Effects of Paracetamol on NOS, COX, and CYP Activity and on Oxidative Stress in Healthy Male Subjects, Rat Hepatocytes, and Recombinant NOS

Abstract

Paracetamol (acetaminophen) is a widely used analgesic drug. It interacts with various enzyme families including cytochrome P450 (CYP), cyclooxygenase (COX), and nitric oxide synthase (NOS), and this interplay may produce reactive oxygen species (ROS). We investigated the effects of paracetamol on prostacyclin, thromboxane, nitric oxide (NO), and oxidative stress in four male subjects who received a single 3 g oral dose of paracetamol. Thromboxane and prostacyclin synthesis was assessed by measuring their major urinary metabolites 2,3-dinor-thromboxane B2 and 2,3-dinor-6-ketoprostaglandin F1α, respectively. Endothelial NO synthesis was assessed by measuring nitrite in plasma. Urinary 15(S)-8-iso-prostaglanding F2α was measured to assess oxidative stress. Plasma oleic acid oxide (cis-EpOA) was measured as a marker of cytochrome P450 activity. Upon paracetamol administration, prostacyclin synthesis was strongly inhibited, while NO synthesis increased and thromboxane synthesis remained almost unchanged. Paracetamol may shift the COX-dependent vasodilatation/vasoconstriction balance at the cost of vasodilatation. This effect may be antagonized by increasing endothelial NO synthesis. High-dosed paracetamol did not increase oxidative stress. At pharmacologically relevant concentrations, paracetamol did not affect NO synthesis/bioavailability by recombinant human endothelial NOS or inducible NOS in rat hepatocytes. We conclude that paracetamol does not increase oxidative stress in humans.

Effect of Liposomal Curcumin on Acetaminophen Hepatotoxicity by Down-regulation of Oxidative Stress and Matrix Metalloproteinases

“…In our study, the levels of oxidative stress molecules (NOx and MDA) significantly increased after APAP administration (250 mg/kg) (Table II, Figures 4 and 5). Similar results were reported by other authors, thus, the suggested mechanism is APAP-induced activation of endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS) in hepatocytes (47). Other authors have reported that APAP can induce liver injury via an oxidative stress mechanism caused by increased MDA production (48).…”

Elevated Serum Oleic Acid Epoxide Concentration in Acetaminophen (Paracetamol) Poisoning

“…Aceta-minophen (1000 µM) was found to inhibit CYP3A4 activity (by 30%), a major CYP isoform contributing to cis-EpOA formation [3]. The temporary almost 6fold increase in cis-EpOA seen in two healthy subjects who ingested 3 g acetaminophen at once could be due to an acetaminophen-induced short-term release of secretory hepatic phospholipase A2 (sPLA2) [7]. This may also have occurred in the acetaminophen-suicided persons of the present study.…”

“…The highest serum cis-EpOA concentration of 3723 nM is about 100 times the mean plasma cis-EpOA concentration measured in healthy subjects [3]. Except for two patients, circulating acetaminophen concentrations were higher than the highest acetaminophen plasma concentrations measured in four healthy subjects after ingestion of 3000 mg acetaminophen at once [7].…”

Protocols for the measurement of the F 2 -isoprostane, 15( S )-8- iso -prostaglandin F 2α , in biological samples by GC–MS or GC–MS/MS coupled with immunoaffinity column chromatography

“…Intake of a single oral dose of 3 g of paracetamol (acetaminophen) by four healthy male subjects did not result in noteworthy changes in plasmatic urinary concentrations of 15(S)-8-iso-PGF 2␣ , prostaglandin E 2 (PGE 2 ) and the thromboxane (Tx) A 2 (TxA 2 ) metabolite 2,3-dinor-TxB 2 [1], while the urinary excretion of the prostacyclin metabolite 2,3-dinor-6-keto-PGF 1␣ was potently and sustainably inhibited [23]. Interestingly, there was a close correlation between 15(S)-8-iso-PGF 2␣ and 2,3-dinorTxB 2 (Fig.…”

“…Selected published findings obtained from the application of these protocols in vitro and in vivo studies are outlined below [17][18][19][20][21][22][23][24][25]. …”