3-nitrotyrosine and Myositis

3-nitrotyrosine (3NT) is regarded as a "footprint" of nitric oxide generation. The study aimed at documenting the presence and distribution of 3-nitrotyrosine (3NT) in muscle tissue samples from patients with idiopathic inflammatory myopathies (IIM) as well as from those with non-inflammatory myopathies to consider whether polymyositis (PM) and dermatomyositis (DM) could be distinguished based on 3NT immunohistochemistry in muscle biopsy. Cryosections prepared from muscle biopsies of 54 patients with either IIM, i.e., PM and DM, or various non-inflammatory myopathies were immunostained using monoclonal antibody against 3NT. The 3NT immunostaining was localized to endothelial cells and their close surroundings in muscle biopsies of DM and PM patients but only in those areas of tissue sections where inflammatory cell infiltrates were present. No 3NT positivity was found in tissue sections of IIM patients without inflammatory infiltrates in the studied sample as well as in muscle tissue sections of patients with non-inflammatory myopathies. However, the endothelial cells were also positive in cases of confirmed non-inflammatory myopathies with secondary lymphocytic infiltration (myodystrophies, myasthenia gravis). Despite the pathogenetic significance, the 3NT immunohistochemistry is of low diagnostic value for the differential diagnosis of IIM in muscle biopsy.

Topics: Adult; Aged; Dermatomyositis; Endothelium; Female; Humans; Immunohistochemistry; Male; Middle Aged; Muscle, Skeletal; Myositis; Polymyositis; Protein Binding; Tyrosine

Systemic diseases affect skeletal muscle, and inflammation and oxidative stress are some of the involved mechanisms. There is scarce information about the effects of essential hypertension on skeletal muscle. The soleus and extensor digitorum longus (EDL) muscles of spontaneously hypertensive rats (SHR) were studied compared to control Wistar Kyoto (WKY) rats. The levels of nitrite and nitrate in micromol/mg-protein; endothelial (eNOS), neuronal (nNOS), and inducible (iNOS) nitric oxide synthases, nitrotyrosine and tumour necrosis factor alpha (TNF-alpha) in ng/mg-protein were determined. Compared with controls, the SHR showed increased levels of nitrotyrosine (soleus 24.4 +/- 5.0 vs. 3.3 +/- 0.3, p<0.001; EDL 20.2 +/- 4.3 vs. 4.5 +/- 0.4, p<0.0037), iNOS (soleus 26.6 +/- 3.7 vs. 8.3 +/- 0.9; EDL 21.3 +/- 3.7 vs. 11.0 +/- 0.8, both p<0.0001) and TNF-alpha (soleus 2.2 +/- 0.5 vs. 0.6 +/- 0.1, p<0.05; EDL 1.9 +/- 0.2 vs. 0.6 +/- 0.1, p<0.02). A decrease of eNOS was found in soleus muscle (20.6 +/- 1.4 vs. 30.3 +/- 1.2, p<0.00001); of nNOS (soleus 16.8 +/- 1.4 vs. 20.7 +/- 1.8, p< 0.05; EDL 13.6 +/- 1.3 vs. 21.9 +/- 1.8, p<.005) and nitrite in EDL (5.8 +/- 0.3 vs. 7.1 +/- 0.5, p<0.026).There was a positive correlation between TNF-alpha vs. nitrotyrosine in soleus (r=0.798; p<0.031) and a tendency in EDL (r=0.739; p=0.059); iNOS vs. nitrotyrosine (soleus: r=0.908; p<0.0001; EDL: r=0.707; p<0.01), a tendency between TNF-alpha and iNOS (EDL: r=0.736; p<0.059); and a negative correlation between eNOS vs. nitrotyrosine in soleus muscle (r=-0.816; p<0.0012). In conclusion, in skeletal muscles of SHR an inflammatory process was found evidenced by the increase in TNF-alpha, nitrotyrosine and iNOS. The decreased levels of constitutive synthases, together with the higher level of iNOS, are indicative of endothelial dysfunction.

Topics: Animals; Endothelium, Vascular; Hypertension; Male; Muscle, Skeletal; Myositis; Nitric Oxide Synthase Type I; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Oxidative Stress; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Tumor Necrosis Factor-alpha; Tyrosine