it reached a maximum at 18 hr and declined rapidly by 24 hr. EMT-6 cells recovered from inhibition if the CS was removed from culture, but no recovery was observed if the target cells were in continuous exposure to CS for 72 hr. Fractionation of CS by using a molecular exclusion column of Sephacryl S-200 resulted in the recovery of two peaks that showed respiration inhibitory activity. These peaks, eluting at 55,000 and 80,000 daltons, mediated the inhibition of malate and succinate oxidation and were cytostatic for EMT-6 cells.

Activated macrophages secrete a soluble factor that inhibits mitochondrial respiration of tumor cells

Conditioned supernatants (CS) obtained from activated murine peritoneal macrophages inhibit tumor cell mitochondrial respiration. EMT-6 cells exposed to CS were markedly inhibited in their ability to oxidize succinate (11.8 ng-atoms 02/min/10(6) cells base line; 3.2 CS treated), malate (15.4 base line, 3.6 CS treated), and tetramethylphenylenediamine (27.6 base line, 10.6 CS treated). The CS was also found to inhibit DNA synthesis in EMT-6 cells (98.9% inhibition of [3H]thymidine incorporation), but did not cause cell lysis. Mitochondrial respiration inhibition activity was not detected in CS until 4 hr; it reached a maximum at 18 hr and declined rapidly by 24 hr. EMT-6 cells recovered from inhibition if the CS was removed from culture, but no recovery was observed if the target cells were in continuous exposure to CS for 72 hr. Fractionation of CS by using a molecular exclusion column of Sephacryl S-200 resulted in the recovery of two peaks that showed respiration inhibitory activity. These peaks, eluting at 55,000 and 80,000 daltons, mediated the inhibition of malate and succinate oxidation and were cytostatic for EMT-6 cells.