For this purpose, we decided to investigate the liver of DS mice model, which were previously generated and characterized by Barone and Perlugi’s lab [
19][31-33]. Interestingly, we found that 12-months old mice liver were characterized by a decreased GSH concentration, a well-known antioxidant molecule [
34]. The decreased level of antioxidant defenses prompted us to investigate the concentration of LOOH in this context. We therefore highlight an increased oxidative environment in DS 12-months old mice liver. This outcome has been reported to be related to the dysregulation of different factor occurring in the ROS balancing, as recently reviewed by our group [
3]. Furthermore, we also reported a significant decrease in HMOX1 expression in 12-months old livers. This data correlates with the increased Bach1 protein level reported in the brain of DS subject, and further mirrored in Ts2Cje mice model, by Perluigi group [
31,
35]. Bach1 is a master transcription repressor having HMOX1 as one of the main targets [
35,
36]. In particular, the HO1 protein play a role in the complex pathophysiological cascade involved in insulin resistance mechanisms, oxidative stress, metabolic syndrome and cardiovascular diseases [36-38].The rewire of the oxidative balance in DS livers might also have a crucial role in rewiring the inflammatory response of this organ. Interestingly, we report here a repression of IL-1β transcription, along with an increase of IL-10 expression. As recently reported, an enhancement of IL-10 expression inhibits IL-1β production [
39]. This outcome might be related to the increased susceptibility displayed by DS individuals in the development of several infections, given the lack of an inflammatory response [
40].
To further assess the inflammatory response in our model, we evaluated the protein accumulation of Hsp90, which was decreased in DS-livers. Despite any significative change in Hsp90 accumulation within DS brains has been reported [
41]. Furthermore, its downregulation might be related to an impaired inflammatory response, corroborating the previous data on IL-1β and IL-10 expression [
42]. In addition to this, we also reported a decrease in the protein levels of the mitochondrial shock protein Hsp60. This data is in line with a previous report describing a deficit in Hsp60 on skin fibroblasts derived from DS individuals [
43]. Interestingly, Hsp60 is the major mitochondrial heat shock protein, in charge for preventing protein aggregation following ROS unbalancing [
44]. Therefore, we sought to assess the protein accumulation of one of the master regulators of mitochondrial fitness, Clpp, which we found to be upregulated in our DS model. It has been reported that under high fat diet, Clpp downregulation correlates with an increased protection against obesity and hepatic steatosis, also preventing insulin resistance [
45,
46]. Furthermore, Clpp is also part of the machinery preventing hepatocytes senescence [
45]. Therefore, we speculate that the upregulation of this protein might be linked to the increased insulin resistance extensively described in DS individuals [
13]. Furthermore, it might also be part of a compensatory effect preventing cellular senescence and liver cirrhosis, typical of DS individuals. To further investigate this point, we sought to perform a real-time PCR aiming to assess the expression level of PPARα and PPARγ, two ligand-activated transcription factors part of the nuclear hormone receptor superfamily, in turn in charge for regulating adipogenesis and insulin resistance [
47]. Interestingly, the downregulation of PPARα and PPARγ, as the one we unveiled in our mode, might be correlated to the accumulation of lipid droplets within hepatocytes, also contributing to the insulin resistance reported in DS individuals [
48,
49]. The accumulation of lipid droplets in DS liver is further supported by our data showing an increased expression of FATP5 and CTP2 in 12-months old liver compared to the wild-type counterpart. The former is in charge for the uptake of long-chain fatty acids [
50]. Corroborating this, its expression has been reported to be inversely correlated to NAFLD progression [
51]. The increase in fatty acids uptake might also be correlated to increased CTP2 expression, in turn in charge for initiating fatty acids oxidation eventually promoting their clearance [
52]. In this context, fatty acids accumulation might work as a driver for the onset of liver fibrosis. In agreement with this, we reported an enhanced expression of Col1a1 in 12-month-old DS mice liver. Therefore, we decided to assess the fibrotic rate of wild-type and DS livers by histopathology. Interestingly, our results corroborated a scenario in which DS livers display higher fibrosis and hepatocellular ballooning, together with increased steatosis and inflammation. Overall, these data unveil a significant increased risk for DS individuals to develop liver pathologies. Interestingly, liver failure has been reported to DS newborns showing transient abnormal myelopoiesis, a pathology characterized by transient appearance of blast cells and eventually also affecting liver homeostasis [
53]. Furthermore, a diffuse lobular fibrosis around proliferating ductular elements and residual hepatocytes, as the one characterizing our DS models, was reported in DS newborns individuals presenting a severe liver disease [
54]. These effects are further enhanced by the higher obesity rate reported in DS individuals, in turn promoting NAFLD onset by accumulation of hepatic fatty acids [
55].
Overall, our work unveils a scenario in which DS liver is characterized by an impaired ROS scavenging system, locally unbalancing the oxidative stress level, and leading to an impaired response to inflammatory stimuli. This outcome correlates with the increased fibrotic rate reported in this context, along with the accumulation of fatty lipids, mirroring NAFLD profile. Given this evidence, the usage of antioxidants compounds might therefore represent a novel strategy in DS treatment to prevent liver-associated pathologies.