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2, 4-diamino-6- hydroxy pyrimidine inhibits NSAIDs induced nitrosyl-complex EPR signals and ulcer in rat jejunum.

Somasundaram S, Simpson R, Rafi S, Shergill JK, Bjarnason I, Wrigglesworth J - BMC Gastroenterol (2002)

Bottom Line: In contrast, nabumetone and 2,4 diamino-6-hydroxy pyrimidine pre-treated animals receiving indomethacin exhibited electron paramagnetic resonance spectra identical to those of controls at 24 hrs and neither was associated with small intestinal ulcers.The results suggest that the in vivo effects of indomethacin modulate the mitochondrial respiratory chain directly at 1 h and 24 h through formation of nitric oxide.NO* appears to play an important role in the late pathogenic stages of NSAID enteropathy and may be the site for targeted treatment to reduce their toxicity.

View Article: PubMed Central - HTML - PubMed

Affiliation: Lineberger Comprehensive Cancer Center, CB#7295, University of North Carolina, Chapel Hill, NC 27599, USA. sivasoma@med.unc.edu

ABSTRACT

Background: It has been suggested that one aspect of non-steroidal anti-inflammatory drugs induced intestinal damage is due to either uncoupling of mitochondrial oxidative phosphorylation or inhibition of electron transport. We investigated the latter possibility using electron paramagnetic resonance spectroscopy.

Results: Electron paramagnetic studies of NSAIDS on sub-mitochondrial particles revealed that indomethacin, but not with nabumetone, bound to a site near to Complex I and ubiquinone to generate a radical species. Normal rats exhibited prominent [3Fe-4S]ox signals (g approximately 2.01) at 20 K. One hour after indomethacin there was a prominent, intense and broad absorption pattern at (g approximately 2.07) suggesting, appearance of radical species overlapping [3Fe-4S]ox and was unaffected by pretreatment with 2,4 diamino -6-hydroxy pyrimidine. At 24 hrs, when macroscopic ulcers were seen, there was a new signal due to a nitric oxide radical (NO*). In contrast, nabumetone and 2,4 diamino-6-hydroxy pyrimidine pre-treated animals receiving indomethacin exhibited electron paramagnetic resonance spectra identical to those of controls at 24 hrs and neither was associated with small intestinal ulcers. Indomethacin and 2,4 diamino hydroxy pyrimidine pre-treated rats, but not nabumetone, had increased intestinal permeability.

Conclusion: The results suggest that the in vivo effects of indomethacin modulate the mitochondrial respiratory chain directly at 1 h and 24 h through formation of nitric oxide. NO* appears to play an important role in the late pathogenic stages of NSAID enteropathy and may be the site for targeted treatment to reduce their toxicity.

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The EPR spectra of rat jejunal homogenates at 20 K after 1 hr oral gavage of (a) DMSO, (b) nabumetone (500 mg / kg b.wt) and (c) indomethacin (20 mg/kg b.wt)
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Figure 2: The EPR spectra of rat jejunal homogenates at 20 K after 1 hr oral gavage of (a) DMSO, (b) nabumetone (500 mg / kg b.wt) and (c) indomethacin (20 mg/kg b.wt)

Mentions: At 20 K, control rat intestinal homogenates also displayed a signal indicative of Centre S3, albeit weaker (Fig. 2a). A similar signal could be detected 1 hr and 24 hr after nabumetone administration. [Fig. 2b and Fig 3b)] However, with indomethacin the [3Fe-4S]ox signal intensity was decreased at 1 hr, and by 24 hr the EPR spectrum of intestinal homogenates displayed a prominent new resonance centered at g ~ 2.0, with a peak at g ~ 2.07 and a triplet splitting centered at g ~ 2.01, indicative of nitrosyl-haem (haem-NO) formation. [Fig. 2c and Fig 3c]. DAHP pre treated indomethacin group significantly decreased the haem-NO intensity at 24 hr after administration [Fig. 4], thereby allowing detection of the Centre S3 signal at 8 K [Fig. 5]. DAHP pretreated indomethacin group displayed the similar signals at 1 hr, when compared to indomethacin alone treated group [.i.e., decreased in the [3Fe-4S]ox signal at 1 hr, Data not shown]. The haem-NO signal observed in Fig. 3c shows a splitting of A (14N) ~ 330 mT [Fig. 4 at 30 K]. Similar signals have been observed for the NO-adducts of type II haem proteins such as cytochrome c oxidase and hemoglobin [21] Figure 3 explains the unique features of nitrosyl signals (g ~ 2.04) at 20 K only in indomethacin treated group and not in the DMSO-control or nabumetone group. Figure 4 displays the differential pattern of the nitrosyl signals (i)-(ii) at 30K after 24 hr of indomethacin (i) and DAHP treated indomethacin group(ii) when compare to the DMSO-control (iii) spectra. This prominent nitrosyl signals at 30 K is the characteristics of the free radical species and temperature sensitive when compare to the signals at 8 K, displayed in Figure 5. In indomethacin alone treated group (Figure 4) this broad signal displayed a peak at g ~ 2.04, a distinct trough at g ~ 1.98 and complex splitting (triplet) centered at g ~ 2.01 at temperature above 25 K, indicative of haem-nitrosyl formation.[21]


2, 4-diamino-6- hydroxy pyrimidine inhibits NSAIDs induced nitrosyl-complex EPR signals and ulcer in rat jejunum.

