Ageing, Presbyopia and Cataract Research
Group Leader
• Roger Truscott BSc PhD rjwt@eye.usyd.edu.au   (or rjwt@uow.edu.au)
 

Roger Truscott
 
Postdoctoral Fellows
• Peter Hains
• Anastasia Korlimbinis
• Yoke Berry (Wollongong)
Research Fellow
• Eric Wei
PhD Students
• Karl Heys (Wollongong)
• Michael Friedrich (Wollongong)
• Jane Deeley (Wollongong) - co-supervised with Steve Blanksby
• Jasminka Mizdrak (Macquarie University) - co-supervised by Joanne Jamie and Mike Davies
     
Research Activities
The research activities of our group centre on ageing and the consequences of lens ageing for human vision. In particular we are seeking to understand the molecular bases for two common conditions that are associated with age: presbyopia and age-related nuclear cataract (ARNC). ARNC, where the lens becomes opaque, is a major cause of world blindness. Presbyopia, the inability to focus on nearby objects, affects almost everyone by age 50. It is the reason why most middle-aged people need reading glasses.  
 
Age-related Nuclear Cataract

The past five years has seen a quantum leap in our knowledge of ARNC. For the first time we have an understanding of the molecular mechanism that underpins this previously baffling condition. Much of this research has originated from this laboratory. Some scientific discoveries are listed below. For example, we have:

  1. discovered a biochemical basis for human lens colouration. This affects our colour vision as we age 120
  2. shown why it is that oxidation, which is the hallmark of nuclear cataract, occurs in the lens nucleus 136
  3. isolated and elucidated the structures of the major UV filters of the human lens 111, 106
  4. synthesised the major UV filters and uncovered the reason for the instability of these compounds. 
  5. demonstrated the importance of the iron in the aetiology of nuclear cataract and  linked all of these phenomena together to provide, for the first time, a comprehensive picture of how nuclear cataract develops 120, 136.

This is summarised below.

The sequence of events, as we now understand it, is as follows 136: With age, an internal barrier to the movement of small molecules within the lens develops. As a result, antioxidants from the biochemically-active lens cortex can no longer gain access the centre of the lens at a rate sufficient to cope with the oxidative stress. This oxidative stress is generated principally from the reaction of O2 with reactive small molecules, such as ascorbate and 3-hydroxykynurenine, in the centre of the lens. Highly-diffusible O2 130 can readily pass through the barrier and thus H2O2 is formed. Intrinsically unstable molecules, in particular UV filters, decompose to a greater extent than normal in the centre of the aged lens due to their increased residence time (half-life) - due, in turn to the barrier. This results in increased protein binding of UV filter decomposition products and greater oxidation of crystallins leading to accelerated protein denaturation. Denaturation of macromolecules such as ferritin, liberates redox-active iron which, in the presence of H2O2, leads to the formation of damaging hydroxyl radicals. Massive oxidation of protein cysteine and methionine residues ensues which is accompanied by insolubilisation and lens opacity. UV light, and its interaction with the proteins that have been modified UV filters, may also play a role 128. We are now trying to determine the reasons for the onset of the lens barrier.

 
 
Presbyopia

Our recent research suggests that the fundamental cause of presbyopia can be traced to changes that occur in the human lens with age 127. The centre of the lens becomes progressively much stiffer - by a factor of approximately 1000! In young people, contraction of the ciliary muscles normally leads to a shape change of the flexible lens and this therefore allows close focussing. It appears that by age 45-50, that the lens becomes too stiff to change its shape. We are now trying to understand what is responsible for the massive change in lens stiffness as we age. It may be that presbyopia and ARNC may be linked 137.

The work of our research team covers areas as diverse as molecular biology, immunohistochemistry, cell biology, chemical synthesis, enzymology and structural identification based on NMR and mass spectrometry.

