Low-dose intranasal deferoxamine modulates memory, neuroinflammation, and the neuronal transcriptome in the streptozotocin rodent model of Alzheimer's disease

Abstract

Introduction: Intranasal (IN) deferoxamine (DFO) has emerged over the past decade as a promising therapeutic in preclinical experiments across neurodegenerative and neurovascular diseases. As an antioxidant iron chelator, its mechanisms are multimodal, involving the binding of brain iron and the consequent engagement of several pathways to counter pathogenesis across multiple diseases. We and other research groups have shown that IN DFO rescues cognitive impairment in several rodent models of Alzheimer Disease (AD).

Methods: This study was designed to probe dosing regimens to inform future clinical trials, while exploring mechanisms within the intracerebroventricular (ICV) streptozotocin (STZ) model.

Results: Five weeks of daily IN dosing of Long Evans rats with 15 μL of a 1% (0.3 mg), but not 0.1% (0.03 mg), solution of DFO rescued cognitive impairment caused by ICV STZ administration as assessed with the Morris Water Maze (MWM) test of spatial memory and learning. Furthermore, IN DFO modulated several aspects of the neuroinflammatory milieu of the ICV STZ model, which was assessed through a novel panel of brain cytokines and immunohistochemistry. Using RNA-sequencing and pathway analysis, STZ was shown to induce several pathways of cell death and neuroinflammation, and IN DFO engaged multiple transcriptomic pathways involved in hippocampal neuronal survival.

Discussion: To our knowledge this study is the first to assess the transcriptomic pathways and mechanisms associated with either the ICV STZ model or DFO treatment, and the first to demonstrate efficacy at this low dose.

Keywords: Alzheimer’s disease; deferoxamine; intranasal; neuroinflammation; streptozotocin; transcriptome.

Figure 1

Visual representation of study design and timeline. (A) Five treatment groups dosed for 5 weeks and subjected to behavior tests followed by multiplex and RNA-sequencing. (B) Groups of four rats dosed for 1 week before immunohistochemistry. MWM, Morris Water Maze; ICV-STZ, intracerebroventricular streptozotocin; DFO, deferoxamine; IN, intranasal; TBB, tapered balance beam; OF, open field; Sal, Saline; IHC, immunohistochemistry.

Figure 2

Morris water maze data with fixed platform (A) and moving platform (B) for sham and ICV-STZ model mice treated with intranasal saline or DFO. Concentrations of DFO were 0.1 and 1% solutions and mice were treated 5×/week for 5 weeks. Repeated measures ANOVA showed that there was a clear model effect of the ICV-STZ treatment, and that treatment with 1% IN DFO significantly decreased escape latency as compared to controls (p < 0.05), while treatment with 0.1% DFO did not.

Figure 3

Mulitplex data from a panel of 27 inflammatory markers performed on hippocampal tissue from sham or ICV-STZ rats treated with intranasal saline or DFO. Data are only shown for the six markers with significant differences as measured with ANOVA with post-tests (*p < 0.05, #p < 0.1). (A) GMCSF, (B) IL13, (C) IL10, (D) RANTES, (E) Fractalkine, (F) TNFα. Sample sizes for each group are as follows: Sham-DFO = 7, Sham-Sal = 8, STZ-Sal = 12, STZ-0.1% DFO = 11, STZ-1% DFO = 11.

Figure 4

Immunohistochemical analyses of hippocampus in rats with either sham surgery or an ICV-STZ model of memory impairment at 14 days after model induction. A representative brain slice for imaging with PARP, NeuN, and Caspase 3 is in Panel (A), while a slice with Iba1, CD68, and GFAP is included in panel (B). The three antibodies on each slide had different absorbances and representative colors as follows: green (PARP), red (NeuN), and yellow (Caspase3), or green (Iba1), red (GFAP), and yellow (CD68). Both images are from an STZ rat treated with DFO (1%). Histograms are included and expressed as percent area fraction for PARP (C), Iba1 (D), CD68 (E), and GFAP (F). Sample size is 3/group, and # = p < 0.1. ANOVA with post-tests showed an insignificant trend toward a treatment effect with DFO for PARP and Iba1.