Impairment of acetylcholine-mediated endothelium-dependent relaxation in isolated parotid artery of the alloxan-induced diabetic rabbit

Relationship between impaired parasympathetic vasodilation and hyposalivation in parotid glands associated with type 2 diabetes mellitus

We examined the relationship between hemodynamics in the three major salivary glands and salivary secretion in urethane-anesthetized and sympathectomized type 2 diabetic and nondiabetic rats via laser speckle imaging and by collecting the saliva. Lingual nerve stimulation elicited rapid increases in glandular blood flow and induced salivary secretion from the three glands in both diabetic and nondiabetic rats. In the parotid gland, the magnitude of blood flow increase and salivary secretion was significantly lower in the diabetic rats when compared with the nondiabetic rats; however, this was not observed in the other glands. Although the intravenous administration of acetylcholine increased blood flow in the parotid gland in a dose-dependent manner, the response was significantly lower in the diabetic rats when compared with the nondiabetic rats. Similarly, mRNA expression levels of M1 and M3 muscarinic acetylcholine receptors in the parotid gland were relatively lower in the diabetic rats compared with the nondiabetic rats. Our results indicate that type 2 diabetes impairs parasympathetic vasodilation and salivary secretion in the parotid gland and suggest that disturbances in the cholinergic vasodilator pathway may contribute to the underlying mechanisms involved in the disruption of parasympathetic nerve-mediated glandular vasodilation.

The enhancement of serotonin-induced contraction of rat femoral artery is mediated by angiotensin II release from intact endothelium

We have performed an in vitro study on isolated intact or denuded femoral artery (FA) of healthy, diabetic, and/or rats submitted to the FA occlusion. The aim was to determine the contribution of endothelium and endothelial dysfunction (ED) on serotonin-induced action in FA. Further, the contribution of angiotensin II and cyclooxygenase products of arachidonic acid was investigated. A marker of ED, vWF was measured in animal serum. Serotonin induced contraction-dependent contraction of isolated FA, which was increased in preparations with endothelium. Pathological conditions such as endothelial denudation, nicotine-induced ED, diabetes or occlusion of FA reduced serotonin-induced contraction. Comparable reduction of serotonin-induced contraction was achieved after inhibition of AT1 receptors with losartan in isolated FA with intact endothelium. Our results demonstrate that angiotensin II contributes to the enhancement of serotonin-induced contraction of femoral arteries with intact endothelium. This increase is attenuated by endothelium removal, nicotine treatment, vascular occlusion, and/or hyperglycemia.

Experimental diabetes induced by alloxan and streptozotocin: The current state of the art

Diabetes mellitus is a chronic metabolic disorder with a high prevalence worldwide. Animal models of diabetes represent an important tool in diabetes investigation that helps us to avoid unnecessary and ethically challenging studies in human subjects, as well as to obtain a comprehensive scientific viewpoint of this disease. Although there are several methods through which diabetes can be induced, chemical methods of alloxan- and streptozotocin-induced diabetes represent the most important and highly preferable experimental models for this pathological condition. Therefore, the aim of this article was to review the current knowledge related to quoted models of diabetes, including to this point available information about mechanism of action, particular time- and dose-dependent protocols, frequent problems, as well as major limitations linked to laboratory application of alloxan and sterptozotocin in inducing diabetes. Given that diabetes is known to be closely associated with serious health consequences it is of fundamental importance that current animal models for induction of diabetes should be continuously upgraded in order to improve overall prevention, diagnosis and treatment of this pathological condition.

Comparison of pulpal anesthesia and cardiovascular parameters with lidocaine with epinephrine and lidocaine with clonidine after maxillary infiltration in type 2 diabetic volunteers

OBJECTIVES

The pulpal anesthetic and cardiovascular parameters obtained by 2 % lidocaine with epinephrine (LE; 1:80,000) or clonidine (LC; 15 mcg/ml) were studied in diabetes mellitus (DM) type 2 and healthy volunteers (72), after maxillary infiltration anesthesia.

MATERIALS AND METHODS

Onset and duration of pulpal anesthesia were measured by electric pulp tester; vasoconstrictive effect of used local anesthetic mixtures by laser Doppler flowmetry (LDF) through pulpal blood flow (PBF); systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) were registered by electrocardiogram monitoring.

RESULTS

Onset of pulpal anesthesia was shorter for LC than for LE in healthy, while it was not different in diabetic participants; duration of pulpal anesthesia was significantly longer in type 2 diabetic participants, regardless of used anesthetic mixture. Significant reduction of PBF with LE was observed during 45 min in healthy and 60 min in diabetic participants, while with LC such reduction was observed during 45 min in both groups. LE caused a significant increase of SBP in the 5th and 15th minutes in diabetic versus healthy participants, while LC decreased SBP from the 10th to 60th minutes in healthy versus diabetic participants.

CONCLUSIONS

DM type 2 influences duration of maxillary infiltration anesthesia obtained with LE and LC, and systolic blood pressure during LE anesthesia.

