Biomedical subjects

Jörg Hoffmann

Publications and source records attributed to Jörg Hoffmann.

17 recordsLinked to original sources

PubMed2006

[Validation of the German version of the Inflammatory Bowel Disease Questionnaire (Competence Network IBD, IBDQ-D)].

The Inflammatory Bowel Disease Questionnaire (IBDQ) is the standard disease-specific instrument for assessment of health-related quality of life (HRQOL) in patients with inflammatory bowel diseases (IBD). A German translation has not been validated. 415 outpatient IBD-patients (Crohn's Disease n = 306, Ulcerative Colitis n = 109) completed the German version of the IBDQ (Competence network IBD, IBDQ-D), the Hospital Anxiety and Depression Scale German Version (HADS-D) and the Questions on Life Satisfaction FLZ. Face validity was assessed by a physicians' and patients' panel. Disease activity was measured by the German Inflammatory Bowel Disease Activity Index (GIBDI). With 97.3 % completed items the acceptance was high. The Cronbach's alpha for the subscales ranged from 0.88 to 0.89. The correlation coefficients with comparable subscales of other instruments ranged between 0.09 and 0.70. Patients in remission and different disease activities differed significantly (p < 0.001) in all IBDQ-D-subscales.

Adult↗

PubMed2006

Field study to explore possible effects of styrene on auditory function in exposed workers.

OBJECTIVES: We conducted this study to examine, whether occupational styrene exposures are associated with reduced hearing ability. METHODS: The auditory function was investigated by pure tone audiometry and registration of transitory evoked otoacoustic emissions (TEOAE) in 32 workers of a fibre-reinforced plastic boat building factory. Sixteen subjects were laminators (mean age: 41 yr (SD: 8)) and therefore regularly exposed to styrene with mean duration of exposure to styrene of 7.5 yr (SD 5.0). The tests were applied to a reference group of 16 workers (mean age: 39 yr (SD: 8)) who were not directly exposed to styrene but had a similar noise exposure. RESULTS: A few and isolated correlations between the parameters of hearing acuity and exposure indices, such as current internal styrene exposures (sum of MA and PGA) and duration of styrene exposure, were statistically significant, but no consistent association was found. CONCLUSION: The results of this study do not support the assumption of an ototoxic effect of chronic styrene exposure in workers.

Adult↗

PubMed2005

Impaired CXCR4 signaling contributes to the reduced neovascularization capacity of endothelial progenitor cells from patients with coronary artery disease.

Transplantation of bone marrow cells as well as circulating endothelial progenitor cells (EPC) enhances neovascularization after ischemia. The chemokine receptor CXCR4 is essential for migration and homing of hematopoietic stem cells. Therefore, we investigated the role of CXCR4 and its downstream signaling cascade for the angiogenic capacity of cultured human EPC. Ex vivo, differentiated EPC derived from peripheral blood abundantly expressed CXCR4. Incubation of EPC from healthy volunteers with neutralizing antibodies against CXCR4 profoundly inhibited vascular endothelial growth factor- and stromal-derived factor-1-induced migration as well as EPC-induced angiogenesis in an ex vivo assay. Preincubation of transplanted EPC with CXCR4 antibody reduced EPC incorporation and impaired blood-flow recovery in ischemic hindlimbs of nude mice (57+/-4% of normal perfusion versus untreated EPC: 80+/-11%, P<0.001). Bone marrow mononuclear cells (BM-MNC) or EPC of heterozygous CXCR4(+/-) mice displayed reduced CXCR4 expression and disclosed impaired in vivo capacity to enhance recovery of ischemic blood flow in nude mice (blood flow 27+/-11% versus 66+/-25% using wild-type cells, P<0.01). Importantly, impaired blood flow in ischemic CXCR4(+/-) mice was rescued by injection of wild-type BM-MNC. Next, we investigated the role of CXCR4 for functional capacities of EPC from patients with coronary artery disease (CAD). Surface expression of CXCR4 was similar in EPC from patients with CAD compared with healthy controls. However, basal Janus kinase (JAK)-2 phosphorylation was significantly reduced and less responsive to stromal-derived factor-1 in EPC from patients with CAD compared with healthy volunteers, indicating that CXCR4-mediated JAK-2 signaling is dysregulated in EPC from patients with CAD. The CXCR4 receptor signaling profoundly modulates the angiogenic activity and homing capacity of cultured human EPC. Disturbance of CXCR4 signaling, as demonstrated by reduced JAK-2 phosphorylation, may contribute to functional impairment of EPC from patients with CAD. Stimulating CXCR4 signaling might improve functional properties of EPC and may rescue impaired neovascularization capacity of EPC derived from patients with CAD.