Somasundaram S, Simpson R, Rafi S, Shergill JK, Bjarnason I, Wrigglesworth J - BMC Gastroenterol (2002)

The EPR spectra of rat jejunal homogenates at 20 K after 1 hr oral gavage of (a) DMSO, (b) nabumetone (500 mg / kg b.wt) and (c) indomethacin (20 mg/kg b.wt)
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC103670&req=5

Figure 2: The EPR spectra of rat jejunal homogenates at 20 K after 1 hr oral gavage of (a) DMSO, (b) nabumetone (500 mg / kg b.wt) and (c) indomethacin (20 mg/kg b.wt)
Mentions: At 20 K, control rat intestinal homogenates also displayed a signal indicative of Centre S3, albeit weaker (Fig. 2a). A similar signal could be detected 1 hr and 24 hr after nabumetone administration. [Fig. 2b and Fig 3b)] However, with indomethacin the [3Fe-4S]ox signal intensity was decreased at 1 hr, and by 24 hr the EPR spectrum of intestinal homogenates displayed a prominent new resonance centered at g ~ 2.0, with a peak at g ~ 2.07 and a triplet splitting centered at g ~ 2.01, indicative of nitrosyl-haem (haem-NO) formation. [Fig. 2c and Fig 3c]. DAHP pre treated indomethacin group significantly decreased the haem-NO intensity at 24 hr after administration [Fig. 4], thereby allowing detection of the Centre S3 signal at 8 K [Fig. 5]. DAHP pretreated indomethacin group displayed the similar signals at 1 hr, when compared to indomethacin alone treated group [.i.e., decreased in the [3Fe-4S]ox signal at 1 hr, Data not shown]. The haem-NO signal observed in Fig. 3c shows a splitting of A (14N) ~ 330 mT [Fig. 4 at 30 K]. Similar signals have been observed for the NO-adducts of type II haem proteins such as cytochrome c oxidase and hemoglobin [21] Figure 3 explains the unique features of nitrosyl signals (g ~ 2.04) at 20 K only in indomethacin treated group and not in the DMSO-control or nabumetone group. Figure 4 displays the differential pattern of the nitrosyl signals (i)-(ii) at 30K after 24 hr of indomethacin (i) and DAHP treated indomethacin group(ii) when compare to the DMSO-control (iii) spectra. This prominent nitrosyl signals at 30 K is the characteristics of the free radical species and temperature sensitive when compare to the signals at 8 K, displayed in Figure 5. In indomethacin alone treated group (Figure 4) this broad signal displayed a peak at g ~ 2.04, a distinct trough at g ~ 1.98 and complex splitting (triplet) centered at g ~ 2.01 at temperature above 25 K, indicative of haem-nitrosyl formation.[21]

Bottom Line: In contrast, nabumetone and 2,4 diamino-6-hydroxy pyrimidine pre-treated animals receiving indomethacin exhibited electron paramagnetic resonance spectra identical to those of controls at 24 hrs and neither was associated with small intestinal ulcers.The results suggest that the in vivo effects of indomethacin modulate the mitochondrial respiratory chain directly at 1 h and 24 h through formation of nitric oxide.NO* appears to play an important role in the late pathogenic stages of NSAID enteropathy and may be the site for targeted treatment to reduce their toxicity.

View Article: PubMed Central - HTML - PubMed

Affiliation: Lineberger Comprehensive Cancer Center, CB#7295, University of North Carolina, Chapel Hill, NC 27599, USA. sivasoma@med.unc.edu

ABSTRACT

Background: It has been suggested that one aspect of non-steroidal anti-inflammatory drugs induced intestinal damage is due to either uncoupling of mitochondrial oxidative phosphorylation or inhibition of electron transport. We investigated the latter possibility using electron paramagnetic resonance spectroscopy.

Results: Electron paramagnetic studies of NSAIDS on sub-mitochondrial particles revealed that indomethacin, but not with nabumetone, bound to a site near to Complex I and ubiquinone to generate a radical species. Normal rats exhibited prominent [3Fe-4S]ox signals (g approximately 2.01) at 20 K. One hour after indomethacin there was a prominent, intense and broad absorption pattern at (g approximately 2.07) suggesting, appearance of radical species overlapping [3Fe-4S]ox and was unaffected by pretreatment with 2,4 diamino -6-hydroxy pyrimidine. At 24 hrs, when macroscopic ulcers were seen, there was a new signal due to a nitric oxide radical (NO*). In contrast, nabumetone and 2,4 diamino-6-hydroxy pyrimidine pre-treated animals receiving indomethacin exhibited electron paramagnetic resonance spectra identical to those of controls at 24 hrs and neither was associated with small intestinal ulcers. Indomethacin and 2,4 diamino hydroxy pyrimidine pre-treated rats, but not nabumetone, had increased intestinal permeability.

Conclusion: The results suggest that the in vivo effects of indomethacin modulate the mitochondrial respiratory chain directly at 1 h and 24 h through formation of nitric oxide. NO* appears to play an important role in the late pathogenic stages of NSAID enteropathy and may be the site for targeted treatment to reduce their toxicity.

Show MeSH
Related in: MedlinePlus