 
 
References 2001-2006

 
106) Bova, L.M., Sweeney, M.H.J., Jamie, J.F. and Truscott, R.J.W.
Major Changes in Human Ocular UV Protection with Age.
Invest. Ophthalmol. Vis. Sci. 42(1), 200-205 (2001)

107) Takikawa, O., Littlejohn, T. K. and Truscott, R.J.W.
Indoleamine 2,3-Dioxygenase in the Human Lens, the First Enzyme in the Synthesis of UV Filters.
Exp. Eye. Res. 72, 271-277 (2001)

108) Berry, Y. and Truscott, R.J.W.
The Presence of a Human UV Filter within the Lens Represents an Oxidative Stress.
Exp. Eye. Res. 72, 411-421 (2001)

109) Davies, M.J. and Truscott, R.J.W.
Photo-oxidation of proteins and its role in cataractogenesis.
J. Photochem. Photobiol. 63, 114-125 (2001)

110) Aquilina, J.A.and Truscott, R.J.W.
Kynurenine Binds to the Peptide Binding Region of α-B crystallin.
Biochem. Biophys. Res. Comm. 285, 1107-1113 (2001)

111) Bova, L.M., Aquilina, J. A.,Willis, R.H., Jamie, J.F. and Truscott, R.J.W.
Identification of a new Human Lens UV filter Compound.
FEBS Letters. 509, 6-10 (2001)

112) Vazquez, S., O'Hair, R.A.J., Weimann, A., Truscott, R.J.W. and Sheil, M.M.
A study of kynurenine fragmentation using electrospray tandem mass spectrometry.
J. Am. Soc. Mass Spectrom. 12, 786-794 (2001)

113) Aquilina, J.A.and Truscott, R.J.W.
Identifying Sites of Attachment of UV filters to Proteins in Older Human Lenses.
Biochem. Biophys. Acta. 1596, 6-15 (2002)

114) Vazquez, S., Aquilina, J. A., Jamie, J.F., Sheil, M.M. and Truscott, R.J.W.
Novel protein modification by kynurenine in human lenses.
J. Biol. Chem. 277, 4867-4873 (2002)

115) Taylor, L.M., Aquilina, J.A., Jamie, J.F. and Truscott, R.J.W.
Glutathione and NADH, but not Ascorbate, Protect Lens Proteins From Modification by UV Filters.
Exp. Eye Res.74, 503-511 (2002)

116) Littlejohn, T.K., Takikawa, O., Jamie, J.F., Walker, M.J. and Truscott, R.J.W.
Production of Truncated Enzymically-Active Human Indoleamine 2,3-Dioxygenase (IDO) Using Site-Directed Mutagenesis.
Excerpta Medica International Congress Series (ICS). 1233, 157-160 (2002)

117) Hazell, L.J., Fu, H.,Dean, R.T., Stocker, R. and Truscott, R.J.W.
Is Hypochlorous acid (HOCl) involved in age-related nuclear cataract?
Clin. and Experimental Ophthalmol. 85, 97-100 (2002)

118)Taylor, L.M., Aquilina, J.A., Jamie, J.F. and Truscott, R.J.W.
UV filter instability: Consequences for the Human Lens.
Exp. Eye Res. 75, 165-175 (2002)

119) Terentis, A.C., Thomas, S.R., Takikawa O., Littlejohn T.K., Truscott R.J.W., Armstrong R.S., Yeh, S.R., and Stocker R.
The heme environment of recombinant human indoleamine 2,3-dioxygenase. Structural properties and substrate-ligand interactions.
J. Biol. Chem. 277(18), 15788-15794 (2002)

120) Truscott. R.J.W.
Human cataract: the mechanisms responsible; light and butterfly eyes.
Int. J. Biochem. Cell Biol. 35, 1500-1504 (2003)

121) Hains, P.G., Gao, L. and Truscott. R.J.W.
The photosensitiser xanthurenic acid is not present in normal human lenses.
Exp. Eye Res. 77, 547-553 (2003)

122) Sweeney, M.H.J., Garland, D.L. and Truscott, R.J.W.
Movement of cysteine in intact monkey lenses: the major site of entry is the germinative region.
Exp. Eye Res. 77, 245-251 (2003)

