Chapter 7 Interaction of Emf With Cells

8/3/2019 Chapter 7 Interaction of Emf With Cells

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Chapter 7 Interaction of Electromagnetic Field With Cells

In this section we shall discuss have electromagnetic field interacts with cell and sub cellular organ cell,

in this section most of the studies done are from invitro studies done one individual cells as it is not

possible monitor all the cells in a living organism at a same time. Now we shall split the electromagneticelectromagnetic field into two components i.e. (a) electric field, (b) Magnetic field. The cell membrane

blocks the electric component from penetrating the cytoplasma. But magnetic component pass through the

cells without any resistance. Before we understand the mechanism by which EMF interacts with cells lets

first study the normal structure and function of the cell.

Normal cell structure

An adult human being is made up of approximately 100,000 billion cells. A cell contains many

different compartments, organelles, each surrounded by a membrane. The organelles are

specialized to carry out different tasks. A large number of proteins carrying out essential

functions are constantly being made

within our cells. These proteins have to be

transported either out of the cell, or to the

different compartments - the organelles -

within the cell, newly synthesized

proteins have an intrinsic signal that is

essential for governing them to and across

the membrane of the endoplasmic

reticulum,. The cell nucleus contains the

genetic material (DNA) and thus governs

all functions of the cell. The mitochondria

are the "power plants" producing energy

needed by the cell, and the endoplasmic

reticulum is, together with the ribosomes, responsible for synthesizing proteins, every cell

contains approximately one billion protein molecules. The different proteins have a large number

of important functions. Some constitute the building blocks for constructing the cell while others

function as enzymes catalyzing thousands of specific chemical reactions. The proteins within a

cell are constantly degraded and resynthesized.

Figure 1.1 structure of atypical cell


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Structure of cell membrane

Membrane Structure,

Structurally, cell membranes are thought to be field mosaic composed of large proteins

embedded in a thin planar bilayer of aliphatic phospholipids molecules, as indicated in Figure 1.2

A pure phospholipid bilayer arrangement is one of the strongest electric insulators known and is

therefore quite suitable for maintaining large electrochemical potential gradients at minimal

energy expense,. In cell membranes, most ionic current permeates through channels formed by

large transmembrane proteins. Some cells have specialized protein channels thatallow regulation

and selective permeation of ions.

Many membrane proteins serve as receptors for external ligands that cannot penetrate to the

interior of the cell. The attachment of a ligand, such as a hormone, to a receptor protein in the

membrane forms a complex that activates a secondary messenger within the cell to affect a

cellular response. Generally, three different schemes of ligand-mediated signal transduction have

been described. The first involves activation of cyclic adensosine monophosphate (cAMP) as the

secondary messenger. Including inositol triphosphate (IP3), diacylglycerol, and calcium ions. The

third involves ligand-mediated opening (gating) of ion channels in membrane receptors. Here I

have described these signal mechanisms and the ways in which electric fields may perturb them.

Figure 1.2 structure of atypical cell membrane showing (from left to right) c AMP pathway,voltage gated ion channels, inositol phosphate pathway. (Courtesy by lee. Doong et al)


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The cAMP Pathweay.

Signal transduction through the cAMP pathway begins with the arrival of an external signal at

either a stimulatory or an inhibitory membrane receptor. Activation of the stimulatory receptor

molecule signals G3 proteins within the membrane to react with guanine triphosphate (GTP).

The G3 protein then activates another membrane-bound enzyme, adenylate cyclase, to form

cAMP. CcAMP molecules bind to the regulatory sub-unit of protein kinases within the cell,

allowing these enzymes to activated latent proteins by phosphorylation to perform a genetically

programmed fundion. cAMP molecules also work by modulating the flow of other secondary

messengers such as calcium ions. In contrast, activation of the inhibitory receptor provokes a

similar mechanism that results in the inhibition of adenylate cyclase, thereby slowing the

production of cAMP. Although these schemes are similar across a wide range of cell types, the

responses to activation of this pathway vary tremendously.

