Inhibition of phosphodiesterase 4 (PDE4) reduces dermal fibrosis by interfering with the release of interleukin-6 from M2 macrophages.

Objectives: To investigate the disease-modifying effects of phosphodiesterase 4 (PDE4) inhibition in preclinical models of systemic sclerosis (SSc).

Methods: We studied the effects of PDE4 inhibition in a prevention and a treatment model of bleomycin-induced skin fibrosis, in the topoisomerase mouse model as well as in a model of sclerodermatous chronic graft-versus-host disease. To better understand the mode of action of PDE4 blockade in preclinical models of SSc, we investigated fibrosis-relevant mediators in fibroblasts and macrophages from healthy individuals and patients suffering from diffuse-cutaneous SSc on blockade of PDE4.

Merkel cell polyomavirus-infected Merkel cell carcinoma cells require expression of viral T antigens.

Merkel cell carcinoma (MCC) is the most aggressive skin cancer. Recently, it was demonstrated that human Merkel cell polyomavirus (MCV) is clonally integrated in approximately 80% of MCC tumors. However, direct evidence for whether oncogenic viral proteins are needed for the maintenance of MCC cells is still missing.

Synthesis and carbonic anhydrase inhibitory activity of 4-substituted 2-thiophenesulfonamides.

A series of 4-substituted 2-thiophenesulfonamides was prepared from 3-thiophenecarboxaldehyde using metalation chemistry developed for 3-furaldehyde. Several of these compounds inhibit carbonic anhydrase II in vitro at concentrations of less than 10 nM. In addition, none of these compounds exhibit sensitization potential as determined from in vitro measurement of cysteine reactivity.

Effects of four penetration enhancers on corneal permeability of drugs in vitro.

The usefulness of penetration enhancers in promoting drug permeation across the cornea was investigated for drugs varying from hydrophilic to lipophilic. Four purported penetration enhancers [Azone (laurocapram), hexamethylenelauramide, hexamethyleneoctanamide, and decylmethylsulfoxide] were employed. Corneal permeability coefficients of drugs that were either hydrophilic (acetazolamide, cimetidine, guanethidine, and sulfacetamide), moderately lipophilic (bunolol and prednisolone), or lipophilic (flurbiprofen and its amide analogue) were measured in the absence or in the presence of various Azone concentrations.

Lack of prostaglandin F2 alpha metabolism by human ocular tissues.

The ability of human and rabbit ocular tissues to degrade prostaglandins (PGs) was compared by following the metabolic fate of PGF2 alpha. No metabolism was observed in vitro after 5.0 hr incubation with human cornea, iris/ciliary body, or sclera, as indicated by the absence of a decrease in [3H]-PGF2 alpha concentration or the appearance of [3H]-PGF2 alpha metabolites with time.

A kinetic model of the cell culture cytotoxicity of metabolically activated agents: N-methyl-N-(acetoxymethyl)nitrosamine, methylnitrosourethane, and (methylazoxy)methanol acetate.

The activity of three metabolically activated methylating agents, N-methyl-N-(acetoxymethyl)nitrosamine (DMN-OAc), methylnitrosourethane (MNUT), and (methylazoxy)methanol acetate (MAM-Ac), were determined in cell culture by using a P388 cell growth rate inhibition assay. Experiments were conducted with normal P388 cells in Fischer's medium and under conditions in which the esterase-mediated activation was modified by pretreating cells with the irreversible esterase inhibitor paraoxon and by adding acetylcholinesterase to the medium. Inhibition of intracellular esterase had a much greater effect on activity than did addition of enzyme to medium.

Intracellular activation of cytotoxic agents: kinetic models for methylnitrosoureas and N-methyl-N'-nitro-N-nitrosoguanidine in cell culture.

The cytotoxic activity of N-methyl-N-nitrosourea (MNU), streptozotocin, and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was determined in cell culture by using a P388 cell growth rate inhibition assay. These agents appear to have very different activities when inhibition is related to the agent concentration in the culture medium: ED50(C0) = 40 microM for MNNG to 875 microM for streptozotocin. The mechanism of action of these three agents involves conversion to the active methanediazonium ion and subsequent methylation of cellular macromolecules.

