Disruption of histamine/H3 receptor signal reduces collagen deposition in cultures scar myofibroblasts

A suitable inflammatory signal influences extracellular matrix accumulation and determines the quality of the myocardial infarction scar. The aim of the present study was to determine the influence of mast cell sonicates or histamine on collagen accumulation in heart myofibroblast culture and on the deposition of collagen in the myocardial infarction scar. The histamine receptor involved in the process was investigated. Myocardial infarction was induced by ligation of the left coronary artery. Myofibroblasts were isolated from the scar of myocardial infarction. The effects of mast cell sonicates, histamine and its receptor antagonists, i.e. ketotifen (H₁-receptor inhibitor), ranitidine (H₂-receptor inhibitor), ciproxifan (H₃-receptor inhibitor), JNJ7777120 (H₄-receptor inhibitor), imetit (H₃ receptor agonist), were investigated. The mast cell sonicates or histamine (10^-10 - 10^-5M) augmented collagen content in myofibroblast cultures; however, histamine-induced elevation was reduced by ciproxifan (10^-5M, 10^-6M). Imetit (10^-9 - 10^-5M) elevated collagen content in the culture. H₃ receptor expression on myofibroblasts was confirmed. Our findings indicate that histamine increases the deposition of collagen in cultures of myofibroblasts isolated from the myocardial infarction scar. This effect is dependent on H₃ receptor activation.

Melatonin-induced glycosaminoglycans augmentation in myocardium remote to infarction

Elevated levels of collagen as well as transient increases of glycosaminoglycans (GAG) have been shown in the myocardium remote to the infarction. The aim of the study is to observe the effect of melatonin on the accumulation of collagen and GAG in the left ventricle wall, remote to the infarction. A second aim is to determine whether the effect of the pineal indole is mediated by the membrane melatonin receptors of heart fibroblasts. Rats with myocardial infarction induced by ligation of the left coronary artery were treated with melatonin at a dose of 60 μg/100 g b.w. or vehicle (2% ethanol in 0.9% NaCl). The results were compared with an untreated control. In the second part of the study, the fibroblasts from the non-infarcted part of myocardium were isolated and cultured. Melatonin at a range of concentrations from 10(-8) M to 10(-6) M was applied to the fibroblast cultures. In the final part of the study, the influence of luzindole (10(-6) M), the melatonin membrane receptor inhibitor, on melatonin-induced GAG augmentation was investigated. Both collagen and GAG content were measured in the experiment. Melatonin elevated GAG content in the myocardium remote to the infarcted heart. Collagen level was not changed by pineal indoleamine. Fibroblasts isolated from the myocardium varied in shape from fusiform to spindle-shaped. Moreover, the pineal hormone (10(-7)M and 10(-6)M) increased GAG accumulation in the fibroblast culture. Luzindole inhibited melatonin-induced elevation of GAG content at 10(-6)M. Melatonin increased GAG content in the myocardium remote to infarction. This effect was dependent on the direct influence of the pineal indole on the heart fibroblasts. The melatonin-induced GAG elevation is blocked by luzindole, the melatonin membrane receptors inhibitor, indicating a direct effect of this indole.

Pharmacological doses of melatonin reduce the glycosaminoglycan level within the infarcted heart scar

The aim of the study was to define the effect of pharmacological doses of melatonin, an agent known to be a scavenger of reactive oxygen species, on the extracellular matrix composition (glycosaminoglycans and collagen) in the infarcted heart scar. Rats were administered with melatonin at doses of 300 μg/100 g b.w. or 3 mg/100 g b.w. once daily (between 5:00 and 6:00 in the afternoon) or with 1.5 mg/100 g b.w. twice daily (between 8:00 and 9:00 in the morning and additionally between 5:00 and 6:00 in the afternoon). The levels of collagen, glycosaminoglycans (GAG) and some oxidative stress markers (lipid oxidation, the content of sulphydryl groups in proteins and glutathione) were evaluated. In the second part of the experiment, cells were isolated from the scar, identified as myofibroblasts, cultured and treated with melatonin at concentrations ranging from 10⁻⁷ M to 10⁻¹⁰ M. The pineal indoleamine was seen to reduce the GAG content of the scar, while the collagen content of the scar remained unchanged. A 10⁻⁷ M concentration of melatonin caused an increase in the GAG level in the myofibroblast cultures, while lower concentrations (10⁻⁸ M-10⁻¹⁰ M) of pineal indoleamine were not effective. Melatonin decreased lipid oxidation and increased the sulphydryl groups of total proteins and glutathione, which suggests its antioxidative activity in the applied doses. The present study shows that pharmacological doses of melatonin reduce the GAG level in an infarcted heart scar. Since the mechanism of GAG content reduction cannot be explained by direct action of the pineal indoleamine on myofibroblasts in the myocardial infarction scar, we hypothesise that changes in GAG content could be indirectly induced by melatonin, that is caused by changes in regulatory systems or reduction of the inflammatory reaction in the area of the infarction. In addition, this paper shows that long-term treatment with melatonin of rats affected by myocardial infarction may reduce oxidative stress in the infarction area.

