Could Reduced Bone Mineral Densities in HIV Be Caused by Nanobacteria? Andrei P. Sommer* Central Institute of Biomedical Engineering, University of Ulm, 89081 Ulm, Germany Received January 4, 2004
From the observations of different research groups reporting on reduced bone mineral density (BMD) and on a pronounced tendency for kidney stone formation, both in HIV-infected patients, and from results achieved in the treatment of severest peripheral neuropathy with lasers, it is concluded that nanobacteria (NB) could actively contribute to the reduction of BMD. A reduced BMD could primarily stem from NB, extracting calcium and phosphate from blood, affecting the calcium and phosphate homeostasis in humans. Keywords: HIV • calcium phosphate • apatite • bone mineral density • nanobacteria
Nanobacteria (NB) may grow in HIV-infected patients at the expense of bone mineral content. The picture receives support from two sides: the experimental side, with evidence for reduced BMD in HIV;1,2 and the theoretical side, predicting a possibly crucial role of NB in various manifestations of peripheral neuropathy (PN).3,4 PN is a condition frequently accompanying HIV-infection, and it can considerably aggravate the state of the patients. Most importantly, the decrease in BMD in HIV-infected patients was found to be independent of antiretroviral therapy.5 Thus, a decreased BMD appears to be intrinsic to HIV. The underlying mechanism triggering bone loss in HIV-infected patients is unknown. It could be instructive to point out the chemical relationship between bone and NB. Bone is the principal reserve supply for calcium and phosphate, components which are stored mostly in the form of hydroxyapatite. NB are best described as nanovesicles protected by a porous mineral shell with diameters on the order of 80-300 nm, consisting of densely packed carbonate apatite crystals.6 In cell culture media and under favorable physiological conditions, NB have been observed to replicate and grow.6 NB growth is practically equivalent with reducing available concentrations of calcium and phosphate in their immediate environment. In this way, NB circulating in blood are likely to have an impact on the calcium and phosphate homeostasis, and to eventually compete with bone for calcium and phosphate. NB’s need for additional amounts of calcium and phosphate could be activated by rapid changes in their environment, corresponding to physiological and/or biomechanical stress. Under stress, cultured NB tended to assemble in colonies with individual NB interconnected by self-secreted slime.7 The precise constitution of the slime is not clear. However, it is expected that the slime is actively participating in collecting the components promoting the mineralization of the shell. Consequently, the slime should be rich in calcium and phosphate, and probably in proteins. For small biosystems in metabolic exchange with their sur* To whom correspondence should be addressed. E-mail: samoan@ gmx.net.
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rounding, collective slime production is an adequate response to externally induced stress.8 In NB, it could have, in principle, three major biological functions, all serving one single scope: maximizing survivability: (I) NB attachment to surfaces, facilitated by the slime’s bonding property (immobilizing function); (II) biomineralization, promoted by locally elevated levels of the chemical components of the apatite (protective function); and (III) total surface sealing, probably securing the survival of NB in the atmosphere.9 Hermetical surface sealing is not specific to the NB. There are deserts in the Sahara in which no rain has been seen for years, but when short, heavy rains come, molluscs, which have sealed their shells with dry mucus, revive in the sand and amid arid rocks where they were buried. There is a synergistic interaction between function (I) and (II): by attachment to surfaces within the body, NB colonies may create around themselves a nutrient-rich milieu, and protect themselves transiently from elimination from the body. Notably, NB are eliminated from the body via the urine.10 If indeed NB contribute to the loss in BMD in HIV-infected patients, one could expect their massive presence in the body of such patients, in particular in their kidneys. Remarkably, HIVinfected patients presented an unusual abundance of kidney stones, evidently independent of their use of protease inhibitors.11 NB have been identified in a representative number of stones,12 proposed to be nucleated by giant NB entrapped in the kidneys.13 The prominent role of the NB in stone formation is supported by recent data suggesting that kidney stones are nucleated by calcium phosphate.14 In pathogenic situations where bone and NB may compete for calcium and phosphate, irradiation of parts of the body with low level lasers may shift the balance to the disadvantage of the NB: NB have been observed to reduce slime release when they were irradiated with low level light.15,16 In this way, their deposition could be prevented and/or existing plaques progressively destabilized. Low level light has been demonstrated to compensate various forms of environmental stress, in living cells and in NB,17 an effect successfully exploited in the treatment of a patient 10.1021/pr049978b CCC: $27.50
2004 American Chemical Society
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Role of NB in Reduced BMD in HIV Patients
Figure 1. Image on the left shows the feet of patient with severest peripheral neuropathy, prior to laser therapy.3 Image on the right shows situation after successful laser treatment, and is attached to illustrate the practical aspects of the therapy. The employed laser light intensity had with about 2000 Wm-2 per irradiated spot twice the value of the surface solar irradiation. Irradiation time per spot was two minutes, resulting in a total light dose of about 100‚104 Jm-2, delivered by four laser modules with a power of 35 mW each, all operating at a wavelength of 660 nm.