CLINICAL RELEVANCE

The obtained results provide elements for future protocols concerning intraoral local anesthesia in DM type 2 patients.

The effects of anti-hypertensives and type 2 diabetes on salivary flow and total antioxidant capacity

OBJECTIVE

The present cross-sectional study aimed to determine the effect of first-line anti-hypertensive drugs (enalapril, metoprolol, and combinations of enalapril with metoprolol and/or hydrochlorothiazide) on salivary gland function and salivary total antioxidant capacity (TAC) in hypertensive patients with/without diabetes mellitus (DM) type 2.

MATERIALS AND METHODS

Salivary gland function was measured as xerostomia (interview) and unstimulated whole saliva flow rate (UWSFR) in 447 subjects (387 hypertensive and 60 healthy). Salivary TAC was evaluated by spectrophotometric assay.

RESULTS

Enalapril is not xerogenic, while metoprolol and drug combinations are. In the presence of DM type 2, all drugs, except metoprolol, had pronounced xerogenic effect. Binary logistic regression analysis found enalapril to be significantly associated with decreased risk of xerogenic effect development, while DM type 2 with increased risk. In the presence of enalapril in hypertensive patients with/without DM type 2 salivary TAC was similar to that in healthy subjects, while for metoprolol was reduced.

CONCLUSIONS

Enalapril is not xerogenic but is antioxidant, which moderately reduces the risk of xerogenic effect development even in the presence of DM type 2. However, metoprolol and drug combinations exhibit xerogenic effect. In DM type 2, xerogenic effect of all drugs was pronounced except of metoprolol.

Reduced muscarinic parotid secretion is underlain by impaired NO signaling in diabetic rabbits

OBJECTIVES

The influence of experimental diabetes (alloxan, 100 mg kg(-1) ) was studied on rabbit parotid gland function.

MATERIAL AND METHODS

Carbachol-induced parotid secretion in vivo, and in vitro quantification of inducible nitric oxide synthase (iNOS) mRNA expression, by real-time RT-PCR, and activity of superoxide dismutase (SOD) and total antioxidant capacity (TAC) in commercial colorimetric assays were measured in parotid glands of non-diabetic and diabetic rabbits.

RESULTS

Carbachol-induced dose-dependent increase in parotid secretion significantly reduced in diabetic rabbits. Functional studies in the presence of muscarinic receptor and nitric oxide synthase (NOS) antagonists revealed that in M3 receptor-mediated carbachol secretion, nitric oxide, deriving mainly from neuronal NOS (nNOS) in control, and iNOS in diabetic rabbits, was involved. Also, upregulation of iNOS mRNA expression and enhanced SOD activity and TAC were detected in diabetic glands.

CONCLUSIONS

Our data suggest that decreased M3 receptor-mediated parotid secretion in diabetic rabbits appears to be due to alterations in NO signaling, mainly due to iNOS induction, accompanied by elevated antioxidant response.

Attenuated vasodilator effectiveness of protease-activated receptor 2 agonist in heterozygous par2 knockout mice

Studies of homozygous PAR2 gene knockout mice have described a mix of phenotypic effects in vitro and in vivo. However, there have been few studies of PAR2 heterozygous (wild-type/knockout; PAR2-HET) mice. The phenotypes of many hemi and heterozygous transgenic mice have been described as intermediates between those of wild-type and knockout animals. In our study we aimed to determine the effects of intermediary par2 gene zygosity on vascular tissue responses to PAR2 activation. Specifically, we compared the vasodilator effectiveness of the PAR2 activating peptide 2-furoyl-LIGRLO-amide in aortas of wild-type PAR2 homozygous (PAR2-WT) and PAR2-HET mice. In myographs under isometric tension conditions, isolated aortic rings were contracted by alpha 1-adrenoeceptor agonist (phenylephrine), and thromboxane receptor agonist (U46619) and then relaxation responses by the additions of 2-furoyl-LIGRLO-amide, acetylcholine, and nitroprusside were recorded. A Schild regression analysis of the inhibition by a PAR2 antagonist (GB-83) of PAR2 agonist-induced aortic ring relaxations was used to compare receptor expression in PAR2-WT to PAR2-HET. PAR2 mRNA in aortas was measured by quantitative real-time PCR. In aortas contracted by either phenylephrine or U46619, the maximum relaxations induced by 2-furoyl-LIGRLO-amide were less in PAR2-HET than in the gender-matched PAR2-WT. GB-83 was 3- to 4-fold more potent for inhibition of 2fly in PAR2-HET than in PAR2-WT. PAR2 mRNA content of aortas from PAR2-HET was not significantly different than in PAR2-WT. Acetylcholine- and nitroprusside-induced relaxations of aortas from PAR2-HET were not significantly different than in PAR2-WT and PAR2 knockout. An interesting secondary finding was that relaxations induced by agonists of PAR2 and muscarinic receptors were larger in females than in males. We conclude that the lower PAR2-mediated responses in PAR2-HET aortas are consistent with evidence of a lower quantity of functional receptor expression, despite the apparently normal PAR2 mRNA content in PAR2-HET aortas.