Abstract
Glaucoma, a multifactorial neurodegenerative disease, is the second most common cause
of blindness. Since early diagnosis facilitates timely treatment, it is therefore
essential to identify
appropriate markers. In the future, so-called biomarkers could be helpful in
early detection and follow-up. In glaucoma, these parameters could be obtained in
the aqueous humour. Altered
antibodies, proteins, microRNA (miRNA) and trace element levels have already
been identified. This review provides insight into possible changes in the aqueous
humour of patients with
primary open-angle glaucoma (POAG), normal tension glaucoma (NTG) or pseudoexfoliation
glaucoma (PEXG). Studies on antibody changes in POAG patients identified an upregulation
of immune
system associated antibodies such as heat shock protein (HSP) 27. HSP27 was also
upregulated in PEXG patients but decreased in NTG. In POAG and PEXG samples, the levels
of certain proteins,
including interleukins and endothelin-1, were elevated. The vasoconstrictor endothelin-1
may play a role in regulating intraocular pressure. By contrast, proteins playing
a role in the
response to oxidative stress were downregulated. In NTG patients, proteins responsible
for the elimination of toxic by-products from the respiratory chain were downregulated.
In addition,
the aqueous humour of POAG and PEXG patients contained several miRNAs that have
been linked to tissue development, neurological disease and cellular organisation.
Other miRNAs regulated in
glaucoma play a role in extracellular matrix remodelling and thus may affect
drainage resistance in the trabecular meshwork. It is also interesting to note that
the aqueous humour of
glaucoma patients showed changes in the levels of trace elements such as zinc
and selenium. The elevated zinc levels could be responsible for the imbalance of intraocular
matrix
metalloproteinases and thus for increased intraocular pressure. All these studies
demonstrate the complex changes in aqueous humour in glaucoma. Some of these biomarkers
may be useful in the
future for early diagnosis of the disease.
Key words
antibodies - aqueous humour - glaucoma - immune system - microRNA - protein - trace
elements