The Inositol-Membrane Lipid Pathway.

In the inositol-membrane lipid pathway, a phospholipid constituent of the inner membrane,

phosphatidylinositol4.5

biphosphate, is used as the precursor of the second messengers.

Activation begins when ligand interaction with a receptor protein signals a G protein to react

with GTP. This causes activation of phosphatdylinositol biphosphate on the inner membrane and

its hydrolyzation into the secondary messengers IP3 and diacylglycerol. IP3 is water-soluble and

dissolves into the cytosol. It is thought that IP3 acts by stimulating the release of calcium ions

from intracellular organelles such as the endoplasmic reticulum. Like other cellular organelles,

IP3 released from the plasma membrane causes the organelles to rapidly release calcium back

into the cytosol. Increased cytoplasmic free calcium has many known effects, including the

activation of calmodulin, a molecule that regulates many transport and metabolic processes.

Diacylglycerol molecules diffuse laterally with the membrane, activating the membrane-bound

enzyme protein kinase C. Protein kinase C, in turn, activates additional latent proteins to regulate

cellular metabolic function.

Ligand Gated Channels.

Both the cAMP and inositollipid pathways use calcium ions as secondary messengers within the

cell. Besides being released from internal stores such as the endoplasmic reticulum, the internal

calcium concentration can also be raised in response to an external ligand by an increase in flux

across the cell membrane. The external concentration of calcium ion is four times greater than


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internal levels, and the regulation of specific ion channels permits the careful control of calcium

influx. As an example, the binding of parathyroid hormone (PTH) is accompanied by an increase

in calcium influx. In addition to ligand-gates channels, many ion channels are sensitive to the

strength of the transmembrane potential changes in the voltage across the membrane. Changes in

the voltage across the membrane directly turn the channel on and off. Compared with electrically

excitable cells like nerve and muscle, relatively few calcium channels exist in non excitable cells

such as blood cells and bone cells. However, two distinct voltage-gated calcium ion channels in

non excitable cells have been discovered. One type is activated by a change in transmembrane

potential from -30 mV to 20 mV. Relatively large changes in transmembrane potential (i.e., 40

mV to 50 mV) are required to significantly alter calcium ion flux. These channels are the most

direct membrane-bound electrochemical transducers.

Important Note:-

Cell membrane does not permit the electric field to enter into the cytoplasm hence the electric

field acts on the cell via membrane channels and proteins to bring changes inside the cell. The

magnetic field can pass through the cell without any resistance it directly acts on the intra

cellular molecules and organellae to bring about the changes. Hence in following section we will

discuss the effects of electric field and magnetic field differently even though they are two sides

of a same coin.

Mechanismofelectric field interaction with cell membrane,Cell membrane is considered to be the main site where the electric field interacts with the cell.

There are four reasons for this notion.

a) An applied electric field is amplified within the cell membrane.

b) The cell membrane is major transduction pathway as many ligand gated channels and

voltage gated channels are located in it.

c) Changes in the ion flow across the membrane especially calcium ion have been reported

in many EMF studies.

d) Membrane itself is involved in controlling the electrical aspects of the cell, maintaining a

potential gradient of almost 100 mV across the membrane through ion pumps.

Dose ofelectric field


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Cell membrane has a high dielectric constant it behaves as a good insulator for electric field.

Only less than 1% electric field penetrates anterior of the cell i.e if 1 Volt is applied only 1mV

enters the cytoplasma1,2

.

The conductivity of cell membrane is 10-6

times lesser than the conductivity of the plasma. In

cell cultures it is observed that cell which are placed parallel to the electric field are more

sensitive to applied electric field than cells which are perpendicular to the electric field, this is

because when the cells are placed parallel to the electric field the electric fiels is distributed

equallt around the cell as shown in the figure 1.3 below.

figure 1.3 schematic diagram showing distribution of electric field around the cell placed parallel

to the electric field (Eo) (Courtesy by lee. Doong et al).

