- Email: [email protected]
Biomarkers for painSee related article by Eisenach et al., pages 207–212 of this issue
Pain 107 (2004) 199–201 www.elsevier.com/locate/pain
Editorial
Biomarkers for pain See related article by Eisenach et al., pages 207 –212 of this issue Cystatin C measured in plasma is a sensitive marker of renal function (Shimizu-Tokiwa et al., 2002). Recently, it was suggested that cystatin C in cerebrospinal fluid could be a marker for human pain (Mannes et al., 2003). The paper by Eisenach et al. in this issue of Pain shows that this is not the case. Cystatin C is a low molecular weight basic protein that belongs to the cystatin superfamily. Cystatins are endogenous cysteine protease inhibitors that modulate the turnover of intracellular and extracellular proteins. Cystatins may play a defensive role in extracellular fluids by protecting organs from the cysteine proteases of invading pathogens (Barrett et al., 1986). Cystatin C is widely distributed in almost all tissues of vertebrates and is secreted by many kinds of cell types into a number of body fluids (Abrahamson et al. 1990). Cystatin C is involved in e.g. tissue remodelling, including tumour metastasis and invasion (Coulibaly et al., 1999; Cox et al., 1999), embryo implantation (Afonso et al., 1997), bone matrix remodelling (Lerner and Grubb, 1992) and cell proliferation (Taupin et al., 2000). In the nervous system cystatin C immunoreactivity has been detected in microglial cells, astrocytes, the choroid plexus and some neurones (Ishimaru et al., 1996; Yasuhara et al., 1993). In the immune system, cystatins have important immunomodulatory functions. They induce tumour necrosis factor and the production of interleukin 10 and nitric oxide (Vray et al., 2002). Cystatin C may play an important role in inflammatory neurologic diseases (Bollengier, 1987). Increased CSF cystatin C concentrations have been found in meningitis, encephalitis and myelitis (Lo¨fberg et al., 1980). However, CSF cystatin C levels were significantly reduced in the acute phase of inflammatory neurologic diseases such as Guillain – Barre´ syndrome, chronic inflammatory demyelinating polyneuropathy and multiple sclerosis (Nagai et al., 2000). Cystatin C is also involved in the development of many degenerative disorders of the CNS such as Alzheimer’s disease (Levy et al., 2001). A group of researchers identified the gene that codes for cystatin C as one of the genes whose expression was upregulated by carrageenan-induced peripheral inflammation in the rat using subtraction cloning and differential hybridization (Yang et al., 2001). It was hypothesized that
cystatin C is a biomarker for pain. The hypothesis was then tested in 10 women at term, five in active labour and pain and another five scheduled for an elective caesarean section without pain. The CSF concentrations of cystatin C were marginally higher ðP , 0:018Þ in the five women that were in painful labour. The authors then suggested that cystatin C would be a cerebrospinal fluid biomarker for pain in humans (Mannes et al., 2003). Eisenach et al. have now studied 131 subjects including healthy volunteers, women in labour with or without pain and patients with chronic neuropathic pain. Their results indicated a minimal association with acute or chronic pain and cystatin C concentrations in the CSF. A separate covariate analysis showed a significant effect of pregnancy. The highest CSF concentrations of cystatin C were measured in the chronic pain patients who had an indwelling intrathecal (i.th.) catheter for the administration of morphine whereas the chronic pain patients without an i.th. catheter had low levels of cystatin C. This could indicate that either the inflammation caused by the catheter or morphine that was infused could increase cystatin C levels. Mannes et al. took a real shortcut in suggesting that cystatin C is a biomarker for pain. As described above, cystatin C is involved in many functions that may or may not have direct relevance to pain. The concentrations of cystatin C in various body fluids most likely reflect the state of the individual disease process rather than pain. We therefore do not have an objective biomarker for pain which Mannes et al. suggested. Such an objective biomarker could be used in conditions when pain cannot be not only assessed directly e.g. in children, elderly and demented, but also be demanded by those who pay for health care delivery, as suggested by Eisenach et al. Such development has many implications. Both papers suggest that ‘pain may lead to an increased spillover of cystatin C into CSF’. Rather than pain causing the spillover of cystatin C into the CSF cystatin C can be a measure of inflammation and tissue injury. But is it conceivable that there would be one single reliable measure even for nociception? Considering the crucial role of pain for survival it is unlikely that nature would have designed a system that relies on one enzyme or neuropeptide only. Several other neuropeptides such as substance P, dynorphin
0304-3959/$20.00 q 2003 Published by Elsevier B.V. on behalf of International Association for the Study of Pain. doi:10.1016/j.pain.2003.12.009
200
E. Kalso / Pain 107 (2004) 199–201
Acknowledgements Dr Vesa Kontinen drew the figure which is acknowledged with gratitude.
