An essential requirement for ß1 integrin in the assembly of extracellular matrix proteins within the vascular wall.

ß1 integrin has been shown to contribute to vascular smooth muscle cell differentiation, adhesion and mechanosensation in vitro. Here we showed that deletion of ß1 integrin at the onset of smooth muscle differentiation resulted in interrupted aortic arch, aneurysms and failure to assemble extracellular matrix proteins. These defects result in lethality prior to birth. Our data indicates that ß1 integrin is not required for the acquisition, but it is essential for the maintenance of the smooth muscle cell phenotype, as levels of critical smooth muscle proteins are gradually reduced in mutant mice. Furthermore, while deposition of extracellular matrix was not affected, its structure was disrupted. Interestingly, defects in extracellular matrix and vascular wall assembly, were restricted to the aortic arch and its branches, compromising the brachiocephalic and carotid arteries and to the exclusion of the descending aorta. Additional analysis of ß1 integrin in the pharyngeal arch smooth muscle progenitors was performed using wnt1Cre. Neural crest cells deleted for ß1 integrin were able to migrate to the pharyngeal arches and associate with endothelial lined arteries; but exhibited vascular remodeling defects and early lethality. This work demonstrates that ß1 integrin is dispensable for migration and initiation of the smooth muscle differentiation program, however, it is essential for remodeling of the pharyngeal arch arteries and for the assembly of the vessel wall of their derivatives. It further establishes a critical role of ß1 integrin in the protection against aneurysms that is particularly confined to the ascending aorta and its branches.

When Cre-mediated recombination in mice does not result in protein loss.

Cre/loxP recombination enables cellular specificity and, in the case of inducible systems, temporal control of genomic deletions. Here we used a SM22α tamoxifen-inducible Cre line to inactivate ß1 integrin in adult smooth muscle. Interestingly, analysis of two distinct ß1 loxP transgenic mice revealed vastly different outcomes after ß1 integrin deletion. Lethality occurred 4 weeks postinduction in one Cre/loxP line, while no apparent phenotype was seen in the other line. Genetic analysis revealed appropriate DNA excision in both cases; however, differences were found in the degree of protein loss with absolutely no change in protein levels in the model that lacked a phenotype. Seeking to understand protein persistence despite appropriate recombination, we first validated the flox allele using a constitutive Cre line and demonstrated its ability to mediate effective protein inactivation. We then examined the possibility of heterozygous cell selection, protein turnover, and deletion efficiency with no success for explaining the phenotype. Finally, we documented the presence of the Cre-recombination episomal product, which persisted in tissue samples with no protein loss. The product was only noted in cells with low proliferative capacity. These findings highlight the potential for protein expression from the products of Cre-recombinase excised genes, particularly when deletion occurs in low turnover populations.

Adverse effects of antiretroviral treatment.

BACKGROUND: The introduction of highly active antiretroviral therapy (HAART) has led to significant reduction in acquired immune deficiency syndrome (AIDS)-related morbidity and mortality. Adverse drug reactions (ADRs) to antiretroviral treatment (ART) are however, major obstacles in its success. AIMS: We sought to study the adverse effects of ART in a resource-restricted setting in India. METHODS: Hundred patients on ART were studied prospectively over a period of two years. All patients were asked to visit the clinic if they developed any symptoms or on a monthly basis. They were screened clinically and investigated suitably for any ADRs. RESULT: Out of the 100 patients, ten patients did not come for follow-up; only 90 cases were available for evaluation. ADRs were observed in 64 cases (71.1%) - the maximal frequency of ADRs was seen with zidovudine (AZT) (50%) followed by stavudine (d4T) (47.9%), efavirenz (EFV) (45.4%) and finally, Nevirapine (NVP) (18.4%). Most common ADRs were cutaneous (44.4%) followed by hematological (32.2%), neurological (31.1%), metabolic (22.2%) and gastrointestinal (20%). Most common cutaneous ADRs observed were nail hyperpigmentation (14.4%) and rash (13.3%). Immune reconstitution inflammatory syndrome (IRIS) was observed as a paradoxical reaction to ART in 20 (22.2%) cases. CONCLUSION: To optimize adherence and thus, efficacy of ART, clinicians must focus on preventing adverse effects whenever possible, and distinguish those that are self-limited from those that are potentially serious.