melitten and Pain

Melittin is a basic 26-amino-acid polypeptide that constitutes 40-60% of dry honeybee (Apis mellifera) venom. Although much is known about its strong surface activity on lipid membranes, less is known about its pain-producing effects in the nervous system. In this review, we provide lines of accumulating evidence to support the hypothesis that melittin is the major pain-producing substance of bee venom. At the psychophysical and behavioral levels, subcutaneous injection of melittin causes tonic pain sensation and pain-related behaviors in both humans and animals. At the cellular level, melittin activates primary nociceptor cells through direct and indirect effects. On one hand, melittin can selectively open thermal nociceptor transient receptor potential vanilloid receptor channels via phospholipase A2-lipoxygenase/cyclooxygenase metabolites, leading to depolarization of primary nociceptor cells. On the other hand, algogens and inflammatory/pro-inflammatory mediators released from the tissue matrix by melittin's pore-forming effects can activate primary nociceptor cells through both ligand-gated receptor channels and the G-protein-coupled receptor-mediated opening of transient receptor potential canonical channels. Moreover, subcutaneous melittin up-regulates Nav1.8 and Nav1.9 subunits, resulting in the enhancement of tetrodotoxin-resistant Na(+) currents and the generation of long-term action potential firing. These nociceptive responses in the periphery finally activate and sensitize the spinal dorsal horn pain-signaling neurons, resulting in spontaneous nociceptive paw flinches and pain hypersensitivity to thermal and mechanical stimuli. Taken together, it is concluded that melittin is the major pain-producing substance of bee venom, by which peripheral persistent pain and hyperalgesia (or allodynia), primary nociceptive neuronal sensitization, and CNS synaptic plasticity (or metaplasticity) can be readily induced and the molecular and cellular mechanisms underlying naturally-occurring venomous biotoxins can be experimentally unraveled.

Topics: Animals; Bee Venoms; Bees; Melitten; Nociceptors; Pain

The aim of the present study was to investigate whether melittin, the principal toxin of the honeybee (Apis mellifera) venom, can be used as an algogenic agent in the study of pain in humans. Five micrograms of melittin in 0.5 ml of saline was intradermally injected into the volar aspect of the forearm. Resultant pain was scored by a visual analogue scale (VAS), and skin temperature change was analyzed by means of a computer-assisted infrared thermography. Intradermal melittin temporarily produced severe pain, followed by a sustained increase in skin temperature. The skin temperature increase peaked in about 10 min and outlasted 1 h. Topical application of 10% lidocaine gel did not significantly suppress the melittin-induced pain, but markedly suppressed both the increase in the peak temperature and the area of temperature increase. In conclusion, 5 microg of melittin is sufficient to produce pain in humans and 10% lidocaine gel differentially decreases the melittin-induced axon reflex without any significant analgesic effect.

Topics: Administration, Topical; Adult; Aged; Anesthetics, Local; Axons; Diagnosis, Computer-Assisted; Female; Gels; Humans; Injections, Intradermal; Lidocaine; Male; Melitten; Middle Aged; Pain; Reflex; Skin Temperature; Thermography; Time Factors

Most species of bee are capable of delivering a defensive sting which is often painful. A solitary lifestyle is the ancestral state of bees and most extant species are solitary, but information on bee venoms comes predominantly from studies on eusocial species. In this study we investigated the venom composition of the Australian great carpenter bee, Xylocopa aruana Ritsema, 1876. We show that the venom is relatively simple, composed mainly of one small amphipathic peptide (XYTX

Topics: Animals; Apamin; Australia; Bee Venoms; Bees; Mammals; Melitten; Mice; Pain; Peptides; Phospholipases A2; Toxins, Biological

The present study was aimed to establish a model of chronic prostatitis in rat with the use of intraprostatic injection of Complete Freund's Adjuvant, and to examine the anti-inflammatory and analgesic effects of melittin on the newly-developed chronic prostatic pain model.. Adult male Sprague-Dawley rats were injected with Complete Freund's Adjuvant (CFA) into the prostate. Twelve days after model rats of the treatment group were injected melittin into the prostate, while those of the control group received sterile saline injection. The nociceptive effects of CFA were evaluated by using a behavior approach (i.e. mechanical pain threshold measurement) on the day of CFA injection and 6, 12, and 18days after CFA injection. After the in-live study was done, the prostate was collected for histological examination of inflammatory cell infiltration. Levels of cyclooxygenase (COX)-2 in prostate and glial fibrillary acidic protein (GFAP) in spinal cord were determined using immunohistochemistry. Rats of the sham control group received intraprostatic injection of sterile saline and were studied using the same methods RESULTS: Intraprostatic CFA injection induced local allodynia that lasted over at least 2 weeks. The pain behavior of rat was associated with increases in inflammatory cell infiltration into the prostate. Levels of COX-2 in prostate and GFAP in spinal cord were also elevated. Treatment with melittin significantly raised pain threshold, decreased inflammatory infiltrates, and suppressed COX-2 and GFAP expression.. Intraprostatic injection of CFA induced neurogenic prostatitis and prostatic pain. The established model will be useful to the study of CP/CPPS pathogenesis. Melittin demonstrated profound anti-inflammatory and analgesic effects on the chronic prostatic pain model, suggesting melittin may hold promise as a novel therapeutic for treatment of CP/CPPS.