References
Fig. 1. Biomarkers of neuronal activity provide information from the early parts of the nociceptive pathway on its way to pain behaviour. Pain behaviour demands treatment that, when successful, has effects on all levels of pain (sensation, experience, behaviour).
(Iadarola et al., 1988), neuropeptide FF (Vilim et al., 1999) are also upregulated in inflammation and could be labelled as biomarkers for pain. All these proteins can be classified as markers of inflammation or tissue injury, not pain. However, like cystatin C they all are involved in many other different physiological functions that have little to do with pain. Neuropathic and inflammatory pain induce very different changes in the neuropeptide profiles. These profiles also change over time. Instead of one biomarker there should be several for different painful states at different time points. But pain is not equivalent to nociception and tissue damage (Fig. 1). Pain needs the brain to be perceived. Pain is defined by IASP as ‘an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage’. This definition refutes the possibility of having a biomarker for pain. Depression, anxiety and pain are all controlled not only by neuropeptides but also by the environment, experience, interaction, the life of the patient in general. They cannot be measured with peptide levels. The danger of making pain too simplistic, something that can be measured in the CSF, is in forgetting the individual experience that is essential in pain. Do we trust the patient’s report or the biomarker’s concentration in the CSF? What information would we get from the biomarkers in the clinic that we would not get through the patient’s report? If the patient’s CSF level of cystatin C is low but the patient reports severe pain which report would you trust? Which report would the insurance company trust? Various proteins can be measured in the CSF and other body fluids. They will increase our understanding of the mechanisms that underlie inflammation, nerve injury and tissue damage. These proteins can also be tested as new targets for therapeutic approaches. The pain experience, however, will remain subjective and outside the reach of a biochemistry lab. Even substance P(ain) turned out to be more complicated than what we expected. Antagonists for the receptor of substance P(ain) turned out to be potential drugs for depression, not pain!
