Učešće serotonergičkih mehanizama u antinociceptivnom dejstvu metformina

Metformin, a well-known antidiabetic drug, has been shown to possess analgesic properties in inflammatory pain models, but the mechanisms of its antinociceptive effects are not completely understood (1,2). We aimed to examine the involvement of serotonergic mechanisms in metformin-induced antinociception in a model of inflammatory pain, using the formalin test in mice. Firstly, we examined the antinociceptive effects of intraperitoneally administered metformin in the first and second phase of the test. Then, the involvement of serotonergic receptors was evaluated by intraperitoneally pretreating mice with a 5-HT1B/1D (GR127935) or 5-HT1A receptor antagonist (WAY100635). Further, we examined the effect of metformin after depletion of endogenous serotonin with a tryptophan-hydroxylase inhibitor (PCPA; applied intraperitoneally for 4 days). Additionally, to avoid misinterpretation of motor incoordination, we performed the rotarod test with the highest tested metformin dose. Metformin (50-200 mg/kg) produced significant and dose-dependent antinociceptive effects (17-81%) in the second (inflammatory) phase of the test. Pretreatment with antagonists significantly reduced the antinociceptive effect of metformin (150 mg/kg). GR127935 inhibited the effects of metformin by 67% (1 mg/kg) and 100% (3 mg/kg), whereas the inhibitory effects for WAY100635 were 19% (1 mg/kg) and 68% (3 mg/kg). Depletion of serotonin with PCPA (100 mg/kg/day) significantly reduced the antinociceptive effects of higher metformin doses (150 and 200 mg/kg). Metformin (200 mg/kg) had no influence on rotarod performance. This study demonstrates that 5-HT1B/1D and 5-HT1A receptors are involved in metformin’s antinociceptive effects and that metformin’s action on these receptors seems to be indirect (mediated by endogenous serotonin released by metformin).Metformin je dobro poznat antidijabetik, za koji je pokazano da poseduje analgetička svojstva u modelima inflamatornog bola. Međutim, mehanizmi njegovog antinociceptivnog dejstva nisu u potpunosti rasvetljeni (1,2). Cilj ovog rada je bio ispitati učešće serotonergičkih mehanizama u antinociceptivnom dejstvu metformina u inflamatornom modelu bola – korišćenjem formalinskog testa kod miševa. Inicijalno su ispitani antinociceptivni efekti metformina, nakon intraperitonealne primene, u prvoj i drugoj fazi testa. Uključenost serotoninskih receptora je procenjena nakon intraperitonealne primene antagonista 5-HT 1B/1D (GR127935) ili 5-HT1A (WAY100635) receptora. U nastavku eksperimenata, efekat metformina je ispitan nakon deplecije endogenog serotonina, primenom inhibitora triptofan-hidroksilaze (PCPA; primenjen intraperitonealno tokom 4 dana). Dodatno, efekat najveće testirane doze metformina je ispitan u rotarod testu, kako bi se isključila mogućnost pogrešnog tumačenja motorne inkoordinacije. Metformin (50-200 mg/kg) je pokazao značajno i dozno-zavisno antinociceptivno dejstvo (17-81%) u drugoj (inflamatornoj) fazi testa. Primena antagonista je značajno smanjila antinociceptivni efekat metformina (150 mg/kg). GR127935 je inhibirao efekte metformina za 67% (1 mg/kg) i 100% (3 mg/kg), dok su inhibitorni efekti WAY100635 bili 19% (1 mg/kg) i 68% (3 mg/kg). Deplecija serotonina korišćenjem PCPA (100 mg/kg/dan) je značajno smanjila antinociceptivne efekte metformina primenjenog u većim dozama (150 i 200 mg/kg). Metformin (200 mg/kg) nije imao značajan uticaj na performanse miševa u rotarod testu. Ova studija je pokazala uključenost 5-HT1B/1D i 5-HT1A receptora u antinociceptivnom dejstvu metformina, koje je verovatno posledica indirektnog uticaja leka na receptore (posredstvom oslobađanja endogenog serotonina od strane metformina).VIII Kongres farmaceuta Srbije sa međunarodnim učešćem, 12-15.10.2022. Beogra