Animals↗

PubMed2005

Differentiation of circulating endothelial progenitor cells to a cardiomyogenic phenotype depends on E-cadherin.

Progenitor cells may contribute to cardiac regeneration. Here, we investigated the role of cadherins and integrins for differentiation of human adult circulating endothelial progenitor cells (EPCs) into cardiomyocytes (CM) in a co-culture system. N- and E-cadherin were expressed in EPCs and were localized at the interface between EPCs and CM. Incubation of a blocking antibody against E-cadherin reduced the expression of CM marker protein in EPCs. Blocking antibodies against N- or P-cadherin or the beta1- and beta2-integrins were not effective. These data suggested that cell-to-cell communication mediated by E-cadherin contributes to the acquirement of a cardiomyogenic phenotype of human endothelial progenitor cells.

Antibodies, Blocking↗

PubMed2005

Survivin as a radioresistance factor, and prognostic and therapeutic target for radiotherapy in rectal cancer.

Apoptosis levels have been shown to predict tumor response to preoperative radiochemotherapy in rectal cancer. Recently, the prominent role of survivin, a structurally unique member of the inhibitor of apoptosis protein family, has been shown in colorectal cancer tumorigenesis and prognosis. In this study, we investigated whether survivin plays a direct role in mediating radiation resistance. We used short interfering RNA molecules to decrease survivin in radioresistant SW480 and intermediately radioresistant HCT-15 colorectal cancer cells. This resulted in a significant decrease of survivin mRNA and protein expression with a maximum at 24 to 48 hours after transfection. If irradiated during this sensitive period, an increased percentage of apoptotic cells and an increased caspase 3/7 activity in parallel with a decreased cell viability and a reduced clonogenic survival was shown. These effects were more pronounced in the radioresistant SW480 cell line with a radiation-induced cytotoxicity enhancement factor at 10% and 50% survival of 1.8 to 2.2 for SW480 and 1.5 to 1.7 for HCT-15, respectively. Furthermore, transfection with survivin short interfering RNA increased levels of G2-M arrest and levels of DNA double-strand breaks in irradiated cells. These observations indicate that cell cycle and DNA repair mechanisms may be associated with apoptosis induction in tumor cells that are otherwise resistant to killing by radiation. In a translational study of 59 patients with rectal cancer treated with a combination of radiotherapy and chemotherapy, increased survivin expression was inversely related to the levels of apoptosis, and was also associated with a significantly higher risk of a local tumor recurrence.

Adenocarcinoma↗

PubMed2005

Non-canonical Wnt signaling enhances differentiation of human circulating progenitor cells to cardiomyogenic cells.

Human endothelial circulating progenitor cells (CPCs) can differentiate to cardiomyogenic cells during co-culture with neonatal rat cardiomyocytes. Wnt proteins induce myogenic specification and cardiac myogenesis. Here, we elucidated the effect of Wnts on differentiation of CPCs to cardiomyogenic cells. CPCs from peripheral blood mononuclear cells were isolated from healthy volunteers and co-cultured with neonatal rat cardiomyocytes. 6-10 days after co-culture, cardiac differentiation was determined by alpha-sarcomeric actinin staining of human lymphocyte antigen-positive cells (fluorescence-activated cell-sorting analysis) and mRNA expression of human myosin heavy chain and atrial natriuretic peptide. Supplementation of co-cultures with Wnt11-conditioned medium significantly enhanced the differentiation of CPCs to cardiomyocytes (1.7+/-0.3-fold), whereas Wnt3A-conditioned medium showed no effect. Cell fusion was not affected by Wnt11-conditioned medium. Because Wnts inhibit glycogen synthase kinase-3beta, we further determined whether the glycogen synthase kinase-3beta inhibitor LiCl also enhanced cardiac differentiation of CPCs. However, LiCl (10 mM) did not affect CPC differentiation. In contrast, Wnt11-conditioned medium time-dependently activated protein kinase C (PKC). Moreover, the PKC inhibitors bisindolylmaleimide I and III significantly blocked differentiation of CPCs to cardiomyocytes. PKC activation by phorbol 12-myristate 13-acetate significantly increased CPC differentiation to a similar extent as compared with Wnt11-conditioned medium. Our data demonstrate that Wnt11, but not Wnt3A, augments cardiomyogenic differentiation of human CPCs. Wnt11 promotes cardiac differentiation via the non-canonical PKC-dependent signaling pathway.