Abrahamson M, Olafsson I, Palsdottir A, Ulvsback M, Lundwall A, Jensson O, Grubb A. Structure and expression of the human cystatin C gene. Biochem J 1990;268:287 –94. Afonso S, Romagnano L, Babiarz B. The expression and function of cystatin C and cathepsin B and cathepsin L during mouse embryo implantation and placentation. Development 1997;124:3415–25. Barrett AJ, Fritz H, Grubb A, Isemura S, Jarvinen M, Katunuma N, Machleidt W, Muller-Esterl W, Sasaki M, Turk V. Nomenclature and classification of the proteins homologous with the cysteine-proteinase inhibitor chicken cystatin. Biochem J 1986;236:312. Bollengier F. Cystatin C alias post-g-globulin: a marker for multiple sclerosis? J Clin Chem Clin Biochem 1987;25:589–93. Coulibaly S, Schwihla H, Abrahamson M, Albini A, Cerni C, Clark JL, Ng KM, Katunuma N, Schlappack O, Glossl J, Mach L. Modulation of invasive properties of murine squamous carcinoma cells by heterologous expression of cathepsin B and cystatin C. Int J Cancer 1999;83: 526 –31. Cox JL, Sexton PS, Green TJ, Darmani NA. Inhibition of B16 melanoma metastasis by overexpression of the cysteine protease inhibitor cystatin C. Melanoma Res 1999;9:369–74. Iadarola MJ, Brady LS, Draisci G, Dubner R. Enhancement of dynorphin gene expression in spinal cord following experimental inflammation: stimulus specificity, behavioral parameters and opioid receptor binding. Pain 1988;35:313–26. Ishimaru H, Ishikawa K, Ohe Y, Takahashi A, Maruyama Y. Cystatin C and apolipoprotein E immunoreactivities in CA1 neurons in ischemic gerbil hippocampus. Brain Res 1996;709:155 –62. Lerner UH, Grubb A. Human cystatin C, a cysteine protease inhibitor, inhibits bone resorption in vitro stimulated by parathyroid hormone and parathyroid hormone-related peptide of malignancy. J Bone Miner Res 1992;7:433–40. Levy E, Sastre M, Kumar A, Gallo G, Piccardo P, Ghetti B, Tagliavini F. Codeposition of cystatin C with amyloid-beta protein in the brain of Alzheimer disease patients. J Neuropathol Exp Neurol 2001;60: 94 –104. Lo¨fberg H, Grubb AO, Sveger T, Olsson JE. The cerebrospinal fluid and plasma concentrations of g-trace and b2-microglobulin at various ages and in neurological disorders. J Neurol 1980;223:159– 70. Mannes AJ, Martin BM, Yang H-YT, Keller JM, Lewin S, Gaiser RR, Iadarola MJ. Cystatin C as a cerebrospinal fluid biomarker for pain in humans. Pain 2003;102:251–6. Nagai A, Murakawa Y, Tereshima M, Shimode K, Umegae N, Takeuchi H, Kobayashi S. Cystatin C and cathepsin B in CSF from patients with inflammatory neurologic diseases. Neurology 2000;55:1828– 32. Shimizu-Tokiwa A, Kobata M, Io H, Kobayashi N, Shou I, Funabiki K, Fukui M, Horikoshi S, Shirato I, Saito K, Tomino Y. Serum cystatin C is a more sensitive marker of glomerular function than serum creatinine. Nephron 2002;92:224–6. Taupin P, Ray J, Fisher WH, Suhr ST, Hakanson K, Grubb A, Gage FH. FGH-2-responsive neural stem cell proliferation requires CCg, a neural autocrine/paracrine cofactor. Neuron 2000;28:385–97. Vilim FS, Aarnisalo AA, Nieminen ML, Lintunen M, Karlstedt K, Kontinen V, Kalso E, States B, Panula P, Ziff E. Gene for pain modulatory neuropeptide FF: induction in spinal cord by noxious stimuli. Mol Pharmacol 1999;55:804–11. Vray B, Hartmann S, Hoebeke J. Immunomodulatory properties of cystatins. Cell Mol Life Sci 2002;59:1503 –12.
E. Kalso / Pain 107 (2004) 199–201 Yang H-YT, Wilkening S, Iadarola MJ. Spinal cord genes enriched in rat dorsal horn and induced by noxious stimulation identified by subtraction cloning and differential hybridization. Neuroscience 2001; 103:493–502. Yasuhara O, Hanai K, Ohkubo I, Sasaki M, McGeer PL, Kimura H. Expression of cystatin C in rat, monkey and human brains. Brain Res 1993;628:85 –92.
a
Eija Kalsoa,b,* Pain Clinic, Department of Anaesthesia and Intensive Care
* Address: Pain Clinic, Department of Anaesthesia and Intensive Care Medicine, Helsinki University Central Hospital, P.O. Box 340, 00029 Helsinki, Finland. Tel.: þ358-9-47175885; fax: þ358-9-47175641.
