Tuesday, September 22, 2015

Some Genes Are "More" Sensitive to Long-Term, Low-Level Microwave Exposure

The Screening of Genes Sensitive to Long-Term, Low-Level Microwave Exposure and Bioinformatic Analysis of Potential Correlations to Learning and Memory

Zhao YL, Li YX, Ma HB, Li D, Li HL, Jiang R, Kan GH, Yang ZZ, Huang ZX. The Screening of Genes Sensitive to Long-Term, Low-Level Microwave Exposure and Bioinformatic Analysis of Potential Correlations to Learning and Memory. Biomed Environ Sci. 2015 Aug;28(8):558-570.


OBJECTIVE: To gain a better understanding of gene expression changes in the brain following microwave exposure in mice. This study hopes to reveal mechanisms contributing to microwave-induced learning and memory dysfunction.

METHODS: Mice were exposed to whole body 2100 MHz microwaves with specific absorption rates (SARs) of 0.45 W/kg, 1.8 W/kg, and 3.6 W/kg for 1 hour daily for 8 weeks. Differentially expressing genes in the brains were screened using high-density oligonucleotide arrays, with genes showing more significant differences further confirmed by RT-PCR.

RESULTS: The gene chip results demonstrated that 41 genes (0.45 W/kg group), 29 genes (1.8 W/kg group), and 219 genes (3.6 W/kg group) were differentially expressed. GO analysis revealed that these differentially expressed genes were primarily involved in metabolic processes, cellular metabolic processes, regulation of biological processes, macromolecular metabolic processes, biosynthetic processes, cellular protein metabolic processes, transport, developmental processes, cellular component organization, etc. KEGG pathway analysis showed that these genes are mainly involved in pathways related to ribosome, Alzheimer's disease, Parkinson's disease, long-term potentiation, Huntington's disease, and Neurotrophin signaling. Construction of a protein interaction network identified several important regulatory genes including synbindin (sbdn), Crystallin (CryaB), PPP1CA, Ywhaq, Psap, Psmb1, Pcbp2, etc., which play important roles in the processes of learning and memory.

CONCLUSION: Long-term, low-level microwave exposure may inhibit learning and memory by affecting protein and energy metabolic processes and signaling pathways relating to neurological functions or diseases.

Mice were divided randomly into exposure and sham groups (6 animals/group), with the exposure groups further divided into groups 1, 2, and 3, with average whole-body SARs of 0.45 W/kg, 1.8 W/kg, and 3.6 W/kg. Subjects were placed at a distance of 30 cm from the exposure source at power densities of 1, 4, and 8 mW/cm2. The SAR calculation was based on the finite difference time domain (FDTD) method. Animals in the exposure groups were placed in polypropylene cages with apertures and partitions. Mice whole bodies were exposed to microwaves, with their body axes oriented in parallel to the electric field polarization for 1 h daily in a temperature controlled room at acontinuous frequency of 2100 MHz for 8 weeks. To negate any other type of psychophysiological effects, sham group animals were processed in parallel to the exposed groups, but without microwave exposure. After irradiation, RNA was extracted from each brain independently, with RNA from each group pooled prior to gene microarray analysis. Three RNA samples from the 3.6 W/kg group were utilized for RT-PCR. 

Microwave exposure is speculated to decrease LTP induction, increase LTD induction, disrupt the balance of LTD and LTP, reduce dendrite spines formation, affect the inflammatory response and impact early AD responses by the directly or indirectly modulating important pathway regulatory molecules, eventually impairing learning and memory. Among the pathways affected by microwaves, the LTP and LTD pathways were affected the most. The most notable genes were sbdn and Cryab, since they responded sensitively to microwaves at all 3 SAR levels. Microwaves are thought to inhibit learning and memory by sbdn mediating LTP and dendrite formation, while Cryab mediates inflammation and early AD reactions. These findings provide important clues into the mechanisms and possible counter measures pertaining microwave induced learning and memory inhibition (Figure 5). However, more research is required to further characterize the roles of both the known or unknown genes and how they function in microwaves affecting learning and memory.

This work was supported by SN03-2 from the Astronaut Research and Training Center of China.


Joel M. Moskowitz, Ph.D., Director
Center for Family and Community Health
School of Public Health
University of California, Berkeley

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