Animals↗

PubMed2004

Low doses of reactive oxygen species protect endothelial cells from apoptosis by increasing thioredoxin-1 expression.

The redox regulator thioredoxin-1 (Trx-1) is required for the redox potential of the cell and exerts important functions in cell growth and apoptosis. Severe oxidative stress has been implicated in the oxidation of proteins and cell death. However, the role of low doses of reactive oxygen species (ROS) is poorly understood. Here, we show that 10 and 50 microM H2O2 and short-term exposure to shear stress significantly increased Trx-1 mRNA and protein levels in endothelial cells. Since it is known that Trx-1 exerts anti-apoptotic functions, we next investigated whether low doses of ROS can inhibit basal and serum-depletion induced endothelial cell apoptosis. Indeed, treatment of endothelial cells with 10 and 50 microM H2O2 significantly reduced apoptosis induction. Reduction of Trx-1 expression using an antisense oligonucleotide approach resulted in the induction of apoptosis and abolished the inhibitory effect of low doses of H2O2. Taken together, our results demonstrate that low doses of ROS act as signaling molecules and exert anti-apoptotic functions in endothelial cells via upregulation of the redox-regulator Trx-1.

Apoptosis↗

PubMed2004

Antioxidant effects of statins via S-nitrosylation and activation of thioredoxin in endothelial cells: a novel vasculoprotective function of statins.

BACKGROUND: HMG-CoA reductase inhibitors (statins) are lipid-lowering drugs that also exert pleiotropic vasculoprotective effects via activation of the endothelial NO synthesis. NO induces S-nitrosylation of target proteins. S-Nitrosylation of the antioxidant enzyme thioredoxin was recently shown to enhance its activity, thereby reducing intracellular reactive oxygen species. Therefore, we investigated whether statins may exert an antioxidant activity in endothelial cells via S-nitrosylation of thioredoxin. METHODS AND RESULTS: Statins dose- and time-dependently increased the overall level of S-nitrosylated proteins in endothelial cells (atorvastatin 0.1 micromol/L, 206+/-30% increase; simvastatin 1 micromol/L, 214+/-19% increase; mevastatin 1 micromol/L, 191+/-10% increase). The increased S-nitrosylation was blocked by an NO-synthase inhibitor and mevalonate. Moreover, S-nitrosylation of thioredoxin was also significantly augmented after atorvastatin treatment. The atorvastatin-mediated increase in S-nitrosylation was associated with an enhanced enzymatic activity of thioredoxin (atorvastatin, 157+/-9% increase). This resulted in a significant reduction of intracellular reactive oxygen species within the endothelial cells. In contrast, in endothelial cells overexpressing a thioredoxin construct in which the S-nitrosylation acceptor amino acid cysteine 69 was replaced by serine [TRX(C69S)], atorvastatin did not activate the redox-regulatory activity of thioredoxin. Moreover, overexpression of the non-nitrosylatable thioredoxin TRX(C69S) abolished atorvastatin-mediated reduction of reactive oxygen species. CONCLUSIONS: Here, we demonstrate a novel antioxidant mechanism by which statins reduce reactive oxygen species in endothelial cells. Statin-mediated S-nitrosylation of thioredoxin enhanced the enzymatic activity of thioredoxin, resulting in a significant reduction in intracellular reactive oxygen species.

Amino Acid Substitution↗

PubMed2004

Antioxidants inhibit nuclear export of telomerase reverse transcriptase and delay replicative senescence of endothelial cells.