The half-lives of alkylating intermediates from diethylnitrosamine and N-nitrosopyrrolidine: a method for the measurement of metabolically generated reactive species.

The half-times of the alpha-hydroxylated intermediates formed during metabolism of diethylnitrosamine and N-nitrosopyrrolidine have been determined. The method for determining half-times involved in vitro enzymatic conversion of the nitrosamine to a hydroxylated intermediate followed by trapping of the alkylating species generated from the chemical decomposition of the intermediate as it flowed through a column containing bound nucleophile. Half-times of less than 1 min at pH 7.

Ocular and systemic bioavailability of ophthalmic flurbiprofen.

Flurbiprofen, a nonsteroidal antiinflammatory agent which is not ocularly metabolized, was employed as a probe compound to investigate the drug kinetic relationship between systemic and ocular humoral circulation. The ocular and systemic bioavailabilities of topically applied flurbiprofen were also quantitated. Anesthetized albino female rabbits received flurbiprofen doses intracamerally, topically, and intravenously at 2 to 4 week intervals.

An analysis of 1-(2-chloroethyl)-1-nitrosourea activity at the cellular level.

The effect of five different 1-(2-chloroethyl)-1-nitrosoureas on the growth of cultured P388 cells has been analyzed in terms of physical, chemical, and kinetic parameters that are related to the mechanism of action of this class of cancer chemotherapeutic agent. This study correlates structure with activity at the cellular level by using a dose function that is related to the amount of active species, the (2-chloroethyl)diazonium ion, that is formed during the period of exposure of cells to drug rather than to the initial drug dose. 1-(2-Chloroethyl)-1-nitrosourea analogues that rapidly enter the P388 cells are shown to have the same activity relative to the amount of active species formed.

A method for measuring the lifetime of chemically and metabolically generated electrophilic species.

A method is presented for the characterization of the reaction order and rate constant for chemically and metabolically generated reactive electrophilic intermediates. The procedure employs flow kinetics and trapping of the electrophilic species. Reactive agents or metabolic intermediates are passed through a column containing a bound nucleophilic reagent.

The in vivo cytotoxic activity of procarbazine and procarbazine metabolites against L1210 ascites leukemia cells in CDF1 mice and the effects of pretreatment with procarbazine, phenobarbital, diphenylhydantoin, and methylprednisolone upon in vivo procarbazine activity.

An in vivo assay of the activity of procarbazine, N-isopropyl-alpha-(2-methylhydrazino)-p-toluamide hydrochloride, and several metabolic intermediates against IP-implanted L1210 leukemia cells in CDF1 male mice is described. Treatment of tumor-bearing mice with procarbazine at doses of 300-500 mg/kg IP increased the mean lifespan of treated mice by 29%-32% relative to that of untreated animals. Procarbazine treatment with doses of 200-400 mg/kg/day given IP for 3 consecutive days increased mean lifespan by 39%-46%.

Quantitative analysis of procarbazine, procarbazine metabolites and chemical degradation products with application to pharmacokinetic studies.

Quantitative analytical methods are described for the analysis of the anticancer drug procarbazine and eight known metabolites including those known to have cytotoxic activity. A direct sample insertion mass spectrometric assay for procarbazine and the urinary excretion product, N-isopropyl-terephthalamic acid, has been developed. This method employs stable isotope labeled variants in a procedure that minimizes analytical errors that may be encountered in the quantitation of the chemically unstable parent drug.

Quantitative dose-response relations for the cytotoxic activity of chloroethylnitrosoureas in cell culture.

A dose-response relation for the cytotoxic activity of chloroethylnitrosourea cancer chemotherapeutic agents in cell culture has been developed. Data for the activity of 1,3-bis(2-chloroethyl)-1-nitrosourea, 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea, 1-(2-chloroethyl)-3-(trans-4-methylcyclohexyl)-1-nitrosourea, and 1-(2-chloroethyl)-3-(piperidine-3,6-dion-3-yl)-1-nitrosourea against 9L rat brain tumor cells are presented. Cytotoxicity resulting from treatment schedules at different initial drug concentrations, exposure periods, and preincubation periods are correlated using a proposed dose function.