Aktivacija perifernih serotoninskih 5‐HT1A i 5‐HT 1B/1D receptora doprinosi antinociceptivnom dejstvu metformina

Several lines of (pre)clinical evidence have emerged that the antidiabetic drug metformin can alleviate inflammatory/neuropathic pain (1). Although the mechanism is not completely understood, there are reports that metformin can affect neurotransmitters involved in pain modulation, such as its ability to increase peripheral serotonin release (2). Here, we evaluated metformin’s efficacy following local peripheral administration in an inflammatory pain model and examined the potential involvement of serotonin receptors. We used the formalin test in mice, where we measured duration of nociceptive behavior in the first and second phase of the test. First, we examined the metformin’s antinociceptive effects following intraplantar administration. Additionally, the highest tested metformin dose was applied contralateral to the formalin-injected side, to exclude possible systemic effects. In the second part, we evaluated the effects of a 5-HT1A (WAY100635) and 5-HT1B/1D antagonist (GR127935) on the antinociceptive effects of a fixed, effective dose of metformin (antagonists were co-administered intraplantarly with metformin). Metformin (0.1-2 mg/paw) produced significant and dose-dependent antinociceptive effects (32-72%) in the second (inflammatory) phase. Contralateral application of metformin (2 mg/paw) had no significant antinociceptive effects. Both antagonists significantly reduced the antinociceptive effects of metformin (1 mg/paw). The levels of inhibition of metformin’s antinociceptive effect produced by WAY100635 were 56% (5 μg/paw) and 82% (7.5 μg/paw), whereas GR127935 inhibited metformin’s efficacy by 24% (3.75 μg/paw) and 80% (5 μg/paw). This study demonstrates that peripheral metformin application can produce antinociceptive effects against inflammatory pain and that activation of peripheral 5-HT 1A and 5-HT1B/1D receptors contributes to these effects.Postoje brojni dokazi iz (pre)kliničkih studija da metformin, lek iz grupe antidijabetika, može ublažiti inflamatorni/neuropatski bol (1). Iako mehanizam dejstva nije u potpunosti razjašnjen, podaci ukazuju da metformin može uticati na neurotransmitere uključene u modulaciju bola, poput sposobnosti da poveća oslobađanje serotonina na periferiji (2). U ovom radu je ispitana efikasnost metformina nakon lokalne periferne primene u modelu inflamatornog bola, kao i potencijalna uključenost serotoninskih receptora. Korišćen je formalinski test kod miševa, u kome je mereno vreme provedeno u nociceptivnom ponašanju, u prvoj i drugoj fazi testa. Prvo su ispitani antinociceptivni efekti metformina nakon intraplantarne primene. Dodatno, najveća testirana doza metformina je primenjena kontralateralno u odnosu na mesto injektovanja formalina, kako bi se isključili mogući sistemski efekti. U drugom delu studije, ispitani su efekti antagoniste 5-HT 1A (WAY100635) i 5-HT1B/1D (GR127935) receptora na antinociceptivno dejstvo fiksne, efektivne doze metformina (antagonisti su primenjeni intraplantarno, istovremeno sa metforminom). Metformin (0,1-2 mg/šapi) je ispoljio značajan i dozno-zavisan antinociceptivni efekat (32-72%) u drugoj (inflamatornoj) fazi testa. Kontralateralna primena metformina (2 mg/šapi) nije imala značajan antinociceptivni efekat. Primenjeni antagonisti su značajno smanjili antinociceptivne efekte metformina (1 mg/šapi). Stepeni inhibicije antinociceptivnog dejstva metformina koje je postigao WAY100635 su bili 56% (5 μg/šapi) i 82% (7,5 μg/šapi), dok je GR127935 inhibirao efikasnost metformina za 24% (3,75 μg/šapi) i 80% (5 μg/šapi). Ova studija je pokazala da periferna primena metformina proizvodi antinociceptivni efekat kod inflamatornog bola i da aktivacija perifernih 5-HT1A i 5- HT1B/1D receptora doprinosi ovom efektu.VIII Kongres farmaceuta Srbije sa međunarodnim učešćem, 12-15.10.2022. Beogra