Myelin basic protein induces heme oxygenase‐1 in human astroglial cells

Abstract

Heme oxygenase-1 (HO-1), also known as heat-shock protein 32 (HSP-32), is induced in many cells by a large variety of stimuli. Its induction in nervous system cells following toxic and oxidative stress was suggested to play a protective role. Its presence was recently detected by immunohistochemical studies at the level of inflammatory lesions of rat experimental autoimmune encephalomyelitis. In the present study, we demonstrate that myelin basic protein (MBP) induces HO-1 in human astroglial cells, as shown by Western blots and RT-PCR. Proteolytic fragments derived from the whole MBP show a different behavior in the HO-1 induction: MBP152-167 was able to produce a light but still significant increase in HO-1 mRNA and protein levels, whereas MBP68-84 was not. The increase in HO-1 production seems to be mediated by a Ca(2+)-dependent mechanism, since MBP addition to astrocytoma cultures induced a strong and immediate increment of [Ca(2+)](i) increase; MBP152-167 elicited a delayed and less pronounced [Ca(2+)](i) increase; no [Ca(2+)](i) changes were induced following cell treatment with MBP68-84. NO pathway involvement in the induction of HO-1 by MBP was ruled out since the expression of the inducible isoform of nitric oxide synthase was not upregulated in treated cells, neither nitrite levels were modified, as demonstrated by Greiss reaction. The possible significance of HO-1 induction following MBP stimulation is discussed.

Regulation of haeme oxygenase‐1 for treatment of neuroinflammation and brain disorders

“…HO‐1 expression in brain tissue and in vitro cultures of brain cells has been shown to be inducible by several drugs, chemicals and dietary‐derived substances (Table 1), which is similar to the response of other cells and tissues (reviewed in Shibahara, 2003 ; Wagener et al ., 2003 ; Ogborne et al ., 2004 ; Ryter et al ., 2006 ). Athough there is an extensive literature dealing with HO‐1 expression by rodent glial, particularly the microglia ( Matsuoka et al ., 1998 ; Calingasan et al ., 1999 ; Mautes et al ., 2000 ; Nakaso et al ., 2000 ; Stahnke et al ., 2007 ), there is surprisingly little data available on HO‐1 expression by human neural cells, being restricted to a few studies on human tumour cell lines ( Takahashi et al ., 1996 ; Businaro et al ., 2002 ; Goldstein et al ., 2003 ; Rieder et al ., 2004 ). As might be expected, exposure of 118 INI human glioma cells ( Yoshida et al ., 1988 ) or differentiated SH‐SY5Y human neuroblastoma cells ( Goldstein et al ., 2003 ) to haemin induced HO‐1 protein expression and, similar to mouse primary astrocytes and rat C6 glioma cells, dopamine exposure induced HO‐1 expression in the SK‐N‐SH human neuroblastoma cell line ( Rieder et al ., 2004 ).…”

“…As might be expected, exposure of 118 INI human glioma cells ( Yoshida et al ., 1988 ) or differentiated SH‐SY5Y human neuroblastoma cells ( Goldstein et al ., 2003 ) to haemin induced HO‐1 protein expression and, similar to mouse primary astrocytes and rat C6 glioma cells, dopamine exposure induced HO‐1 expression in the SK‐N‐SH human neuroblastoma cell line ( Rieder et al ., 2004 ). Myelin basic protein, which is released during demyelination, was found to induce HO‐1 mRNA and protein in the T67 astrocytoma cell line ( Businaro et al ., 2002 ), whereas agents that release nitric oxide and cause nitrosative stress increased HO‐1 expression in T98G glioblastoma cells ( Takahashi et al ., 1996 ). The paucity of information on the response to human neurons, neuroglia and microglial cells to many agents known to induce HO‐1 expression in rodent neural cells, and rodent and human non‐neural cells, is an impediment to understanding if human brain cells possess or have lost unique regulatory mechanisms that can help in the development of new drugs and therapeutics to better target this system in the brain and spinal cord.…”

Heme Oxygenase‐1: Transducer of Pathological Brain Iron Sequestration under Oxidative Stress

“…In a neuropathological survey,24 the percentage of GFAP‐positive astrocytes expressing HO‐1 in spinal cord plaques derived from MS patients (57.3%) was noted to be significantly greater than that observed in the spinal white matter of normal subjects (15.4%). In MS, glial HO‐1 overexpression may be secondary to the enhanced release of TNFα, IL‐1β (see HO‐1: Transducer of Mitochondrial Iron Trapping in “Stressed” Astroglia), or myelin basic protein39 within the affected tissues. Upregulation of HO‐1, in turn, may amplify intracellular oxidative stress and give rise to mitochondrial iron deposits reported in this condition (see HO‐1: Transducer of Mitochondrial Iron Trapping in “Stressed” Astroglia).…”

Regulation of heat shock protein 70 release in astrocytes: Role of signaling kinases

“…Furthermore, in response to these stressors, astrocytes increase the expression of other members of the heat shock protein family, including Hsp90, Hsp60, Hsp27, heme oxygenase-1 (hsp32), and alphaB-crystallin (Chopra et al, 1995;Bajramovic et al, 2000;Bidmon et al, 2001;Salvador-Silva et al, 2001;Acarin et al, 2002;Businaro et al, 2002;Fauconneau et al, 2002;Bidmon et al, 2004;Dabir et al, 2004). Although it has been suggested for some time, only recently it has become generally accepted that many cells, including astrocytes can release Hsp/c70 in response to stress both in vitro and in vivo (Tytell et al, 1986;Hightower and Guidon, 1989;Edbladh et al, 1994;Sheller et al, 1995Sheller et al, , 1998Guzhova et al, 2001;de Freitas et al, 2002;Dybdahl et al, 2002;Broquet et al, 2003;Robinson et al, 2005).…”