As we know there is lot of electrochemical activity is going on in a cell, the applied field must

overcome this background noise i.e. signal to noise ratio should be greater then (one) 1, in a

typical mammalian cell a electric field signal of 20-5-mV/cm2

is must to stimulate cell

membrane3-5

Field Interaction Mechanisms

One possible method of electrochemical transduction involves the ability of applied fields to

alter the density and distribution of charged cell-surface proteins6. Several binding interactions

between physiologic ligands and cell-surface receptors have been shown to obey second-order

reversible binding kinetics. Because of this, it is likely that ligand-receptor binding can be

regulated by redistribution and local concentration of surface receptors. This receptor

redistribution would directlyperturb the cAMP and IP3 mechanisms described above by acting

on the ligand-receptor bidning kinetics7.


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In an oscillating electrical field of 1 V/cm and a frequency of 1 Hz, the expected distance

traveled in half a cycle by a single-membrane-imbedded concanavalin A receptor with

effective electrophoretic mobility of ~2x10-7 cm2/V-sec is less than 1 A0

Although this

distance is negligible compared with Brownian motion, if resistance-to-receptor movement in the

plane of the cell membrane is anisotropic, mechanical rectification of electrophoretic movement

may result. Rectification would lead to a net lateral displacement of the receptor over many

cycles. Receptor crowding toward one part of the cell may occur and may change the probability

of ligand binding or dissociation. Because hormone-receptor binding also regulates Trans

membrane ion fluxes, electric fields could in theory indirectly regulate intracellular calcium

transport68,9.

Established evidence exists for anisotropic resistance to movement along certain cells, including

fibroblasts. In 1978 Smith et al. demonstrated that succinyl concanavalinA receptors diffuse

anisotropically on murine fibroblasts10

, with the most rapid diffusion occurring in the direction

parallel to the underlying actin stress fibers. Controversy still exists regarding the existence of

this mechanism in different cell types. Kaptza et al., using a video-FRAP (Fluorescent

Recovery After Photo bleaching) technique, observed that concanavalinA receptor diffusion on

human foreskin fibroblasts is independent of direction11

. Recently, Stolpen et al., using a new

technique called line FRAP,: observed that human dermal fibroblasts exhibit anisotropic

diffusion of fluorescence recovery in class I major histocompatibility complex proteins but that

human vascular endothelial cells do not exhibit this diffusion12

.

Calcium Modulated Effects.

Many studies implicate intracellular calcium fluxes as an intermediate in EMF stimulation of

cellular response. This has been most clearly shown to occur in calcium-dependent

galvanotaxis13

. Calcium ions mediate the action of many other epigenetic regulatory signals and

are known as one of the universal second messengers14

. The complexity of the calcium

messenger system varies from one cell to another. In some cells the magnitude of the response is

related to the magnitude of the change in cytoplasmic calcium (eg, skeletal muscle contraction).

Cells in which the response to calcium is prolonged (e.g., smooth-muscle constriction, insulin

secretion) exhibit no simple corleation, however, between the magnitude or duration of calcium

change and the magnitude or duration of the cellular response15

.


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Recent work by Grazians et al., has demonstrated the influence of electric fields on the

membrane bound calcium ATPase pumps that maintain the large calcium gradient inside the cell.

Grazana et al., found that 20 V/cm electric field exposure increases Na+

Ca2+

transport activity in

plant protoplasts in a frequency-dependent manner. They attribute this change to an indirect

mechanism in which electric field stimulation of membrane-bound ATPsynthase and increases

the intracellular concentration of ATP, which then increases Na+

Ca2+

membrane transport16

.

