Imperial College London

DrAkifKhawaja

Faculty of MedicineNational Heart & Lung Institute

Research Associate
 
 
 
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Contact

 

akif.khawaja10 Website

 
 
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Location

 

Desk 8Sir Alexander Fleming BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

4 results found

Khawaja AA, Pericleous C, Ripoll VM, Porter JC, Giles IPet al., 2019, Autoimmune rheumatic disease IgG has differential effects upon neutrophil integrin activation that is modulated by the endothelium, Scientific Reports, Vol: 9, ISSN: 2045-2322

The importance of neutrophils in the pathogenesis of autoimmune rheumatic diseases, such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), is increasingly recognised. Generation of reactive oxygen species (ROS) and release of neutrophil extracellular traps (NETs) by activated neutrophils are both thought to contribute to pathology; although the underlying mechanisms, particularly the effects of IgG autoantibodies upon neutrophil function, are not fully understood. Therefore, we determined whether purified IgG from patients with SLE or RA have differential effects upon neutrophil activation and function. We found that SLE- and RA-IgG both bound human neutrophils but differentially regulated neutrophil function. RA- and SLE-IgG both increased PMA-induced β1 integrin-mediated adhesion to fibronectin, whilst only SLE-IgG enhanced αMβ2 integrin-mediated adhesion to fibrinogen. Interestingly, only SLE-IgG modulated neutrophil adhesion to endothelial cells. Both SLE- and RA-IgG increased ROS generation and DNA externalisation by unstimulated neutrophils. Only SLE-IgG however, drove DNA externalisation following neutrophil activation. Co-culture of neutrophils with resting endothelium prevented IgG-mediated increase of extracellular DNA, but this inhibition was overcome for SLE-IgG when the endothelium was stimulated with TNF-α. This differential pattern of neutrophil activation has implications for understanding SLE and RA pathogenesis and may highlight avenues for development of novel therapeutic strategies.

Journal article

Taylor KA, Smyth E, Rauzi F, Cerrone M, Khawaja AA, Gazzard B, Nelson M, Boffito M, Emerson Met al., Pharmacological impact of antiretroviral therapy on platelet function to investigate HIV-associated cardiovascular risk, British Journal of Pharmacology, ISSN: 0007-1188

Background and purposeSome clinical studies have reported increased myocardial infarction in people living with HIV taking the antiretroviral abacavir sulphate (ABC). Given that clinical studies contain confounding variables (e.g. HIV status), we investigated the pharmacological impact of antiretrovirals on platelet function in HIV‐negative volunteers in order to identify mechanisms of increased cardiovascular risk.Experimental approachPlatelets were isolated from healthy volunteers and HIV‐negative subjects enrolled on a Phase I clinical trial and platelet function evaluated using aggregometry and flow cytometry. In vivo platelet thromboembolism was monitored in anaesthetised mice.Key resultsHuman platelet aggregation was unaffected by all antiretrovirals tested but ABC treatment led uniquely to increased platelet granule release. ABC also interrupted nitric oxide (NO)‐mediated inhibition of platelet aggregation and increased in vivo aggregation in mice. An alternative antiretroviral, tenofovir, did not affect platelet function. Furthermore, aggregation and activation of platelets isolated from twenty subjects taking clinically‐relevant doses of tenofovir were comparable to baseline samples.Conclusions and implicationsABC can enhance platelet activation, independently of HIV status suggesting a potential pharmacological effect that is absent with tenofovir. Mechanistically, we propose that ABC enhances platelet degranulation and interrupts NO‐mediated platelet inhibition. The interaction of ABC with NO signalling is supported by data demonstrating ABC‐mediated enhancement of aggregation in vivo and in vitro responses that persist in the presence of NO. Although an association between ABC and platelet activation has not been confirmed in patients, these findings provide evidence of a mechanistic link between platelet activation and antiretroviral therapy.

Journal article

Dos Santos Brilha S, Chong D, Khawaja A, Ong C, Guppy N, Porter J, Friedland Jet al., 2018, Integrin α2β1 expression regulates matrix metalloproteinase-1-dependent bronchial epithelial repair in pulmonary tuberculosis, Frontiers in Immunology, Vol: 9, ISSN: 1664-3224

Pulmonary tuberculosis (TB) is caused by inhalation of Mycobacterium tuberculosis, which damages the bronchial epithelial barrier to establish local infection. Matrix metalloproteinase-1 plays a crucial role in the immunopathology of TB, causing breakdown of type I collagen and cavitation, but this collagenase is also potentially involved in bronchial epithelial repair. We hypothesized that the extracellular matrix (ECM) modulates M. tuberculosis-driven matrix metalloproteinase-1 expression by human bronchial epithelial cells (HBECs), regulating respiratory epithelial cell migration and repair. Medium from monocytes stimulated with M. tuberculosis induced collagenase activity in bronchial epithelial cells, which was reduced by ~87% when cells were cultured on a type I collagen matrix. Matrix metalloproteinase-1 had a focal localization, which is consistent with cell migration, and overall secretion decreased by 32% on type I collagen. There were no associated changes in the specific tissue inhibitors of metalloproteinases. Decreased matrix metalloproteinase-1 secretion was due to ligand-binding to the α2β1 integrin and was dependent on the actin cytoskeleton. In lung biopsies, samples from patients with pulmonary TB, integrin α2β1 is highly expressed on the bronchial epithelium. Areas of lung with disrupted collagen matrix showed an increase in matrix metalloproteinases-1 expression compared with areas where collagen was comparable to control lung. Type I collagen matrix increased respiratory epithelial cell migration in a wound-healing assay, and this too was matrix metalloproteinase-dependent, since it was blocked by the matrix metalloproteinase inhibitor GM6001. In summary, we report a novel mechanism by which α2β1-mediated signals from the ECM modulate matrix metalloproteinase-1 secretion by HBECs, regulating their migration and epithelial repair in TB.

Journal article

Cambridge G, Moura RA, Santos T, Khawaja AA, Polido-Pereira J, Canhão H, Leandro MJ, Fonseca JEet al., 2014, Expression of the Inherently Autoreactive Idiotope 9G4 on Autoantibodies to Citrullinated Peptides and on Rheumatoid Factors in Patients with Early and Established Rheumatoid Arthritis, PLoS ONE, Vol: 9, Pages: e107513-e107513

Journal article

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