Effects of the nonsteroidal anti-inflammatory drug piroxicam on energy metabolism in the perfused rat liver

The effects of piroxicam in the attenuation of MPP+/MPTP toxicity in vitro and in vivo

Several lines of evidence support the neuroprotective action of cyclooxygenase-2 (COX-2) inhibitors in various models of Parkinson's disease (PD). In the current study, we investigated the neuroprotective properties of several COX inhibitors against 1-methyl-4-phenylpyridinium (MPP+) in neuroblastoma Neuro 2A (N-2A) cells in vitro and the protection against degeneration of substantia nigra pars compacta (SNc) dopaminergic (DA) neurons after the administration of 1-methyl 4-phenyl 1,2,3,6-tetrahydropyridine (MPTP) in C57/BL6 male mice. The data obtained demonstrate a lack of protective effects observed by COX 1-2 inhibitors ibuprofen and acetylsalicylic acid against MPP+ toxicity in N-2A, where piroxicam was protective in a dose dependent manner (MPP+ control: 15 +/- 2% MPP+ piroxicam: 5 mM 89 +/- 4%). The data also indicate a drop in mitochondrial oxygen (O(2)) consumption and ATP during MPP+ toxicity with no restoration of mitochondrial function concurrent to a heightened concentration of somatic ATP during piroxicam rescue. These findings indicate that the neuroprotective effects of COX inhibitors against MPP+ are not consistent, but that piroxicam may work through an unique mechanism to propel anaerobic energy metabolism. On the other hand, using mice, piroxicam (20 mg/kg) was effective against MPTP-induced dopaminergic degeneration in the (SNc) and loss of locomotive function in mice. Administering a 3 day pre-treatment of piroxicam (20 mg/kg) was effective in antagonizing the losses in SNc tyrosine hydroxylase protein expression, SNc DA concentration and associated anomaly in ambulatory locomotor activity. It was concluded from these findings that piroxicam is unique among COX inhibitors in providing very significant neuroprotection against MPP+ in vitro and in vivo.

Inhibition of acid secretion by the nonsteroidal anti-inflammatory drugs diclofenac and piroxicam in isolated gastric glands: analysis of a multifocal mechanism

In nonstimulated rabbit gastric glands, acetylsalicylic acid (10-500 microM) and indomethacin (3-300 microM) did not significantly modify the basal rate of acid secretion, whereas diclofenac and piroxicam (10-1,000 microM each) caused a marked and dose-dependent inhibitory effect (EC(50) = 138 and 280 microM, respectively). In gastric glands stimulated by histamine (100 microM), diclofenac also reduced the rate of acid formation in a dose-dependent manner. In contrast, acetylsalicylic acid, indomethacin, and piroxicam exerted a biphasic effect; thus low concentrations (3-100 microM) of these three agents significantly increased the rate of histamine-stimulated acid secretion (10-20% over the corresponding control value) by a cAMP-independent mechanism, whereas higher concentrations reduced the rate of acid formation. With respect to underlying biochemical mechanisms that could mediate inhibitory effects of NSAIDs on gastric acid formation, it was observed that both diclofenac and piroxicam, but not acetylsalicylic acid or indomethacin, decreased the glandular content of ATP, inhibited hydrolytic activity of gastric gland microsomal H(+)-K(+)-ATPase, and reduced the rate of H(+)-K(+)-ATPase-dependent proton transport across microsomal membranes in a dose-dependent manner. Furthermore, diclofenac and piroxicam also significantly increased passive permeability of microsomal membranes to protons. In conclusion, our work shows that diclofenac and piroxicam cause a significant reduction in the rate of basal and histamine-stimulated acid formation in isolated rabbit gastric glands at concentrations that can be attained in the gastric lumen of patients treated with these drugs. Mechanisms involved in these inhibitory effects appear to be multifocal and include different steps of stimulus-secretion coupling.

Antagonism between the metabolic responses induced by epinephrine and piroxicam on isolated rat hepatocytes

Nonsteroidal anti-inflammatory drugs (NSAIDs) are one of the most employed therapeutic agents. They have a wide spectrum of biological effects, some of which are independent of cyclooxygenase inhibition, such as the alterations on the components of signal transduction systems. In particular, previous data from our laboratory suggested an antagonism between epinephrine and piroxicam, one of the most prescribed NSAIDs. Thus, this study deals with the epinephrine-piroxicam antagonism recorded for metabolic responses in isolated rat hepatocytes. The obtained results show that epinephrine stimulates lactate and ethanol consumption, stimulates glucose release from lactate only, and has no effect on cellular triacylglycerides content. Otherwise, in a dose-dependent basis, piroxicam stimulates lactate and ethanol consumption accompanied by an increase in triacylglycerides content, without changes in glucose release by hepatocytes. Piroxicam blocks the epinephrine-induced stimulation of glucose release from lactate, and epinephrine blocks the piroxicam-mediated increase in triacylglycerides content from lactate or ethanol. In contrast, the effects of epinephrine and piroxicam, promoting the consumption of lactate and ethanol, are not antagonized or added after the simultaneous administration of both compounds. This last result is probably related to the ability of both compounds to stimulate oxygen consumption. On isolated rat liver mitochondria, micromolar doses of piroxicam partially uncouple oxidative phosphorylation, and paradoxically stimulates an ATP-dependent mitochondrial function as citrullinogenesis. These results show for first time, on isolated rat hepatocytes, an antagonism between the metabolic responses of epinephrine and piroxicam, at the concentration found in plasma after its therapeutical administration.