presenting the severest form of PN. Stress-exposed NB circulating in the blood stream are thought to collect extracellular calcium and phosphate, and synthesize them, possibly together with appropriate proteins to slime. Slime synthesis is a process believed to take place on the mineral surfaces of the NB, in which apatite may serve as a platform to bind proteins, and the rough topography as efficient reservoir for storage and rapid expulsion of the slime. Expulsion could be stimulated by short exposures to light intensities of the order of the solar constant. Intensities of that order have been shown to induce a transient depletion of nanoscopic water films attached to polymer surfaces,18 and were predicted to induce powerful pumping processes pressing aqueous liquids from the central cavity of the NB, across the tubular channels of their mineral shell, to their surface. Prolonged exposure of NB to the light intensity employed may result in complete desiccation of the central cavity. Prolongation of the irradiation time is equivalent with an elevation of the energy density. The associated long-lasting desiccation of the pores could probably result in a spontaneous surface sealing, inactivating NB for some time, as could be programmed for atmospheric survival. The hypothesis regarding the importance of the irradiation period is consistent with the finding that irradiation with solitary wavelengths (655 or 810 nm), delivered by lasers scanning in a linear mode at a frequency of 3 Hz, had virtually no effect on cultured NB.15 For both wavelengths, the variable irradiation parameters intensity and energy density were adjusted to values known to induce biological effects in most of the cells and NB. This model could be indirectly validated by realizing that the irradiation parameters (wavelength, intensity, and dose), found to compensate stress in cultured NB,15,16 were not in ranges inducing thermal or photobiochemical effects which could potentially control slime production outside the mineral shell of the NB. Such effects could be protein coagulation, or cross-linking of suspended proteins,19 respectively. It is worth noting that the basic laser irradiation parameters (intensity and dose) employed in the therapy of PN (Figure 1)3 were significantly higher than
those utilized to irradiate cultured NB in Petri dishes,15,16 nonetheless, still at levels fully tolerated by human skin. Thus, noninvasive irradiation of the kidneys with lasers, at levels tolerated by the skin, may help preventing or blocking stone formation nucleated by stressed NB. Since low level light therapy works within relatively narrow intensity windows, applied at moderate doses (1-4‚104 Jm-2), irradiation of the kidneys with biologically effective light intensities could only be achieved at the price of surface intensities exceeding by far the levels common in low level laser therapy.20 Experiments optimizing the laser parameters, in particular evaluating the maximum tolerated skin surface dose for a desired target intensity and relevant wavelength, are recommended. Appropriate in vitro experiments and animal models may help to elucidate the presumed interplay between bone and NB. Additional investigations are needed to determine the slime’s chemical composition, which seems to act as a transient storage medium for calcium and phosphate.
References (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13)
Glesby, M. J. Clin. Infect. Dis. 2003, 37 Suppl 2, S91. Thomas, J.; Doherty, S. M. JAIDS 2003, 33, 281. Sommer, A. P. J. Proteome Res. 2003, 2, 665. Sommer, A. P. J. Proteome Res., in print. Bruera, D.; Luna, N.; David, D. O.; Bergoglio, L. M.; Zamudio J. AIDS 2003, 17, 1917. Kajander, E. O.; Ciftcioglu, N. Proc. Natl. Acad. Sci. U.S.A. 1998, 95, 8274. Sommer, A. P.; Pretorius, A. M.; Kajander, E. O.; Oron, U. Cryst. Growth Des. 2004, 4, 45. Sommer, A. P.; McKay, D. S.; Ciftcioglu, N.; Oron, U.; Mester, A. R.; Kajander, E. O. J. Proteome Res. 2003, 2, 441. Sommer, A. P.; Pavla´th, A. E. J. Proteome Res. 2003, 2, 558. Akerman, K. K.; Kuikka, J. T.; Ciftcioglu, N.; Parkkinen, J.; Bergstro¨m, K. A.; Kuronen, I.; Kajander, E. O. Proc. SPIE Int. Soc. Opt. Eng. 1997, 3111, 436. Nadler, R. B.; Rubenstein, J. N.; Eggener, S. E.; Loor, M. M.; Smith, N. D. J. Urol. 2003, 169, 475. Ciftcioglu, N.; Bjo¨rklund, M.; Kuorikoski, K.; Bergstro¨m, K.; Kajander, E. O. Kidney Int. 1999, 56, 1893. Sommer, A. P.; Kajander, E. O. Cryst. Growth Des. 2002, 2, 563.
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letters (14) Bushinsky, D. A. J. Clin. Invest. 2003, 111, 602. (15) Sommer, A. P.; Hassinen, H. I.; Kajander, E. O. J. Clin. Laser Med. Surg. 2002, 20, 241. (16) Sommer, A. P.; Oron, U.; Pretorius, A. M.; McKay, D. S.; Ciftcioglu, N.; Mester, A. R.; Kajander, E. O.; Whelan, H. T. J. Clin. Laser Med. Surg. 2003, 21, 229. (17) Sommer, A. P.; Oron, U.; Kajander, E. O.; Mester, A. R. J. Proteome Res. 2002, 1, 475.
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Sommer (18) Sommer, A. P.; Franke, R. P. NanoLett. 2003, 3, 19. (19) Pashev, I. G.; Dimitrov, S. I.; Angelov, D. Trends. Biochem. Sci. 1991, 16, 323. (20) Sommer, A. P.; Pinheiro, A. L. B.; Mester, A. R.; Franke, R. P.; Whelan, H. T. J. Clin. Laser Med. Surg. 2001, 19, 29.
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