Changing intracellular calcium concentration has profound effects on cell migration,

proliferation, and the synthesis of tissue components. The migration of fibroblasts into the

wound during the healing process is probably related to a 90 Kd protein, geloslin. When gelsolin

is activated by the binding of calcium ions, it breaks up the cross-linked network of actin

filaments within the cell and makes the cell more fluid and mobile. By alternately breaking and

reassembling the filaments of cytoskeleton, gelsolin may help the overall migration of

fibroblasts17

.

One role of calcium in biosynthesis involves exocytosis of procollagen into the extracellular

matrix. Experiments by Kelly and others have shown that exocytosis is a calcium-dependent

process. Blocking calcium ion flow into the cell may interrupt the secretion of cell matrix

constituents and may therefore inhibit the formation of tissue collagen. The modulation of

calcium concentration may therefore provide the mechanisms by which electric fields effect the

synthesis of extracellular tissue products18

.

Because IP3 release can be triggered by elevated free calcium in the cytoplasm a feedback loop

may exist that can drive large oscillations in cytoplasmic free calcium ion concentration.

Berridge and Galione recently reported that the oscillation frequency appears to be cell-type

specific and seems to vary with the presence of external ligands, indicating that the oscillation

frequency itself may act as a secondary signal for mediating cellular activity20

.

These calcium oscillations may contain a transmembrane ion flux component sensitive to electric

field changes in ion transport. Because variations in oscillation frequency have been linked to

ligand in terection at the membrane, field-imposed variations might similarly modulte cellular

behavior . Imposed transmembrane potentials are small, yet any alteration in the transport of

calcium ion channels might shift the frequency of these oscillations and provide a signal to the

cell.


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Metaphore illustration

Compare the lipid bilayer if the csll

membrane with butter, compare the

transmembrane receptors to emall iron pins

with cap, now place butter in a jar and

place the iron pins above its surface this is

analogous to the cellmembrane with

receptosa, now place a strong magnet near

the jar after some time the iron pins will be

collected towards the side of magnet, this

is what exactly happens to receptors and

this is called anisotropic property, due to

this movement channels open and ions

flow across the membrane.

Figure 1.5 shows displacement of membrane proteins

along the direction of the electric field, note that with

each pule or wave of electric field more number of

transmembrane proteins displaced increases. (Courtesy

by lee. Doong et al).

Figure 1.4 schematic diagram of effect of electric field on

the membrane receptors, arrows show the direction of

electric field (Courtesy by lee. Doong et al).


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Other Mechanisms

Some other less accepted theories are available which attempts to explain effect of electric field

on the cell membrane. A new theory proposed by Blank and Goodman suggests that counter ion

migration away from the equilibrium position around charged intracellular proteins may result

from applied electrical fields. The exposed fixed charges on the protein could alter protein

conformation and result in altered mRNA transcription or translation. This theory predicts the

frequency dependence of biosynthetic response that has been reported21,22.

Mechanismofmagnetic field interaction with cell

Cellular responses to magnetic fields are even more complex and difficult to understand because

the field penetrates the cell uniformly. Cyclotron resonance is one mechanism proposed toexplain the experimentally observed interaction of electric and magnetic fields are applied that

corresponds to the natural resonant frequency of the ion. This energetic response includes

absorbing sufficient velocity to traverse a membrane channel more easily. As evidence, the

authors cite changes in applied magnetic fields that have been observed to shift the frequency

window of cell sensitivity to applied electric fields23,24.

Magnetic field in living tissues effects directly and/or induces electrical currents that interacts

with the cell and its organellae to bring about the biological response, it is beyond the scope of

this book to explain all the effects, in the following section we have covered only those

phenomenon which are supported by a good amount of scientific evidence, the major

phenomenon are;

1. Stabilize cytosolic Calcium

2. Restore equilibrium in ROS (free radical)/antioxidant chemistry

3. Upregulate classes of protective and restorative gene loci

4. Downregulate dysregulatory and apoptotic gene loci.

1, Cytosolic Calcium

The magnetic field increases the free energy or entropy of the intracellular organellae cells

preview this as homeostatic challenge and cellular response to homeostatic challenge is the

release of calcium from intracellular stores that prompts mitochondria to produce free radicals


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(in physiological limit) and heightens DNA response which eventually leads to protein

synthesis25,26

.

