Sean M. Lynch, Ph.D.

Professor, Dept Biochemistry, Chicago College of Osteopathic Medicine


Midwestern University
Chicago College of Osteopathic Medicine
College of Dental Medicine - Illinois
Department of Biochemistry
Science Hall - Room 421J
555 31st St.
Downers Grove, IL 60515

Office: (630) 515-6156
e-mail: slynch@midwestern.edu



EDUCATION

B.Sc.          Biochemistry                     Queen's University Belfast, Northern Ireland
Ph.D.         Nutritional Biochemistry      University of Ulster, Northern Ireland

RESEARCH SUMMARY

Blood levels of high-density lipoprotein (HDL) are inversely associated with risk for heart disease.  During inflammation, oxidation of HDL by myeloperoxidase-derived pro-oxidants, such as hypochlorous acid (HOCl), results in loss of its cardio-protective properties including the antioxidant paraoxonase-1 (PON1) enzyme activity.  We are currently investigating the role of thiocyanate (SCN-), a pseudohalide substrate for myeloperoxidase, in modulating oxidation of HDL.  Preliminary studies indicate that while myeloperoxidase-derived hypothiocyanous acid (HOSCN) promotes oxidation of HDL and loss of PON1 activity, under some conditions, SCN- can serve as an antioxidant and prevent loss of PON1 activity from HDL.  SCN- may also mediate altered HDL function through carbamylation of lysine amino acid residues.  Furthermore, we are investigating the potential role of taurine as a mediator of myeloperoxidase-dependent oxidation of HDL.  Overall, it is anticipated that results from our studies will provide important new insights into the biochemical mechanisms by which myeloperoxidase participates in the inflammatory process currently recognized as central to the pathologic development of heart disease.

RESEARCH PROJECTS

Project I:

Investigate the biochemical mechanism(s) by which SCN- protects HDL from myeloperoxidase-dependent oxidation and prevents loss of PON1 activity.

Project II:

Investigate how SCN--mediated carbamylation can alter HDL's PON1 activity and its ability to prevent atherogenic transformation (oxidation) of low-density lipoprotein.

Project III:

Investigate how taurine may modulate pro-inflammatory effects of hypohalous acids produced by myeloperoxidase from (pseudo)halide substrates during inflammation and their effects on HDL.

SELECTED PUBLICATIONS

(see full PubMed results)

Inclusion of calcium during isolation of high-density lipoprotein from plasma maintains antioxidant function.
Lynch SM, Lorenz J, Klotz S.
Anal Biochem 2014;454:41-3.

Vitamin C attenuates hypochlorite-mediated loss of paraoxonase-1 activity from human plasma.
Kunes JP, Cordero-Koning KS, Lee LH, Lynch SM.
Nutr Res 2009;29:114-22.

Modification with homocysteine does not increase susceptibility of human low-density lipoprotein to iron-mediated oxidation.
Lynch SM.
Nutr Res 2008;28:615-9.

Vitamin C preserves the cardioprotective paraoxonase activity of high-density lipoprotein during oxidant stress.
Calla MS, Lynch SM.
Arch Biochem Biophys 2006;452:129-37.

Vitamin C inhibits lipid oxidation in human HDL.
Hillstrom RJ, Yacapin-Ammons AK, Lynch SM.
J Nutr 2003;133:3047-51.

Vitamin C protects low-density lipoprotein from homocysteine-mediated oxidation.
Alul RH, Wood M, Longo J, Marcotte AL, Campione AL, Moore MK, Lynch SM.
Free Rad Biol Med 2003;34:881-91.

Plasma thiols inhibit hemin-dependent oxidation of human low-density lipoprotein.
Lynch SM, Campione AL, Moore MK.
Biochim Biophys Acta 2000;1485:11-22.