201
Medicine, Helsinki University Central Hospital, P.O. Box 340, 00029 Helsinki, Finland b MGH Pain Center, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA E-mail address: [email protected]
Editorial
Biomarkers for pain See related article by Eisenach et al., pages 207 –212 of this issue Cystatin C measured in plasma is a sensitive marker of renal function (Shimizu-Tokiwa et al., 2002). Recently, it was suggested that cystatin C in cerebrospinal fluid could be a marker for human pain (Mannes et al., 2003). The paper by Eisenach et al. in this issue of Pain shows that this is not the case. Cystatin C is a low molecular weight basic protein that belongs to the cystatin superfamily. Cystatins are endogenous cysteine protease inhibitors that modulate the turnover of intracellular and extracellular proteins. Cystatins may play a defensive role in extracellular fluids by protecting organs from the cysteine proteases of invading pathogens (Barrett et al., 1986). Cystatin C is widely distributed in almost all tissues of vertebrates and is secreted by many kinds of cell types into a number of body fluids (Abrahamson et al. 1990). Cystatin C is involved in e.g. tissue remodelling, including tumour metastasis and invasion (Coulibaly et al., 1999; Cox et al., 1999), embryo implantation (Afonso et al., 1997), bone matrix remodelling (Lerner and Grubb, 1992) and cell proliferation (Taupin et al., 2000). In the nervous system cystatin C immunoreactivity has been detected in microglial cells, astrocytes, the choroid plexus and some neurones (Ishimaru et al., 1996; Yasuhara et al., 1993). In the immune system, cystatins have important immunomodulatory functions. They induce tumour necrosis factor and the production of interleukin 10 and nitric oxide (Vray et al., 2002). Cystatin C may play an important role in inflammatory neurologic diseases (Bollengier, 1987). Increased CSF cystatin C concentrations have been found in meningitis, encephalitis and myelitis (Lo¨fberg et al., 1980). However, CSF cystatin C levels were significantly reduced in the acute phase of inflammatory neurologic diseases such as Guillain – Barre´ syndrome, chronic inflammatory demyelinating polyneuropathy and multiple sclerosis (Nagai et al., 2000). Cystatin C is also involved in the development of many degenerative disorders of the CNS such as Alzheimer’s disease (Levy et al., 2001). A group of researchers identified the gene that codes for cystatin C as one of the genes whose expression was upregulated by carrageenan-induced peripheral inflammation in the rat using subtraction cloning and differential hybridization (Yang et al., 2001). It was hypothesized that
cystatin C is a biomarker for pain. The hypothesis was then tested in 10 women at term, five in active labour and pain and another five scheduled for an elective caesarean section without pain. The CSF concentrations of cystatin C were marginally higher ðP , 0:018Þ in the five women that were in painful labour. The authors then suggested that cystatin C would be a cerebrospinal fluid biomarker for pain in humans (Mannes et al., 2003). Eisenach et al. have now studied 131 subjects including healthy volunteers, women in labour with or without pain and patients with chronic neuropathic pain. Their results indicated a minimal association with acute or chronic pain and cystatin C concentrations in the CSF. A separate covariate analysis showed a significant effect of pregnancy. The highest CSF concentrations of cystatin C were measured in the chronic pain patients who had an indwelling intrathecal (i.th.) catheter for the administration of morphine whereas the chronic pain patients without an i.th. catheter had low levels of cystatin C. This could indicate that either the inflammation caused by the catheter or morphine that was infused could increase cystatin C levels. Mannes et al. took a real shortcut in suggesting that cystatin C is a biomarker for pain. As described above, cystatin C is involved in many functions that may or may not have direct relevance to pain. The concentrations of cystatin C in various body fluids most likely reflect the state of the individual disease process rather than pain. We therefore do not have an objective biomarker for pain which Mannes et al. suggested. Such an objective biomarker could be used in conditions when pain cannot be not only assessed directly e.g. in children, elderly and demented, but also be demanded by those who pay for health care delivery, as suggested by Eisenach et al. Such development has many implications. Both papers suggest that ‘pain may lead to an increased spillover of cystatin C into CSF’. Rather than pain causing the spillover of cystatin C into the CSF cystatin C can be a measure of inflammation and tissue injury. But is it conceivable that there would be one single reliable measure even for nociception? Considering the crucial role of pain for survival it is unlikely that nature would have designed a system that relies on one enzyme or neuropeptide only. Several other neuropeptides such as substance P, dynorphin
0304-3959/$20.00 q 2003 Published by Elsevier B.V. on behalf of International Association for the Study of Pain. doi:10.1016/j.pain.2003.12.009
200
E. Kalso / Pain 107 (2004) 199–201
Acknowledgements Dr Vesa Kontinen drew the figure which is acknowledged with gratitude.