2, Stabilized free radical chemistry.

Free radicals of oxygen are paramagnetic in nature and they exhibit dipole alignment when

exposed to a magnetic field, due to this when a magnetic field is applied to the cell as the free

radicals carry a negative charge they exhibit dipole alignment and become stabilized in one

position, this makes the anti oxidant machinery to detect the free radical very easy, thus

antioxidation process is facilitated27,28

.

3, Upregulation ofcytoprotective and restoration genes.

Cytoprotective genes come in to play when there is challenge to the survival of the cell, for

example reperfusion injury, transplant survival, bone graft survival, ischemic injury and so on

whenever such threat is detected the cytoprotective genes are activated, one of the most

important cytoprotective gene is HSP 70, application of magnetic field of 8 micro T, 60 Hz

frequency for 20 minutes (in invitro setting) upregulates HSP70 gene and decreases cell

mortality by 80%, which is of great therapeutic significance29-32

.

Downregulate dysregulatory genes.

In the NASA study some 13,000 gene loci responses to square wave with rapid dB/dt pulse

characteristics were studied with two software programs at an n96. It found that 3,000 loci

were upregulated that represented classes of restorative genes, 2,000 were down regulated

representing dysregulatory loci, and 8,000 loci were unaffected. The latter were reported as

house-keeping loci and other closely conserved sites. This also seems a logical

phenomenology among living systems to achieve homeostasis; this knowledge may pose

interesting possibilities when cancer mitigation becomes part of this technology33

.


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References

1. Rodan GA, Bourett LA, Norton LA. Synthesis in cartilage cells in stimulated by oscillating electric fields.

Science 1978;199:690-2.

2. Poo M. In situ electrophoresis of membrane components. Ann Rev Biophys Bioeng 1981;10:245-76.

3. Blackman CF, Benane SG, Elliot DJ et al. Influence of electromagnetic fields on the efflux of calcium ions

from brain tissue in vitro. Bioelectromagnetics 1988;9:215-7.

4. Adey WR. Tissue interactions with nonionizing electromagnetic fields. Physiol Rev 1981;61:435-514.

5. Blank M, Goodman R. An electrochemical model for the stimulation of biosynthesis by external electric

fields. Biochem and Bioenerg 1988;19:569.

6. McLaughlin S, Poo M. The role of electro-osmosis in the electric field-induced movement of changed

macromolecules on the surface of cells. Biophys J 1981;34:85-93.

7. Axelrod D. Lateral motion of membrane proteins and biological function. J Member Biol 1983;75:1-10.

8. Paris S, Pouyssegur J. Growth factors activate the bumetanide-sensitive Na+/K+/Ci-cotransport in hamster

fibroblasts. J Bio Chem 1986;261:6177-83.

9. Jhonson MA, Weber MJ. Serum stimulation of potassium fluxes, oubain binding, and sodiumfluxes in

quiescent chicken embryo fibroblasts. J Cell Phys 1980;103:363-70.

10. Smith BA, Clark WR, McConnell HM. Determination of molecular motion in membranes using periodic

pattern photobleaching. Proc Natl Acad Sci U S A 1978;75:2759-63.

11. Kapitza HA, McGregor G, Jacobson KA. Direct measurement of lateral transport in membranes by usin

time-resolved spatial photometry. Biophys J 1985;82:4122-26.

12. Stolpen AH, Pober JS, Brown CA, Golan DE. Class I MHC prote ins diffuse isotropically on immune

interferon-activated endothelial cells despite anisotropic cell shape and cytoskeletal organization:

application of fluorescence photobleaching recovery with an elliptical beam. Proc Natl Acad Sci U S A

1987;85:1844-48.

