The article by Wilcock et al. describes tauopathy development in a transgenic APP mouse lacking NOS. NO is known as a peripheral and central mediator in temperature regulation (Simon, 1998). In addition, there is extensive literature showing that NOS knockout mice have problems regulating body temperature, and are prone to hypothermia in stress situations (Koedel et al., 2001; Spanagel et al., 2002; Saia and Carnio, 2006; Saia et al., 2008). Hypothermia induces tau hyperphosphorylation both in vivo and in vitro (Planel et al., 2004). This phenomenon is extremely sensitive to body temperature (+80 percent per degree C drop), and a decrease of 1-3 degrees C will induce a 200-300 percent increase in tau phosphorylation (Planel et al., 2007). Moreover, transgenic APP mice are also prone to hypothermia (Huitron-Resendiz et al., 2002; Iivonen et al., 2003). It is therefore possible that the increase in phospho-tau shown in the APP/NOS-/- mice reflects that the NOS-/- derived mice have deficits in thermoregulation, which might be exacerbated by stress imposed by elevated Aβ levels....  Read more

The article by Wilcock et al. describes tauopathy development in a transgenic APP mouse lacking NOS. NO is known as a peripheral and central mediator in temperature regulation (Simon, 1998). In addition, there is extensive literature showing that NOS knockout mice have problems regulating body temperature, and are prone to hypothermia in stress situations (Koedel et al., 2001; Spanagel et al., 2002; Saia and Carnio, 2006; Saia et al., 2008). Hypothermia induces tau hyperphosphorylation both in vivo and in vitro (Planel et al., 2004). This phenomenon is extremely sensitive to body temperature (+80 percent per degree C drop), and a decrease of 1-3 degrees C will induce a 200-300 percent increase in tau phosphorylation (Planel et al., 2007). Moreover, transgenic APP mice are also prone to hypothermia (Huitron-Resendiz et al., 2002; Iivonen et al., 2003). It is therefore possible that the increase in phospho-tau shown in the APP/NOS-/- mice reflects that the NOS-/- derived mice have deficits in thermoregulation, which might be exacerbated by stress imposed by elevated Aβ levels. Monitoring of body temperature at time of sacrifice and/or normalization of body temperature would address whether the increase in phospho-tau is an artifact or not.

References:
Huitrón-Reséndiz S, Sánchez-Alavez M, Gallegos R, Berg G, Crawford E, Giacchino JL, Games D, Henriksen SJ, Criado JR. Age-independent and age-related deficits in visuospatial learning, sleep-wake states, thermoregulation and motor activity in PDAPP mice. Brain Res. 2002 Feb 22;928(1-2):126-37. Abstract

Iivonen H, Nurminen L, Harri M, Tanila H, Puoliväli J. Hypothermia in mice tested in Morris water maze. Behav Brain Res. 2003 May 15;141(2):207-13. Abstract

Koedel U, Paul R, Winkler F, Kastenbauer S, Huang PL, Pfister HW. Lack of endothelial nitric oxide synthase aggravates murine pneumococcal meningitis. J Neuropathol Exp Neurol. 2001 Nov 1;60(11):1041-50. Abstract

Planel E, Miyasaka T, Launey T, Chui DH, Tanemura K, Sato S, Murayama O, Ishiguro K, Tatebayashi Y, Takashima A. Alterations in glucose metabolism induce hypothermia leading to tau hyperphosphorylation through differential inhibition of kinase and phosphatase activities: implications for Alzheimer's disease. J Neurosci. 2004 Mar 10;24(10):2401-11. Abstract

Planel E, Richter KE, Nolan CE, Finley JE, Liu L, Wen Y, Krishnamurthy P, Herman M, Wang L, Schachter JB, Nelson RB, Lau LF, Duff KE. Anesthesia leads to tau hyperphosphorylation through inhibition of phosphatase activity by hypothermia. J Neurosci. 2007 Mar 21;27(12):3090-7. Abstract

Saia RS, Carnio EC. Thermoregulatory role of inducible nitric oxide synthase in lipopolysaccharide-induced hypothermia. Life Sci. 2006 Sep 5;79(15):1473-8. Abstract

Saia RS, Anselmo-Franci JA, Carnio EC. Hypothermia during endotoxemic shock in female mice lacking inducible nitric oxide synthase. Shock. 2008 Jan 1;29(1):119-26. Abstract

Simon E. Nitric oxide as a peripheral and central mediator in temperature regulation. Amino Acids. 1998 Jan 1;14(1-3):87-93. Abstract

Spanagel R, Siegmund S, Cowen M, Schroff KC, Schumann G, Fiserova M, Sillaber I, Wellek S, Singer M, Putzke J. The neuronal nitric oxide synthase gene is critically involved in neurobehavioral effects of alcohol. J Neurosci. 2002 Oct 1;22(19):8676-83. Abstract

View all comments by Karen Duff
View all comments by Emmanuel PLANEL

Reply by CA Colton, DM Wilcock, J Oddo, WE Van Nostrand, MP Vitek, and D Christensen
We would like to thank Drs. Duff and Planel for their comments on our mouse model of AD. We believe, however, that the tau pathology we observed in the old mice is not due to hypothermia. As shown in Table 1, the core body temperatures of APPSwDI and of APPSwDI/NOS2-/- mice at 52-60 weeks of age are not significantly different. The only difference between APPSwDI and APPSwDI/NOS-/- mice is the deletion of a functional NOS2 gene. When combined with deposition of β amyloid, this NOS2 deletion is associated with a significantly increased level of AT8-positive immunoreactivity in APPswDI/NOS2-/- mice when compared to the APPSwDI mice (Colton et al., 2007, Wilcock et al., 2008).