Aging is associated with a rise in intracellular reactive oxygen species (ROS) and a loss of telomerase reverse transcriptase activity. Incubation with H2O2 induced the nuclear export of telomerase reverse transcriptase (TERT) into the cytosol in a Src-family kinase-dependent manner. Therefore, we investigated the hypothesis that age-related increase in reactive oxygen species (ROS) may induce the nuclear export of TERT and contribute to endothelial cell senescence. Continuous cultivation of endothelial cells resulted in an increased endogenous formation of ROS starting after 29 population doublings (PDL). This increase was accompanied by mitochondrial DNA damage and preceded the onset of replicative senescence at PDL 37. Along with the enhanced formation of ROS, we detected an export of nuclear TERT protein from the nucleus into the cytoplasm and an activation of the Src-kinase. Moreover, the induction of premature senescence by low concentrations of H2O2 was completely blocked with the Src-family kinase inhibitor PP2, suggesting a crucial role for Src-family kinases in the induction of endothelial cell aging. Incubation with the antioxidant N-acetylcysteine, from PDL 26, reduced the intracellular ROS formation and prevented mitochondrial DNA damage. Likewise, nuclear export of TERT protein, loss in the overall TERT activity, and the onset of replicative senescence were delayed by incubation with N-acetylcysteine. Low doses of the statin, atorvastatin (0.1 micromol/L), had also effects similar to those of N-acetylcysteine. We conclude that both antioxidants and statins can delay the onset of replicative senescence by counteracting the increased ROS production linked to aging of endothelial cells.

Acetylcysteine↗

PubMed2004

p21Cip1 levels differentially regulate turnover of mature endothelial cells, endothelial progenitor cells, and in vivo neovascularization.

p21(Cip1) (p21) controls cell cycle progression and apoptosis in mature endothelial cells (ECs) and regulates size and cycling of the hematopoietic progenitor cell pool. Because circulating endothelial progenitor cells (EPCs) contribute to postnatal neovascularization in addition to mature ECs, we investigated the regulation of ECs and EPCs in p21-deficient mice. Mature aortic EC proliferation was increased in homozygous p21(-/-) and heterozygous p21(+/-) mice, in which p21 protein levels are reduced to one third of wild-type (WT). In contrast, apoptosis sensitivity was increased by 3.5-fold only in p21(-/-), but not in p21(+/-) mice. Consistently, in vivo apoptosis of ECs within areas of neovascularization was elevated in p21(-/-) but not in p21(+/-) mice. EPC numbers were elevated 2-fold in p21(-/-) mice compared with WT (P<0.001), and clonal expansion capacity of EPCs was increased from 25+/-4 (WT) to 57+/-8 colony-forming units in p21(-/-) mice (P<0.005). EPC numbers and expansion were likewise increased in p21(+/-) mice. As the integrative endpoint, in vivo neovascularization reflecting all p21-affected parameters was increased over WT only in p21(+/-) (P<0.001), but not in p21(-/-) mice. In conclusion, reduced p21 protein levels of mice lacking one p21 allele are associated with increased proliferation of ECs and EPCs, whereas survival of ECs to apoptotic stimuli in vitro and in vivo is not impaired. Under these conditions, neovascularization was increased. In contrast, complete p21 deficiency did not result in an increased neovascularization despite increased mature EC and EPC proliferation. This may be due to the sensitization of ECs against apoptosis.

Alleles↗

PubMed2003

Shear stress increases the amount of S-nitrosylated molecules in endothelial cells: important role for signal transduction.

Laminar flow (shear stress) is an important stimulus for nitric oxide (NO) synthesis in endothelial cells. NO can react with free SH-groups of different proteins leading to S-nitrosylation. Since S-nitrosylation of proteins is an important regulator of protein functions, we investigated the effect of endogenously synthesized NO. Exposure to shear stress significantly increased the overall S-nitrosylation of proteins in endothelial cells. Interestingly, shear stress increased S-nitrosylation of specific target proteins, i.e. the catalytic p17 subunit of caspase-3, the GTPase p21ras and the oxidoreductase thioredoxin. S-nitrosylation resulted in an inhibition of caspase-3 and in an augmented activity of p21ras and thioredoxin. These data suggest that long term exposure to shear stress exerts its different atheroprotective effects at least in part via increased S-nitrosylation of specific signaling proteins.

Caspase 3↗

PubMed2003

Regulation of telomerase activity and anti-apoptotic function by protein-protein interaction and phosphorylation.