Quantitation of lipophilic chloroethylnitrosourea cancer chemotherapeutic agents.

A simple and rapid quantitative method for the derivatization and determination of lipophilic chloroethylnitrosoureas is described. This procedure involves the ether extraction of the chloroethylnitrosourea from plasma and conversion of the parent drug to an O-methylcarbamate by reaction in anhydrous methanol. The product O-methylcarbamate may be separated with gas chromatography (GC) and detected with nitrogen-specific GC detectors or with mass spectrometry using multiple-ion detection.

Comparative pharmacokinetics of 1-(2-chloroethyl)-3-(2,6-dioxo-1-piperidyl)-1-nitrosourea in rats and patients and extrapolation to clinical trials.

The plasma pharmacokinetics of 1-(2-chloroethyl)-3-(2,6-dioxo-1-piperidyl)1-nitrosourea (PCNU) were determined in ambulatory rats and in patients receiving PCNU chemotherapy in Phase 1 and II studies. After derivativization to the methyl carbamate, both rat and human PCNU plasma levels were measured by gas chromatography-mass spectrometry. Comparison of the tolerated dose levels and pharmacokinetics of PCNU to the values determined for 1,3-bis(2-chloroethyl)-1-nitrosourea in humans indicated that PCNU has a lower plasma drug area under the curve at equitoxic doses.

Metabolism of 1,3-bis(2-chloroethyl)-1-nitrosourea by rat hepatic microsomes.

The in vitro metabolism of the anticancer agent 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) has been studied in male Fischer 344 rat liver microsomal preparations. The previously identified product. 1,3-bis(2-chloroethyl)urea (BCU), has been shown to be the major metabolite.

Lipophilic drugs and lipoproteins: partitioning effects on chloroethylnitrosourea reaction rates in serum.

Chloroethylnitrosoureas are anticancer agents that undergo chemical reactions in vitro and in vivo to form active alkylating agents. The rate at which lipophilic chloroethylnitrosourease decompose in serum is faster than in aqueous solution and comparable to in vivo clearance rates. The increase in reaction rate is known to be caused by a reaction catalyzed by protein.

Protein mediated chemical reactions of chloroethylnitrosoureas.

The rates of chemical degradation of chloroethylnitrosoureas in serum are significantly higher than in aqueous buffer at the same pH and temperature. This rate enhancement is shown to be produced by a non-specific protein mediated chemical reaction that involves the formation of a protein-chloroethylnitrosourea (CENU) complex. Purified human serum albumin catalyzed reactions have been studied and Vm- and Km-values obtained for 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU), and 1-(2-chloroethyl)-3-(4-methylcyclohexyl)-1-nitrosourea (MeCCNU).

Reactions of 1,3-bis(2-chloroethyl)-1-nitrosourea and 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea in aqueous solution.

Products formed from the reaction of two chloroethylnitrosoureas in neutral aqueous solution have been identified and quantified. Mixture components recovered after a 1-h incubation period accounted for 75--85% of the starting nitrosourea. Approximately 65--85% of the reaction products were formed by an initial cleavage of the nitrosourea to the proposed intermediates 2-chloroethyl azohydroxide and an isocyanate and by subsequent hydrolytic reactions.

The effect of phenobarbital pretreatment on the antitumor activity of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) and 1-(2-chloroethyl)-3-(2,6-dioxo-3-piperidyl-1-nitrosourea (PCNU), and on the plasma pharmacokinetics and biotransformation of BCNU.

Many patients being treated for primary and secondary brain tumors receive phenobarbital as an anticonvulsant. The effects of chronic oral administration of phenobarbital on the antitumor activity of BCNU, CCNU and PCNU against the intracerebral 9L tumor in rats were determined. Phenobarbital pretreatment eliminated the antitumor activity of BCNU and reduced the activity of PCNU and CCNU.

Pharmacokinetics of BCNU in man: a preliminary study of 20 patients.

Using the technique of direct sample insertion selected ion monitoring chemical ionization mass spectroscopy, BCNU levels were measured in vivo in patients and in vitro in serum, sera ultrafiltrates, and buffered Ringer's solution. The disappearance of BCNU in vitro was found to be first-order with a half-time of 11.6 minutes (+/- 0.