PLAN
B AND RETURN TO THE MOON SPACEFLIGHT 49:358, 2007
When large complex ventures are planned by nations it seems
appropriate to have a plan B. The potential cardiovascular hazards complicating
a lunar venture before the end of the next decade clearly require an
alternative plan to offset the lack of availability of pharmaceuticals; this is
because pharmaceuticals are contraindicated in space stemming from invariable
malabsorption necessitating parenteral administration, deterioration of some
(no longer meeting U.S.P. standards) and potential impairment in their hepatic
metabolism and renal excretion.(1)
In addition to the vascular complications of space flight there
are those vascular complications resulting from the inhalation of moon dust –
particularly ultra-fine particles ( < 100 nm.)- brought into the lunar
habitats on the space suits.(2) On earth
there has been growing concern regarding the industrial exposure to these “
nanotechnology products “ with
inhalation of these particles and then circulating throughout the body.
(3)
Similarly Apollo 17
astronaut Schmitt emphasized his
concern with his statement : “ NASA has
made no attempt to learn whether the Apollo astronauts’ limited exposure to
this dust has had any lasting effects “ ----(4) During the recent Rutgers Symposium on Lunar Settlements (June
3-8, 2007) (www.lunarbase.rutgers.edu ) Schmitt indicated
however his confidence that the problems with exposure in the lunar
habitats of this ultra-fine dust could be solved ultimately
perhaps by the combination of
electrostatic processes and development of the technology to remove the space
suits before entering the lunar habitat and leaving the space suits outside the
habitat.
But in case of failure of these options is there a plan B? Should
NASA begin NOW looking for a substitute for pharmaceuticals which can’t be
utilized in space? With promising
studies in experimental animals it appears that gene therapy may provide for
lunar explorers an option which might offset a few of the vascular
complications.
For example a major vascular complication in space appears to be
the reduction in circulating platelets because they can adhere to the injured
lining of the blood vessels
(endothelium) or aggregate. Since
platelets are the primary source of a vital
growth factor ( vascular endothelial growth factor )( VEGF) and platelets have been shown to be reduced both
with space flight (5) and with exposure to dust ( 6), the studies in
experimental animals of gene therapy to
enhance the supply of VEGF appears
promising.(7) VEGF is necessary for
endothelial ( the lining of blood vessels) function, repair and the development
of collateral circulation . (1,2)
Another preliminary study in experimental animals ( rats ) has
shown that gene therapy with a peptide
(atrial natriuretic peptide) ANP
(8) may conceivably offset the
invariable reduction in ANP complicating space flight.(1) This reduction in
ANP may be a partial explanation for Apollo 15 Astronaut Irwin’s extraordinary elevations of stress test
–related blood pressures (> 275/125) after his mission ,which I postulated was secondary to
inhalation of ultra-fine dust in the lunar module(2). Such blood pressure
levels have not been reported – to my knowledge- from dust inhalation on earth.
It is important to keep in mind however that inhalation of urban dust-
superimposed upon vascular disease- does not always precipitate hypertension.
The explanation may be because on earth the presence of ANP in sufficient
quantities prevents this from occurring because ANP counteracts the effects of
vessel constrictors, and by another mechanism also enhances vasodilatation. (
1,2,9)
If we indeed are serious about exploring and ultimately colonizing
the moon and then on to Mars now is the time to explore as well the
opportunities gene therapy may provide.
William J. Rowe M.D. FBIS
References
1. WJ Rowe. The case for a subcutaneous magnesium product and
delivery device for space missions. J Am Coll Nutr 23, pp 525 S-528S, 2004
2 WJ Rowe. Moon dust may simulate vascular hazards of urban
pollution. JBIS 60 pp. 133-136,2007
3 BJ.Feder. New rules
expected on safety of nanotechnology products.
New York Times, June 21, 2007
4 HH.Schmitt. Return to the moon. Copernicus Books ,
5
E.Gunsillius , AL Petzer , G Gastl. Space flight and growth factors. Lancet 353 : p 1529, 1999
6. K Donaldson, V Stone, A Seaton,
7. MM Gaffney , SO Hynes ,
F Barry , T O’Brien. Cardiovascular gene
therapy ; current status and therapeutic potential. Brit.
J. Pharmacol , 11 June, pp1-14,
2007
8. KF Lin, J Chao, L Chao. Human atrial natriuretic peptide gene
delivery reduces blood pressure in hypertensive rats. Hypertension 26,
pp.847-853,1995.
9. MA Costa,