The enzyme telomerase is necessary for the synthesis and maintenance of telomere length. The catalytic subunit, telomerase reverse transcriptase (TERT), is regulated by interaction with the 90 kDa heat shock protein (HSP90) and by Akt-dependent phosphorylation. Here, we demonstrate that HSP90 and Akt physically interact with TERT. Treatment of cells with novobiocin, which blocks C-terminal interaction of HSP90, disrupted HSP90 binding to Akt, induced Akt dephosphorylation and significantly reduced telomerase activity. The reduction of TERT activity by novobiocin was associated with an increase in apoptosis. Likewise, the induction of Akt dephosphorylation by protein phosphatase 2A (PP2A) reduced telomerase activity. HSP90 is known to prevent PP2A-mediated dephosphorylation of Akt. To investigate whether the effect of novobiocin is due to the reduction of Akt or TERT phosphorylation, we overexpressed a phospho-mimetic, active Akt (T308D/S473D). Akt (T308D/S473D) prevented novobiocin-induced reduction of telomerase activity and the stimulation of apoptosis. Moreover, overexpression of a dominant negative PP2A construct (PP2A(L199P)) as well as incubation with the PP2A inhibitor okadaic acid blocked the inhibition of telomerase activity by novobiocin. These data suggest that the association between HSP90, Akt and TERT in concert with the phosphorylation of TERT is necessary for maintaining telomerase activity and inhibition of apoptosis.

Apoptosis↗

PubMed2003

Hydrogen peroxide triggers nuclear export of telomerase reverse transcriptase via Src kinase family-dependent phosphorylation of tyrosine 707.

The regulation of telomerase reverse transcriptase (TERT) plays an important role in the proliferative capacity and survival of cells. Here, we report that exogenously as well as endogenously induced oxidative stress leads to translocation of endogenous as well as overexpressed human TERT from the nucleus into the cytosol. TERT is transported through the nuclear pores in a leptomycin-sensitive and Ran GTPase-dependent process. H(2)O(2)-induced nuclear export of TERT is preceded by TERT tyrosine phosphorylation at position 707 and prevented by the Src kinase family inhibitor PP1. Oxidative stress-induced nuclear export of TERT depends on association with the Ran GTPase. In contrast, mutation of tyrosine 707 inhibits phosphorylation induced by oxidative stress and prevents association with Ran and nuclear export of TERT. Moreover, inhibition of tyrosine phosphorylation at 707 increases the antiapoptotic capacity of TERT. Taken together, depletion of nuclear TERT by tyrosine phosphorylation-dependent nuclear export of TERT is a novel mechanism for regulation of TERT localization, which reduces the antiapoptotic activity of TERT.

Active Transport, Cell Nucleus↗

PubMed2002

Hypoxic induction of the hypoxia-inducible factor is mediated via the adaptor protein Shc in endothelial cells.

Tyrosine kinase cascades may play a role in the hypoxic regulation of hypoxia-inducible factor (HIF)-1. We investigated the role of tyrosine kinase phosphorylation and of the Shc/Ras cascade on hypoxic HIF-1 stabilization. Exposure of human umbilical vein endothelial cells to hypoxia results in HIF protein stabilization as early as 10 minutes, with a maximum at 3 hours, and also in Shc tyrosine phosphorylation, with a maximum at 10 minutes. To test whether Shc directly mediates hypoxia-induced HIF stabilization, human umbilical vein endothelial cells were transfected with a dominant-negative Shc mutant (dnShc), resulting in significantly reduced HIF protein levels compared with control. Similar results were obtained with cells transfected with dominant-negative Ras, a known downstream effector of Shc. Hypoxia-induced Ras activity was significantly reduced in cells transfected with dnShc compared with control levels, indicating that Ras indeed acts downstream from Shc. Moreover, cells pretreated with a specific Raf-1 kinase inhibitor, a known downstream effector of Ras, exhibited reduced HIF protein levels. To examine the functional consequences of Shc in hypoxic signaling, HIF-1 ubiquitination, protein stabilization, and endothelial cell migration were assessed. Overexpression of dnShc increased ubiquitination of HIF-1 and reduced the half-life of the protein. Moreover, dnShc, dominant-negative Ras, or the Raf-1 kinase inhibitor significantly inhibited migration under hypoxia. Thus, Shc in concert with Ras and Raf-1 contributes to hypoxia-induced HIF-1alpha protein stabilization and endothelial cell migration.

Adaptor Proteins, Signal Transducing↗

PubMed2002

The vascular NADPH oxidase subunit p47phox is involved in redox-mediated gene expression.

