Altered protein kinase C and protein kinase A activities in erythrocyte membrane, platelets and lymphocytes of Duchenne muscular dystrophy (DMD) patients

Platelet m-calpain: a facile marker and STR polymorphism analysis for the identification of true carriers of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a neuromuscular-degenerative fatal disorder caused by mutations in the dystrophin gene. The incidence rate is one in 3300 live male births in every part of the world. A study into the detection of true carriers of DMD has been performed using gene deletion and non-deletion cases to devise a reliable and cost-effective diagnosis of DMD. The study uses a sample of 130 people (70 males and 60 females), consisting of 105 risk patients (60 male and 45 female) and 25 patients from normal carrying families, analyzed by CPK, M-PCR, Q-PCR and STR. This study aims to perform diagnosis of non-deletional and true carriers of DMD by enzyme-linked immunosorbent assay (ELISA), assessing the amount of m-calpain in the platelets of participants. In order to diagnose DMD patients, true carriers and controls, an ELISA has been standardized using polyclonal antibodies raised against m-calpain purified from human placenta. From the sample group, 45 at risk females were analyzed for m-calpain by quantitative ELISA. It was found that 90% of tests were informative, showing enhanced levels of m-calpain when compared to controls. The quantitative ELISA has proved to be an accurate, reliable, rapid and cost-effective test for DMD patients and true carriers, and also useful for the prenatal diagnosis.

What's new in using platelet research? To unravel thrombopathies and other human disorders

This review on platelet research focuses on defects of adhesion, cytoskeletal organisation, signal transduction and secretion. Platelet defects can be studied by different laboratory platelet functional assays and morphological studies. Easy bruising or a suspected platelet-based bleeding disorder is of course the most obvious reason to test the platelet function in a patient. However, nowadays platelet research also contributes to our understanding of human pathology in other disciplines such as neurology, nephrology, endocrinology and metabolic diseases. Apart from a discussion on classical thrombopathies, this review will also deal with the less commonly known relation between platelet research and disorders with a broader clinical phenotype. Classical thrombopathies involve disorders of platelet adhesion such as Glanzmann thrombastenia and Bernard-Soulier syndrome, defective G protein signalling diseases with impaired phospholipase C activation, and abnormal platelet granule secretion disorders such as gray platelet disorder and delta-storage pool disease. Other clinical symptoms besides a bleeding tendency have been described in MYH9-related disorders and Duchenne muscular dystrophy due to adhesion defects, and also in disorders of impaired Gs signalling, in Hermansky Pudlack disease and Chediak Higashi disease with abnormal secretion. Finally, platelet research can also be used to unravel novel mechanisms involved in many neurological disorders such as depression and autism with only a subclinical platelet defect.

Decreased calcineurin activity in circulation of Duchenne muscular dystrophy

OBJECTIVES

In an analysis of enzymes in easily accessible tissues like blood cells, serum can provide a valuable information and a simple tool for disease and carrier detection. In the study presented we have analyzed calcineurin activity in Duchenne muscular dystrophy (DMD) and carrier sera and lymphocytes for its diagnostic value and its status in DMD pathology.

DESIGN AND METHODS

We have monitored calcineurin activity in sera and lymphocytes of DMD, in carriers and in controls using colorimetric method by following the p-nitrophenol released in the presence and absence of Trifluoperazine (TFP), an inhibitor of calcineurin.

RESULTS

Results showed a significant decrease in serum and lymphocyte calcineurin activity in DMD (p<0.001) without alteration in carriers compared to normal.

CONCLUSION

Further studies are required to understand possible alterations mediated by calcineurin with reference to DMD lymphocytes as any alteration in phosphorylation/dephosphorylation pathway can disturb the normal functioning of these cells. The decreased calcineurin activity observed in DMD serum compared with controls could be further examined for its diagnostic utility.

Altered expression, intracellular distribution and activity of lymphocyte calpain II in Duchenne muscular dystrophy

BACKGROUND

Calpain II is an calcium-dependent cysteine protease involved in essential regulatory or processing functions of the cell, mediated by physiological concentrations of Ca(2+). However, in an environment of abnormal intracellular calcium as in Duchenne muscular dystrophy (DMD), calpain is suggested to cause membrane alterations.

METHODS

Twelve individuals with dystrophin gene deletion and an equal number of age and sex matched controls were chosen for the study. The expression pattern of calpain II (both at RNA and protein levels), its cellular location upon activation and its activity in lymphocytes were specifically assessed to know if our earlier report of increased calpain activity in DMD lymphocytes is a result of de novo synthesis or is due to basic defect in calcium handling.

RESULTS

We found a significant increase in the expression, alteration in calpain II distribution and increased activity of this enzyme.

CONCLUSION

Membrane abnormalities and altered signaling pathways observed in DMD lymphocytes may be due to increased association of calpain II onto membrane and cytosol.