chapter  7
MicroRNAs and Pain
Pages 24

Pain is a global health problem and one of the most common conditions for which people seek medical attention (Goldberg and McGee, 2011). Pain management has been considered a human right (Lohman et al., 2010). The International Association for the Study of Pain denes pain as an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage (Merskey, 1979; Merskey and Bogduk, 1986). Acute pain can be brief and short lasting or persistent until the disease or injury heals. However, chronic pain is pain without biological value that persists beyond the normal anticipated healing time. Chronic pain is dened as pain lasting more than 3 months and can be recurrent or persistent with a high negative impact on the quality of life and daily functioning (Breivik et al., 2006). About 20% of adults suffer from pain and 10% are newly diagnosed with chronic pain each year (Breivik et al., 2013). Recent studies in Europe have consistently estimated that 25%–35% of adults report chronic pain, which is considered a burden to health-care systems with estimated costs of billions of Euros annually (Reid et  al., 2011). Pain affects all populations, regardless of age, sex, income, race/ethnicity, or geographical borders; although the percentage and format of its effect might vary extensively. For instance, it is known that pain increases with age and is overrepresented in women (Gerdle et  al., 2004; Leresche, 2011). With the demographic changes of an ageing population, a challenge is expected globally (Tsang et al., 2008). Chronic pain is often seen in the neck, back, knee, hip, and other joints; but headaches and neuropathic pain are also common and to an equal extent

7.1 Burden of Pain: A Brief Overview ............................................................... 183 7.1.1 Pain Processing Pathways ................................................................. 184 7.1.2 Nonneuronal Components in Pain .................................................... 185

7.2 Emerging Role of MicroRNAs as Modulators in Pain Processing .............. 185 7.2.1 Transcriptional Changes of MicroRNA in Neurons

in Response to Pain........................................................................... 187 7.2.2 Involvement of MicroRNA in Pain Processing ................................ 188

7.2.2.1 MicroRNA Alterations in Inammatory Pain ................... 188 7.2.2.2 MicroRNA Alterations in Neuropathic Pain ..................... 192

7.3 Role of NeurimmiRs as Modulators of Inammation.................................. 195 7.4 MicroRNAs as Potential Biomarkers in Patients with Pain Conditions ....... 197 7.5 Conclusion and Future Perspectives ............................................................. 198 References .............................................................................................................. 199

disabling (Tsang et al., 2008). Several different risk factors including genetic, environmental, and personality traits have been associated with chronic pain; however, it is not yet completely understood how these factors can lead to abnormal processing of painful signals at molecular, cellular, and network levels (Denk et al., 2014). Not only is the etiology of pain complex but it also coexists with several other conditions such as depression, that makes it even more complicated to approach for a proper management (Dahan et  al., 2014). A better understanding of pain processing is a key factor to assist identifying individuals at risk and eventually will lead to new therapeutic developments. Early identication and adequate management of chronic pain minimize long-term personal suffering and disability (Dworkin, 2012). Better diagnosis, prevention, or treatment of chronic pain may eventually lead to dramatic reduce of the global burden of this disorder.