Presence of Systemic Amyloidosis in Mice with Partial Deficiency in Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) in Aging

Pituitary adenylate cyclase-activating polypeptide (PACAP), a neuropeptide with widespread expression and general cytoprotective effects, is also involved in aging. Previously, we observed accelerated systemic senile amyloidosis in PACAP knockout (KO) mice. As mice partially lacking PACAP (heterozygous-HZ) show variable symptoms, here we investigated whether HZ mice have accelerated aging, completed with observations in PAC1 receptor KO mice. As we have limited data on qualitative or quantitative changes in the blood of PACAP-deficient mice, we investigated whether these changes could be in the background of the amyloidosis. Routine histological staining was used to examine amyloid deposits, rated on a severity scale 0–3. Blood was collected from PACAP wild type/HZ mice for complete blood analysis. In contrast to receptor KO mice showing no amyloidosis, histopathological analysis revealed severe deposits in PACAP HZ mice, with kidney, spleen, skin, and intestines being most affected. Increased cholesterol, lipoprotein levels, and differences in several blood count parameters were found in HZ mice. In summary, amyloidosis also develops in partial absence of PACAP, in contrast to the lack of its PAC1 receptor. In addition to the earlier identified inflammatory and degenerative disturbances, the alteration in lipid metabolism and bone marrow activity can also be additional factors leading to systemic degenerative processes

Peripheral neuropathy in metachromatic leukodystrophy: current status and future perspective

Metachromatic leukodystrophy (MLD) is an autosomal recessively inherited metabolic disease characterized by deficient activity of the lysosomal enzyme arylsulfatase A. Its deficiency results in accumulation of sulfatides in neural and visceral tissues, and causes demyelination of the central and peripheral nervous system. This leads to a broad range of neurological symptoms and eventually premature death. In asymptomatic patients with juvenile and adult MLD, treatment with allogeneic hematopoietic stem cell transplantation (HCT) provides a symptomatic and survival benefit. However, this treatment mainly impacts brain white matter, whereas the peripheral neuropathy shows no or only limited response. Data about the impact of peripheral neuropathy in MLD patients are currently lacking, although in our experience peripheral neuropathy causes significant morbidity due to neuropathic pain, foot deformities and neurogenic bladder disturbances. Besides, the reasons for residual and often progressive peripheral neuropathy after HCT are not fully understood. Preliminary studies suggest that peripheral neuropathy might respond better to gene therapy due to higher enzyme levels achieved than with HCT. However, histopathological and clinical findings also suggest a role of neuroinflammation in the pathology of peripheral neuropathy in MLD. In this literature review, we discuss clinical aspects, pathological findings, distribution of mutations, and treatment approaches in MLD with particular emphasis on peripheral neuropathy. We believe that future therapies need more emphasis on the management of peripheral neuropathy, and additional research is needed to optimize care strategies