Doxycycline could aggravate the absence-like epileptic seizures of WAG/Rij rats via matrix metalloproteinase inhibition

Doxycycline Promotes Carcinogenesis & Metastasis via Chronic Inflammatory Pathway: An In Vivo Approach

Background

Doxycycline (DOX) exhibits anti-inflammatory, anti-tumor, and pro-apoptotic activity and is being tested in clinical trials as a chemotherapeutic agent for several cancers, including colon cancer.

Materials & Methods

In the current study, the chemotherapeutic activity of doxycycline was tested in a rat model of colon carcinogenesis, induced by colon specific cancer promoter, 1,2, dimethylhydrazine (DMH) as well as study the effect of DOX-alone on a separate group of rats.

Results

Doxycycline administration in DMH-treated rats (DMH-DOX) unexpectedly increased tumor multiplicity, stimulated progression of colonic tumor growth from adenomas to carcinomas and revealed metastasis in small intestine as determined by macroscopic and histopathological analysis. DOX-alone treatment showed markedly enhanced chronic inflammation and reactive hyperplasia, which was dependent upon the dose of doxycycline administered. Moreover, immunohistochemical analysis revealed evidence of inflammation and anti-apoptotic action of DOX by deregulation of various biomarkers.

Conclusion

These results suggest that doxycycline caused chronic inflammation in colon, small intestine injury, enhanced the efficacy of DMH in tumor progression and provided a mechanistic link between doxycycline-induced chronic inflammation and tumorigenesis. Ongoing studies thus may need to focus on the molecular mechanisms of doxycycline action, which lead to its inflammatory and tumorigenic effects.

Matrix metalloproteinase-9 involvement in the structural plasticity of dendritic spines

Dendritic spines are the locus for excitatory synaptic transmission in the brain and thus play a major role in neuronal plasticity. The ability to alter synaptic connections includes volumetric changes in dendritic spines that are driven by scaffolds created by the extracellular matrix (ECM). Here, we review the effects of the proteolytic activity of ECM proteases in physiological and pathological structural plasticity. We use matrix metalloproteinase-9 (MMP-9) as an example of an ECM modifier that has recently emerged as a key molecule in regulating the morphology and dysmorphology of dendritic spines that underlie synaptic plasticity and neurological disorders, respectively. We summarize the influence of MMP-9 on the dynamic remodeling of the ECM via the cleavage of extracellular substrates. We discuss its role in the formation, modification, and maintenance of dendritic spines in learning and memory. Finally, we review research that implicates MMP-9 in aberrant synaptic plasticity and spine dysmorphology in neurological disorders, with a focus on morphological abnormalities of dendritic protrusions that are associated with epilepsy.

Effect of novel limited-spectrum MMP inhibitor XL784 in abdominal aortic aneurysms

BACKGROUND

Inhibiting the growth of small abdominal aortic aneurysms (AAAs) is a clinically valuable goal and fills an important therapeutic void. Based on studies in animals and humans, inhibition of the activity of elastolytic matrix metalloproteinases (MMPs) has the potential to slow AAA expansion and limit morbidity and the need for surgery. Previous attempts to make use of the synthetic MMP inhibitors in the treatment of chronic conditions have been limited by intolerable side effects. The limited-spectrum synthetic MMP inhibitor, XL784, was well tolerated and devoid of side-effects associated with other nonspecific MMP inhibitors in phase I studies. We hypothesized that clinically relevant doses of XL784 would be effective at inhibiting aneurysm development in a mouse model.

METHODS

The 14-day elastase-perfusion model of AAA in mice was used. An initial screening study of XL784 (50 [n = 17], 125 [n = 17], and 250 mg/kg [n = 18]) administered via gavage daily until harvest. Controls received diluent alone (n = 18) or doxycycline in drinking water (n = 19). Aortic diameter was measured pre-perfusion (AD(pre)) and at harvest (AD(har)). A second study used XL784 (250 [n = 9]; 375 [n = 9], and 500 mg/kg [n = 14]) and diluent alone (n = 9) administered via gavage. The percentage dilatation [%ΔAD = [(AD(har) - AD(pre))/AD(pre)] ×100] was calculated and elastin and inflammatory content was scored.

RESULTS

All mice tolerated the treatments similarly. Control mice all developed aneurysms with a mean %ΔAD of 158.5% ± 4.3%. Treatment with all doses of XL784 and doxycycline were effective in inhibiting aortic dilatation. There was a clear dose-response relationship between XL784 and reductions in aortic dilatation at harvest (50 mg/kg 140.4% ± 3.2%; 125 mg/kg 129.3% ± 5.1%; 250 mg/kg 119.2% ± 3.5%; all Ps < .01 compared to control). This continued with the higher doses (375 mg/kg 88.6% ± 4.4%; 500 mg/kg 76.0% ± 3.5%). The highest 2 doses of XL784 tested were more effective than doxycycline (112.2% ± 2.0%, P < .05) in inhibiting maximal dilatation of the aorta after elastase perfusion.

Dendritic spine pathology in epilepsy: cause or consequence?

Abnormalities in dendritic spines have commonly been observed in brain specimens from epilepsy patients and animal models of epilepsy. However, the functional implications and clinical consequences of this dendritic pathology for epilepsy are uncertain. Dendritic spine abnormalities may promote hyperexcitable circuits and seizures in some types of epilepsy, especially in specific genetic syndromes with documented dendritic pathology, but in these cases it is difficult to differentiate their effects on seizures versus other comorbidities, such as cognitive deficits and autism. In other situations, seizures themselves may cause damage to dendrites and dendritic spines and this seizure-induced brain injury may then contribute to progressive epileptogenesis, memory problems and other neurological deficits in epilepsy patients. The mechanistic basis of dendritic spine abnormalities in epilepsy has begun to be elucidated and suggests novel therapeutic strategies for treating epilepsy and its complications.