Allopurinol prevents ischaemia-dependent haemorheological changes

In vivo excision and amplification of large human genomic segments using the Cre/loxP-and large T antigen/SV40 ori-mediated machinery

In vivo excision and amplification of pre-determined large genomic segments, directly from the genome of a natural host, can be a powerful tool for obtaining the genomic sequences with minimum rearrangements. In this study, an in vivo excision and amplification system in human BJAB cells was devised by combining the Cre/loxP system of bacteriophage P1 and the large T antigen/SV40 ori system of Simian virus 40. Two loxP sequences, each of which serves as a recognition site for recombinase Cre, were integrated unidirectionally into 5'- and 3'-untranslated regions (UTRs) of the human iNOS. An SV40 ori sequence, which serves as a conditional replication system, was inserted between the loxP sites. Trans-acting genes cre and large T antigen, which were under the control of a tetracycline responsive promoter, were also inserted into the 5'- and 3'-UTRs of the iNOS, respectively, by homologous recombination. Upon induction by doxycycline, the 45-kb iNOS genomic fragment of human chromosome 17 flanked by two loxP sites was excised and amplified up to about 45 copies per cell. Our method is very useful for obtaining large genomic fragments in quantities directly from human cells without using foreign hosts. Therefore, our approach can be used effectively for gap sequencing of a genome, gene therapy, and functional analysis of unknown genes in human cells.

Leukocyte modulation inhibits endotoxin-induced disruption of intracellular calcium homeostasis

OBJECTIVE

Sepsis is associated with disruption of intracellular calcium homeostasis. The specific mechanisms responsible for these changes remain unclear. This study attempts to modify endotoxin-induced alterations in erythrocyte intracellular calcium dynamics through modulation of the activated leukocyte and its products.

METHODS

Paired anticoagulated whole-blood specimens were obtained from healthy adult volunteers (n = 30). Specimens were incubated with 2 micrograms/mL endotoxin [lipopolysaccharide (LPS)] or saline control in the presence and absence of the white blood cell. Studies were repeated in specimens pretreated with allopurinol, superoxide dismutase, and pentoxifylline (PTX). After incubation, erythrocytes were separated, washed, and loaded with the fluorescent calcium chelator, FURA-2. Free cytosolic calcium concentration was determined on 10(6) cells using fluorescent spectroscopy. Values were computer-calculated every 1.8 seconds for 1 minute, and mean results were used for analysis. Differences were evaluated by analysis of variance.

RESULTS

The LPS resulted in a significant increase in intracellular calcium concentration (LPS 70.95 nM vs. control 44.04 nM). This increase was dependent on the presence of the white blood cell and could not be induced in its absence (control 30.15 --> LPS 32.78). Pretreatment inhibited these endotoxin-induced alterations: allopurinol, 50.49 nM; superoxide dismutase, 49.12 nM; and PTX, 40.23 nM (p < 0.01).

CONCLUSIONS

Endotoxin induces a significant increase in intracellular calcium concentration. This alteration seems to be mediated by activated neutrophils and can be ameliorated by both leukocyte modulation (PTX) and free radical scavengers.

Neutrophils may contribute to the morbidity and mortality of claudicants

Peripheral arterial occlusive disease is a common cause of morbidity in middle-aged men; 5 per cent of those aged over 50 years suffer from intermittent claudication. While claudication itself is not fatal, claudicants have a mortality rate approximately three times that of non-claudicating men of the same age, mainly from cardiovascular disease. This review examines the evidence for involvement of the neutrophil in this increased mortality and describes the possible pathogenesis. It also discusses how treatment of claudication may modify neutrophil behaviour, reducing subsequent mortality and morbidity rates.

Allopurinol and amlodipine improve coronary vasodilatation after myocardial ischaemia and reperfusion in anaesthetized dogs

1. We have assessed the effect of allopurinol, amlodipine and propranolol pretreatment on both endothelium-dependent and endothelium-independent coronary vasodilatation in vivo, by comparing pre-ischaemic responses with those measured after 60 min of coronary artery occlusion and 30 min of reperfusion in anaesthetized dogs. 2. In 15 untreated dogs ischaemia and reperfusion attenuated the increases in coronary blood flow produced by either acetylcholine (0.01-0.05 micrograms kg-1, i.a.) or glyceryl trinitrate (0.05-0.2 micrograms kg-1, i.a.), to an average of 39 +/- 4% and 42 +/- 5% of the pre-ischaemic control response, respectively (both P < 0.05). 3. In 5 dogs treated with allopurinol (25 mg kg-1, orally, 24 h previously, plus 50 mg kg-1, i.v., 5 min before occlusion), the increases in coronary blood flow after ischaemia and reperfusion (acetylcholine: 78 +/- 12%, glyceryl trinitrate: 60 +/- 3% of pre-ischaemic response) were significantly larger than post-ischaemic responses in untreated dogs (both P < 0.05). 4. Similarly, amlodipine treatment (3 micrograms kg-1 min-1, i.v., starting 90 min before occlusion) in 5 dogs improved post-ischaemic increases in blood flow (acetylcholine: 58.5%, glyceryl trinitrate: 66 +/- 6% of pre-ischaemic response, significantly greater than post-ischaemic responses in untreated dogs, P < 0.05). 5. In contrast, in a further 6 dogs pretreated with propranolol (1 mg kg-1, i.v., 30 min before occlusion,plus 0.5 mg kg-1 h-1, i.v.), blood flow responses after ischaemia and reperfusion were not different from post-ischaemic responses in untreated dogs (acetylcholine: 46 +/- 6%, glyceryl trinitrate: 46 +/-6% of pre-ischaemic response).6. These results suggest that allopurinol and amlodipine protect against the post-ischaemic impairment of endothelium-dependent and endothelium-independent coronary vasodilatation in vivo by mechanisms additional to endothelial protection.

Anti-inflammatory effects of pentoxifylline in claudication

We measured neutrophil elastase/alpha 1 proteinase inhibitor complex (E/alpha) levels by ELISA in plasma samples drawn from 19 patients with claudication, before and at 1 and 2 months after initiation of pentoxifylline (PTF), 400 mg. p.o. tid. Plasma E/alpha levels declined in all eight patients whose initial values were more than 300 ng elastase per ml. Whole blood viscosity (wbv) was reduced by two months' treatment in 12 of 14 patients tested. The relative change in wbv was significantly related to the relative change in E/alpha (R2 = 0.8), for patients with elevated initial E/alpha levels, suggesting a common or related mechanism for the two effects. Plasma crosslinked fibrin D-dimer fragments (XDP) measured by ELISA as indicators of coagulation activity were lower compared to pretreatment levels in 9 of 10 samples drawn when symptoms were improved on PTF, whereas they were increased in 6 of 9 samples drawn when symptoms were worse or unchanged. Plasma viscosity, C-reactive protein and alpha 1-acid-glycoprotein did not change significantly with PTF treatment. Together these findings are consistent with the possibility that reduced microvascular neutrophil activation and coagulation play a role in the clinical efficacy of PTF in intermittent claudication.