123) Littlejohn, T.K., Takikawa, O., Truscott, R.J.W. and Walker, M.J.
Asp 274 and His 346 are essential for Heme binding and catalytic function of Human Indoleamine 2,3-Dioxygenase.
J. Biol. Chem. 278, 29525-29531 (2003)

124) Truscott, R.J.W., Vazquez, S. and Parker, N. R.
Protein-bound Kynurenine decreases with the progression of age-related nuclear cataract.
Invest. Ophthalmol. Vis. Sci. 45, 879-883 (2004)

125) Austin, C., Jasminka Mizdrak, J., Matin, A., Sirijovski, N., Kosim-Satyaputra, P., D. Willows, R.D., Roberts, T., Truscott, R.J.W., Polekhina, G., Parker, M.V. and. Jamie, J.F.
Optimised Expression and Purification of Recombinant Human Indoleamine 2,3-Dioxygenase.
Protein Expression and Purification 37, 392-398 (2004)

126) Streete, I. M., Jamie J.J.and Truscott, R.J.W.
Lenticular levels of free amino acids and UV filters differ significantly between normals and cataract patients.
Invest. Ophthalmol. Vis. Sci. 45, 4091-4098 (2004)

127) Heys, K., Cram, S. and Truscott, R.J.W.
Massive increase in the stiffness of the human lens nucleus with age: the basis for presbyopia?
Mol. Vision 10, 956-963 (2004)

128) Parker, N. R., Jamie, J.J., Davies, M. and Truscott, R.J.W.
Protein-bound kynunerine is a photosensitizer of oxidative damage.
Free Rad. Biol. Med. 37, 1479-1489 (2004)

129) Hains, P.G., Gao, L. and Truscott. R.J.W.
Reply to ‘Comment on ‘The photosensitiser xanthurenic acid is not present in normal human lenses’ by P.G. Hains et al. in Exp. Eye Res. Vol. 77 (2003) pp. 547-553' by H.Z. Malina
Exp. Eye Res. 79, 447-448 (2004)

130) McNulty R., Wang, H., Mathias, R.T., Ortwerth, B.J., Truscott R.J W. and Bassnett, S.
Regulation of tissue oxygenation in the vertebrate lens.
J. Physiol. 559, 883-898 (2004)

131) Ferry, G., Ubeaud, C., Lambert P-H, Bertin, S., Coge, F., Chomarat, P., Delagrange, P., Serkiz, B., Truscott, R. J.W. and Boutin, J.A.
Molecular evidence that melatonin is enzymatically oxidized in a different manner than tryptophan: investigations with both indoleamine 2,3-dioxygenase and myeloperoxidase.
Biochem. J. 388, 205-215 (2005)

132) Matin, A., Streete, I.M., Jamie I.M., Truscott, R.J.W and Jamie J.J.
A fluorescence-based assay for indoleamine 2,3-dioxygenase.
Anal. Biochem. 349, 96-102 (2006)

133) Korlimbinis, A., Hains, P.G., Truscott. R.J.W. and Aquilina, J.A.
3-Hydroxykynurenine Oxidizes α-Crystallin: Potential Role in Cataractogenesis.
Biochemistry. 45,1852-1860 (2006)

134) Korlimbinis, A. and Truscott. R.J.W.
Identification of 3-Hydroxykynurenine bound to proteins in the human lens. A possible role in age-related nuclear cataract.
Biochemistry 45, 1950-1960 (2006)

135) Hains, P.G., Simpanya, M.F., Giblin, F. and Truscott. R.J.W.
UV filters in the thirteen lined ground squirrel (Spermophilus tridecemlineatus).
Exp. Eye Res. 82, 730-737 (2006)

136) Truscott, R.J.W.
Age-related nuclear cataract - oxidation is the key.
Exp. Eye Res. 80, 709-725 (2006)

137) McGinty, S. and Truscott, R.J.W.
Presbyopia: the first stage of nuclear cataract?
Ophthal. Res. 699, 38, 137-148 (2006)