Topics: Animals; Chronic Disease; Cyclooxygenase 2; Disease Models, Animal; Freund's Adjuvant; Glial Fibrillary Acidic Protein; Hyperalgesia; Inflammation; Male; Melitten; Pain; Pain Measurement; Pain Threshold; Prostatitis; Rats; Rats, Sprague-Dawley; Spinal Cord

Tetrodotoxin-resistant (TTX-R) sodium channels NaV1.8 and NaV1.9 in dorsal root ganglion (DRG) neurons play important roles in pathological pain. We recently reported that melittin, the major toxin of whole bee venom, induced action potential firings in DRG neurons even in the presence of a high concentration (500 nM) of TTX, indicating the contribution of TTX-R sodium channels. This hypothesis is fully investigated in the present study. After subcutaneous injection of melittin, NaV1.8 and NaV1.9 significantly upregulate mRNA and protein expressions, and related sodium currents also increase. Double immunohistochemical results show that NaV1.8-positive neurons are mainly medium- and small-sized, whereas NaV1.9-positive ones are only small-sized. Antisense oligodeoxynucleotides (AS ODNs) targeting NaV1.8 and NaV1.9 are used to evaluate functional significance of the increased expressions of TTX-R sodium channels. Behavioral tests demonstrate that AS ODN targeting NaV1.9, but not NaV1.8, reverses melittin-induced heat hypersensitivity. Neither NaV1.8 AS ODN nor NaV1.9 AS ODN affects melittin-induced mechanical hypersensitivity. These results provide previously unknown evidence that upregulation of NaV1.9, but not NaV1.8, in small-sized DRG neurons contributes to melittin-induced heat hypersensitivity. Furthermore, melittin-induced biological effect indicates a potential strategy to study properties of TTX-R sodium channels.

Topics: Action Potentials; Animals; Cells, Cultured; Down-Regulation; Drug Resistance; Ganglia, Spinal; Hot Temperature; Hyperalgesia; Ion Channel Gating; Male; Melitten; NAV1.8 Voltage-Gated Sodium Channel; NAV1.9 Voltage-Gated Sodium Channel; Nerve Tissue Proteins; Nociception; Oligodeoxyribonucleotides, Antisense; Pain; Patch-Clamp Techniques; Rats; Rats, Sprague-Dawley; Sensory Receptor Cells; Sodium; Tetrodotoxin; Touch

The effects induced by Apis mellifera venom (AMV), melittin-free AMV, fraction with molecular mass < 10 kDa (F<₁₀) or melittin in nociceptive and inflammatory pain models in mice were investigated. Subcutaneous administration of AMV (2, 4 or 6 mg/kg) or melittin-free AMV (1, 2 or 4 mg/kg) into the dorsum of mice inhibited both phases of formaldehyde-induced nociception. However, F<₁₀ (2, 4 or 6 mg/kg) or melittin (2 or 3 mg/kg) inhibited only the second phase. AMV (4 or 6 mg/kg), but not F<₁₀, melittin-free AMV or melittin, induced antinociception in the hot-plate model. Paw injection of AMV (0.05 or 0.10 mg), F<₁₀ (0.05 or 0.1 mg) or melittin (0.025 or 0.050 mg) induced a nociceptive response. In spite of inducing nociception after paw injection, scorpion (Tityus serrulatus) or snake (Bothrops jararaca) venom injected into the dorsum of mice did not inhibit formaldehyde-induced nociception. In addition, AMV (6 mg/kg), but not F<₁₀ (6 mg/kg) or melittin (3 mg/kg), inhibited formaldehyde paw oedema. Concluding, AMV, F<₁₀ and melittin induce two contrasting effects: nociception and antinociception. AMV antinociception involves the action of different components and does not result from non-specific activation of endogenous antinociceptive mechanisms activated by exposure to noxious stimuli.