An NADPH oxidase is thought to be a main source of vascular superoxide (O(2)(-)) production. The functional role of this oxidase, however, and the contribution of the different subunits of the enzyme to cellular signaling are still incompletely understood. We determined the role of the p47phox subunit of the oxidase in O(2)(-) generation and signaling in aortic rings and cultured smooth muscle cells (SMC) from wild-type (WT) and p47phox-deficient (p47phox -/-) mice. Basal O(2)(-) levels in aortae of p47phox -/- mice were lower than those in WT aortae. Infusion of [val(5)]-angiotensin II increased O(2)(-) levels in aortae from WT more than in aortae from p47phox -/- mice. O(2)(-) generation was similar in quiescent SMC from WT and p47phox -/- mice. However, exposure to thrombin selectively increased O(2)(-) generation in VSMC from WT, but not from p47phox -/- mice. Thrombin-activated redox-mediated signal transduction and gene expression was attenuated in VSMC from p47phox -/- compared to cells from WT mice as determined by p38 MAP kinase activation and VEGF gene expression. We conclude that p47phox is important for vascular ROS production and redox-modulated signaling and gene expression in VSMC.

Angiotensin II↗

PubMed2002

High survivin expression is associated with reduced apoptosis in rectal cancer and may predict disease-free survival after preoperative radiochemotherapy and surgical resection.

BACKGROUND: Spontaneous apoptosis has been shown to predict tumor response to preoperative radiochemotherapy in rectal cancer. It remains to be elucidated, however, which genetic profile determines whether a tumor is more or less prone to apoptosis. Recently, a novel member of the inhibitor of apoptosis family, designated survivin, was identified. In the present study, we investigated the impact of survivin on tumor cell apoptosis and the risk to develop distant metastases or local failure after preoperative radiochemotherapy and surgical resection. PATIENTS AND METHODS: The expression of survivin, p53, bcl-2 and the apoptotic index was evaluated by immunohistochemistry on pretreatment biopsies of 54 patients with locally advanced adenocarcinoma of the rectum. Survivin expression was correlated to clinical and histopathological markers, the levels of spontaneous apoptosis, p53 and bcl-2, as well as to disease-free survival, 5-year rates of local failure and distant disease after preoperative radiochemotherapy and surgical resection. RESULTS: Survivin expression inversely correlated with the apoptotic index: High survivin expression was found in 56% of rectal carcinoma biopsies with a median apoptotic index of 1.22%. Conversely, low survivin expression in tumor cells was associated with a high median apoptotic index (2.29%, p = 0.0001). High survivin expression also segregated with bcl-2 overexpression (65% bcl-2+ in tumors with high survivin expression as compared to 35% bcl-2+ in tumors with low survivin expression), but the difference was not statistically significant (p = 0.1). Low survivin expression was significantly related to an increased disease-free survival rate (77% vs 18% at 5 years in tumors with high survivin expression, p = 0.02) and to a reduced risk for distant metastases (18% vs 78% at 5 years in tumors with high survivin expression, p = 0.05) and local failure (6% vs 37% at 5 years in tumors with high survivin expression, p = 0.07). CONCLUSION: An inverse correlation between survivin expression and the level of spontaneous apoptosis in pretreatment biopsies suggests that survivin strongly inhibits tumor cell apoptosis in rectal cancer. Survivin expression may provide a novel predictive indicator for disease-free survival after preoperative radiochemotherapy and surgical resection in rectal cancer.

Adenocarcinoma↗

PubMed2002

Redox regulatory and anti-apoptotic functions of thioredoxin depend on S-nitrosylation at cysteine 69.

Thioredoxin 1 (Trx) is a known redox regulator that is implicated in the redox control of cell growth and apoptosis inhibition. Here we show that Trx is essential for maintaining the content of S-nitrosylated molecules in endothelial cells. Trx itself is S-nitrosylated at cysteine 69 under basal conditions, and this S-nitrosylation is required for scavenging reactive oxygen species and for preserving the redox regulatory activity of Trx. S-nitrosylation of Trx also contributes to the anti-apoptotic function of Trx. Thus, Trx can exert its complete redox regulatory and anti-apoptotic functions in endothelial cells only when cysteine 69 is S-nitrosylated.

Amino Acid Sequence↗