The Hypothalamic and Neurohypophysial Oxytocic Activities in Stressed Rats: Independence from Beta-Adrenergic Blockade1)

A distinct decrease of oxytocin was found in the hypothalamus of immobilized rats but not of those exposed to cold. Similarly, the content of oxytocin was lower in the neurohypophysis of rats immobilized for 24 hr but, on the contrary, increased in animals exposed to cold for 24 hr. Propranolol did not modify the mentioned changes brought about by immobilization or exposure to cold.

[Clinical application of cyclooxygenase-2 inhibitors]

Nonsteroidal antiinflammatory drugs (NSAIDs) are a group of compounds with similar therapeutic and side effects. Their therapeutic effects depend on blockade of prostaglandin synthesis through enzyme cyclooxygenase (COX) inhibition. Two isoforms of the enzyme cyclooxygenase have been identified: COX-1 and COX-2. Selective COX-2 inhibitors i.e. meloxicam, nimesulid, etodolac or highly selective COX-2 inhibitors i.e. celecoxib, rofecoxib have antiinflammatory and analgesic properties with less or no gastrointestinal or other NSAIDs-typical adverse effects. Highly selective COX-2 inhibitors may also be active in colonic polyposis, colorectal cancer and Alzheimer's disease.

The relationship between diabetic amputees and vascular reviews

This paper reviews the data in the literature pertaining to risk factors for amputation in the diabetic population, and describes a retrospective study to assess the vascular and other assessments carried out on a sample of 50 diabetic patients undergoing minor (toe and foot) and major (below-knee and above-knee) amputations. The study found that 50% of the patients did not have Doppler studies, 52% did not have angiography, and 78% did not have angioplasty. Major amputations were performed in 76% of the sample. This is an unacceptably high figure. Thorough vascular assessments need to be performed in an attempt to save lower limbs from potential amputation.

The hypothalamic and neurohypophysial vasopressor and oxytocic activities in stressed rats treated with haloperidol

A decrease of oxytocin and vasopressin content was observed in the hypothalamus and neurohypophysis of immobilized rats but not of those exposed to cold. In rats otherwise not treated, dopaminergic blockade due to haloperidol was followed by an increase of the vasopressin content in the neurohypophysis. In immobilized animals, the hypothalamic and neurohypophysial content of oxytocin decreased and could be further reduced by haloperidol. In contrast haloperidol prevented the decrease of the hypothalamic and neurohypophysial vasopressin under conditions of stress owing to immobilization. In cold-exposed animals, however, haloperidol did not affect the storage of neurohypophysial vasopressin and oxytocin. Thus, it may be supposed that the response of oxytocinergic and vasopressinergic neurones to stress is dependent on the kind of stressor; furthermore, the dopaminergic transmission seems to be involved in the functional regulation of these neurones under conditions of stress due to immobilization.

The hypothalamic and neurohypophysial vasopressor and oxytocic content as influenced by alpha-adrenergic blockade in stressed rats

The hypothalamic and neurohypophysial vasopressor and oxytocic content as influenced by alpha-adrenergic blockade in stressed rats. Acta physiol. pol., 1985, 36 (3): 193-200. The effects of phenoxybenzamine (PBA; an alpha-adrenergic blocker) on hypothalamic and neurohypophysial vasopressin and oxytocin were investigated in stressed rats. Immobilization resulted in a decrease of both vasopressor and oxytocic activities in the hypothalamus and neurohypophysis, whereas in rats, exposed to cold the vasopressin and oxytocin content in the hypothalamo-neurohypophysial system was increased. Under treatment with PBA the vasopressin and oxytocin content in the neurohypophysis was diminished in stressed (both immobilized and cold-exposed) rats when compared to respective groups of untreated animals subjected to appropriate kind of stress. The response of the vasopressinergic and oxytocinergic neurones seems, therefore, to be dependent on the type of stress. The alpha-adrenergic transmission is probably in some way involved in the mechanisms of modified neurohypophysial function in stressed animals.

The effects of stress on the hypothalamic and neurohypophysial vasopressin content and plasma renin activity in rats

Rats were stressed by immobilization of exposure to cold. The hypothalamic vasopressor activity increased in immobilized animals and did not change in cold-exposed ones. The neurohypophysial vasopressor potency increased in cold-exposed animals and decreased following immobilization. The plasma renin activity in immobilized animals was significantly lower when compared with the respective controls. It seems, therefore, that different kinds of stress (cold exposure and immobilization) may cause different responses of the hypothalamo-neurohypophysial system.