Topics: Analysis of Variance; Animals; Bee Venoms; Formaldehyde; Inflammation; Male; Melitten; Mice; Motor Activity; Pain; Pain Measurement

Bee venom (BV) has been used for millennia in Chinese traditional medicine to treat rheumatoid arthritis (RA). However, its components and mechanism remain unclear, which has hampered its development and application for the treatment of RA. In this study, we examined the anti-arthritis effects of melittin, which composes nearly 50% of the dry weight of whole BV, on the complete Freund's adjuvant-induced (CFA-induced) RA model in rats. The RA animal models were treated with solutions of BV, melittin, and saline by injection into a specific acupoint (Zusanli). The BV and melittin treatments statistically diminished the thickness of the arthroses in the injected side of the paw, compared to the saline treatment. Melittin therapy also significantly reduced arthritis-induced nociceptive behaviors, as assessed by the thermal hyperalgesia test. In addition, CFA-induced Fos expression in the superficial layer of the lumbar spinal cord was significantly suppressed by the BV and melittin treatments, compared to the saline treatment. These results indicate that melittin is an effective anti-arthritis component of whole bee venom, making it a promising candidate as an anti-arthritis drug.

Topics: Acupuncture Points; Animals; Antirheumatic Agents; Apitherapy; Arthritis, Experimental; Arthritis, Rheumatoid; Bee Venoms; Disease Models, Animal; Freund's Adjuvant; Hot Temperature; Hyperalgesia; Lower Extremity; Male; Melitten; Pain; Rats; Rats, Sprague-Dawley; Spinal Cord

A recent report from our laboratory shows that subcutaneous (s.c.) injection of melittin could induce persistent spontaneous nociception (PSN) and primary thermal or mechanical hyperalgesia. However, the exact peripheral mechanisms underlying melittin-induced multiple pain-related behaviors remain unclear. In this study, behavioral tests combined with pharmacological manipulations were used to explore potential roles of local P2X and P2Y receptors in melittin-induced inflammatory pain and hyperalgesia. Post-treatment of the primary injury site with s.c. injection of A-317491 (a potent P2X(3)/P2X(2/3) receptor antagonist) and Reactive Blue 2 (a potent P2Y receptor antagonist) could significantly suppress the development of melittin-evoked PSN and hypersensitivity (thermal and mechanical). Our control experiments demonstrated that local administration of either antagonist into the contralateral hindpaw produced no significant effect on any kind of pain-associated behaviors. Taken together, these data indicate that activation of P2X and P2Y receptors might be essential to the maintenance of melittin-induced primary thermal and mechanical hyperalgesia as well as on-going pain.

Topics: Animals; Hypersensitivity; Male; Melitten; Nociceptors; Pain; Phenols; Polycyclic Compounds; Rats; Rats, Sprague-Dawley; Receptors, Purinergic P2; Receptors, Purinergic P2X

To identify the active components of honeybee venom in production of inflammation and pain-related behaviors, five major peptidergic subfractions were separated, purified and identified from the whole honeybee venom. Among them, four active peptidergic components were characterized as apamin, mast-cell degranulating peptide (MCDP), phospholipase A(2) (PLA(2))-related peptide and melittin, respectively. All five subfractions were effective in production of local inflammatory responses (paw edema) in rats although the efficacies were different. Among the five identified subfractions, only MCDP, PLA(2)-related peptide and melittin were able to produce ongoing pain-related behaviors shown as paw flinches, while only apamin and melittin were potent to produce both thermal and mechanical hypersensitivity. As shown in our previous report, melittin was the most potent polypeptide in production of local inflammation as well as ongoing pain and hypersensitivity. To further explore the peripheral mechanisms underlying melittin-induced nociception and hypersensitivity, a single dose of capsazepine, a blocker of thermal nociceptor transient receptor potential vanilloid receptor 1, was treated s.c. prior to or after melittin administration. The results showed that both pre- and post-treatment of capsazepine could significantly prevent and suppress the melittin-induced ongoing nociceptive responses and thermal hypersensitivity, but were without influencing mechanical hypersensitivity. The present results suggest that the naturally occurring peptidergic substances of the whole honeybee venom have various pharmacological potencies to produce local inflammation, nociception and pain hypersensitivity in mammals, and among the five identified reverse-phase high pressure liquid chromatography subfractions (four polypeptides), melittin, a polypeptide occupying over 50% of the whole honeybee venom, plays a central role in production of local inflammation, nociception and hyperalgesia or allodynia following the experimental honeybee's sting. Peripheral transient receptor potential vanilloid receptor 1 is likely to be involved in melittin-produced ongoing pain and heat hyperalgesia, but not mechanical hyperalgesia, in rats.