Genotype 	               Core body temperature (oC)
APPSwDI 	               35.69 + 0.13 (n = 14)
APPSwDI/NOS2-/-                35.61 + 0.13 (n = 7)

Table 1: Core body temperature: Core body temperature was measured at 10 a.m. using a soft tip, small diameter YSI temperature probe inserted 1...  Read more

Reply by CA Colton, DM Wilcock, J Oddo, WE Van Nostrand, MP Vitek, and D Christensen
We would like to thank Drs. Duff and Planel for their comments on our mouse model of AD. We believe, however, that the tau pathology we observed in the old mice is not due to hypothermia. As shown in Table 1, the core body temperatures of APPSwDI and of APPSwDI/NOS2-/- mice at 52-60 weeks of age are not significantly different. The only difference between APPSwDI and APPSwDI/NOS-/- mice is the deletion of a functional NOS2 gene. When combined with deposition of β amyloid, this NOS2 deletion is associated with a significantly increased level of AT8-positive immunoreactivity in APPswDI/NOS2-/- mice when compared to the APPSwDI mice (Colton et al., 2007, Wilcock et al., 2008).

Genotype 	               Core body temperature (oC)
APPSwDI 	               35.69 + 0.13 (n = 14)
APPSwDI/NOS2-/-                35.61 + 0.13 (n = 7)

Table 1: Core body temperature: Core body temperature was measured at 10 a.m. using a soft tip, small diameter YSI temperature probe inserted 1 cm into the rectum in each mouse. (n) = number of mice tested; mixed gender, age 52-60 weeks.

Our APP/NOS2-/- model shows other important features of Alzheimer pathology that are not observed with simple hypothermia. We observe significant somatodendritic redistribution of AT8-positive phospho-tau in our APPSwDI/NOS2-/- mouse (Wilcock et al., 2008). In contrast, Planel et al. (2007) clearly state that no somatodendritic redistribution of AT8-positive tau is observed in mice that are hypothermic.

More importantly, we observe neuronal loss and significant behavioral deficits in normothermic APP/NOS2-/- mice that are only seen when Aβ pathology and tau pathology are coexpressed. These behavioral deficits are seen in the Barnes maze test that employs walking on dry land to learn and remember an escape port and does not alter core body temperature. These behavioral deficits were also seen in a warm-water radial arm water maze. Although cold-water mazes may reduce body temperature in mice, Iivonen et al. (2003) showed that induced hypothermia could be prevented by increasing the water temperature to 24 oC or above and by increasing the inter-test interval. The water temperature used in our study is 24-30 oC, the inter-test interval is 10-15 minutes, and similar values used by Iivonen et al. resulted in no change of core body temperature in mice. Furthermore, we do not measure the swimming time because we use the number of errors as our outcome measure. This combined behavioral testing strategy eliminates hypothermia as a potential confounding issue in our results that show a behavioral deficit in normothermic APP/NOS2-/- mice.

References:
Colton CA, Vitek MP, Wink DA, Xu Q, Cantillana V, Previti ML, Van Nostrand WE, Weinberg JB, Weinberg B, Dawson H. NO synthase 2 (NOS2) deletion promotes multiple pathologies in a mouse model of Alzheimer's disease. Proc Natl Acad Sci U S A. 2006 Aug 22;103(34):12867-72. Abstract

Iivonen H, Nurminen L, Harri M, Tanila H, Puoliväli J. Hypothermia in mice tested in Morris water maze. Behav Brain Res. 2003 May 15;141(2):207-13. Abstract

Planel E, Richter KE, Nolan CE, Finley JE, Liu L, Wen Y, Krishnamurthy P, Herman M, Wang L, Schachter JB, Nelson RB, Lau LF, Duff KE. Anesthesia leads to tau hyperphosphorylation through inhibition of phosphatase activity by hypothermia. J Neurosci. 2007 Mar 21;27(12):3090-7. Abstract

Wilcock DM, Lewis MR, Van Nostrand WE, Davis J, Previti ML, Gharkholonarehe N, Vitek MP, Colton CA. Progression of amyloid pathology to Alzheimer's disease pathology in an amyloid precursor protein transgenic mouse model by removal of nitric oxide synthase 2. J Neurosci. 2008 Feb 13;28(7):1537-45. Abstract

Yoshida S, Maeda M, Kaku S, Ikeya H, Yamada K, Nakaike S. Lithium inhibits stress-induced changes in tau phosphorylation in the mouse hippocampus. J. Neural Transm. 2006 113: 1803-1814. Abstract

View all comments by Carol Colton
View all comments by William Van Nostrand
View all comments by Michael Vitek
View all comments by Donna M. Wilcock