References
Fig. 1. Biomarkers of neuronal activity provide information from the early parts of the nociceptive pathway on its way to pain behaviour. Pain behaviour demands treatment that, when successful, has effects on all levels of pain (sensation, experience, behaviour).
(Iadarola et al., 1988), neuropeptide FF (Vilim et al., 1999) are also upregulated in inflammation and could be labelled as biomarkers for pain. All these proteins can be classified as markers of inflammation or tissue injury, not pain. However, like cystatin C they all are involved in many other different physiological functions that have little to do with pain. Neuropathic and inflammatory pain induce very different changes in the neuropeptide profiles. These profiles also change over time. Instead of one biomarker there should be several for different painful states at different time points. But pain is not equivalent to nociception and tissue damage (Fig. 1). Pain needs the brain to be perceived. Pain is defined by IASP as ‘an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage’. This definition refutes the possibility of having a biomarker for pain. Depression, anxiety and pain are all controlled not only by neuropeptides but also by the environment, experience, interaction, the life of the patient in general. They cannot be measured with peptide levels. The danger of making pain too simplistic, something that can be measured in the CSF, is in forgetting the individual experience that is essential in pain. Do we trust the patient’s report or the biomarker’s concentration in the CSF? What information would we get from the biomarkers in the clinic that we would not get through the patient’s report? If the patient’s CSF level of cystatin C is low but the patient reports severe pain which report would you trust? Which report would the insurance company trust? Various proteins can be measured in the CSF and other body fluids. They will increase our understanding of the mechanisms that underlie inflammation, nerve injury and tissue damage. These proteins can also be tested as new targets for therapeutic approaches. The pain experience, however, will remain subjective and outside the reach of a biochemistry lab. Even substance P(ain) turned out to be more complicated than what we expected. Antagonists for the receptor of substance P(ain) turned out to be potential drugs for depression, not pain!
Abrahamson M, Olafsson I, Palsdottir A, Ulvsback M, Lundwall A, Jensson O, Grubb A. Structure and expression of the human cystatin C gene. Biochem J 1990;268:287 –94. Afonso S, Romagnano L, Babiarz B. The expression and function of cystatin C and cathepsin B and cathepsin L during mouse embryo implantation and placentation. Development 1997;124:3415–25. Barrett AJ, Fritz H, Grubb A, Isemura S, Jarvinen M, Katunuma N, Machleidt W, Muller-Esterl W, Sasaki M, Turk V. Nomenclature and classification of the proteins homologous with the cysteine-proteinase inhibitor chicken cystatin. Biochem J 1986;236:312. Bollengier F. Cystatin C alias post-g-globulin: a marker for multiple sclerosis? J Clin Chem Clin Biochem 1987;25:589–93. Coulibaly S, Schwihla H, Abrahamson M, Albini A, Cerni C, Clark JL, Ng KM, Katunuma N, Schlappack O, Glossl J, Mach L. Modulation of invasive properties of murine squamous