Influence of Genotype on Reproductive Effects of Air Pollution in Young MenEPA Grant Number: R827019
Title: Influence of Genotype on Reproductive Effects of Air Pollution in Young Men
Investigators: Marshall, Don , Rubes, Jiri , Sram, Radim
Current Investigators: Evenson, Donald P. , Marshall, Don , Rubes, Jiri , Sram, Radim
Institution: South Dakota State University
EPA Project Officer: Hahn, Intaek
Project Period: September 1, 1998 through September 30, 2000 (Extended to November 30, 2003)
Project Amount: $274,670
RFA: Interindividual Variation in Human Susceptibility to Environmentally-caused Disease (1998) RFA Text | Recipients Lists
Research Category: Health Effects , Human Health , Health
Objectives/Hypotheses: The overall hypothesis is that the human genotype influences the extent of pollution exposure damage to sperm chromatin integrity
We will test the hypothesis that men with commonly occurring genetic mutations for enzymes involved in metabolizing reactive intermediates of PAH components of air pollution will be more susceptible to DNA damage and/or aneuploidy induced in their germ cells. Genotypes for GSTM1, GSTT1 and NAT2 will be determined from archived blood samples. DNA damage will be evaluated in archived semen samples using both established and promising new tests for nuclear integrity. These biomarkers of effect include: a) altered chromatin structure as measured by the flow cytometric Sperm Chromatin Structure Assay (SCSA), b) DNA strand breaks as measured by a DNA end labeling technique (TUNEL) and single cell gel electrophoresis (COMET assay), and c) sperm aneuploidy (hyperhaploidy and diploidy) measured using 3-color fluorescence in situ hybridization (FISH). Samples available for study include semen obtained from young men (in their early 20s) living in the Teplice district of the Czech Republic. These men were sampled seven times over the course of two years (1995-97), in winter at times when air pollution was extremely high (due to temperature inversions that hold pollution in the locale) and in early autumn when it was low. This longitudinal design is advantageous because each man serves as his own baseline, and the interval between exposure episodes and sampling can be varied. The latter is important since the kinetics of spermatogenesis (~74 days) must be considered when interpreting the results of such studies. Questionnaire data and urinary cotinine will be used to control for potential modifiers (e.g., smoking, alcohol and caffeine consumption, recent high fever, occupational exposures).
Our laboratory has measured the first two (first autumn and first January) samples provided by 22 donors. Eleven of the 22 (50%) samples showed a very significant increase in altered chromatin structure in the January sample compared to the previous fall sample. From our experience, it is evident that a perturbing agent significantly altered the SCSA data in these samples, thus providing solid preliminary data of a exposure/response. The 50:50 response provides compelling evidence supporting the hypothesis of genetic mechanisms involved. It is of importance that samples were collected each month during three early winter months since this time frame covers just over one spermatogenic cycle. Some toxicants are known to exert effects on specific windows of the spermatogenic cycle, e.g., meiotic disrupters would lead to aneuploidy whereas agents affecting protamine-DNA packaging would be susceptible as late spermatids. Based on these preliminary data, we anticipate that exposure-related increases in sperm DNA damage and/or aneuploidy will also be found, and these may be observed in samples obtained with different windows of exposure. Furthermore, and of relevance to this RFA, men with susceptible genotypes may show a greater response to this environmental stressor. It will be particularly interesting to see if men with mutations in both genes are more susceptible than men with a single mutation. To our knowledge, this is the first study to evaluate interindividual susceptibility to germ cell damage in men exposed to high levels of air pollution (PAH).