Role of bradykinin B₁ receptors in diabetes-induced hyperalgesia in streptozotocin-treated mice

Abstract

Insulin-dependent diabetes mellitus (type-1 diabetes) is an inflammatory autoimmune disease associated with vascular permeability changes leading to many complications including nephropathy, retinopathy, hypertension, hyperalgesia and neuropathy. The bradykinin B₁ receptor was recently found to be upregulated during the development of the diabetes and to be involved in its complications. Kinins are known to be important mediators of a variety of biological effects including cardiovascular homeostasis, inflammation and nociception. In the present study, we studied the effect of the selective B₁ receptor agonist, des-Arg⁹-bradykinin, and its specific antagonists, Ac-Lys-[d-β Nal⁷, Ile⁸]des-Arg⁹-bradykinin (R-715) and Ac-Orn-[Oic², αMe Phe⁵, d-β Nal⁷, Ile⁸]des-Arg⁹-bradykinin (R-954), on diabetic hyperalgesia. Diabetes was induced in male CD-1 mice by injecting a single high dose of streptozotocin (200 mg kg⁻¹, i.p.) and the nociception was assessed using the hot plate and the tail flick tests, 1 week following the injection of streptozotocin. Our results showed that induction of diabetes by streptozotocin provoked a marked hyperalgesia in diabetic mice expressed as about 11% decrease in hot plate reaction time and 26% decrease in tail flick reaction time. Following acute administration of R-715 (200–800 μg kg⁻¹, i.p.) and R-954 (50–600 μg kg⁻¹, i.p.), this hyperalgesic activity was blocked and the hot plate and tail flick latencies of diabetic mice returned to normal values observed in control healthy mice. In addition, the acute administration of des-Arg⁹-bradykinin (200–600 μg kg⁻¹, i.p.) significantly potentiated diabetes-induced hyperalgesia, an effect that was totally reversed by R-715 (1.6–2.4 mg kg⁻¹, i.p.) and R-954 (0.8–1.6 mg kg⁻¹, i.p.). These results provide a major evidence for the implication of the bradykinin B₁ receptors in the development of hyperalgesia associated with diabetes and suggest a novel approach to the treatment of this diabetic complication using the bradykinin B₁ receptor antagonists.

Introduction

Chronic inflammatory and cardiovascular diseases that often lead to pain are of increasing importance for health care in aging populations. Pain is a normal physiological protective mechanism to avoid tissue damage. In the periphery, it is signalled by fine C and Aδ afferent fibres that respond to noxious stimuli (mechanical, heat, cold, chemical). Indeed, all tissues, with the exception of the neuropil of the central nervous system (CNS), are innervated by such afferent fibres. However, pain is not a uniform sensation, and the quality of pain as well as the initiation of protective responses is determined by many factors within the spinal cord and in higher brain structures involved in the integration and modification of nociceptive signals (Dray, 1997).

When significant tissue damage occurs, pain is often more persistent and is associated with inflammation. In these circumstances, hyperalgesia and tenderness around the inflamed region occur. Activation and sensitization of peripheral nociceptors by chemical mediators produced by tissue injury and inflammation partially accounts for this. However, in hyperalgesia, there is also facilitation of transmission at the level of the dorsal horn and the thalamus associated with changes in the central processing of pain signals, which allows signals generated by normally innocuous stimuli, such as gentle stroking, to be perceived as painful. In most cases, inflammation is a common and complex feature of clinical pain. The action of chemical mediators produced during inflammation is responsible for the multiplicity of events that occur, including hyperalgesia, alterations in cell phenotype, and the expression of new molecules (neurotransmitters, enzymes, ion channels, receptors) in the peripheral nervous system and the CNS Levine et al., 1993, Dray, 1994.

Kinins have been known for some time to be important mediators implicated in a variety of biological effects including cardiovascular homeostasis, inflammation and nociception (for review, see Marceau et al., 1998, Calixto et al., 2000). They are probably the first mediators released in injured tissues from kininogens either by plasma kallikrein, which is activated early in the coagulation cascade, or tissue kallikrein, which is activated by proteases released at injured sites (Bhoola et al., 1992). Their production is critical for the initiation of pain and exaggeration of sensory signalling to produce hyperalgesia and allodynia. In addition, they promote many features of inflammation including an increase in blood flow and tissue oedema as well as the release of several mediators such as prostanoids and cytokines Levine et al., 1993, Dray, 1994, Dray, 1995. Kinins mediate their biological effects by acting on two types of receptors, namely, B₁ and B₂. The B₂ receptors, which mediate many of the physiological effects of kinins, are constitutively expressed and involved in the acute phase of the inflammation and pain response. On the other hand, the B₁ receptors, usually absent in normal tissues, are highly induced and overexpressed during tissue injury and following treatment with inflammatory mediators like bacterial endotoxins and cytokines. They do not desensitize after agonist binding and participate in the chronic phase of the inflammation and pain response (Couture et al., 2001). The therapeutic value of intervention in the kallikrein–kinin system has not been fully explored. The known kinin receptors might be suitable pharmacological targets to treat chronic inflammatory and cardiovascular diseases and support new concepts of analgesic drug design through blockade of kinin receptors (Pesquero et al., 2000).

Diabetes mellitus is a term that describes a series of complex and chronic disorders characterized by symptomatic glucose intolerance due to defective insulin secretion, insulin action or both. The chronic hyperglycemia of diabetes mellitus is associated with significant long-term sequelae, particularly damage, dysfunction and failure of various organs. The dysfunction of the vascular endothelium and the micro- and macrovascular permeability changes lead to many diabetic complications including nephropathy, retinopathy, neuropathy, hypertension and hyperalgesia (Steil, 1999).

Experimental evidence suggests that diabetes upregulates bradykinin B₁ receptors as a consequence of the overproduction of cytokines and of the oxidative stress effect of hyperglycemia Rabinovitch, 1998, Yerneni et al., 1999. Other pharmacological studies suggest that the B₁ receptor intervenes in the pathogenesis of streptozotocin-induced diabetes in mice as bradykinin B₁ receptor antagonists could normalize glycemia and renal function Zuccollo et al., 1996, Zuccollo et al., 1999. In addition, it has been recently demonstrated that these antagonists were able to inhibit the increase in plasma extravasation associated with diabetic mice (Simard et al., submitted for publication). The Streptozotocin model is the most commonly used to study the cardiovascular and neuropathic complications of type-1 diabetes. Streptozotocin is an antibiotic extracted from Streptomyces acromogens, which is selectively toxic for pancreatic islet β-cells. The decomposition products of streptozotocin alter the cellular membrane proteins so that they are no longer recognized as self and thus initiating an autoimmune inflammatory process associated with cytokines Wilson and Leiter, 1990, Lukić et al., 1998 resulting in the destruction of pancreatic β-islets. In addition, streptozotocin can alter DNA in such a manner that a previously silent gene is expressed or a normal protein is altered by point mutation (Wilson and Leiter, 1990). The objective of the present study was to investigate the role of bradykinin B₁ receptors in hyperalgesia associated with the development of diabetes induced by streptozotocin in mice. The effects of the selective bradykinin B₁ receptor agonist des-Arg⁹-bradykinin Regoli et al., 1998, Regoli et al., 2001 and its specific antagonists Ac-Lys-[d-β Nal⁷, Ile⁸]des-Arg⁹-bradykinin (R-715) and Ac-Orn-[Oic², αMe Phe⁵, d-β Nal⁷, Ile⁸]des-Arg⁹-bradykinin (R-954) (Neugebauer et al., 2002) were studied on the hyperalgesic response in diabetic mice.