Topics: Amino Acid Sequence; Animals; Apamin; Bee Venoms; Inflammation; Injections, Subcutaneous; Melitten; Molecular Sequence Data; Pain; Peptides; Rats; Sequence Alignment; Sequence Homology, Amino Acid; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization

Recently, we have reported that following s.c. injection of a solution containing the whole bee-venom (BV; Apis mellifera), into one hind paw of a rat, the experimentally produced honeybee's sting, the animal shows altered pain-related behaviors and inflammation relevant to pathological pain state. To see whether melittin, the major (over 50%) toxic component of the BV, is responsible for the above abnormal pain behavioral changes, the present study was designed to investigate the effects of s.c. melittin on either nociceptive behaviors in conscious rats or spinal dorsal horn neuronal responses in anesthetized rats. In the behavioral surveys, s.c. injection of three doses of both melittin (5, 25 and 50 microg) and BV (10, 50 and 100 microg) into the posterior surface of one hind paw of rats produced an immediate tonic nociceptive response displaying as persistent spontaneous paw flinching reflex. Similar to the BV test, the melittin response was also monophasic and dose-dependent in terms of both intensity and time course. As an accompanied consequence, both heat and mechanical hypersensitivity (hyperalgesia and allodynia) and inflammatory responses (paw swelling and plasma extravasation) were induced by s.c. melittin injections. In the electrophysiological recordings, s.c. injection of the same three doses of melittin into the cutaneous receptive field produced an immediate, dose-dependent increase in spontaneous spike discharges of spinal dorsal horn wide-dynamic-range (WDR) neurons which are believed to be responsible for the spinally-organized nociceptive flexion reflex. The melittin-induced ongoing spike responses are similar to the behavioral flinching reflex in terms of both duration and frequency. Furthermore, the responsiveness of the WDR neurons to both heat (42 degrees C, 45 degrees C, 47 degrees C and 49 degrees C) and mechanical (brush, pressure and pinch) stimuli was significantly enhanced by s.c. injection of melittin shown as a leftward shift of the stimulus-response functional curves. Taken together, the present results suggest that melittin, the major toxin of the whole BV, is likely to be responsible for production of the long-term spinal neuronal changes as well as persistent spontaneous nociception, heat/mechanical hypersensitivity and inflammatory responses that are produced by experimental honeybee's sting.

Topics: Animals; Dose-Response Relationship, Drug; Electrophysiology; Hindlimb; Hot Temperature; Inflammation; Male; Melitten; Neurons; Pain; Physical Stimulation; Rats; Rats, Sprague-Dawley; Spinal Cord

Melittin (a main compound of bee venom) and capsaicin were injected intradermally in healthy human volunteers: (1) to study secondary mechanical hyperalgesia (static hyperalgesia and dynamic hyperalgesia) around the injection site; and (2) to correlate the sensory changes to the neurogenic inflammation assessed by laser-doppler blood flowmetry. Melittin 50 microg and capsaicin 10 microg induced comparable spontaneous pain and increased blood flow (neurogenic inflammation). Intradermal injection of melittin induced regions of secondary mechanical hyperalgesia around the injection site, however, they were not as large as the hyperalgesia induced by capsaicin. This is the first report studying mechanical hyperalgesia induced by melittin in humans, and the results were in agreement with the previous observations in rats. Melittin seems to be a valuable model to study a possible contribution of neurogenic inflammation to hyperalgesia in humans.

Topics: Analysis of Variance; Bee Venoms; Capsaicin; Humans; Hyperalgesia; Injections, Intradermal; Melitten; Neurogenic Inflammation; Pain; Pain Measurement; Physical Stimulation; Regional Blood Flow; Skin; Time Factors

Melittin is the main toxin of honeybee venom. Previously, we have reported that intradermal injection of melittin into the volar aspect of forearm in humans produces a temporary pain and a subsequent sustained increase in the skin temperature due to axon reflex. To clarify the interaction between nociceptive inputs and vascular changes, we studied the influence of noxious stimulation by intradermal melittin on the vasomotor control of the distal extremities in human volunteers. Temperature changes of the bilateral palmar surface were recorded by means of a computer-assisted infrared thermography. Unexpectedly, we found a biphasic response of skin temperature. The skin temperature of both fingers and hands decreased immediately after the melittin injection and then increased well above the control level, prior to the injection. There was a considerable individual variation in the baseline skin temperature, prior to melittin. The skin temperature in a finger/hand with lower preinjection value increased more markedly in the second phase. Consequently, the individual variation in the peak temperature of the second phase was less pronounced. The initial decrease was interpreted as sympathetic vasoconstrictor reflex induced by noxious stimulation and the later increase as release of sympathetic vasomotor tone.

Topics: Adult; Blood Vessels; Female; Functional Laterality; Humans; Male; Melitten; Nerve Fibers, Unmyelinated; Nociceptors; Pain; Pain Measurement; Reflex; Skin; Skin Temperature; Sympathetic Fibers, Postganglionic; Vasoconstriction; Vasodilation; Vasomotor System