carcinoma cells by heterologous expression of cathepsin B and cystatin C. Int J Cancer 1999;83: 526 –31. Cox JL, Sexton PS, Green TJ, Darmani NA. Inhibition of B16 melanoma metastasis by overexpression of the cysteine protease inhibitor cystatin C. Melanoma Res 1999;9:369–74. Iadarola MJ, Brady LS, Draisci G, Dubner R. Enhancement of dynorphin gene expression in spinal cord following experimental inflammation: stimulus specificity, behavioral parameters and opioid receptor binding. Pain 1988;35:313–26. Ishimaru H, Ishikawa K, Ohe Y, Takahashi A, Maruyama Y. Cystatin C and apolipoprotein E immunoreactivities in CA1 neurons in ischemic gerbil hippocampus. Brain Res 1996;709:155 –62. Lerner UH, Grubb A. Human cystatin C, a cysteine protease inhibitor, inhibits bone resorption in vitro stimulated by parathyroid hormone and parathyroid hormone-related peptide of malignancy. J Bone Miner Res 1992;7:433–40. Levy E, Sastre M, Kumar A, Gallo G, Piccardo P, Ghetti B, Tagliavini F. Codeposition of cystatin C with amyloid-beta protein in the brain of Alzheimer disease patients. J Neuropathol Exp Neurol 2001;60: 94 –104. Lo¨fberg H, Grubb AO, Sveger T, Olsson JE. The cerebrospinal fluid and plasma concentrations of g-trace and b2-microglobulin at various ages and in neurological disorders. J Neurol 1980;223:159– 70. Mannes AJ, Martin BM, Yang H-YT, Keller JM, Lewin S, Gaiser RR, Iadarola MJ. Cystatin C as a cerebrospinal fluid biomarker for pain in humans. Pain 2003;102:251–6. Nagai A, Murakawa Y, Tereshima M, Shimode K, Umegae N, Takeuchi H, Kobayashi S. Cystatin C and cathepsin B in CSF from patients with inflammatory neurologic diseases. Neurology 2000;55:1828– 32. Shimizu-Tokiwa A, Kobata M, Io H, Kobayashi N, Shou I, Funabiki K, Fukui M, Horikoshi S, Shirato I, Saito K, Tomino Y. Serum cystatin C is a more sensitive marker of glomerular function than serum creatinine. Nephron 2002;92:224–6. Taupin P, Ray J, Fisher WH, Suhr ST, Hakanson K, Grubb A, Gage FH. FGH-2-responsive neural stem cell proliferation requires CCg, a neural autocrine/paracrine cofactor. Neuron 2000;28:385–97. Vilim FS, Aarnisalo AA, Nieminen ML, Lintunen M, Karlstedt K, Kontinen V, Kalso E, States B, Panula P, Ziff E. Gene for pain modulatory neuropeptide FF: induction in spinal cord by noxious stimuli. Mol Pharmacol 1999;55:804–11. Vray B, Hartmann S, Hoebeke J. Immunomodulatory properties of cystatins. Cell Mol Life Sci 2002;59:1503 –12.
E. Kalso / Pain 107 (2004) 199–201 Yang H-YT, Wilkening S, Iadarola MJ. Spinal cord genes enriched in rat dorsal horn and induced by noxious stimulation identified by subtraction cloning and differential hybridization. Neuroscience 2001; 103:493–502. Yasuhara O, Hanai K, Ohkubo I, Sasaki M, McGeer PL, Kimura H. Expression of cystatin C in rat, monkey and human brains. Brain Res 1993;628:85 –92.
a
Eija Kalsoa,b,* Pain Clinic, Department of Anaesthesia and Intensive Care
* Address: Pain Clinic, Department of Anaesthesia and Intensive Care Medicine, Helsinki University Central Hospital, P.O. Box 340, 00029 Helsinki, Finland. Tel.: þ358-9-47175885; fax: þ358-9-47175641.
201
Medicine, Helsinki University Central Hospital, P.O. Box 340, 00029 Helsinki, Finland b MGH Pain Center, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA E-mail address: [email protected]