13. Cooper MS, Schliwa M. Electrical and ionic controls of tissue cell locomotion in DC electrical fields. J Cell

Phys 1985;103:363-70.

14. Rasmussen H, Barrett P. Calcium messenger system: an integrated view. Physiol Rev 1984;64:938-84.

15. Rasmussen H. The calcium messenger system. N Engl J Med 1986;314:1095-101.

16. Graziana A, Ranjeva R, Tessie J. External electric fields stimtoplasts, Bichemistry 1990;29:8313-8.

17. Matsudaira P, Janmey P. Pieces in the actin-severing protein puzzle. Cell 1988;54:139-40.

18. Kelly R. Pathways of protein secretion in eukaryotes. Science 1985;230:25-32.

19. Harootunian A, Kao J, Paranjape S, Tsien R. Generation of calcium oscillations in fibroblasts by positive

feedback between calcium and IP3. Science 1991;251:75-8.

20. Berridge MJ, Galione A. Cytosolic calcium oscillators. FASEB J 1988;2:3074-82.


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21. Goodman R, Henderson A. Exposture of salivary gland cells to low-frequency electromagnetic field alters

polypeptide synthesis. Proc Natl Acad Sci 1988;85:3298.

22. Cleary SF, Liu LM, Graham R, Diegelmann RF. Modulation of tendon fibroplasias by exogenous electric

currents. Bioelectromagnetics 1988;9:183-4.

23. Blackman CF, Benane SG, Elliot DJ et al. Influence of electromagnetic fields on the efflux of calcium ions

from brain tissue in vitro. Bioelectromagnetics 1988;9:215-7.

24. Liboff AR, Smith SD, McLeod BR. Experimental evidence for ion cyclotron resonance mediation of

membrane transport. In: Blank M, Findl E, cd. Mcchanistic approaches to interactions of electric and

electromagnetic fields with living systems. New York: Plenum Press, 1987:109-32.

25. Schild L, Reiser G. 2005. Oxidative stress is involved in the permeabilization of the inner

membrane of brain mitochondria exposed to hypoxia/reoxygenation and low micromolar Ca2.

FEBS J 272:35933601.

26. Ikehara T, Yamaguchi H, Hosokawa K, Houchi H, Park KH, Minakuchi K, Kashimoto H, Kitamura

M, Kinouchi Y, Yoshizaki K, Miyamoto H. 2005. Effects of a timevarying strong magnetic field on

transient increase in Ca2 release induced by cytosolic Ca2 in cultured pheochromocytoma

cells. Biochim Biophys Acta 1724:816.

27. Zumdahl S. 1992. Chemical principles. Lexington: DC Heath and Co. 670 p.

28. Eichwald C, Walleczek J. 1996b. Model for magnetic field effects on radical pair ecombination in

enzyme kinetics. Biophys J 71:623631.

29. BlankM, Goodman R. 2004. Initial interactions in electromagnetic field-induced interactions. J Cell Physiol

199:359363.

30. Lin H, Blank M, Rossol-Haseroth K, Goodman R. 2001. Regulating genes with electromagnetic response

elements. J Cell Biochem 81:143148.

31. Crowe MJ, Sun ZP, Battocletti JH,Macias MY, Pintar FA,Maiman DJ. 2003. Exposure to pulsed magnetic

fields enhances motor recovery in cats after spinal cord injury. Spine 28:2660 2666.

32. Grant G, Cadossi R, Steinberg G. 1994. Protection against focal cerebral ischemia following exposure to a

pulsed electromagnetic field. Bioelectromagnetics 15:205216.

33. Dennis R, Goodwin T. 2003. Physiological and molecular genetic effects of time-varying

electromagnetic fields on human neuronal cells. NASA Technical Paper TP-2003-212054.

9/1/2003.

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Chapter 7 Interaction of Emf With Cells

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